Nutritional modulators of hepatic energy metabolism during the periparturient period of dairy cattle.

摘要

Periparturient dairy cattle experience dramatic changes in nutrient demands to support lactation. To provide energy, adipose tissue is mobilized releasing non-esterified fatty acids (NEFA) into the blood. Liver takes up much more NEFA than it can immediately use for oxidation or packaging into very low density lipoproteins (VLDL) and the subsequent development of fatty liver impairs health and performanceThe focus of this research was to identify and evaluate nutritional modulators of hepatic fatty acid metabolism and gluconeogenesis in periparturient dairy cows.; Forty-eight multiparous Holstein cows were fed either 0, 45, 60, or 75 g/d of a rumen-protected choline (RPC) during the periparturient period to determine whether choline supplementation to the diet would affect hepatic energy metabolism and cow performance. Hepatic capacity for storage of [1- 14C]palmitate as esterified products within liver slices tended to decrease linearly by feeding RPC. These data implied that choline may increase the rate of very low density lipoprotein synthesis and secretion of esterified lipid products from liver.; In a second study, Forty-eight periparturient Holstein cows were utilized to determine the effects of feeding 2-hydroxy-4-(methylthio)-butanoic acid (HMB; 0, 0.10, 0.20% of the prepartum diet and 0, 0.15, and 0.23% of the postpartum diet) in a methionine deficient diet on milk production and hepatic energy metabolism. The middle concentration of HMB increased milk yield, the concentration of triacylglycerol in liver, and days to first ovulation without improving either [1-14C]palmitate or [1-14C]propionate metabolism in liver slices.; Liver was sampled from 7 periparturient Holstein cows and used to test the effects of physiological concentrations of choline, methionine, propionate, and essential fatty acids (EFA) on hepatic [1-14C]palmitate metabolism in vitro. Choline and EFA showed the greatest potential for increasing hepatic lipid export immediately postpartum.; Pooling the data from these three experiments showed that over conditioned cows at calving tended to have higher accumulation of triacylglycerol in liver shortly postpartum. High hepatic triacylglycerol was associated negatively with gluconeogenesis from [1-14C]propionate. Proper dietary management during late lactation and the dry period to prevent excessive weight gain is suggested to limit metabolic disorders and optimize production.