Productivity and energy partition of late lactation dairy cows during heat exposure |
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Authors: | Kyoung Hoon KIM Do-Hyung KIM Young-Kyoon OH Sung-Sill LEE Hyun-Jeong LEE Dong-Woon KIM Yong-Joo SEOL Nobuhiro KIMURA |
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Institution: | National Institute of Animal Science, RDA, Suweon,;Division of Animal Science and Technology, Gyeongsang National University, Jinju, South Korea;and;Laboratory of Animal Nutrition, Department of Animal Science, Nippon Veterinary and Life Science University, Musashino, Tokyo, Japan |
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Abstract: | Three late-lactation Holstein cows were used to determine the effects of environmental temperature on performance and energy partitioning. Each cow was housed in a respiratory chamber for 30 consecutive days and exposed to three different conditions of environmental temperature: (i) 20°C and 20°C (20°C), (ii) 25°C and 20°C (25°C), (iii) 30°C and 25°C (30°C) during the day and night, respectively. The temperature was switched in an interval of 10 days. Humidity in the chamber was maintained at 55–65% through the entire experimental period. The daily mean as well as morning and evening rectal temperatures of Holstein cows increased linearly ( P < 0.05) as chamber temperature increased. There was a significant linear reduction in dry matter (DM) intake ( P < 0.05) and an increase in DM digestibility ( P < 0.05). The response in milk yield, however, was not affected by heat stress. There were no significant differences among treatments for intake energy, heat production, net energy for lactation and net energy for gain. This results of this study disagreed with the assumption that late lactation cows gave priority to increasing body tissue at the expense of milk production under thermal stress. |
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Keywords: | energy partitioning heat stress late lactation |
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