Journal of Dairy Science (Jun 2022)
Hepatic triacylglycerol associations with production and health in dairy cows
Abstract
ABSTRACT: The objectives were to evaluate the associations between hepatic triacylglycerol content and production, blood metabolites, incidence of diseases, reproduction, and survival in Holstein cows. Data were collected from 4 experiments including 329 cows in which hepatic tissue was sampled with a mean (± standard deviation) of 8.3 ± 1.5 d postpartum (6 to 11 d) and analyzed for triacylglycerol concentration. The mean (± standard deviation) concentration was 4.4 ± 2.8% on a wet basis and ranged from 0.4 to 16.1%. Intakes of dry matter (DM), energy balance, body weight (BW), body condition (BCS), productive performance, and incidence of diseases were evaluated for the first 105 d postpartum, whereas blood metabolites were assayed in the first 21 d postpartum. Reproductive performance and survival were monitored in the first 300 d postpartum. Mixed models were fitted to the data to investigate the linear and quadratic associations of hepatic triacylglycerol concentration with responses of interest. Increased concentration of hepatic triacylglycerol was associated with a quadratic increase in yields of milk, energy-corrected milk (ECM), and milk components. A change in hepatic triacylglycerol from 2.5 to 7.5% of the wet tissue was associated with an increase in yield of ECM of 1.8 kg/d, and with 0.2 kg more ECM per kg of DM intake. However, the increased efficiency was accompanied by decreases in DM intake, BCS, more exacerbated losses of BW, and a more negative body energy change. Increased concentration of hepatic triacylglycerol was associated with a quadratic increase in blood fatty acids and a linear increase in blood β-hydroxybutyrate concentrations, concurrent with linear decreases in concentrations of glucose and total Ca in blood. Moreover, a change in hepatic triacylglycerol from 2.5 to 7.5% was associated with linear increases in the relative risk of hyperketonemia by 2.5 times (15.2 vs. 37.5%), hypocalcemia by 1.7 times (30.3 vs. 52.4%), metritis by 2.1 times (12.5 vs. 25.7%), and diagnosis of multiple diseases postpartum by 2.4 times (8.7 vs. 21.1%). Survival in the herd by 300 d postpartum tended to decrease from 91.1 to 86.3% with an increase in hepatic triacylglycerol from 2.5 to 7.5% of the wet tissue, but no association was observed between hepatic triacylglycerol and measures of reproduction in the first 300 d postpartum. Concentrations of hepatic triacylglycerol in early lactation varied substantially, and increments resulted in quadratic association with productive performance, but at the expense of tissue reserves as those cows had increased tissue catabolism and risk of diseases that reduced survival.
