ISSN Volume 7, Number 4 December 2015

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1 ISSN Volume 7, Number 4 December

2 Editor-in-Chief Tsanko Yablanski Faculty of Agriculture Trakia University, Stara Zagora Bulgaria Co-Editor-in-Chief Radoslav Slavov Faculty of Agriculture Trakia University, Stara Zagora Bulgaria Editors and Sections Genetics and Breeding Atanas Atanasov (Bulgaria) Nikolay Tsenov (Bulgaria) Max Rothschild (USA) Ihsan Soysal (Turkey) Horia Grosu (Romania) Bojin Bojinov (Bulgaria) Stoicho Metodiev (Bulgaria) Nutrition and Physiology Nikolai Todorov (Bulgaria) Peter Surai (UK) Zervas Georgios (Greece) Ivan Varlyakov (Bulgaria) Production Systems Dimitar Pavlov (Bulgaria) Bogdan Szostak (Poland) Dimitar Panaiotov (Bulgaria) Banko Banev (Bulgaria) Georgy Zhelyazkov (Bulgaria) Agriculture and Environment Georgi Petkov (Bulgaria) Ramesh Kanwar (USA) Martin Banov (Bulgaria) Product Quality and Safety Marin Kabakchiev (Bulgaria) Stefan Denev (Bulgaria) Vasil Atanasov (Bulgaria) English Editor Yanka Ivanova (Bulgaria) Scope and policy of the journal Agricultural Science and Technology /AST/ an International Scientific Journal of Agricultural and Technology Sciences is published in English in one volume of 4 issues per year, as a printed journal and in electronic form. The policy of the journal is to publish original papers, reviews and short communications covering the aspects of agriculture related with life sciences and modern technologies. It will offer opportunities to address the global needs relating to food and environment, health, exploit the technology to provide innovative products and sustainable development. Papers will be considered in aspects of both fundamental and applied science in the areas of Genetics and Breeding, Nutrition and Physiology, Production Systems, Agriculture and Environment and Product Quality and Safety. Other categories closely related to the above topics could be considered by the editors. The detailed information of the journal is available at the website. Proceedings of scientific meetings and conference reports will be considered for special issues. Submission of Manuscripts All manuscripts written in English should be submitted as MS-Word file attachments via to editoffice@agriscitech.eu. Manuscripts must be prepared strictly in accordance with the detailed instructions for authors at the website and the instructions on the last page of the journal. For each manuscript the signatures of all authors are needed confirming their consent to publish it and to nominate on author for correspondence. They have to be presented by a submission letter signed by all authors. The form of the submission letter is available upon from request from the Technical Assistance or could be downloaded from the website of the journal. Manuscripts submitted to this journal are considered if they have submitted only to it, they have not been published already, nor are they under consideration for publication in press elsewhere. All manuscripts are subject to editorial review and the editors reserve the right to improve style and return the paper for rewriting to the authors, if necessary. The editorial board reserves rights to reject manuscripts based on priorities and space availability in the journal. The journal is committed to respect high standards of ethics in the editing and reviewing process and malpractice statement. Commitments of authors related to authorship are also very important for a high standard of ethics and publishing. We follow closely the Committee on Publication Ethics (COPE), elines The articles appearing in this journal are indexed and abstracted in: EBSCO Publishing, Inc. and AGRIS (FAO). The journal is accepted to be indexed with the support of a project BG051PO Science and business financed by Operational Programme Human Resources Development of EU. The title has been suggested to be included in SCOPUS (Elsevier) and Electronic Journals Submission Form (Thomson Reuters). Address of Editorial office: Agricultural Science and Technology Faculty of Agriculture, Trakia University Student's campus, 6000 Stara Zagora Bulgaria Telephone.: Technical Assistance: Nely Tsvetanova Telephone.: editoffice@agriscitech.eu

3 Volume 7, Number 4 December 2015 ISSN

4 AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 7, No 4, pp , 2015 Review Effect of feeding program for first two months after birth of female calves on growth, development and first lactation performance G. Ganchev*, E. Yavuz, N. Todorov Departmet of Morphology, Physiology and Animal Nutrition, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria Abstract. The aim of this paper was to review the available literature examining the relationship between milk feeding method of dairy calves during preweaning period on their growth and development. We conclude that delayed and inadequate colostrum feeding can result in increased morbidity and mortality. The higher level of milk feeding for dairy calves has the potential to increase growth rates during the preweaning period, to reduce time needed to reach a necessary body weigh at first calving and improve milk yield at first calving. Providing more milk however, may decrease intake of solid feed during the period of feeding milk. So far is it not clear, whether it is possible to combine intensive liquid feeding with sufficient dry feed intakes at weaning to continue normal growth of calves; otherwise, what is the level of milk feeding allowing small, or even to avoid, slump in growth at weaning. It is not known what level of milk feeding plus free access to starter allows obtaining a high level of live body gain during the first two months necessary for enhancing future milk yield of heifer calves. Additional studies are needed to clarify effect of different levels of milk feeding and scheme of feeding female dairy calves on growth rate, development, feed efficiency and health status during pre weaning and post weaning period. Keywords: dairy calf, liquid feeding, growth, development, health, feed efficiency, lactocrine effect Abbreviations: ADG average daily gain, BW body weight, CP crude protein, DM dry matter, Ig Immunoglobulin, MR milk replacer, FPT failure of passive transfer Introduction The aim for the last years has been to reduce the liquid foods consumption (milk or milk replacer) during the first months of rearing calves in order to reduce the cost of feeding. This can be achieved through encourage early intake of dry food that stimulates the rumen development and allows achieving satisfactory growth and good health using less milk or milk replacer. The last 10 years have been proposed new feeding strategies with increased amounts liquid feed milk or milk replacer in the first months of rearing calves, which improve the growth of calves and future performance (Khan et al., 2011). These programs called by different names including accelerated, enhanced, and intensified demonstrated the remarkable improvements in growth and feed efficiency (Bartlett, 2001; Diaz et al., 2001; Flower and Weary, 2001; Tikofsky et al., 2001; Jasper and Weary, 2002; Blome et al., 2003; Brown et al., 2005a; Bartlett et al., 2006; Cowles et al., 2006; Khan et al., 2007a,b; Raeth-Knight et al., 2009). Intensified nutrition for dairy calves have the potential to increase growth rates (higher average daily gain) during the preweaning period (Jasper and Weary, 2002; Shamay et al., 2005), reduction of time needed to reach a necessary BW at first calving (Davis Rincker et al., 2006; Raeth-Knight et al., 2009; Davis Rincker et al., 2011), and improved milk yield at first calving (Shamay et al., 2005; Drackley et al., 2007; Terré et al., 2009; Moallem et al., 2010; Soberon et al., 2012) or milk fat yield (Shamay et al., 2005; Moallem et al., 2010). Disadvantages of providing more milk include reduced solid feed intake during the milk feeding period (Terré et al., 2007; Weary et al., 2008, Uys et al., 2011; de Passillé et al., 2011) and slower rumen development (Khan et al., 2007a,b). This review describes the importance of feeding colostrum in sufficient quantities and quickly after birth to improve calf immunity and health. Discussed studies on the effect of feeding milk and milk replacer on growth and development of dairy calves. Describe the effect of providing higher milk volumes on solid feed consumption, rumen development, performance, health and future milk production. Colostrum Colostrum is the first secretion from the mammary gland of female mammals after the birth of their progeny (Jaster, 2005; Kehoe et al., 2007). Colostrum is a mixture of lacteal secretions and constituents of blood serum that accumulate in the mammary gland during the pre-partum dry period and are collected via milking of the early-lactating cow. Colostrum and the subsequent milk provide a complete diet which is essential to the survival of the neonate while the calf is unable to collect, chew or digest solid food (Kehoe et al., 2007; Piccione et al., 2009). Colostrum contains also a variety of non-nutrient biologically active substances, such as growth factors, hormones, lactoferrin, lysozyme and lactoperoxidase (Blum and Baumrucker, 2002; Blum, 2006; Blum and Baumrucker, 2008). Most non-nutritional components of colostrum are accumulated in the mammary gland during the end of pregnancy. Colostrogenesis ends at parturition. Therefore, concentrations of many of its components are greatest in the first secretion after calving, then decline steadily over the next milkings to much lower concentrations after about 1 week (Blum and Hammon, 2000; Blum and Baumrucker, 2008; * glen62@abv.bg 389

