MANAGING THE DAIRY COW DURING THE DRY PERIOD

Transcription

1 Department of Animal Science MANAGING THE DAIRY COW DURING THE DRY PERIOD Dairy Cattle Production A Page 1 of 11

2 Background The dry period is a critical period for the health, production and reproduction of the dairy cow. It is the end of lactation and the start of the next. It has been estimated that an optimal dry cow program can increase milk production by kg per cow per lactation Objectives of the dry period - Allows mammary gland to go through a normal period of involution - Ensures maximum number of secretory cells early in lactation. - Stimulates immune system to minimize disease. - Stimulates rumen bacteria and papillae - Minimizes metabolic disorders The dry period is also a good time for hoof trimming, worming, mineral-vitamin injections, and necessary vaccinations that are safe during pregnancy. Length of the dry period A typical dry period in about 60 days in length (50-70 days). Either shorter or longer periods will reduce subsequent milk yield and increase the incidence of metabolic disorders. A dry period can be divided into two phases: 1- Far-off dry cow. The length of this phase is 6-7 weeks (minimum 4 weeks) to allow a proper involution of the mammary gland. 2- close-up dry cow. The length of this phase in about 3 weeks (minimum 2 weeks) to allow for mammary gland regeneration and colostrum formation. Phase 3 3 Fresh Phase 4 Peak Milk Phase 5 Peak DMI Phase 6 Tail End Dry Matter Intake Far Far Off Off Close Close Up Up Phase 1 Phase 2 Milk Production Body Weight Month Page 2 of 11

3 Drying off A recommended procedure for drying off is to discontinue all grain feeding and offer only poor quality forage for about a week before drying off. If the cow is producing less than 10 kg of milk daily, milking can be stopped abruptly. It might take up to a week to bring the cow to that production level. The cow may have to be milked once a day and she should be milked out completely. When milk is ceased, treat all quarters immediately with a dry-treatment product. And teat dip. If possible continue teat dipping for up to a week. A clean and wellbedded environment is essential to reduce the chances of udder infections. Body condition score The body condition score of a cow at drying off should be 3 to 3.5. The body condition score of the cow should not change considerably during the dry period and cows should calf with the same body condition score they had at drying off. This is because the dry period is too short to considerably change the body condition score. Therefore the best time to prepare for how a cow will score at drying off is about 150 days into lactation. This will allow the cow to draw on some of the body reserves in early lactation where milk production peaks earlier (4-6 weeks after calving) than intake (8-12 weeks after calving). It is recommended that the body condition score should not fluctuate by more than during the dry period. Feeding the far-off cow (phase one) Nutrient requirements according to the NRC (1989) for the dry pregnant cow is given in Table 1. Table 1. Daily nutrient requirements of dry cow (maintenance plus last two months of gestation) Energy Minerals Vitamins (1000 IU) Weight NEl ME DE TDN CP Ca P (g) A D (kg) (Mcal) (Mcal) (Mcal) (kg) (g) (g) In the early stages of the dry period cows are usually fed low energy diets and thus forages constitute the major portion of the dry cow diet (Table 3). Dry matter intake during this period is about % of body weight. Page 3 of 11

4 Table 2. Recommended nutrient contents of diets for cows in the dry period (phase one) Dry matter intake (kg) Total Digestible Nutrients (%) 56 Crude protein (%) Ruminally degraded protein (% of CP) 70 Neutral detergent fiber (% minimum) Non-forage carbohydrates (%) 30 Calcium (%) 0.6 Phosphorous (%) 0.26 Magnesium (%) 0.16 Potassium (%) 0.65 Sodium (%) 0.10 Chlorine (%) 0.20 Sulfur (%) 0.16 Vitamin A (IU/day) 100,00 Vitamin D (IU/day) 30,000 Vitamin E (IU/day) 1000 Table 3. Examples of dry cow rations Ration I Ration II Ration III kg (DM) Alfalfa hay (17% CP, 58% TDN) 5 to Corn silage (8% CP, 68% TDN) 5 to 6 Corn stalks (6% CP, 45% TDN) 4 Grass hay (8% CP, 52% TDN) 5 Corn (10% CP, 88% TDN) 1.5 Protein supplement (49% CP, 84% TDN) 0.5 Trace mineral supplement Corn silage can make up to 30-40% of dry matter intake (Table 3). Higher levels will provide excess energy and increase the risk of over-conditioned cows (fat cows). Legume forages (e.g. alfalfa hay, alfalfa silage) contains high levels of Ca and K. This may limit their levels in dry cow diets to 30-50%. Combining corn silage or legume forages with a medium- to low-quality grass forage. Total mixed rations will ensure sufficient intake of all nutrients. If finely chopped silage is fed, long coarse hay should be included (about 10-25% of the diet) to offset any digestive problems such as acidosis. Concentrate requirements for dry cows are minimal (Table 3). It is recommended that one kg of grain concentrate is fed daily. This will help maintaining a rumen microbial population, which is adapted to diets containing grains and also reduce the occurrence of digestive problems after calving should reduce. The grain mixture can also be used as a carrier to ensure adequate vitamin-mineral intake. Page 4 of 11

