Effect of supplementation of a mixture of gluconeogenic precursors during the transition period on performance, blood metabolites and insulin concentrations and hepatic gene expression of dairy cows

Abstract

Clinical and subclinical ketosis are associated with low productivity and poor well-being of dairy cattle. Dietary supplementation of gluconeogenic precursors during the transition period is a strategy to prevent the occurrence of these diseases. However, there is a lack of information regarding the effect of feeding mixed gluconeogenic precursors on intake, and systemic and hepatic metabolism of transition dairy cows. Our objective was to examine the effect of supplementing a mixture of gluconeogenic precursors (Glucose Booster, GB) on intake, milk yield and composition, blood metabolites, and hepatic gene expression in transition dairy cows. Twenty-nine multiparous Holstein cows blocked by previous 305-d mature-equivalent milk yield were randomly assigned to one of the two treatments: GB supplementation or not (CTL). Cows received their respective dietary treatments from 28 d before expected calving to 21 d after parturition. Then, all cows were fed the CTL diet until d 56 of the lactation. Ambient temperature and relative humidity in the barn were assessed hourly. Vaginal temperature was determined weekly during the prepartum period from a subset of cows. Dry matter intake was recorded daily, and body condition score and body weight assessed every two weeks during the experiment. Milk yield was recorded daily and composition measured weekly in early lactation. Plasma samples were collected on d 28 and 10 before expected calving, calving, and 3, 7, 14, 21, 28 and 42 d after calving for analysis of metabolites and insulin. Liver biopsies were collected at 28 d before the expected calving and 14 d after calving to measure mRNA expression of genes related to gluconeogenesis, ketogenesis, and fatty acid oxidation. Data were analyzed using the PROC GLM or MIXED procedures of SAS. The temperature-humidity index averaged 74 and 65 in the pen for dry and lactating cows, and the vaginal temperature averaged 39.2 ○C before calving and was not different between treatments, suggesting that dry cows were exposed to heat stress. Treatment had no impact on intake, lactation performance, blood metabolites and insulin and hepatic gene expression. In conclusion, supplementation of GB did not affect performance or metabolism of transition dairy cows, indicating that exposure to heat stress may diminish the benefits of feeding gluconeogenic precursors during the transition period.