Seasonal changes in weight and body composition of yak grazing on alpine-meadow grassland in the Qinghai-Tibetan plateau of China.
Seasonal changes in weight and body composition of yak grazing on alpine-meadow grassland in the Qinghai-Tibetan plateau of China.
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DOI：
10.2527/2005.8381908x
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发表时间：
2005-08
影响因子：
3.3
通讯作者：
B. Xue;X. Zhao;Y. Zhang
中科院分区：
文献类型：
--
作者：
B. Xue;X. Zhao;Y. Zhang
研究人员对 45 头雄性牦牛（2001 年 4 月出生）进行了研究，以确定青藏高原的季节变化如何影响体重和身体成分。从出生到 26 月龄，每月对 30 头牦牛进行称重，以确定体重的季节变化。其余 15 头牦牛随机分为 5 组（每组 3 头牦牛），指定在 13、15、18、22 和 25 个月屠宰，以测量季节性对身体化学成分的影响。所有牦牛均在高原高山草甸草原上放牧，不加任何补给。所有体重和身体成分数据均按个人计算。体重和身体成分数据均在跨越 2 年的七个生长期进行比较，并按季节定义。 4月（出生）至第一个生长季2001年12月，牦牛体重增加（P<0.01）；然而，在随后的寒冷季节（2001年12月至2002年5月），BW下降（P<0.01）。第二个生长季为2002年5月（13月龄）至2002年10月（18月龄），第二个活体减重季为2002年10月至2003年5月。第一个减重季牦牛的减重量占第一个生长季总增重的25.64%。牦牛第二个减肥季的减重占第二个生长季总增重的29.73%。第二个生长季的能量保留为291.07 MJ，其中50.8%在随后的冷季消耗掉。第二个生长季夏季（5月至7月）和秋季（7月至10月）的能量积累没有差异（EBW增益分别为5.01和6.30 MJ/kg；P = 0.63）。第二个冬季（2002年10月至2003年2月）动员的能量为16.49 MJ/kg EBW，第二个春季（2003年2月至2003年5月）动员的能量为9.06 MJ/kg EBW。这些数据表明，第一个寒冷季节放牧牦牛体重的减少量远小于第二个寒冷季节，并且冬季每单位体重动员的能量含量高于春季（P = 0.02）。这项研究的结果表明，放牧牦牛在第一个寒冷季节的第一个体重减轻期后出现了高效的补偿性生长。牧民可以利用这一优势来提高牦牛产量。牦牛可能已经发展出一种自我保护机制来克服青藏高原漫长的寒冷季节。
Forty-five male yaks (born April 2001) were studied to determine how seasonal changes on the Qinghai-Tibetan plateau affected BW and body composition. Thirty yaks were weighed monthly from birth to 26 mo of age to determine seasonal changes in BW. The remaining 15 yaks were allocated randomly to five groups (three yaks per group), designated for slaughter at 13, 15, 18, 22, and 25 mo to measure seasonal effects on body chemical composition. All yaks were grazed on the alpine-meadow grassland of the plateau without any supplementation. All BW and body composition data were calculated on an individual basis. Body weight and body composition data were both compared across seven growth periods spanning 2 yr and defined by season. From April (birth) to December 2001 of the first growing season, yak BW increased (P < 0.01); however, during the subsequent cold season (December 2001 to May 2002), BW decreased (P < 0.01). The second growing season ran from May 2002 (13 mo of age) to October 2002 (18 mo of age), and the second live weight-loss season ran from October 2002 until May 2003. The weight loss experienced by yaks during the first weight-loss season was 25.64% of the total weight gain in the first growing season. The weight loss experienced by yaks during the second weight-loss season was 29.73% of the total weight gain in the second growing season. Energy retention in the second growing season was 291.07 MJ, 50.8% of which was consumed during the subsequent cold season. Energy accumulation in the summer (from May to July) and fall (from July to October) of the second growing season did not differ (5.01 and 6.30 MJ/kg of EBW gain, respectively; P = 0.63). The energy mobilized during the second winter (from October 2002 to February 2003) was 16.49 MJ/kg of EBW, and in the second spring (from February to May 2003), it was 9.06 MJ/kg of EBW. These data suggest that the decrease in grazing yak BW during the first cold season is much less than during the second cold season, and that the energy content per unit of BW mobilized is greater (P = 0.02) in winter than in spring. Results from this study demonstrate highly efficient compensatory growth in grazing yaks following the first weight loss period during the first cold season. This benefit could be exploited by herders to improve yak production. Yaks may have developed a type of self-protection mechanism to overcome the long cold seasons in the Qinghai-Tibetan plateau.