Evaluation of Meskit (Prosopis juliflora) pods as a feed for goats

Transcription

1 Animal Feed Science and Technology 121 (2005) Evaluation of Meskit (Prosopis juliflora) pods as a feed for goats Osman Mahgoub, Isam T. Kadim, Neil E. Forsberg 1, Dawood S. Al-Ajmi, Naseeb M. Al-Saqry, Abdullah S. Al-Abri, Kanthi Annamalai Department of Animal and Veterinary Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O. Box 34, Al-Khod , Oman Received 7 August 2003; received in revised form 9 December 2004; accepted 21 January 2005 Abstract A study was completed to evaluate effects of increasing dietary levels of dry pods of Meskit (Prosopis juliflora) on Omani native goat performance. Individual feed intake and body weight were determined during a 50-day experimental period. Rations with four levels (0, 100, 200 and 300 g/kg) of Meskit pods were fed to Omani goats by reducing the proportion of Rhodes grass (Chloris guyana) hay in the diet. The ripened Meskit pods contained 930 g/kg dry matter, 120 g/kg crude protein, 317 g/kg acid detergent fibre, 402 g/kg neutral detergent fibre, 26 g/kg ether extract and 40 g/kg ash. Feed intake, growth rate and feed conversion were maximized with Meskit in the diet at 200 g/kg. However, these values dropped sharply when Meskit pod proportion in the ration was increased to 300 g/kg. Feeding diets containing levels of Meskit pods up to 300 g/kg did not affect proportions of body components or carcass chemical composition. Results indicate that P.juliflora pods can be used up to proportions of 200 g/kg in Omani goat diets to improve feed intake, feed conversion and body weight gain without compromising carcass yield or quality. Keywords: Prosopis juliflora; Meskit; Mesquite; Oman; Goats; Growth Abbreviations: ADF, acid detergent fibre; BW, body weight; CP, crude protein; DM, dry matter; EBW, empty body weight; EE, ether extract; NDF, neutral detergent fibre; RGH, Rhodes grass hay Corresponding author. Tel.: ; fax: address: osmahgob@squ.edu.om (O. Mahgoub). 1 Present Address: Department of Animal Science, Oregon State University, Corvallis, OR , USA.

2 320 O.Mahgoub et al./ Animal Feed Science and Technology 121 (2005) Introduction The acute shortage of fresh water in arid areas, such as Oman, is a major limiting factor to livestock production as it results in high costs of forage and other feedstuffs. Systems of keeping small ruminants in Oman include transhumant and nomadic with settled villages as well as hill and small farms. Animals in the first three systems graze and browse poor range vegetation early in the day and are later fed Rhodes grass hay (RGH), dates, dried sardines and house leftovers. Rhodes grass consumes a lot of fresh water in irrigation, and currently cost up to US$ 150/t, which is nearly as high as that of barley grain. Therefore, replacing RGH in Omani ruminant diets would reduce feeding cost and maximize economic returns for livestock farmers. Oman has natural rangeland plant species, which have not yet been fully exploited as livestock feeds. These include two species of Prosopis, the local Prosopis cineraria (ghaf) and the introduced Prosopis juliflora (Meskit, Mesquite). P.juliflora is native to Peru, Chile and Argentina and has spread to central and North America. Meskit had been introduced to many arid zone countries, with rainfall of less than 200 mm/year, including Oman, to combat desertification as it is an N-fixing legume and livestock consume its pods. However, the tree is invasive to natural rangeland and regarded as a weed. However, it tolerates moderate draught and salinity to yield well under these adverse growing conditions. Its yield was estimated as t/feddan (4200 m 2 )/season (Ibrahim and Gaili, 1985). Meskit pods have been used in livestock diets and produced encouraging results with various animal species in many countries. Studies in Brazil showed that P.juliflora pod flour could replace up to 600 g/kg of wheat flour in rations of lactating cows and that dry matter (DM) intake, weight gain and milk production increased with an increasing proportion of pod flour (Habit and Saavedra, 1988). In beef cattle diets, it was possible to totally replace wheat flour by ground pods. In Mexico, replacement of sorghum flour with P.juliflora pod flour up to 450 g/kg, but not 600 g/kg, increased body weight (BW) gain in sheep. In Brazil, replacement of sugarcane molasses with P.juliflora pods at 0, 150, 300, 450 and 600 g/kg of total ration was most effective in terms of BW gain at the 300 and the 450 g/kg levels (Habit and Saavedra, 1988). The Meskit tree grows over most of Oman and performs well under the harsh semi-desert conditions of the country. Trees grown for landscaping under irrigation, mostly with treated sewage water, grow and yield extremely well. Therefore, Meskit has good potential as a range or irrigated tree for production of animal feed under Omani conditions. Recently the Meskit tree has come to be regarded as a weed, due to its ability to produce large number of seeds and its efficiency in outperforming native flora. One cause for the fast spread of Meskit trees is that they broadcast their seeds due to grazing range animals. However, if the pods are collected and ground before their use as livestock feed, the possibility of spreading will be reduced. Methods of pod collection may be improved by clearing twigs, old pods and undesirable material from under trees before the collection season, and by the use of plastic sheets. Omani native goats have good potential for meat production, reflected by their high growth rates and good carcass characteristics, when raised under optimum management and nutritional conditions (Mahgoub, 1997; Mahgoub and Lodge, 1996, 1998). The present

