ANN 121: Applied Animal Nutrition-I (2+1)

PHASE 4. DRY PERIOD - 60 TO 14 DAYS BEFORE PARTURITION

• The dry period is a critical phase of the lactation cycle to increase milk yield during the following lactation and minimize metabolic problems at or immediately following calving.

The reasons for the dry period

(a) Involution of the udder

• The principal reason for the dry period is to allow the secretory tissue of the udder to involute.
• During this period, the secretory cells of udder actually break down and are resorbed, and a new set of secretory cells is formed. This cell renewal process takes approximately six weeks and, if a cow is allowed no dry period at all, will result in a loss of milk of at least 30% in the subsequent lactation.

(b) Foetal development

• During the last eight weeks before calving the foetus gains almost 60% of its birth weight, an overall rate of gain for the cow of about 0,75 kg/day.
• At the very least, the cow must be fed for foetal growth.

(c ) Replenishment of body reserves

• Mineral reserves are an entirely different matter to energy reserves.
• The high-producing cow will have severely depleted her body reserves of minerals, especially calcium and phosphorus, during her lactation. These reserves can only be completely replenished when the cow is dry.
• Adequate mineral nutrition during the dry period is very important. If the cow is very weak or underweight, the dry period helps her to replenish body reserves and she may be fed to gain about 20-25 kg body weight during the dry period.

(d) The length of the dry period

• It is wise to aim for a dry period of eight weeks (56 days).
• Rations should be formulated to specifically meet the nutrient requirements of dry cows: body maintenance, fetal growth, and for replacing any additional body weight not replaced during phase. P regnant animals are to be offered extra nutrients during the last two months of gestation.
• The aim is that by the end of gestation period the cows should not only gain their initial body weight but also put on an extra 25 to 30 kg of body weight. This is necessary to enable the animal to withstand the stress of parturition and to maintain the persistency of milk production during the subsequent lactation period, The provision of extra nutrients should be given in the form of concentrate mixture and not as forage because roughages are not as efficient as concentrates in increasing the body weight. The rest of the ration must contain sufficient green feeds so that the colostrum secreted after parturition should be rich in vitamin A.
• DM intake will be near 2 percent of the cow's body weight. A minimum of 12 percent CP in the DM is recommended.
• Meet calcium and phosphorus needs, but avoid large excesses. Calcium intakes of 60 to 80 grams and phosphorus intakes of 30 to 40 grams are sufficient for most cows.
• Avoid excess calcium and phosphorus intakes
• Dry cow rations above 0 .6 percent calcium and 0 .4 percent phosphorus (DM basis) have substantially increased milk fever problems.
• Provide adequate amounts of vitamin A, D, and E in rations to improve calf survival and lower retained placenta and milk fever problems. Trace minerals, including selenium for most producers, should be adequately supplemented in dry cow diets.
• Change to a transition ration starting 2 weeks before calving . During the last 3 days prior to calving, the amount of concentrate mixture should be reduced and a little warm bran is fed to keep the animal in laxative condition before calving.