5 Piccione et al., 2009). Colostrum is higher in protein and fat than milk and lower in carbohydrates. The major proteins in colostrum include immunoglobulins (Ig), lactoferrin, transferrin, α-lactalbumin and βlactoglobulin, and albumin (Kehoe and Heinrichs, 2007). Colostrum contains 3 types of Ig, IgG, IgM, and IgA. Immunoglobulin A is the main source of immunoglobulins in human, and is it 90% of all the immunoglobulin in colostrum (Stelwagen et al., 2009). In cattle the main immunoglobulin in colostrum is IgG, representing 81 85% of all the immunoglobulins (Beam et al., 2009; Stelwagen et al., 2009). Concentrations of immunoglobulin in colostrum are the measure of colostrum quality. Parity (Moore et al., 2005), heat stress during the pre-calving months (Nardone et al., 1997), vitamin and mineral supplementation, immunization status of the mother can affect the IgG concentration of colostrum. The concentration of immunoglobulins in colostrum sharply declines within 6 h post-calving. To evaluate the effects of time harvested on colostrum IgG concentration Moore et al. (2005) sampled colostrum at 2 h, 6 h, 10 h and 14 h postpartum. They found a decrease in IgG content of colostrum corresponding to increased time post-calving. IgG concentration 2 h post calving was 113 g/l and significantly decreased to 94, 82 and 76 g/l at 6, 10 and 14 h respectively. Similar data reported Nardone et al. (1997) when analyzing colostrum at 1, 12, 24 and 36 h post-calving. They also reported a decrease in total protein and fat content and an increase in lactose as time after calving increased. Calves are agammaglobulinemic at birth (Weaver et al., 2000). This means that calves are born without blood Ig. Maternal Ig are not transferred across the placenta during pregnancy and newborn calves are unable to produce their own Ig within the first weeks after birth. Calves start producing their own Ig about 10 days of age. Normal levels of Ig reach by 8 weeks of age. Calves therefore need to acquire Ig post-partum and depend on colostrum from the dam to acquire passive immunity (Quigley et al., 2002). In ruminants, colostrum is the sole source of initial passive immunity. The Ig in colostrum combined with the initial ability of the neonate gut to allow unrestricted passage thereof, act as passive immunization. The absorption of IgG in calves is possible due to the non selective ability of the enterocytes of the small intestine to absorb macromolecules by pinocytosis. The cessation of macromolecule absorption is called gut closure, and in the calf, it occur approximately 24 h post birth. IgG and gut permeability rapidly decrease within the initial 24 hours post-partum (Arthington et al., 2000; Quigley et al., 2005; Weaver et al., 2000). To ensure best results is necessary to provide an adequate amount of colostrum which is rich in IgG within 24 hours postpartum (Moore et al., 2005). The maximum absorption occured in the first 4 h of life and after 12 h the absorptive capacity will be reduced (Weaver et al., 2000). The mortality of calves increases from 5% to as much as 20% if colostrum is offered later than 24 hours post-parturition compared to within the 6 hours limit (Margerison and Downey, 2005). Zanker et al. (2000) showed that calves receiving colostrum 12 to 25h after birth had lower plasma concentrations of β-carotene, retinol, and αtocopherol for nearly a month after birth compared with calves that received colostrum within 7h of birth. Many factors have an effect on passive immunity acquired by the newborn calf: colostrum quality (concentration of IgG in the initial colostrum), timing of ingestion of first colostrum, amount of intake colostrum during the first 24 hours post birth, the degree of selectivity exerted by the intestinal epithelium, age of the mother that provided the colostrum (Ghetie and Ward, 2000; Weaver et al., 2000). To provide proper passive immunity to the calves, the IgG concentration in colostrum is crucial in determining the total amount of colostrum. Good quality colostrum containing more than 50 g of IgG/l (Gooden, 2008; Vasseur et al., 2009). To acquire proper passive transfer, calves would require at least 3 L of good quality colostrum within the first 2 h of life. To obtain proper passive immunity, the calves had to consume at least 153 g of colostral IgG (3 l of colostrum) at 2 hours after birth (Chigerwe et al., 2008). Only first milking colostrum containing more than 50 mg Ig/ml should be used for the initial colostrum feeding. Good quality colostrum from the first milking may be kept frozen for up to 12 months without a significant loss in Ig content (Arthington, 2001). The composition of colostrum is significantly different when compared to that of whole milk as can be seen in Table 1. Table 1. Approximate composition of colostrum and whole milk (adopted from Rice and Rogers, 1990) Item Total solids, % Total protein, % Casein, % Ig, % Fat, % Lactose, % Minerals, % Specific Gravity (approx.) 1st milking (colostrum) 11th milking (whole milk) The Ig concentration of the colostrum from third and older lactation cows is usually greater than those of younger cows. First and second lactation cows, have a lower mean concentration of IgG than cows in their third and greater lactation, but most of the colostrum contains more than 50 g/l of IgG (Tyler et al., 1999; Bielmann et al., 2010). According to Grusenmeyer et al. (2006) however first lactation cattle had IgG concentrations equal to multiparous cattle. The ingestion of optimal amounts of good quality colostrum is 390 critical to the survival of the newborn calf. It supports the calf in adapting to its new environment whilst establishing passive immunity. Additionally, non-nutritional or bioactive factors, such as insulin, IGF-I and -I, or leptin, are present in high concentrations in first colostrum, aids in the development and physiological functioning of the gastrointestinal tract (GIT) and influences the calves metabolic systems and nutritional status (Blum, 2006; Blum and Baumrucker, 2008). Because the volume of voluntarily ingested colostrum depends on the willingness to suck (Vasseur et al., 2009),