3 O.Mahgoub et al./ Animal Feed Science and Technology 121 (2005) study investigated the potential of using the Meskit pods to replace RGH in totally mixed rations on growth, performance and carcass characteristics of Omani native goats. 2. Materials and methods 2.1. Experimental animals Twenty-eight Omani native male Batina and Dhofari goats (18.0 ± 3.0 kg) born and reared at the Agricultural Experiment Station (AES) at Sultan Qaboos University in Oman were used. They were subjected to standard management procedures, including vaccination, deworming and hoof trimming, and allocated randomly to one of four experimental diet groups, of seven each, and fed rations containing various levels of Meskit pods. Throughout the feeding study, goats were individually fed in m pens. The experiment continued for 8 weeks, at the end of which the goats were slaughtered and their carcasses analysed for chemical composition Feeds Dry Meskit pods were collected during the fruit production season and stored in a cool dry shed. The pods were reduced in a grinder to lengths of cm. The chemical composition of the pods was determined according to standard methods of AOAC (2000). Dry matter was determined by drying in an oven for 24 h at 80 C (method ). Crude protein (CP) was determined using a Foss Tecator Kjeltec 2300 Nitrogen/Protein Analyser (method ). Fat (EE) was determined by Soxhlet extraction of the dry sample, using petroleum ether (method ). Ash content was determined by ashing samples in a muffle furnace at 500 C for 24 h (method ). Acid detergent fibre (ADF) was determined by using cetyl trimethyl ammonium bromide (CTAB) and 1N H 2 SO 4 as described by Roberston and Van Soest (1981). Neutral detergent fibre (NDF) was determined using sodium sulphite and sodium lauryl sulphate as described by Van Soest et al. (1991). Alpha amylase was not used to determine NDF. ADF was expressed with ash whereas NDF was expressed without ash. Four rations were formulated containing 0, 100, 200 and 300 g/kg of Meskit pods in the ration. The corresponding proportions of RGH were 500, 400, 300 and 200 g/kg. Each of the four experimental diets contained 300 g/kg barley grain, 50 g/kg dried fish sardines, 80 g/kg soybean meal (SBM 440 g/kg CP), 10 g/kg ground limestone, 10 g/kg of a vitamin/mineral mixture and 20 g/kg salt (Table 1). The RGH was chopped using a tub grinder and incorporated with the other ingredients to be fed as a mixed ration. Vegetable (sunflower, 30 g/kg ration) oil was added to reduce dust. Water and mineral blocks (containing Cu, Mn, Zn, Co, I, Se, Na, Ca, P, Mg and Vitamin D 3 ) were supplied ad libitum. Feeds were analysed for DM, CP, EE, Ash, ADF and NDF according to standard methods of AOAC (2000) as described above for Meskit pods Experimental measurements Daily feed intakes were determined, and the feed allowance was adjusted daily according to the amount of feed consumed, with 50 g/kg refusals as the target, to avoid feed selection.

4 322 O.Mahgoub et al./ Animal Feed Science and Technology 121 (2005) Table 1 Chemical composition of experimental diets based on Meskit (Prosopis juliflora) pods and their ingredients Rations (g/kg of Meskit pods) Ingredients Meskit Rhodes grass hay Dried sardines Ingredient composition (g/kg as mixed) Rhodes grass hay Meskit pods Barley grain Dried fish sardines Soybean meal (440 g/kg CP) Ground limestone Vegetable oil Vitamin/Mineral mix a Salt Chemical composition (g/kg DM) Dry matter Crude protein Ether extract Acid detergent fibre Neutral detergent fibre Ash Calcium Phosphorus a Vitamin-trace mineral pre-mix provides per kg of mixed ration: 18,750 IU Vitamin A; 3750 IU Vitamin D 3 ; 7.5 IU Vitamin E; 5 mg Co; 1.25 mg Cu; 75 mg Fe; 1250 mg Mg; 150 mg Mn; mg Se; and 100 mg Zn. SBM Goats were weighed at the start of the experiment and bi-weekly thereafter to the nearest 100 g. At slaughter, the weights of the fresh non-carcass organs and the warm carcass were recorded. Carcasses were chilled for 24 h, weighed to determine cold carcass weight, and divided into left and right halves using a commercial band saw. The weight of the gut contents was computed as the difference between the full and empty weight of the whole digestive tract. The empty body weight (EBW) was calculated as the difference between the slaughter weight and that of gut contents. The left half carcass was ground in a carcass grinder. The ground material was then further ground in a fine grinder and mixed thoroughly. A sample was taken from the mixture for chemical analyses according to the AOAC (2000) methods described above. Data were subjected to analysis of variance using the General Linear Models (GLM) procedure of SAS (1991) for effects of level of Meskit in the diet, using diet as a class in the GLM statement in a completely randomised experimental design. Significant linear and quadratic effects within treatment means were assessed using SAS (1991). Significant differences were accepted if P < 0.05.

