IMPACT OF CHANGES IN ORGANIC NUTRIENT METABOLISM ON FEEDING THE TRANSITION DAIRY-COW

Pregnancy, decreased feed intake during late gestation, lactogenesis, and parturition have dramatic effects on metabolism in dairy cows duri ng the transition period from 3 wk before calving to 3 wk after calvin g. Increases in plasma NEFA occur during the 10 d before calving and m ay precede the decrease in feed intake. Plasma NEFA concentrations are highest at calving and decrease rapidly after calving. Plasma glucose concentration decreases during the transition period except for a tra nsient increase associated with calving. Hepatic glycogen is reduced a nd lipid is increased during the transition period. Feed intake is usu ally decreased 30 to 35% during the final 3 wk prepartum, but negative energy and protein balances are not as severe as during the week foll owing parturition. Prepartum feed intake is positively correlated to p ostpartum feed intake; therefore, efforts to maximize feed intake shou ld begin before calving. Overconditioned cows maybe more susceptible t o a prepartum decrease in feed intake. Increasing nutrient density of the diet during the transition period may enhance feed intake. Feeding more fermentable carbohydrate during the prepartum transition period may acclimate the microbial population to lactation diets, promote dev elopment of ruminal papillae, increase absorptive capacity of the rume n epithelium, and reduce lipolysis by delivering more glucogenic precu rsor to the liver and enhancing blood insulin. Supplementing fat to tr ansition diets does not seem to alleviate health problems associated w ith negative energy balance. Enhancing amino acid absorption by the pr epartum cow may improve lactation performance and health, although mec hanisms of action have not been identified.