6 the relatively low amount observed in some calves was associated mostly with poor vitality. Early separation of calves from their dams and feeding an increased volume of colostrum within 6 h of birth is significantly associated with a reduced risk of failure of passive transfer (FPT) (Trotz-Williams et al., 2008). Newborn calves should be fed of good quality colostrum as a first food as soon as possible after birth, preferably within 30 minutes to 1 hour with at least 2 4 L (approximately 5 10% of its body weight). The total amounts of colostrum for 24 hours must be 4 8 L. This will improve the chance of ingesting the required minimum Ig concentration (200 g of Ig) (Arthington, 2001). Because dairy farmers feed fixed volumes of colostrum and whole milk it is critical to determine the Ig concentration content to assure adequate transfer of passive immunity. Chigerwe et al. (2009) found that there was no effect of amount of colostrum consumed in the first feeding of Holstein bull calves with amount of colostrum consumed 12 h later. Only 17.2% of the calves consumed the 3 L of colostrum the first 4 h of life. For the calves that consumed 3 L of colostrum, the probability of failure of passive transfer was less than Gooden et al. (2009) studied the effect of method of feeding (nipple bottle vs. esophageal tube feeder) on passive transfer of IgG when either a large or small volume of colostrum was fed. Blood samples collected at 24 h of age showed that serum IgG levels were significantly greater in calves fed large (3 L) volumes of colostrum replacer compared with calves fed small (1.5 L) volumes of colostrum replacer, regardless of feeding method. These differences were attributed to the larger mass of IgG ingested by calves fed 3 L (200 g of IgG) compared with calves fed 1.5 L (100 g of IgG). Calves with low levels of serum immunoglobulins are more susceptible to pneumonia and diarrhea than calves with serum IgG levels of 10mg/ml and higher. If a calf has less than 10 mg/ml of IgG in blood plasma, it is considered to have failure of passive transfer (Weaver et al., 2000; Beam et al., 2009; Furman-Fratczak et al., 2011). Other studies have suggested that failure of passive transfer should be considered for calves with less than 12 mg/ml (Virtala et al., 1999) or even 13.4 mg/ ml (Tyler et al., 1998). Basoglu et al. (1999) and Gungor et al. (2004) stated that after the period of passive transfer, Ig levels <8 g/l indicate FPT in calves and concentrations between 8 and 16 g/l indicate partial failure of passive transfer (PFPT). In properly protected calves, serum Ig levels exceeded 16 g/l. The level of risk differs in calves with FPT and PFPT and influences the efficiency of treatment. In our study, the following classification of calves was made: FPT serum Ig <5 g/l, PFPT 5 to 10 g/l, good protection g/l, and very good protection >15 g/l (Furman-Fratczak et al., 2005). The effects of colostrum on life productivity were described by Faber et al. (2005) in a study with Brown Swiss cattle fed either 2 L or 4 L of colostrum at birth and managed in the same way thereafter. They observed increased average daily gain (ADG) in the calves, increase in the survival rate through the end of the second lactation, and of the surviving cows, the group of cattle that received 4 L of colostrum produced 1027 kg more milk during the first two lactations. Soberon and Van Amburgh (2011) studied the effect of colostrum on preweaning ADG and also the effects of varying milk replacer intake. Calves were fed either high levels 4 L or low levels 2 L of colostrum. Calves fed high levels of colostrum and ad libitum intake of milk replacer had significantly higher ADGs pre- and post weaning compared calves fed low levels of colostrum. Milk Milk is the ideal food for calves. It has a high energy value and the correct balance of protein, minerals and vitamins for good calf growth and development. Whole milk consists on average of 26% protein, 30% fat and 38% lactose on dray matter (DM) basis. Calves reared together with their dam sucking around 4 to 10 times per day, each one lasting an average of 7 to 10 min (de Passillé, 2001). The calves sucking from cows (Flower and Weary, 2001; de Passillé et al., 2008) drink considerably larger volumes of milk (8 12 l/d) and grow approximately twice quickly compare to restricted feeding. When offered milk ad libitum, calves usually consume about 20% BW/d, equivalent to approximately 10 to 12 L of whole milk for Holstein calves (Jasper and Weary, 2002; Khan et al., 2007a; Sweeney et al.,2010). Dairy calves are typically separated from the cow within 24 h of birth and fed milk at only 10% of their body weight/day, about half of their voluntary intake (Appleby et al., 2001) with the aim of encouraging starter intake and promoting early rumen development and weaning. In the United States dairy calves are commonly fed milk twice daily and weaned at the age of 8.4 weeks, but 30 % of farms wean calves at 6 weeks of age or less (Kehoe et al., 2007). In Spain the calves are usually fed 4 l/day and are weaned at the age of 60 days (Terré et al., 2006). Danish recommendation for milk allowance is 4.8 l/day for heavy breeds and 60 % of this amount for Jersey as referred to by Jensen (2006). In Switzerland the typical weaning time is longer than in many other countries up to weeks (Keil and Langhans 2001). For feeding calves can be used whole saleable milk and nonsaleable milk (unpasteurised or pasteurised). Saleable whole milk is optimum feed choice for calves, as this is the natural product from the cow, and is readily available on dairy farms (Davis and Drackley, 1998; Moore et al., 2009). The use of saleable milk, however, is associated with loss of revenue from milk sales. Non-saleable whole milk (pooled mixture of surplus colostrum, transition milk, and milk withheld after drug treatment) is an inexpensive feed option for calves. There are certain risks associated with feeding non-saleable whole milk to calves. The first major risk is that likely has high levels of bacterial contamination and antibiotic residues (Ruzante et al., 2008; Moore et al., 2009), which can negatively affect health and performance of calves (Jamaluddin et al., 1996), and lead to the development of antibiotic resistance (Langford et al., 2003). Another disadvantage is variable composition of non-saleable milk (Moore et al., 2009). Differences in nutrient content make difficult to ensure that calves receive necessary amount of milk solids per day (Hill et al., 2009). With the aim to determine productive, economic and health effects of feeding calves with whole milk in different periods Domacinovic et al. (2009) carried out experiment with 30 Holstein calves. Calves of 1 group consumed whole milk from birth up to the 30th day of age, group 2 from birth up to the 20th day of age and group 3 from birth up to the 10th day of age. Afterwards, all groups were fed with milk replacement formula up to the 60th day of age. Statistical analysis referring to calves body weight, daily gain and liquid feed conversion during the 1st month of experiment proved the best values for group 1 if compared to other groups. Examination of health status of calves determined that diarrhea occurred less frequently in group 1, which led to conclusion that feeding whole milk to calves should be given priority with respect to its nutritive and health benefits. Shamay (2005) found that calves have greater body weights at weaning and greater first lactation milk production when fed whole milk. Gorka et al., (2011) observed greater length of the papillae and better development of the muscle layer of rumen wall in calves fed with whole milk. Whole milk has also been linked to a higher 391

7 functioning immune system based on the presence of nonspecific immune factors (Godden et al., 2005). When comparing whole milk and milk replacer for calf mortality, under thermoneutral conditions, there is no difference. However, in low temperatures, there is a higher incidence in calves fed milk replacer when compared to calves fed whole milk. This can be explained by the higher level of available energy in whole milk (Godden et al., 2005). Studies in recent years show that when calves are fed whole milk ad libitum, they consume increasing amount of milk reaching to 9 11 kg (1.3 kg of DM) (Jasper and Weary, 2002). This increasing the volume of liquid food for dairy calves, increases fat deposition (Diaz et al., 2001; Bartlett et al., 2006) and it may impair the mammary gland development (Silva et al., 2002). Increasing protein intake at the same time as increasing energy intake during the preweaning period increases mammary parenchyma mass without increasing intraparenchymal fat content (Brown et al., 2005b). It is therefore recommended, feeding milk replacer (MR) high in CP (24 28%) for calves feeding with large amounts of MR. Milk replacers The use of MR represents an opportunity to control the ratio between nutrients like protein and fat. The chemical composition of modern MR varies depending on intending use. MR protein levels normally range between 20 23%, whereas fat levels normally range from 16 18%. MR for intensive calf rearing typically has protein levels above 25% of DM and fat levels similar to the conventional MR (Raeth-Knight et al., 2009). There are two main protein sources: milk (dried skim milk, whey protein concentrate, dried whey, sodium caseinate) or vegetable (soy protein, wheat protein, potato protein). In general, there are no differences among the use in either of the milk protein sources (Terosky et al., 1997), and vegetable sources are used to reduce MR costs. Although the replacement of milk proteins by plant protein leads to a decrease in MR apparent digestibility, calf performance and digestible amino acid absorption can be improved by the inclusion of Thr, Met and Lys in MR containing soy protein (Kanjanapruthipong, 1998). Other alternative sources of protein that replaced part of the milk protein supply, such as liquid egg (Touchette et al., 2003), spray-dried whole egg (Quigley, 2002), red blood cells (Quigley et al., 2000) or fish protein, have been used to decrease the cost of MR with variable effects on calves performance. Fat concentration, on the other hand, is usually 10% to 22% of the MR. This is lower than the concentration of fat in the DM of cow's milk, which averages about 28%, with a typical range of 26% to 34%. Although milk fat is highly digestible, milk fat is limited use in MR formulation because of its high cost. Alternative fat sources are vegetable fat. Among vegetable fat sources, coconut oil and palm oil have a digestibility greater than 95%. Most fat sources incorporated in MR contain coconut oil and palm oil in the ratio 20% and 80%, respectively (Tanan, 2005). Requirements for protein in calves are directly related to the growth rate, because maintenance requirements for protein are small (Bartlett et al., 2004). The utilization of protein is affected by the digestibility, amino-acid balance and the presence of antinutritional factors in the protein source (Davis and Drackley, 1998). Lecithin extracted from soya is used as an emulsifier in milk replacers to enhance the mixing of MR powder with water. The levels of minerals in the MR varies, but on average ash content is 76 g/kg DM. Total ash content in whole milk is in the range of 5 7% of DM (Tanan, 2005). In MR the ash content varies with the source. However, it is important to have in mind that high total ash 392 content can lead to diarrhea. Too much calcium when given as calcium formiate reduce fat digestibility by combining with bile acids important for the fat digestion and cause diarrhea (Xu et al., 2002). However, calcium and phosphorus are important for the formation and maintenance of the skeleton and teeth and also in making nerves, muscles and heart function normally, as well as blood clotting (Davis and Drackley, 1998). Magnesium is important in the cellular metabolism of organic compounds and in the skeleton (Davis and Drackley, 1998). The most critical micro minerals are iron, zink, copper and selenium which are important for haemoglobin and enzymes required for normal growth and development. Vitamin E needs to be included in a proper ratio to essential fatty acids ( mg vitamin E per gram of linoleic acid) to prevent oxidation and rancidity problems. Vitamin E supplementation has been a key component in MR and has shown to increase ADG and decrease incidence of scouring (Luhman et al., 1993) with stimulatory effects on antibody formation (Quigley and Bernard, 1995). High quality MR are excellent liquid feeds for young calves and are less expensive per unit of nutrient supplied than whole saleable milk. Although more expensive than colostrum, transition milk, or waste milk, MR have advantages in constant concentration of product from day to day, easy of storage, and disease control. Maintaining constant concentration of product in the diet for young calves minimizes chances for digestive disorders. Usually dairy calves are fed 0.5 kg/d of MR and starter ad libitum. To increase calf growth during the nursing period, calves can be fed higher amounts of MR (1 kg/d of DM milk replacer). The liquid feeding program depends on the desirable calves rate of growth, age at weaning and economic returns. Poor calf performance on MR most often are due to selection of an inappropriate or poor-quality milk replacer, to underfeeding the calf, or to a disease or sanitation problem (Drackley, 2008). To grow at the rate of 500 g/d dairy calves are commonly fed at 10% of their body weight (BW) twice a day. However, achieving greater growth rates at first 2-3 months of life, might be profitable, because increases in relative BW and wither height are most rapid and cost efficient during the first 6 months of life (Kertz et al., 1998). Many studies have shown that greater ADG can be obtained when feeding milk ad libitum (Jasper and Weary, 2002), or feeding milk or MR at increasing rates (Diaz et al., 2001; Quigley et al., 2006). The nutrient content in MR should be consistent to desired calf growth rates. For calves fed on conventional feeding programs, increasing dietary CP concentration of 20% to 26% maximizes ADG, lean tissue growth but decreased fat deposition (Bartlett et al., 2006). For obtaining higher growth rates, CP must be in the range of 26% to 28% (National Research Council, 2001; Van Amburgh and Drackley, 2005). Blome et al., (2003) establish that increasing CP in MR from 16 to 26% and the corresponding increase in protein:energy ratio linearly increased growth rates of calves, even though total energy deposition remained unchanged. Increased ADGs were shown to reflect increases in structural tissues and lean tissue deposition, not additional fat deposition. As growth rate increased, calves also grew larger at a more efficient rate and retained a greater proportion of ingested protein at the same metaholisable energy intake. These results indicate that manipulating MR composition can markedly alter the characteristics of body growth in young dairy calves. The major variable that results in differences in energy content of MR is fat. Increasing fat content leading to increase energy content of the MR increases ADG but may decrease starter intake (Kuehn et al., 1994). Higher fat contents may be more suitable in cold weather conditions (Drackley,