5 Summary of the far-off cow management Drying off Far-off dry period Feeding Abrupt changes Dry cow ration Time period 7 days 30 to 40 days Body condition score 3+ to 4-3+ to 4- Grain level None Depends on body condition, 1 to 3 kg/day Management Dry-treat all quarters, teat dip Check body, vaccinate, parasite control, mineral-vitamin injection, hoof trimming Page 5 of 11

6 Milking herd Dry cow group 1 Main dry cow group Dry cow group 2 Special dry cow group Too thin Other special needs Too fat Dry cow group 3 Pre-freshening group Page 6 of 11

7 Managing the Dairy Cow during the Transition Period Definition Transition period is defined as the period 2 to 4 weeks prior to calving (close-up) through 2 to 4 weeks after calving (fresh cow). In some occasions, transition period refers only to the pre-calving period (i.e. 2 to 4 weeks before calving). Calving and the first month after freshening are critical times for the dairy cow and most problems occur during that period. Feed intake of the transition cow Total nutrient requirements and the proportion needed for pregnancy (fetal development) are much higher during the last month of gestation. During transition period, feed intake is decreasing at time where energy requirements are increasing due to fetus growth. Dry matter intake of the transition cow declines about 30% prior to calving and for the first few weeks post calving, dry matter intake is about 20-30% below 55 DMI 1000 NEFA peak lactation. Inadequate energy intake relative to DMI NEFA requirements causes lb/d um/l mobilization of body reserves non-esterified fatty acids or NEFA), which increases the risk of metabolic disorders Day relative to calving Body condition score Body condition score of cow is an important factor influencing dry matter intake during the transition period. Cows should freshen with a body condition score of 3.5 (range of 3.25 to 3.75). Proper conditioning needs to be done before dry off. Thin cows (freshen with a body condition score of 3 or 3-) do not have enough energy to support high levels of milk yield in early lactation. Lower feed intake for overconditioned cows during the transition period probably contributes to their greater disposition to metabolic disorders. Also these cows often exhibit rapid and excessive weight loss in early lactation leading to poor fertility. Page 7 of 11

8 Feeding the Transition Cow Several changes are needed in the nutrition of the transition cow in order for the rumen microbes and rumen papillae to be adapted to the diets being fed to the lactating cows. For the rumen microbes the transition period entails a shifting of microbial population from fiber fermenters to starch fermenters. For the rumen papillae, adaptation entails the a gradual elongation of papillae as production of volatile fatty acids especially propionic acid increases. Well-adapted papillae are necessary to prevent ruminal acidosis in early lactation. Feeding energy: Compare with cows in the early dry period, transit cows need diets with higher energy density and lower fiber levels due to the increased nutrient requirements for pregnancy (Table 1). One strategy for enhancing energy intake is to feed high-energy diets. An energy density of 1.6 Mcal of NE l per kg of dry matter is recommended for prefresh diet. The diet should be fed for the last three weeks prior to calving. If the firstcalve heifers are being managed in a separate group from the dry cows, they should be fed this diet for the last five weeks. Table 1. Recommended nutrient contents of diets for cows in the dry period Dry cow Phase one Phase two Dry matter intake (kg) Total Digestible Nutrients (%) Net energy for lactation (NE l, Mcal/kg) Crude protein (%) Ruminally degraded protein (% of CP) Neutral detergent fiber, % minimum Non-forage carbohydrates Calcium (%) Phosphorous (%) Magnesium (%) Potassium (%) Sodium (%) Chlorine (%) Sulfur Vitamin A (IU/day) , ,000 Vitamin D (IU/day) 25-30, ,000 Vitamin E (IU/day) The post-fresh cow should be fed diets with intermediate energy levels between the prefresh and the high group diets. If the energy density for the high group diet is 1.76 to 1.80 Mcal of NE l per kg, the energy density of the postfresh diet should be 1.71 to 1.76 Mcal of NE l per kg. Group NEl (Mcal/kg) NDF(%) Far-off dry Close-up Fresh Peak Energy should not be increased by > 10% from one group to another Page 8 of 11

