Ksh. Mahesh Singh, K. Ratika, RK. Mandakini Devi, T. Gyaneshwori Devi and K. Merina
Assistant Professors, College of Veterinary Sciences & AH, Jalukie, Nagaland (CAU)
The transition period for dairy cows refers to the period three weeks before and after calving when the cow changes her metabolic state from being dry to lactating. It is the most critical phase of the lactation cycle. Feeding transitional cow is a challenge due to the nutritional and physiological changes that occur during this period. There has been tremendous changes in how to approach dry cow nutrition, particularly in the areas of dry matter intake, protein and energy requirements, metabolic diseases and the most effective way to group and manage dry cows. Critical physiological events that have to be targeted during the transition period includes adaptation of the rumen to the higher energy diet that will be fed in early lactation, maintenance of normal blood calcium concentration, maintenance of positive energy balance and strong immunity throughout the transitional period is utmost importance as animals during this phase is exposed to higher stress coupled with reduce feed intake making them vulnerable to infections due to reduce immunity. In this article we will be discussing in brief about energy, protein, minerals and vitamin requirement in transitional cows.
Energy
Energy balance of a transition cow is determined by subtracting energy requirements for maintenance and gestation from energy intake. During the transition period, feed intake is decreasing at a time when energy requirements are increasing due to growth of the conceptus. Consequently, to maintain the energy balance the energy density of the diet should increase. Heifers need higher dietary energy density due to lower feed intake and the additional energy requirements to support growth.Increasing energy density may stimulate papillae growth and increase acid absorption from the rumen, adapt the microbial population to higher starch diets, increase blood insulin, decrease fatty acid mobilization from adipose tissue and increase dry matter intake.Grain has to be introduced to the cow’s ration for at least 3 weeks before the due date and for heifers this should be 5 weeks. As per NRC, 2001, the energy density should be between 1.56-1.62 Mcal/kg (Table 1) of Net Energy of lactation (NEL), which corresponds to 1-1.5 kg of concentrates per animals, initially animals should be given 500 gm of concentrates daily and slowly increase to 1.5 kg just before parturition.After parturition animals should be given warm lukewarm water with laxative diet.
Protein
A diet containing 13-14% crude protein should be adequate before calving(Table 1). As protein is absorbed in the small intestine as microbial protein we have to be sure we have enough energy in the rumen for the microbes to grow. However, diets with less than 12% protein can reduce colostrum quality, feed intake and early lactation milk yields. Inadequate protein to meet the high demands of the calf has been shown to reduce milk protein. This is likely to result in inadequate protein for some of the cow’s functions such as hoof growth. During the final 3 weeks prepartum decreased the risk of RFM and uncomplicated ketosis. CP must be increased to 16.5% – 17.5% to begin preparing for high DMI during the lactation phase.
Dry matter intake
Increasing dietary Non-fiber Carbohydrate (NFC) or decreasing Neutral Detergent Fiber (NDF) during the transition period stimulates DMI. When energy density of the diet increased from 1.3 to 1.54 McalENl/kg DM and crude protein increased from 13 to 16% at about 3 weeks prior to calving, DMI increased in 30%. In another study, cows fed high NFC (40-42%) diets consumed more dry matter during the prepartum period, had lower plasma NEFA, had reduced BHB level and there was a reduction in liver triglyceride. There are less NEFA in plasma (176 ws. 233 M) and more insulin-like growth factor-I (472 vs. 390 ng/ml plasma) during the last two weeks prepartum and less triglyceride in liver at parturition (0.9 vs. 1.5% wet tissue basis). Some researcher concluded that increasing the energy and protein density up to 1.6 Mcal of NEl/kg and 16% CP in diets during the last month before parturition improves nutrient balance of cattle prepartum and decreases hepatic lipid content at parturition.
The reduction in DMI during the last week prepartum may be 30%. Feed intake postcalving doesn’t peak until 9-13 weeks of lactation. Dry matter intake in the first week postcalving is about 65% of maximum DMI. This depressed early lactation DMI is accounted for by the NRC. These changes in DMI need to be accounted for in ration formulation to provide adequate nutrient intake. For Holstein cows, DMI should be at least 15-17 kg per day by the end of the first week after calving. Adjustments in ration nutrient density will be needed to compensate for the depressed DMI in these periods. This low DMI in early lactation cows may limit the rate at which concentrate feeding can be increased postcalving.
Table 1. Minimum nutrients requirements for dry, prepartum and fresh cows.