8 2008). Feeding MR with high DM content can cause digestive disorders. High amounts of nutrient in the intestinal lumen may prompt intestinal disorders, caused by undigested lactose that enters the colon and promotes water accumulation to the intestinal lumen caused by an increase of the osmotic pressure in the colon (Roy, 1990). Other research data demonstrate that MR supports gains equivalent to those of calves fed full milk. In a trial conducted by Jaster et al. (1990) calves were fed full milk (34% fat and 31% protein, DM) or a MR with milk protein as the only source of protein (20% fat and 21% protein, DM), reconstituted to 12.5% solids. Both diets were fed at a rate of 9% of BW, and amounts fed were adjusted weekly as calves grew. The ADG of calves during day 3 to day 28 of age was 99 g/day and 120 g/day for calves fed milk or MR, respectively, and did not differ significantly between diets. A study conducted by Lee et al. (2009) compared the performance of female Holstein calves fed either whole milk or MR having similar gross composition to whole milk. Equalizing the gross composition of MR to that of whole milk did not equalize the growth of calves between diets. Although calves consumed equal amounts of liquid and solid feed DM when fed whole milk or MR, BW and body measurements were greater in calves fed whole milk than in those fed MR probably because of better bioavailability (digestion and assimilation) of nutrients and availability of some unknown growth factors from whole milk. Calves fed whole milk consumed less DM for a unit BW gain. Occurrence of diarrhea was similar in calves on both treatments. Inclusion of plant protein (soy protein concentrate and wheat protein concentrate) in MR depressed the growth of MR calves probably by limiting the supply of some indispensable AA. Calf feeding systems Feeding systems have been classified into several categories, but most commonly used programs are defined as conventional and intensive (also known as Accelerated, Enhanced or Biologically normal ). Conventional calf feeding systems have been designed to decrease the cost of raising replacement heifers by encouraging early intake of dry feed (starter), thereby reducing the length of the milk-feeding period. Davis and Drackley (1998) suggested that replacement calves should be fed a restricted liquid diet to encourage dry feed intake, thereby allowing weaning to occur as early as possible. The calves need fermentable carbohydrates and fiber to produce VFA for rumen epithelial development and establish microbial populations (Greenwood et al., 1997). Conventional milk feeding programs for dairy calves have been based on daily feeding rates of 8 10 % of BW (Jasper and Weary, 2002). These restricted feeding systems were intended to encourage the calf to eat a greater quantity of concentrate feed from an earlier age; however, they seriously limit growth potential as they only allow % of biologically normal growth (Appleby et al., 2001) and are detrimental to calf health and welfare. Inadequate nutrition can depress immune function and thus increase susceptibility to disease in calves (Nonnecke et al., 2003). Intensified milk feeding systems provides calves a large amount of milk or MR compared to limited-fed calves, and these MR often contain more protein or have been reconstituted at higher solids concentrations than conventional MRs (Blome et al., 2003; Bartlett et al., 2006; Drackley, 2008; Anderson, 2011). This provides greater nutrient intakes by intensified-fed calves, resulting in greater preweaning weight gain and structural growth, and improved feed efficiency compared with calves reared on traditional restricted milk feeding programs (Diaz et al., 2001; Jasper and Weary, 2002; Quigley et al., 2006; Khan et al., 2007a; De Paula Vieira et al., 2008; Borderas et al., 2009; Davis Rincker et al., 2011). Some intensifiedfed calves may show as much as a two-fold increase in total nutrient intake because they are able to derive greater nutrition from the milk feeding regime. Intensified nutrition for dairy calves have the potential to increase growth rates (greater ADG) during the preweaning period (Jasper and Weary, 2002; Shamay et al, 2005; Terre et al., 2009; Hill et al., 2010; Uys et al., 2011; Ozkaya and Toker, 2012; Daniels et al., 2013) and reduction of time needed to reach a necessary BW at first calving (Davis Rincker et al., 2006), improve immune function (Drackley, 2005), reduce incidence of disease and mortality (Godden et al., 2005) and improve milk yield at first calving (Shamay et al., 2005). Traditional restricted milk feeding programs usually support 0.2 to 0.6 kg/d of BW gain during the pre weaning period, while calves reared on enhanced milk feeding programs are able to achieve of 0.8 kg/d or greater (Drackley 2008). Ozkaya and Toker (2012) investigated the effects of amount of milk fed (10% and 8% of their BW), weaning age and difference of starter protein levels (18% and 22% CP) on growth performance of female Holstein Friesian calves. They found that the ADG was higher in milk fed 10% BW than received milk fed 8% BW at the 8-week age, early weaning tended to increase feed consumption and the protein levels did not affect the performance of calves. Meeting the nutritional requirements of dairy calves during the first weeks of life is essential for their normal biological development, which will ensure optimal milk yields and health later in life (Davis Rincker et al., 2011; Khan et al., 2011). Niwińska et al. (2012) establish that MR containing 220 g CP and about 21 MJ of gross energy per kg of DM do not cover requirements for protein and energy of heifer calves during the liquid feeding period. During this growth period, the increase in CP concentration to 290 g in kg DM of MR improves weight gains and conversion of feed dry matter, CP and gross energy to weight gain, while the increase in gross energy concentration to 23 MJ improves the conversion of feed protein. Enrichment of MR with CP has a positive effect on the intake of concentrate mixture but reduces nutrient conversion to weight gain of the calves in the period of concentrate feeding which immediately follows the liquid feeding period. Conventional MR is generally reconstituted to 12.5% solids and contains 20 22% CP and 15 20% fat. Intensive programs use MR higher in protein (28% CP) (Diaz et al., 2001) but with a similar fat content (Raeth-Knight et al., 2009). Intensive programs are reconstituted to a higher DM, with a solid content ranging from 12.5 to 17.5% (Cowles et al., 2006; Raeth-Knight et al., 2009). Although the fat concentrations may be similar, when the MR is fed at a higher DM content, the calves consume a higher total amount of fat. Hence, these 2 programs create a variation in the amount of protein and fat a calf consumes. The conventional programs provide 20% protein, 20% fat MR to calves twice daily. Accelerated feeding programs require twice as much intake of MR containing fat and protein levels closer to those of whole milk. It is recommended that this MR be fed at twice the feeding rate of the conventional MR to increase ADGs and lean muscle growth (Tikofsky 2001, Blome 2003). Van Amburgh (2003) illustrates further that traditional MR formulations were designed to be fed at close to labeled rates. Exceeding that level of intake in all cases, except for MR with CP of 28% (or above) leads to a deficiency in protein allowable gain. The result is an accumulation of fat and a reduction in protein deposition and feed efficiency (Bartlett, 2001; Diaz et al., 2001). Fat levels of 393

