PERIPARTUM ENERGY METABOLISM OF DAIRY CATTLE (FEEDING LIPIDS, ADIPOSE TISSUE, BLOOD)

Eighteen Holstein heifers were placed into groups of three according to projected calving date, prepartum weight, and prepartum condition score. Following parturition, animals within each group were randomly assigned to a diet and remained on the experiment for 45 days in a tie-stall housing arrangement. Diets consisted of either a 70:30 forage:concentrate ratio (CONTROL), 50:50 ratio (high level of soluble carbohydrates, HLSC), or isocaloric to HLSC containing 8% soybean oil (LIPID). Diets were mixed daily into the form of a complete ration and all cows fed twice daily. Blood, rumen fluid, and adipose tissue were sampled at days -7, 5, 20, and 45 of lactation. Production means for treatments designated as CONTROL, HLSC, and LIPID, respectively, were: dry matter intake (DMI, kg/d) 13.9, 14.9, 12.4; DMI (% BW) 2.77, 2.90, 2.50; milk yield (kg/d) 24.5, 25.8, 18.6; milk fat (%) 3.77, 3.59, 3.62; milk protein (%) 3.03, 2.99, 3.11; body condition score (5 = grossly fat, 0 = very poor) 1.5, 1.9, 2.0; body weight (kg) 514, 523, 505. the LIPID diet increased ruminal iso-acids (molar %) and compared to the HLSC diet, acetate (molar %) was elevated. Diets had no effect on blood metabolites or activity of adipose glycerol-P dehydrogenase. The LIPID diet reduced short-chain and increased long-chain fatty acids in milk. Overall, higher performance was observed for cows receiving the HLSC diet. Animals on the CONTROL diet were unable to consume adequate energy to maintain high production with concurrently resulted in lower body condition scores. Low diet palatability, soybean oil in presence of heating forages, contributed to the poor performance of cows receiving the LIPID diet. Means for blood metabolites and adipose enzyme activity during sampling periods -7, 5, 20, and 45, respectively, were: glucose (mg/dl) 53.81, 44.82, 34.51, 38.20; 3-hydroxybutyrate (mg/dl) 6.58, 9.57, 10.91, 5.03; glycerol (um) 69.02, 78.31, 54.35, 51.52; glycerol-P dehydrogenase (nmoles/mg protein/min) 6.10, 5.05, 3.40, 3.98. Lipolysis was reduced as early as 20 days, but cows did not appear to be recovering from a postpartum energy deficit until day 45 of lactation