Prepartum nutrient intake alters palmitate metabolism by liver slices from peripartal dairy cows1

摘要

We determined the effects of day relative to parturition and prepartum plane of nutrition on hepatic partitioning of palmitate metabolism to CO_2, acid-soluble products (ASP), and esterified products (EP). Multipa-rous Holsteins (n = 74) were fed different amounts of nutrients during the dry period in a 3 (far-off period diet) x 2 (close-up period diet) factorial arrangement. During the far-off period (d -60 to -25) cows received a low-energy control diet fed ad libitum (100NRC) to meet National Research Council (NRC) requirements, a moderate-energy diet fed ad libitum to exceed NRC recommendations for net energy of lactation (NEl) by >50% (150NRC), or the same diet fed at restricted intake to provide 80% of NE_L requirements (80NRC). During the close-up period (d -24 until parturition), cows were fed a diet for ad libitum intake to meet NRC recommendations or in restricted amounts to provide 80% of calculated NE_l requirements. After parturition, all cows had ad libitum access to a lactation diet. Liver slices from biopsies on d -30, -14, 1, 14, and 28 relative to parturition were used to determine conversion of [1-~(14)C] palmitate to CO_2, ASP, and EP. Across diets, oxidation of palmitate to CO_2 was decreased postpar-tum, whereas oxidation to ASP was increased at d 1 postpartum compared with other times. Conversion of palmitate to EP increased markedly postpartum, with the greatest rates at d 1 postpartum. Conversion of palmitate to CO_2 and ASP on d 1 postpartum was lower and the proportion of palmitate metabolism as EP was greater for cows fed 150NRC than for those fed 100NRC or 80NRC. Hepatic triacylglycerol concentration at d 1 postpartum was greatest for cows fed 150NRC. Palmitate metabolism did not differ between close-up diets. Hepatic triacylglycerol was negatively correlated with tissue metabolism of palmitate to CO_2 and ASP but positively correlated with metabolism to EP. Hepatic triacylglycerol was highly correlated with NEFA concentrations on the day of calving and d 1 postpartum but not with NEFA prepartum. In contrast, plasma BHBA postpartum was not correlated with hepatic palmitate metabolism by liver slices but was highly correlated with NEFA concentration prepartum. Excessive energy intake during the far-off dry period decreased hepatic palmitate oxidation and shifted palmitate metabolism toward greater esterification, consistent with greater hepatic triacylglycerol accumulation postpartum.