Nutrient Dry Prepartum Fresh
Dry matter intake (kg/day) 14.4 13.7 16.1
Net Energy for lactation (Mcal/day) 1.25 1.54-1.62 1.73
Maximum crude fat (%) 5 6 6
Crude Protein (%) 13-14 14-15 16.5-17.5
Undegradable intake protein (% CP) 25 32 40
Acid detergent fiber (%) 21 17-21 17-21
Neutral detergent fiber (%) 33 25-33 25-33
Minimum Forage NDF (%) 30 22 20
Maximum NFC (%) 36-43 36-43 36-44
Minimum Calcium (%) 0.44 0.45 0.75
Phosphorus (%) 0.22 0.3-0.4 0.3-0.4
Ca:P ratio 1.5:1 to 5:1 1.5:1 to 5:1 –
Magnesium (%) 0.20 0.35-0.4 0.23-0.29
Potassium (%) 0.55 0.55 1.2
Sulfur (%) 0.11 0.11 0.2
Sodium (%) 0.10 0.10 0.32
Chlorine (%) 0.20 0.8-1.2 0.30
Minerals and Vitamins
Minerals are essential for increasing productivity as well as improve reproduction inanimals. The daily dietary requirement dependents on the amount of dietary mineral that is absorbed into the tissues. The requirement of the cow can be described by:
Maintenance + pregnancy + growth + lactation
Dietary Requirement =
Absorption co-efficient
The absorption coefficient values for some minerals are given bellow. Coefficient of absorption for Calcium(Ca) was 0.38 in NRC (1989) and 0.45 in NRC (1978). Coefficient of absorption for Phosphorus(P) was 0.50 in NRC (1989) and 0.65 in NRC (1978). Rest of the world use 0.60 to 0.75. The average coefficient of absorption for Mg from a wide variety of natural feedstuffs fed to ruminants averaged 0.294 with a standard deviation of 0.135. The coefficient of absorption for Magnesium (Mg) from inorganic sources should be 0.50 based on Mg oxide. The coefficient for Mg absorption should be decreased when Potassium (K) is high in the diet.The dietary coefficient of absorption for Zn is estimated to be 0.15. Dietary Chloride (Cl) is absorbed with at least 80% and closer to 100% efficiency. Often Cl anions accompany the movement of Sodium (Na)cations. Plants contain only small amount of Na. Salt needs to be added to the diet, otherwise cows produce less milk. Animals can tolerate very high levels of salt in the diet if water is provided and kidneys are functioning properly. But, high dietary NaCl will reduce feed intake in animals.Nearly all of the dietary K is absorbed. Intracellular uptake of K following a meal helps buffer blood K concentration. Rumen microbes need 0.2-0.22% Sulphur (S) to operate efficiently. Excessive dietary Sulphur (S) can interfere with absorption of Cu and Se and may become toxic.
Selenium requirement is 0.3 ppm of dry matter basis. Potassium should be not over 1.0% in the total ration for dry cows, but K, Na and Mg should be 1.5, 0.5 and 0.35% of DM respectively in milking cows during heat stress. Nitrogen to sulfur ratio should be 11 to 13:1 in the total ration to meet rumen bacterial needs. The dietary magnesium should be set at 0.4%. Magnesium sulfate or magnesium chloride is recommended because they could be an effective source of anions and magnesium. The proportion of Manganese (Mn) absorbed from the diet generally is between 0.5 and 1%. High dietary Ca, K or P increase Mn excretion in feces.Iron excess (250-500 mg Fe/kg DM) interfere with Cu and Zn absorption. The dietary Fe should not to exceed 1000 mg/kg DM.
Depending on the DMI the dietary requirement of iodine should be about 0.25-0.5 mg/kg DM. Chromium is essential for normal glucose metabolism. The amount of Cr should not exceed 0.47mg/kg dry matter. The major dietary factors that can modify the efficiency of absorption of dietary Zn are interactions of Zn with other metal ions (Cu, Fe) and the presence of organic chelating agents in the diet.
Cobalt is a component of vitamin B12. Microbes in rumen are the only natural source of vitamin B12. Rumen microbes need 0.11% Co to perform efficiently.Between 1 and 5% of dietary Cu will be absorbed by adult cattle. A diet high in Zn (>1000 mg/kg), S and Mo reduces Cu absorption. The Cu:Mo ratio should be 2:1.Selenium is part of glutathione peroxidase and in conjunction with vitamin E act as antioxidant compounds. Selenium is also critical to thyroid hormone metabolism. Selenium can cause deficiency or toxicity. Diets containing 0.1 ppm of Se are recommended but field studies suggest this is not enough. Legally Se can be added up to 0.3 ppm.Vitamin levels should be met to optimize milk production. Vitamin A should be provided at rate of 3600 IU per kgDM/day. Vitamin D 900 IU per kgDM/day and vitamin E 14 IU per kgDM/day.
Table2. Minimum trace mineral and vitamins requirements for dry, prepartum and fresh cows.
Nutrient Dry Prepartum Fresh
Cobalt (ppm) 0.11 0.11 0.11
Copper (ppm) 16 16 16
Iodine (ppm) 0.4 0.4 0.8
Iron (ppm) 26 26 20
Manganese (ppm) 22 22 17-21
Selenium (ppm) 0.30 0.30 0.3
Zinc (ppm) 30 30 77-73
Vitamin A (IU/kg) 5500 6500 5500
Vitamin D (IU/kg) 1500 1700 1500
Vitamin E (IU/kg) 80 88 40
Conclusion
The transition period is a time of considerable metabolic adjustment for dairy cows. Sub-optimal nutrition during this time period may impartnutritionalstress on the cows that may be manifestedin one or more of the common periparturientdisorders, such as milk fever, ketosis, acidosis etc. Attention must be given to formulatingappropriate diets for cows during the far-offandclose-up dry periods and for the fresh cow. The newly released NRC guidelines(NRC, 2001) providea solid foundation for feeding close-up cows. Cowsshould not be fed high-starch diets throughout theentire dryperiod. In addition to ration formulationand monitoring, feeding management and groupingstrategies may impact transition success. Finally,emerging concepts in stress physiology indicate thatbiological effects of multiple stressorsare additiveand maybe a criticalfactor in the high incidence ofhealthproblems and poortransitionsuccess in someherds.Attention to keeping cowsas comfortable aspossible duringthe transition isas important asthe nutritional managementprogram.