5 O.Mahgoub et al./ Animal Feed Science and Technology 121 (2005) Results 3.1. Meskit as goat diet component The P.juliflora pods (Table 1) contained a higher CP, and a lower ADF and NDF than RGH. All rations contained relatively high CP levels (150 g/kg), which are adequate for growing goats (NRC, 1981). There was a trend of decreasing ADF and NDF contents in the rations with increasing levels of Meskit in the diet. Feeding Meskit pods to these goats did not visibly affect their health, as there was no clinical signs of constipation, diarrhea or loss of appetite Feed intake Goats fed rations containing 100 and 200 g/kg Meskit pods had higher (linear P = 0.006; quadratic P = 0.002) feed intakes (Table 2). A similar pattern occurred when feed intake was expressed as a proportion of BW Growth and feed conversion Goats fed the 200 g/kg Meskit ration gained weight consistently (Fig. 1) throughout the feeding period and higher weight gains than the other groups (linear = 0.006; quadratic = 0.002). Goats fed the 300 g/kg pod diet gained the least BW, and had lost the weight by the end of the feeding period (Table 2). The feed conversion ratio (FCR) was highest (linear P = 0.005; quadratic P = 0.001) with the 200 g/kg Meskit (Table 2). Table 2 Mean feed intake, body weight gain and feed conversion ratio, weights of body, carcass and body components (±standard error of means) of Omani goats fed diets containing various levels of Meskit pods Level of Meskit pods in the ration (g/kg) S.E.M. Probability > F Linear Quadratic Feed intake (g/day) Feed intake (g/kg BW) Weight gain (g/day) Feed conversion ratio (kg gain/feed) Hot carcass weight (kg) Cold carcass weight (kg) Shrinkage (kg) Digestive tract content (kg) Digestive tract content (g/kg BW) Dressing out percentage Chemical composition of carcass (g/kg DM) Dry matter Crude protein Ether extract Ash

6 324 O.Mahgoub et al./ Animal Feed Science and Technology 121 (2005) Fig. 1. Growth curves of Omani goats fed diets containing various levels of Meskit pods ( ) 0 g/kg Meskit; ( ) 100 g/kg Meskit; ( ) 200 g/kg Meskit; and ( ) 300 g/kg Meskit) Slaughter and carcass data Goats fed rations with 200 Meskit pods had the highest hot (linear P = 0.051; quadratic P = 0.031) and cold (linear P = 0.034; quadratic P = 0.037) carcass weights (Table 2). Proportions of body organs and fat depots in the EBW were similar for all treatments and there were no differences between goats fed various levels of Meskit pods in carcass chemical composition. 4. Discussion 4.1. Meskit pods The chemical composition of P.juliflora pods in this study was similar to that reported for Meskit pods by others. Ibrahim and Gaili (1985) reported that Meskit pods contained 127 g/kg CP, 254 g/kg CF, 26 g/kg EE and 48 g/kg ash, similar to our values, indicating that Meskit pods are a good potential livestock feed compared to other available feed resources, and to the commonly used RGH (El Hag et al., 2000) General condition of animals Feeding Meskit pods to these goats did not appear to affect their health, although feeding Prosopis in high proportions and for longer periods can cause health problems in small

