Effects of dietary energy density on metabolic status and lactation performance of periparturient dairy cows.

摘要

A study was conducted to evaluate different strategies for increasing energy density of dry cows diets. Cows were fed three diets: low energy [(1.51 Mcal/kg of DM and 35% nonfiber carbohydrates (NFC)], high energy (1.65 Mcal/kg of DM and 39.5% NFC) and high energy, where a portion of alfalfa and corn silage was replaced by straw, soybean meal, and corn starch (1.65 Mcal/kg of DM and 40.5% NFC). Increasing diet energy density of diets fed to dry cows increased DMI, ruminal concentration of propionate, and serum insulin and decreased plasma NEFA. Substitution of corn silage and alfalfa silage with an isocaloric blend of feeds that represent extremes in rate of carbohydrate fermentation increased propionate concentration in the rumen. No effects of this diet on rumen fill was observed.; A second study compared effects of energy density of diets fed during the periparturient period on lactation performance and metabolic status. During the prepartum period (−28 d to calving), animals were fed a low energy density diet (1.58 Mcal/kg and 38% NFC) or a high density energy diet (1.70 Mcal NE_L/kg, 44% NFC). After calving, half of the cows from each prepartum treatment group were assigned to a low energy density diet (L; 1.57 Mcal NE_L/kg and 41% NFC) or a high energy density diet (H; 1.63 Mcal NE_L/kg and 47% NFC) until d 20 postpartum. After d 20, all cows were fed H until d 70. Increasing energy density of diets during the prepartum was associated with higher concentrations of plasma glucose and serum insulin, and lower plasma NEFA. Prepartum metabolic status had minor effects on performance and metabolic status of cows at calving and early lactation. Feeding H immediately postpartum compared with starting at d 21 postpartum resulted in a more favorable metabolic profile and enhanced lactation performance. Cows fed H during the first three wk of lactation had lower plasma BHBA, higher plasma glucose and serum insulin concentrations, and lower liver TG content. In summary, performance and metabolic status during early lactation were affected more by postpartum than prepartum dietary energy density.