9 15% to 20% appeared adequate for normal growth and development in Holstein milk fed calves (Tikofsky et al., 2001). Calf performance on intensive program has resulted in greater ADG, skeletal growth, and lean muscle mass (Tikofsky et al., 2001; Blome et al., 2003). Calves fed at a higher rate typically consume less grain in the time prior to weaning than those fed conventionally (Shamay et al., 2005; Khan et al., 2011), mainly due to a higher milk DM intake. Whole milk provided more CP, fat, and energy intake when fed at similar amounts of DM but supported lower rates of BW gain than calves fed MR or a blend of milk and MR. When MR was fed at an equal weekly intake but variable daily intake, calves had at a lower rate of BW gain than calves fed a consistent daily amount of MR. Additionally, calves fed a high fat (31% fat DM basis) MR had a lower BW gain than did calves fed a low fat (17% fat DM basis) MR formulated with consideration for amino and fatty acid concentrations. A consistent diet supports greater rates of BW gain, and a MR offers better potential to provide a consistent diet than saleable milk (Hill et al., 2008). Morrison et al. (2009) found that calves received high levels of MR grew significantly faster during the milk-feeding period but differences in live weight and body size at weaning (56 days) had disappeared by 3 months of age. There was no benefit, in terms of calf performance, of offering MR containing 270 g CP/kg DM compared to a MR containing 210 g CP/kg DM. There was a significant difference in concentrate intakes between calves offered 5 L MR/day, which consumed an average of 0.43 kg concentrate DM/day, and calves offered 10 L MR/day, which consumed an average of 0.28 kg concentrate DM/day. MR protein concentration hasn't effect of on concentrate or MR intake and no effect on body size or live weight at any stage of development. During the preweaning period, for every 100 g increase in MR allowance, concentrate consumption was reduced by 39 g/day. While, for every 100 g increase in the amount of MR offered, live weight at days 28 and 270 increased by 0.76 and 2.61 kg, respectively. Increasing MR feeding level tended to reduce both age at first observed estrus and age at first service but no significant effect on age at first calving was observed (Morrison et al., 2012). Hill et al. (2006a) conducted an experiment to study the effects of different feeding rates of high protein MR on calf performance. A 28% CP, 20% fat MR fed at 0.68 kg daily was successful at increasing calf gain by 55% vs. a 20% CP, 20% fat MR fed at 0.45 kg daily, with moderate reductions in starter intake (11%) and increases in medical treatment days (27%) for scouring. Compared to feeding 0.45 kg of a 20% CP MR, targeting 1.13 and 1.36 kg maximum daily intake of the 28% CP, 20 fat MR resulted in no improvements in gain, 48% less starter intake, increased medical treatments (52 to 72%) for scouring, and was difficult to manage. When feeding more that 0.45 kg of MR, more than 20% CP was needed to improve BW gain, suggesting that CP was limiting gain. However, the targeted maximum intake of 1.13 and 1.36 kg MR was too high in these trials and resulted in excessive decreases in dry starter intake. Davis Rincker et al. (2011) establish that heifer calves consuming intensive diet consisted of a high-protein MR (30.6% CP, 16.1% fat) fed at 2.1% of BW on a dry matter basis and starter grain (24.3% CP) to achieve 0.68 kg of daily gain during the preweaning period had a larger BW, withers height, and hip width at weaning than did calves consuming standard MR (21.5% CP, 21,5% fat) fed at 1.2% BW on a dry matter basis and starter grain (19.9% CP) to attain 0.45 kg of daily gain. Calves fed the intensive diet had higher fecal scores but no difference in health status was observed. Heifers fed the intensive preweaning diet reached puberty at a younger age 394 and lighter body weight. These heifers also tended to be younger at conception and calving. Calves with a higher pre weaning growth rate calved 17 d earlier than calves with a lower growth rate. Similarly, (Raeth-Knight et al., 2009) observed that calves with the highest ADG during the pre weaning period, calved 27.5 d earlier than slower growing calves. Significantly higher final BW, net gain and ADG were established when fed MR contains 22% CP than 18 and 26 % CP respectively (Li et al., 2008). In addition, the apparent digestibility of CP in group fed MR contain 22% CP was significantly higher than in the other two groups. The values of N intake and fecal N excretion were significantly increased following the increase of dietary protein content. However, in all three groups of animals, dietary protein content had no significant effect on urinary N concentration. In a study Hengst et al., (2012) comparing conventional and intensified MR feeding regimens on intake and growth in Holstein calves were randomly assigned to a 10-week study on d 2 of life. Conventional calves were fed a 20.8% CP and 21.0% fat MR at 1.25% of birth BW from week 1 to 6 of life and 0.625% of birth BW during week 7. A 29.3% CP and 16.2% fat MR was fed to intensified calves at 1.5% of birth BW during week 1, 2% of current BW from week 2 to 6, and 1% of current BW during week 7. Treatment did not affect total dry matter intake. Intensified MR feeding increased ADG, protein intake, fat intake, and feed efficiency compared with the conventional feeding program. Ballard et al. (2002) reported a trend for calves fed a 27% CP, 15% fat MR fed at an elevated rate to consume more starter, gain more BW, carry more condition, and have more body volume than calves fed a 27% CP, 20% fat MR at a similar rate. When feeding MR at rates over approximately g of powder daily, protein must be elevated to approximately 26% CP according suggestion of Diaz et al. (2001); Hill et al. (2001) and Blome et al. (2003). However, the challenge is in getting calves to consume dry starter when MR powders are fed at high rates. Data suggest that 20% fat is too high and contributes to depressions in starter intake (Hill et al., 2001) and contributes to excess fat gain and deposition in the carcass (Tikofsky et al., 2001; Bartlett et al., 2002). Powders with 15 to 17% fat are more appropriate. Lee et al., (2008) performed study to compare the effects of feeding high protein and low energy MR (CP 25%, ME 3.6 Mcal/kg DM) with low protein and high energy MR (CP 21%, ME 4.2 Mcal/kg DM) on feed consumption, BW gain, health and selected blood metabolites in Holstein calves during the preweaning period. They concluded that energy and protein concentrations in MR did not affect feed intake, final BW, daily BW gain and feed efficiency of calve during the preweaning period. The main disadvantage when feeding high amounts of milk or MR was the reduction of starter or forage intake during the preweaning period (Appleby et al., 2001; Jasper and Weary, 2002; Terré et al., 2006; Khan et al., 2007a,b; Kristensen et al., 2007; Borderas et al., 2009). Most calves in intensified feeding programs consume little solid feed during the first several weeks of life. At 1 month of age they begin intake g/d, and intakes continuing to increase thereafter (Appleby et al., 2001; Jasper and Weary, 2002; Khan et al., 2007b; Stamey et al., 2012). In contrast, calves fed restricted amounts of milk begin to consume solid feed 1 to 2 week earlier and at rates greater than twice that of intensified fed calves. It is logical that feeding calves larger amounts of milk or milk replaser can reduce starter intake during the milk-feeding period (Terré et al., 2007; Huuskonen and Khalili, 2008), and this in turn may lead to weight loss when calves are weaned from milk (Terré et al., 2007; Jasper et al., 2008), reducing some of the growth advantages of larger milk rations (Huuskonen and Khalili, 2008).

