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Effects of high ambient temperature and restricted feed intake on nitrogen utilization for milk production in lactating Holstein cows
Author(s) -
KAMIYA Mitsuru,
IWAMA Yuko,
TANAKA Masahito,
SHIOYA Shigeru
Publication year - 2005
Publication title -
animal science journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.606
H-Index - 38
eISSN - 1740-0929
pISSN - 1344-3941
DOI - 10.1111/j.1740-0929.2005.00259.x
Subject(s) - crossover study , chemistry , zoology , whole milk , lactation , food science , biology , pregnancy , medicine , genetics , pathology , placebo , alternative medicine
Three experiments were performed to examine the effects of high ambient temperature and feed restriction on nitrogen (N) utilization in lactating cows. Experiment 1 investigated N utilization in four cows fed ad libitum in a 2 × 2 crossover design under constant moderate (18°C) or high (28°C) ambient temperatures. The milk N secretion ( P < 0.01) and protein concentration ( P < 0.05) decreased under high ambient temperature. Experiment 2 investigated N utilization in four cows under constant moderate ambient temperature in a 2 × 2 crossover design with ad libitum or 70% ad libitum feed intake. The milk N secretion and protein concentration both decreased with feed restriction ( P < 0.05). Experiment 3 investigated N utilization in four cows fed 70% ad libitum in a 2 × 2 crossover design under constant moderate or high ambient temperatures. The milk protein concentration decreased under high ambient temperature ( P < 0.01). The milk N secretion tended to decrease under high ambient temperature ( P < 0.10). Therefore, decreased N utilization for milk production at high ambient temperature is mainly caused by a reduced feed intake and the high ambient temperature itself.