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Milk Protein Production and Plasma 3-Methylhistidine Concentration in Lactating Holstein Cows Exposed to High Ambient Temperatures |
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Mitsuru Kamiya*, Yuko Kamiya, Masahito Tanaka, Shigeru Shioya |
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Correspondence:
Mitsuru Kamiya,
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| Abstract |
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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?? 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, and decreased milk protein production, even though the body protein mobilization tended to be higher. |
| Keywords:
Dairy Cows; Heat Stress; Milk Production; Energy; Protein; Protein Degradation |
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