7 O.Mahgoub et al./ Animal Feed Science and Technology 121 (2005) ruminants. Tabosa et al. (2000) reported that goats fed 600 g/kg and 900 g/kg P.juliflora pods had mandibular tremors, mainly during chewing. These authors concluded that this was caused by a selective toxicity to neurons of some cranial nerve nuclei. Lack of manifestation of health problems in the goats in the current study may be due either to the short period of feeding or to the smaller proportions of the pods in the diet (maximum 300 g/kg here as compared to 600 and 900 g/kg) Feed intake Feed intake results indicate that Meskit pods may be included in goat diets up to 200 g/kg and they will be well consumed. However, increasing their proportion in the diet to 300 g/kg will reduce feed intake. Feed intakes in the current study are comparable to those of goats fed diets containing Meskit pods in the tropics. Ibrahim and Gaili (1985) fed goats rations containing 1000, 850, 700 and 550 g/kg Meskit pods and reported feed intakes of 0.37, 0.39, 0.56 and 0.59 kg/head/day, respectively. Lower feed intakes on the 300 g/kg pod rations in the present study may be due to poor ration palatability due to high proportions of pods. Ibrahim and Gaili (1985) reported similar effects, and suggested that molasses may be added to the diet to improve palatability. Talpada et al. (1982) reported no adverse effects of inclusion up to 300 g/kg Meskit pods in diets of calves containing up to 100 g/kg molasses. The feed intake levels of 26 g/kg in the present study for goats fed 200 g/kg Meskit pods are comparable to those of Omani sheep fed rations containing 150 g/kg P.cineraria pods (Mahgoub et al., 2004). They are also within the range reported for Omani native sheep fed by-product feedstuff based diets (El Hag and Al Shargi, 1998). Reduced feed intakes in the 300 g/kg Meskit level are similar to those reported by Horton et al. (1993), where diets with 290 g/kg P.cineraria pods reduced feed intake in Omani sheep. The authors attributed this reduction to the presence of tannins, and other phenolic compounds, in the pods that resulted in suppressed appetite. Other Prosopis species, such as the honey mesquite (Prosopis glandulosa) were reported to contain trypsin inhibitor, which is concentrated in the seeds (Zolfaghari and Harden, 1982). Becker (1982) also demonstrated that Prosopis seeds contain heat labile hemeaglutins and trypsin inhibitors. Reducing the pods from 0.5 to1.0 cm lengths allowed some degree of feed selection against the Meskit pods. Grinding the pods and incorporating them in a concentrated mixture or pellets, should help to avoid feed selection and increase pod intake. It was found that ground Meskit pods fed with elephant grass was eaten in higher quantities than whole pods (Anon, 2003) Growth Goats fed the 200 g/kg Meskit ration gained the most BW, whereas goats fed the 300 g/kg ration lost weight during the experiment. However, growth curves indicated that goats fed the 0 or the 100 g/kg pod rations did not start gaining weight until half way through the experimental period, indicating that the pattern of BW gain of goats may have changed if the study has been continued for a longer period. It is possible that goats may need time to

8 326 O.Mahgoub et al./ Animal Feed Science and Technology 121 (2005) adapt to Meskit feeding before gaining BW. Indeed, goats fed rations containing 550 and 700 g/kg Meskit pods grew at 26 and 33 g/day, respectively (Ibrahim and Gaili, 1985). The maximum growth rate in this study of 76 g/day in the 200 g/kg pod diet is slightly lower than that recorded for Omani goats fed conventional diets (Mahgoub and Lodge, 1996; Mahgoub, 1997), but higher than that reported for many tropical and sub-tropical goats (Devendra and Burns, 1983) Feed conversion The FCR of the 200 g/kg Meskit goats is comparable to that obtained with Omani sheep fed 150 g/kg P.cineraria and other sheep fed other non-conventional diets based on agricultural by-products (El Hag and Al Shargi, 1995, 1998). The low FCR for the 300 g/kg Meskit goats may be due to the low digestibility of these diets, as Omani sheep diets based on Prosopis and acacia pods had lower organic matter and ADF digestibilities, as well as lower blood urea N levels (Horton et al., 1993) Slaughter and carcass data Feeding various levels of Meskit pods did not cause major effects on body or carcass chemical composition except for goats fed rations with 200 Meskit pods having higher carcass weight. Therefore, Meskit pods may be used in Omani goat rations up to these levels to reduce feed costs and improve farm profit. 5. Conclusions P.juliflora pods included at levels of 200 g/kg in Omani goat diets maximized feed intake, body weight gain and feed conversion. Increasing the proportions of Meskit pods in the rations to 300 g/kg sharply reduced growth rate, feed conversion and feed intake. Further studies are needed to investigate the potential of physical improvement of Prosopis-based diets to increase feed intake and carcass quality in Omani goats. Acknowledgement The authors would like to thank Mr Sadeq M. Al-Lawati for technical help. This study was funded by Sultan Qaboos University. References AOAC, Official Methods of Analysis, 17th ed. Association of Official Analytical Chemists, Gaithersburg, MD, USA. Becker, R., The nutritive value of prosopis pods. In: Parker, H.W. (Ed.), Mesquite Utilization. College of Agricultural Sciences, Texas Tech University, Lubbock, TX, USA, pp. M-1 M-9. Devendra, C., Burns, M., Goat Production in the Tropics. Commonwealth Agricultural Bureaux, Farnham Royal, UK, p. 183.

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