Schrama J W, Arieli A, van der Hel W, Verstegen M W
Department of Animal Husbandry, Agricultural University, Wageningen, The Netherlands.
J Anim Sci. 1993 Jul;71(7):1761-6. doi: 10.2527/1993.7171761x.
Changes in thermal demand in restrictively fed, unadapted, young calves were studied during the first days after transportation. Twenty-three 6-d-old Holstein-Friesian male calves were assigned to one of four ambient temperature treatments: 5, 9, 13, or 18 degrees C. Calves were fed at a constant level below the maintenance requirement (300 kJ of ME.kg-.75.d-1). After arrival, heat production (HP) and energy and nitrogen balance were measured for each calf for 5.5 d. At ambient temperatures of 5 and 9 degrees C, HP was increased compared with temperatures of 13 and 18 degrees C (P < .001). As a consequence, energy retention was decreased at low ambient temperatures (P < .05). At temperatures of 5 and 9 degrees C, body fat mobilization was increased compared with that at temperatures of 13 and 18 degrees C (P < .001). Energy retained as protein was not affected by ambient temperature. During the experimental period, HP decreased with time. Ambient temperature affected this decrease (P < .001), indicating that the relationship between HP and ambient temperature changed with time. The rate of increase in HP below the lower critical temperature was not affected by time, averaging 9.5 kJ.kg-.75.d-1.C degrees-1. Lower critical temperature, however, increased with time by .89 C degrees/d (P < .05). The changing relation between HP and ambient temperature with time in young, unadapted calves after transportation is thus reflected in an alteration in thermal requirement with time.
研究了运输后最初几天内，限饲、未适应环境的幼龄犊牛热需求的变化。将23头6日龄的荷斯坦-弗里生公牛犊分配到四种环境温度处理组之一：5℃、9℃、13℃或18℃。犊牛按低于维持需要量（300kJ代谢能·kg-0.75·d-1）的恒定水平饲喂。到达后，对每头犊牛测量5.5天的产热量（HP）以及能量和氮平衡。在5℃和9℃的环境温度下，与13℃和18℃相比，HP增加（P<0.001）。因此，在低环境温度下能量保留减少（P<0.05）。在5℃和9℃时，与13℃和18℃相比，体脂动员增加（P<0.001）。以蛋白质形式保留的能量不受环境温度影响。在实验期间，HP随时间下降。环境温度影响了这种下降（P<0.001），表明HP与环境温度之间的关系随时间变化。低于下限临界温度时HP的增加速率不受时间影响，平均为9.5kJ·kg-0.75·d-1·℃-1。然而，下限临界温度随时间以0.89℃/天的速度升高（P<0.05）。因此，运输后未适应环境的幼龄犊牛中，HP与环境温度之间随时间变化的关系反映在热需求随时间的改变上。