10 Jasper and Weary (2002) fed whole milk at 4.9 kg (restricted amount by bucket) and 8.8 kg (ad libitum; nursed the cow) of liquid daily for 36 d and reported extremely low dry feed intakes of 0.2 and 0.1 kg daily, respectively. During the 5 d weaning period, dry feed intakes were 1.0 and 0.75 kg daily, and 1.94 and 2.01 kg daily, respectively, for the 20 d post-weaning period. Total BW gain was 17.3 and 28.1 kg preweaning, 2.7 and 1.8 kg during weaning, and 17.0 and 13.6 kg pos-weaning for the low and high milk fed groups. Cowles et al. (2006) establish that intensified MR feeding appears to depress starter intake. Intensified MR-fed calves consumed less starter but had higher ADGs overall and larger frames and greater BW than conventionally fed calves. Intensified MR feeding regimen promotes faster growth during the preweaning period when compared with calves fed conventional treatments. When a 20% CP, 20% fat MR was increased from 0.45 kg to 0.56 kg daily depress starter intakes (Catherman, 2000). Depressions in starter intake (19%), increased scour days (58%) and mortality (22.3 vs. 8.6%), but improvements in calf gains (28%) found Quigley et al. (2006) when a 28% CP, 15% fat MR was fed at elevated rates for 6 week in an 8 week trial. Stamey et al. (2012) compared a conventional MR (20% CP, 20% fat) plus conventional starter 19.6% CP, enhanced MR (28.5% CP, 15% fat) plus conventional starter and enhanced MR plus highcp starter (25.5% CP). Starter intake was greater for calves fed conventional MR. For calves fed enhanced MR, starter intake tended to be greater for calves fed enhanced starter. The ADG was greater for calves fed enhanced MR with either starter and, for calves fed enhanced MR, tended to be greater for calves fed highcp starter. Rates of change in withers height, body length, and heart girth were greater for calves fed enhanced MR but did not differ between starter CP concentrations. Starter CP content did not affect height, length, or heart girth within enhanced MR treatments. Starter with 25.5% CP provided modest benefits in starter intake and growth for dairy calves in an enhanced early nutrition program compared with a conventional starter (19.6% CP). Low starter intakes, low concentrations of serum amylase, and low digestion of starter post-weaning had calves fed increasing amounts of a 27 to 29% CP MR (up to 1.09 kg DM/d) and weaned at 42 or 49 d compared with calves fed a 21% CP, 21% fat MR powder fed at 0.44 kg DM/d (Hill et al., 2010). Although calves fed 1.09 kg of DM/d had the greatest ADG for 0 to 56 d, their lower starter intake and reduced digestion post-weaning reduced their post-weaning ADG. Calves fed 0.66 kg of DM/d of a 27% CP, 17% fat MR powder and weaned at 28 or 42 d had no reduction in starter intake or digestion compared with calves fed the conventional MR, and gained as much or more total BW from 0 to 84 d as calves fed 1.09 kg of DM/d. Calves fed 0.66 kg of DM/d of a 27% CP, 17% fat MR and weaned at 28 d had the greatest intake of starter and greatest concentrations of serum amylase. Calves fed a 21% CP, 21% fat MR powder at 0.44 kg of DM/d had the least ADG. Hess et al. (2001) not found improvement in calf gains when feeding an average of 0.69 kg of 30% CP, 20% fat MR fed ad libitum vs kg of a 22% CP, 20% fat MR in an on farm trial. They did not report differences in starter intake or body size, but medical treatment days were greater in the elevated feeding rate group (1.3 vs. 0.5 d) and they stated that the maximum target intake of powder was not achieved because of health limitations. Hammon et al. (2014) reported that intensive (8 L per day) MR feeding did not impair concentrate intake and slightly affected rumen papillae growth, compare to calves fed 6 L MR daily. Todd et al. (2013) reported that calves receiving 5 L MR started consumption of starter earlier and had greater starter intake, increased rumen wall thickness, longer and wider papillae and reduced papillae density (P<0.05), than more abundant fed calves. However, level of MR feeding do not influence rumen papillae area and sub-mucosal thickness, independently of better growth of calves receiving more MR in trial of Davidson et al. (2013). According to Hill et al. (2007) the maximum amount of a high CP MR that could be fed without creating a weaning and postweaning reduction in performance was kg/d. The 26% CP, 17% fat MR fed to calves at kg/d did not reduce starter intake and increased the ADG of calves compared with calves fed at conventional 20% CP, 20% fat MR at kg/d. In some high MR feeding rate programs has showed by a weaning and post-weaning slump in ADG (Jasper and Weary, 2002; Cowles et al., 2006). This reduced ADG has been because of reduced starter intake and feed efficiency (Strzetelski et al., 2001; Hill et al., 2006a,b), reduced rumen development and function (Terre et al., 2006), or reduced digestion of the starter (Terre et al., 2007). Significant check of live weight gain after weaning of calves fed ad libitum with milk was reported by Miller-Cushon et al. (2011). Hill et al. (2014) reported reduction of ADG after weaning of calves fed high level of MR, compare to those fed low level. However, Stayer et al. (2014) do not found weaning slump of calves fed accelerated MR program compare to moderate level of feeding. Calves having access to larger amounts of milk have markedly different feeding behavior of these unlimited-fed calves. Results from several studies have show that if possible, calves will ingest milk, twice more that calves reared under traditional restricted feeding programs (approximately 8 15 L/d versus 3 6 L/d) (Appleby et al., 2001; Jasper and Weary, 2002; Khan et al., 2007b; De Paula Vieira et al., 2008; Borderas et al., 2009). Calves with access an unrestricted amount of milk routinely spend more than 30 min daily consuming several small, frequent milk meals in a diurnal feeding pattern (Appleby et al., 2001; Miller-Cushon et al., 2013). Calves that are raised on intensified milk feeding programs and are weaned too early, abruptly or over a short period can lose some of the growth advantage of feeding more milk during the pre weaning stage (Sweeney et al., 2010; de Passillé et al., 2011). The method of weaning influenced the lower growth rates in calves intake higher amounts of milk during the pre weaning period. Abrupt weaning in restricted and ad libitum fed calves results in a greater depression in growth than does gradual weaning (Roth et al., 2008; Weary et al., 2008). Gradual weaning methods that encourage the consumption of solid feed during the pre weaning period reduce the lag between demand and supply of nutrients after weaning, minimizing or preventing depressed growth (Khan et al., 2007a,b; Sweeney et al., 2010). Given that enhanced fed calves are lagging behind in solid feed consumption, gradual weaning are recommended as ways to stimulate solid feed intake and ease the weaning transition. (Jasper and Weary, 2002; Khan et al., 2007a,b; Jasper et al., 2008; Sweeney et al., 2010; de Passillé et al., 2011). There is evidence that step-down method of feeding calves allowed higher body weight gain and feed efficiency compare to equal rate of milk feeding during whole preweaning period (Niazi et al. 2010). Calves assigned to the step-down milk feeding method were fed whole milk at a rate of 20% of BW from birth until 23 d of age and then the feeding rate was gradually reduced to 10% of BW. All calves were weaned by diluting their milk with water between 45 and 49 d of age. Step-fed calves consumed less solid feed and mixed hay prior to the milk step-down compared to restricted fed calves. Throughout the remainder of the pre weaning period after the milk step-down and during the first 2 week following weaning off milk, the step-fed calves had greater intakes of solid feed and mixed hay than restricted-fed 395

