Effect of dietary fat supplementation on milk components and blood parameters of early-lactating cows under heat stress
2011
Zhang, H., Sichuan Agricultural Univ., Ya'an (China) | Wang, Z., Sichuan Agricultural Univ., Ya'an (China) | Liu, G., Sichuan Agricultural Univ., Ya'an (China) | He, J. | Su, Ch.
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 less than 0.05), while milk protein and lactose were not significantly altered by fat supplementation (P more than 0.05). The concentration of plasma glucose was increased by fed supplemental fat (P less than 0.05) while that of plasma urea nitrogen was decreased by fed supplemental fat (P less than 0.05). Furthermore, there were significant increases of total triglycerides, total cholesterol and high density lipoprotein (HDL) (P less than 0.05), but low-density lipoprotein (LDL) did not differ significantly by fat supplementation (P more than 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.
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