9 Energy density of the transition cow diets can be increased by increasing the non-forage carbohydrate levels. This can be achieved by reducing the forage component and increase the level of grain (starch) in the diet. Feeding high levels of non-forage carbohydrates increases feed intake, decreases body fat mobilization, and reduces the incidences of metabolic disorders. A recommended level of non-forage carbohydrate is 35 to 40% in pre-fresh diets. The concentrate part should not exceed 40 to 50% of the diet or 4 to 5 kg dry matter per cow. Increasing grains up to 4-5 kg per day helps to shift rumen microbes to the type that can ferment high grain diets and stimulate rumen papillae to elongate and increase papillae surface area. It will also help reduce any weight loss the cow may experience in response to increased fetal growth. The transition cow can also be fed a total mix ration (TMR) to introduce the cow to the lactation diets. However, the amount fed should not exceed one third of the average intake of the high production group. This is because of the high levels of Na and K in the lactation diets that the dry cow should not receive. Long medium quality hay is fed after the cow has eaten the TMR. Feeding protein: Current recommendations suggest that a 12 to 14% crude protein is adequate for pre-fresh cow diets (Table 1). However, a higher crude protein level (e.g. 14%) may be required if separate diets are formulated for first-calve heifers (primiparous cows). Higher protein levels (18 to 19%) are also required for post-fresh diets to offset the low dry matter intake of fresh cows. Anionic Salts Anions are negatively charged elements (e.g. S --, Cl - ) while cations are positively charged elements (e.g. Na +, K + ). Important anions in dairy rations include chloride, sulfur and phosphorous while important cations include sodium, potassium, calcium and magnesium. Rations high in cations relative to anions or having a high cation-anion balance are considered alkaline rations. On the other hand, rations low in cations relative to anions or having a low or negative cation-anion balance are considered acidic rations. Dairy cows during the close-up period should be fed acidic rations. This is because acidic rations help in preventing milk fever by increasing Ca mobilization from bone. Acidic rations also reduce the incidence of retained placenta and udder edema. Reducing Na and K concentrations lowers the cation-anion difference in pre-fresh diets, which helps control metabolic disorders. Legume forages such as alfalfa hay and silage are high in K and therefore the feeding of legume forages during the close-up period should be limited. Anionic salts such as calcium can be used to adjust cation-anion balance. Anionic salts can be helpful when there is a high incidence of milk fever or when it is difficult to limit calcium intake during the dry period. Due to the fact that feeding anionic salts reduces Page 9 of 11

10 intake, reducing the concentration of dietary Na and K should be considered first. Corn silage has a low K content and can be used to dilute high-k forages such as alfalfa hay and silage. Commonly used anionic salts include ammonium chloride, ammonium sulfate, magnesium salt (epsom salts), calcium sulfate (gypsum) and calcium chloride. Because chloride salts are more acidifiers of blood and urine than calcium salts, the use of calcium chloride, ammonium chloride, and hydrochloric acid have become more common. The recommended calcium level in pre-fresh diets containing anionic salts is 1.0 to 1.2%. Prefresh diets should 0.4% magnesium. Anionic salts should not be fed to post-fresh cows. How to calculate dietary cation-anion difference (DCAD): The DCAD is calculated by subtracting the equivalent weight (molecular weight divided by charge) of anions from the equivalent weight of cations. DCAD (meq/kg) = (Na + K) (Cl + S) The following factors should be used to convert dietary anions and cations from percentages to meq; Na = 435, K = 256, Cl = 282, and S = 624. Acidic rations will have negative DCAD values while alkaline rations will have positive DCAD values To be effective in preventing milk fever, rations of the transition cow should have a DCAD value of 100 to 200 meq/kg. Example: Calculate the DCAD of a ration with Na at 0.15%, K at 2.0%, Cl at 0.80% and S at 0.40%. DCAD = (0.15 x * 256) (0.80 x x 624) = 128 meq/kg Mineral and vitamin supplementation The transition cow should also receive a vitamin supplement containing 4-6 grams of niacin (B12) and 400 IU vitamin E. Research has shown that feeding niacin during the transition period aids in preventing ketosis while vitamin E increases the cow's resistance to infection (e.g. mastitis). Page 10 of 11

11 Summary of transition cow management Feeding Transition diet Time period 7 to 14 days Body condition score 3+ to 4- Grain level Prior freshening: % of body weight At freshening: 1% of body weight Management Shift to milk cow forages Move to calving area Watch closely Add niacin to diet (6 g/day) Summary for the whole dry period - Keep accurate records on breeding and calving dates. - Feed cows during late lactation so that they will be in adequate body condition at drying off. - Dry-off cows to allow for a period of days - Provide enough forage and some grain, if needed to ensure that the dry cow will be in proper condition at calving. - Provide supplemental minerals and vitamins. - Feed at least 2.5 to 5 kg/day of concentrates at least 14 to 21 days prior to calving to condition the digestive system for lactation. Further Readings Transition Dairy Cow Management (CD). Feeding and managing dry cows. Pennsylvania State University. Extension Circular 372. Page 11 of 11