11 calves. The step-down milk feeding calves had more physically developed rumens, characterized by longer and wider rumen papillae, greater rumen wall thickness, and heavier forestomachs, than restricted-fed calves (Khan et al., 2007a) Sweeney et al. (2010) reported that when amount of milk was reduced over increasing periods of time, calves that consumed up to 12 L/d of whole milk prior to the onset of gradual weaning were unable to fully compensate for the reduced nutrient supply by ingesting more solid feed during the weaning period. Nevertheless, calves that were gradually weaned over 4, 10 or 22 d had greater solid feed intakes and gained weight during the first week after weaning, whereas, abruptly weaned calves lost weight during this time. Similarly, Khan et al. (2007a,b) established that calves that were reared on step-down milk feeding programs during the pre weaning period and fully weaned off milk by 50 d of age consumed more solid feed and gained more weight after the milk step-down and during the early post weaning period, and maintained their BW advantage beyond 12 week of age, as compared to restricted-fed calves. Davis Rincker et al. (2011) however established that in comparison to restricted-fed calves, those that were gradually weaned from an enhanced milk feeding diet by 42 d of age, had reduced ADG in the week after weaning, and were only able to sustain their BW advantage until 8 week of age, but had greater hip width and withers height until 24 and 40 week, respectively. Studying the impact of different milk feeding levels (3.10; 4.84; 6.60 and 8.34 kg/d of MR) on the measures of calf performance and rumen development Kristensen et al. (2007) found that although calves reared on higher milk feeding levels had reduced solid feed intakes, the length of rumen papillae at 5 week of age was not affected by feeding treatment. Roth et al. (2009) established that the length of papillae in the atrium or ventral ruminal sac was not affected by milk allowance or by the resulting variation in solid feed consumption in calves. There have been conflicting reports as to whether there is any adverse health effects associated with feeding increased amounts of milk or MR. Borderas et al. (2009) is not established increased amount of sickness when high or free choice amounts of milk or MR were fed to Holstein calves. Lee et al. (2009) found similar incidences of diarrhea between Holstein calves fed equal amounts of saleable whole milk (25.8% CP; 27.7% fat; DM basis) or MR (23.9% CP; 25.6% fat; DM basis). Some studies report a higher occurrence of diarrhea in calves supplied higher levels of milk or MR compared with restricted fed calves (Quigley et al., 2006), but other studies report no difference (Diaz et al., 2001; Jasper and Weary, 2002; Khan et al., 2007a). High incidence of diarrhea is more related to poor sanitary, management, and housing conditions than to level of milk intake (Hammon et al., 2002; Jasper and Weary, 2002). Drackley (2004) found that calves fed with large amounts of milk have softer faeces and this effect is enhanced by feeding MR compared to whole milk. By simply increasing milk intake of calves to 18% BW, Bartlett et al. (2006) found that days with elevated fecal score were increased. When administered accelerated growth program is necessary to provide permanent access to water (Davis and Drackley, 1998) and individually feeding, because calves are more susceptible to nutritional diarrhea, especially when MR is fed at greater than 12,5 percent solids (Jones and Heinrichs, 2006). They must have consumed a sufficient quantity of colostrum, because calves that have failure of passive transfer (serum IgG < 10 mg/ml) will not grow as efficiently on the accelerated program as calves that have received optimal colostrum intake. It should be borne in mind that calves fed at a higher rate of milk or MR consume less dry feed, 396 causing the delayed rumen development. The high cost of milk or MR should also be taken into account. Effects of calf feeding program on first lactation milk production Recent studies have shown that pre weaning nutrient intake, from milk or MR, can have profound effects on development of the calf that enhance first lactation and lifetime productivity. Data indicates that for every 100 g increases of pre weaning live weight gain, first lactation milk yield increased by 155 kg (Soberon and Van Amburgh, 2013). There were many reports for positive effect of abundant milk or MR feeding on future milk performance of heifer calves (Shamay et al., 2005; Drackley et al., 2007; Terré et al., 2009; Moallem et al., 2010; Soberon et al., 2011, 2012). However, other trials were not reported difference of milk yield on first lactation of heifers fed with more colostrum or milk as a calves, compare to those fed less colostrum (Pithua et al., 2010; Ozer et al., 2012) or milk and MR (Aikman et al., 2007; Raeth-Knight et al., 2009). Shamay et al. (2005), found that calves fed ad libitum whole milk have a higher growth rates compared with those fed restricted MR. When the whole milk were supplemented with 2% protein during the prepuberty period, yields of milk (kg/305 d) and fatcorrected milk (kg/d) were greater for the whole milk fed heifers than for the MR fed heifers. Positive effect of early life nutrition on first lactation milk production found Drackley et al. (2007). Calves were fed MR in either conventional limit-fed (22% protein and 20% fat fed at 1.25% of the body weight) or an intensified programs (28% protein and 20% fat MR at 2% of the body weight) for week one. From week 2 to 5 at 2.5% of the BW. Then for six days the amount is reduced until reaching to 1.25% of the BW. All calves were weaned by 7 weeks of age. Actual 305-day milk was greater for heifers that were fed the intensified program as calves. Feeding ad libitum whole milk or MR, Moallem et al. (2010) observed significantly 10.3% higher milk yields during first lactation from heifers fed whole milk. They suggested that MR did not contain the same biologically active factors as milk and thus did not impart any lactocrine effects on the calves. A Test Day Model was developed (Soberon et al., 2012) using inputs of preweaning ADG, birth weight, weaning weight, calving age, birth year, birth month, and calculated energy intake over estimated maintenance requirements. For every additional 1 kg of ADG within the range of 0.10 to 1.59, heifers produced 850 kg more milk during their first lactation and produced a total of kg over their first 3 lactations. Conclusions Intensified milk feeding systems for dairy calves have the potential to increase growth rates during the preweaning period, reduction of time needed to reach a necessary BW at first calving, improve immune function, reduce incidence of disease and mortality and improve milk yield at first calving. Increasing protein level was beneficial but increasing fat decreased dry feed intake and increased fat deposition in calf body. There are evidences that increasing period of gradual weaning from 3 7 days to 2 weeks allowed better adoption to dry feed, development of rumen, decreasing stress of weaning and reduction in daily live weight gain. Such enlarged weaning period is even more important for enhance fed calves. It seemed important for intensively fed calves to respond

