Abstract
This experiment was performed to examine the influences of high ambient temperature on milk production, nutrient digestibility, energy and protein sufficiency ratio, and plasma metabolites concentration in lactating cows. In a 2×2 crossover design, four multiparous lactating Holstein cows were maintained in a chamber under treatment of constant moderate (18°C) ambient temperature (MT) or high (28°C) ambient temperatures (HT). The DMI and milk protein yield were significantly lower in HT (p<0.05). The milk yield, milk lactose yield, and milk SNF yield tended to be lower in HT (p<0.10). No statistical differences for 4% fat-corrected milk and milk fat yield were observed. Rectal temperatures were significantly higher in HT than MT (p<0.05). The apparent DM, OM, ether extract, CF, and ash digestibility did not differ between treatments. On the other hand, the apparent CP digestibility was increased significantly (p<0.05) and nitrogen free extract tended to increase (p<0.10) in HT. The sufficiency ratio of ME and DCP intake for each requirement tended to be lower in HT than in MT (p<0.10). Concentrations of total protein (TP), albumin, and urea nitrogen in plasma did not differ between treatments. Plasma 3-methylhistidine (3MH) concentration as a marker of myofibrillar protein degradation tended to be higher in HT (p<0.15). In conclusion, high ambient temperature was associated with a lower energy and protein sufficiency ratio,
Highlights
In southwestern Japan, climatic conditions are such that the hot season is long and the average temperature is higher than the upper critical temperature of lactating Holstein cows during summer. Shibata (1983) reviewed the influence of a hot environment in lactating dairy cows, and reported that milk protein concentration was decreased even though the reported effects of heat stress on milk fat and lactose concentrations differ
This study investigated milk production, nutrient digestibility, energy and protein sufficiency, and plasma markers of myofibrillar protein degradation at the treatment of high ambient temperature
The milk protein yields were significantly lower in high (28°C) ambient temperatures (HT) cows (p
Summary
In southwestern Japan, climatic conditions are such that the hot season is long and the average temperature is higher than the upper critical temperature of lactating Holstein cows during summer. Shibata (1983) reviewed the influence of a hot environment in lactating dairy cows, and reported that milk protein concentration was decreased even though the reported effects of heat stress on milk fat and lactose concentrations differ. In southwestern Japan, climatic conditions are such that the hot season is long and the average temperature is higher than the upper critical temperature of lactating Holstein cows during summer. Shibata (1983) reviewed the influence of a hot environment in lactating dairy cows, and reported that milk protein concentration was decreased even though the reported effects of heat stress on milk fat and lactose concentrations differ. Previous experiment (Kamiya et al, 2005) showed that milk protein production was greatly decreased by high ambient temperature treatment. Body compartments are mobilized to support milk production in lactating dairy cows because they cannot consume sufficient nutrients to meet the production requirements (Komaragiri and Erdman, 1997). The rate and extent of tissue compartment mobilization
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