Effect of dietary fat supplementation on milk components and blood parametersof early-lactating cows under heat stress

Abstract

The objective of the present experiment was to evaluate the effect of dietary fat supplementation on milk components and blood parameters of early-lactating cows under heat stress. Cows in group 1 were fed basal diet without dietary fat (T1) supplementation (control). The other four experimental groups were fed 1.5% palmitic acid (T2), rapeseed oil (T3) or soybean oil (T4), and 1.8% fat powder (T5), respectively. The results showed that the average Temperature Humidity Index (THI) was 76.68. The Dry Matter Intake (DMI) was not affected by fat supplementation, but the milk yield increased for cows fed supplemental fat. Milk fat increased significantly by fat supplementation (P<0.05), while milk protein and lactose were not significantly altered by fat supplementation (P>0.05). The concentration of plasma glucose was increased by fed supplemental fat (P<0.05) while that of plasma urea nitrogen was decreased by fed supplemental fat (P<0.05). Furthermore, there were significant increases of total triglycerides, total cholesterol and high density lipoprotein (HDL) (P<0.05), but low-density lipoprotein (LDL) did not differ significantly by fat supplementation (P>0.05). These results indicate that supplementation of dietary fat on early-lactating cows during hot weather can alter milk components and blood parameters, which may be beneficial for enhancement of energy balance and alleviation of heat stress.