12 well on level of feeding and to keep good health status to have enough immunoglobulin transfer and good management. Additional studies are needed to clarify effect of quantity and quality of colostrum, milk or milk replacers feeding and scheme of feeding calves on solid feed intake during the milk feeding period, and especially at weaning time and avoiding reduction or stopping of daily gain, on rumen development, feed efficiency, health status during pre weaning and post weaning period and future milk production. Complete replacement of whole (sealable or unsealable) milk by milk replacer is steel not clear enough. References Aikman PC, Gould M and Bleach ECL, First lactation milk yield and fertility of Holstein heifers reared using three milk replacer feeding programs. Journal of Dairy Science, 90, 112. Appleby MC, Weary DM and Chua B, Performance and feeding behaviour of calves on ad libitum milk from artificial teats. 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13 Weber Nielson M, Effects of an intensified compared to a moderate feeding program during the preweaning phase on longterm growth, age at calving, and first lactation milk production. Journal of Dairy Science, 89, 438. Davis Rincker LE, VandeHaar MJ, Wolf CA, Liesman JS, Chapin LT and Weber Nielsen MS, Effect of intensified feeding of heifer calves on growth, pubertal age, calving age, milk yield, and economics. Journal of Dairy Science, 94, de Passillé AM, Marnet PG, Lapierre H and Rushen J, Effects of twice-daily nursing on milk ejection and milk yield during nursing and milking in dairy cows. Journal of Dairy Science, 91, de Passillé AM, Borderas TF and Rushen J, Weaning age of calves fed a high milk allowance by automated feeders: Effects on feed, water, and energy intake, behavioral signs of hunger, and weight gains. Journal of Dairy Science, 94, De Paula Vieira A, Guesdon V, de Passillé AM, von Keyserlingk MAG and Weary D M, Behavioural indicators of hunger in dairy calves. 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15 ME, Composition and functional capacity of blood mononuclear leukocyte populations from neonatal calves on standard and intensified milk replacer diets. Journal of Dairy Science, 86, Ozer B, Bach A and Chahine M, Total serum protein in calves is not correlated whit future milk performance. Journal of Dairy Science, 90, 109 (Abstr.). Ozkaya S and Toker MT, Effect of amount of milk fed, weaning age and starter protein level on growth performance in Holstein calves. Archiv Tierzucht, 55, Piccione G, Casella S, Giannetto C, Bazzana I, Niutta PP and Giudice E, Influence of age on serum proteins in the calf. Acta Veterinaria Beograd, 59, Pithua P, Godden SM, Fetrow J and Wells SJ, Effect of a plasma-derived colostrum replacement feeding program on adult performance and longevity in Holstein cows. Journal of the American Veterinary Medical Association, 236, Quigley III JD, 2005 Managing variation in calf and heifer programs. Proc. Southwest Nutrition Conference, pp , April 2-3, Tempe. AZ. 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16 Tyler JW, Steevens BJ, Hostetler DE, Holle JM and Jr Denbigh JL, Colostral immunoglobulin concentrations in Holstein and Guernsey cows. American Journal of Veterinary Research, 60, Uys JL, Lourensand DC, Thompson PN, The effect of unrestricted milk feeding on the growth and healthy of Jersey calves. Journal of the South African Veterinary Association, 82, Van Amburgh ME and Drackley JK, 2005 Current perspectives on the energy and protein requirements of the pre-weaned calf. Chap. 5 in Calf and heifer rearing: Principles of rearing the modern dairy heifer from calf to calving. Nottingham Univ. Press. P.C. Garnsworthy, ed. Pp Van Amburgh ME, A Systematic Approach to Calf and Heifer Rearing: Intensified Feeding and the Target Growth System. In: Proceedings of the 6 th Western Dairy Management Conference. March 12-14, Reno, NV Vasseur E, Rushen J and de Passill AM, Does a calf's motivation to ingest colostrum depend on time since birth, calf vigor, or provision of heat? Journal of Dairy Science, 92, Virtala AM, Grohn YT, Mechor GD and Erb HN, The effect of maternally derived immunoglobulin G on the risk of respiratory disease in heifers during the first 3 months of life. Preventive Veterinary Medicine, 39, Weary DM, Jasper J and Hotzel MJ, Understanding weaning distress. Applied Animal Behaviour Science, 110, Weaver DM, Tyler JW, VanMetre DC, Hostetler DE and Barrington GM, Passive transfer of colostral immunoglobulins in calves. Journal of Veterinary Internal Medicine, 14, Xu C, Wensing T and Beynen AC, High intake of calcium formiate depresses macronutrient digestibility in veal calves fed milk replacers containing either dairy proteins or whey protein plus soya protein concentrate. Journal of Animal Physiology and Animal Nutrition, 83: Zanker IA, Hammon HH and Blum JW, Beta-carotene, retinol and alphatocopherol status in calves fed the first colostrum at 0-2, 6-7, or hours after birth. International Journal for Vitamin and Nutrition Research, 70,

17 AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 7, No 4, 2015 CONTENTS 1/2 Review Effect of feeding program for first two months after birth of female calves on growth, development and 389 first lactation performance G. Ganchev, E. Yavuz, N. Todorov Genetics and Breeding Involvement of the transcriptional variants of histone H3.3 in the development and heat stress response of Arabidopsis thaliana M. Naydenov*, B. Georgieva, V. Baev, G. Yahubyan 402 Study of factors affecting sporophytic development of isolated durum wheat microspores V. Bozhanova, Hlorst Lörz 407 Screening Pisum sp. accessions for resistance to Pseudomonas syringae pv. pisi M. Koleva, I. Kiryakov 411 Investigation on the parthenogenetic response of sunflower lines and hybrids M. Drumeva, P. Yankov 415 Hybridization between cultivated sunflower and wild annual species Helianthus petiolaris Nutt. D. Valkova, G. Georgiev, N. Nenova, V. Encheva, J. Encheva 419 Nutrition and Physiology Ethological and haematological indices in yearling sheep fed various dietary nitrogen sources I. Varlyakov, V. Radev, Т. Slavov, R. Mihaylov 423 Phosphorus fractions in alluvial meadow soil after long-term organic-mineral fertilization S. Todorova, K. Trendafilov, M. Almaliev 431 Energy productivity, fertilization rate and profitability of wheat production after various predecessors 436 I. Energy productivity of wheat Z. Uhr, E. Vasileva Influence of mineral nitrogen and organic fertilization on the productivity of grain sorghum S. Enchev, G. Kikindonov 441 Production Systems Influence of the farm construction, farm regimen and season on the comfort indices of dairy cows D. Dimov, Ch. Miteva, Zh. Gergovska 444 Effect of the way of pre-sowing soil tillage for wheat on the development of its roots P. Yankov, M. Drumeva, D. Plamenov 451

18 AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 7, No 4, 2015 CONTENTS 2/2 Occurrence of grapevine leafroll-associated virus complex in the Republic of Macedonia E. Kostadinovska, S. Mitrev, I. Karov 455 Influence of sowing and fertilization rates on the yield and plant health of einkorn wheat (Triticum Monococcum L.) V. Maneva, D. Atanasova, T. Nedelcheva, M. Stoyanova, V. Stoyanova 460 Effect of stocking density on growth intensity and feed conversion of common carp (Cyprinus caprio L.), reared in a superintensive system S. Stoyanova, Y. Staykov 464 Agriculture and Environment Monitoring of fungal diseases of lavender K. Vasileva 469 Nitrogen mineralization potential of alluvial meadow soil after long-term fertilization V. Valcheva, K. Trendafilov, M. Almaliev 476 Changes in the leaf gas exchange of common winter wheat depending on the date of application of a set of herbicides Z. Petrova, Z. Zlatev 481 Leaves area characteristics of Betonica bulgarica Degen et Neiĉ., during vegetation M. Gerdzhikova1*, N. Grozeva2, D. Pavlov1, G. Panayotova1, M. Todorova1 486 Short communications Design and development of a device for measuring vacuum-pulsation parameters of milking unit G. Dineva, V. Vlashev, L. Tsanov 494

19 Instruction for authors Preparation of papers Papers shall be submitted at the editorial office typed on standard typing pages (A4, 30 lines per page, 62 characters per line). The editors recommend up to 15 pages for full research paper ( including abstract references, tables, figures and other appendices) The manuscript should be structured as follows: Title, Names of authors and affiliation address, Abstract, List of keywords, Introduction, Material and methods,results, Discussion, Conclusion, Acknowledgements (if any), References, Tables, Figures. The title needs to be as concise and informative about the nature of research. It should be written with small letter /bold, 14/ without any abbreviations. Names and affiliation of authors The names of the authors should be presented from the initials of first names followed by the family names. The complete address and name of the institution should be stated next. The affiliation of authors are designated by different signs. 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Title. Full title of the journal, volume, pages. Example: Simm G, Lewis RM, Grundy B and Dingwall WS, Responses to selection for lean growth in sheep. Animal Science, 74, Books: Author(s) surname and initials, year. Title. Edition, name of publisher, place of publication. Example: Oldenbroek JK, Genebanks and the conservation of farm animal genetic resources, Second edition. DLO Institute for Animal Science and Health, Netherlands. Book chapter or conference proceedings: Author(s) surname and initials, year. Title. In: Title of the book or of the proceedings followed by the editor(s), volume, pages. Name of publisher, place of publication. Example: Mauff G, Pulverer G, Operkuch W, Hummel K and Hidden C, C3variants and diverse phenotypes of unconverted and converted C3. In: Provides of the Biological Fluids (ed. H. Peters), vol. 22, , Pergamon Press. Oxford, UK. Todorov N and Mitev J, Effect of level of feeding during dry period, and body condition score on reproductive performance in dairy cows,ixth International Conference on Production Diseases in Farm Animals, September 11 14, Berlin, Germany. Thesis: Hristova D, Investigation on genetic diversity in local sheep breeds using DNA markers. Thesis for PhD, Trakia University, Stara Zagora, Bulgaria, (Bg). The Editorial Board of the Journal is not responsible for incorrect quotes of reference sources and the relevant violations of copyrights. Animal welfare Studies performed on experimental animals should be carried out according to internationally recognized guidelines for animal welfare. That should be clearly described in the respective section Material and methods.

20 Volume 7, Number 4 December