Changes in milk fatty acids and metabolites in dairy cows supplemented with varying levels of rumen-protected glucose during early lactation

Due to insufficient energy intake, postpartum dairy cows experience a decrease in plasma glucose, which may result in lipid metabolism disorders. Rumen-protected glucose can improve energy balance and alter lipid metabolism in postpartum dairy cows. However, research on the changes in milk fatty acid composition and metabolite in early lactating dairy cows fed different levels of rumen-protected glucose is very limited. The purpose of this study was to investigate the effects of dietary rumen-protected glucose supplementation levels on the milk fatty acid composition and metabolome of early lactating dairy cows.Thirty-two Holstein cows were divided into four treatment groups based on body weight, parity and lactation performance in a randomized block design. Dairy cows in each treatment group (n = 8 per diet) were supplemented with 0, 200, 350, and 500 g/d of rumen-protected glucose from calving to day 35 postpartum. Milk samples from these dairy cows were collected on the last day of the experiment for fatty acid composition analysis using gas chromatography and for milk metabolite analysis using untargeted metabolomics.