放牧条件下白牦牛采食的季节性微调整及其效应

为研究牦牛采食模式季节性微调整对摄入的干物质及胃肠道甲烷排放的效应，于2014年9月至2015年9月进行了天祝白牦牛采食试验。结果表明：卷食模式的7?8月，蛋白质摄入最高（10.70%±0.38%）、粗纤维（18.68%±5.31%）和木质素摄入（1.89%±0.49%）最低、反刍间隔最短（1.1±0.3h）。啃食和卷食相结合的4月份半纤维素（15.68%±5.17%）和粗脂肪（1.08%±0.09%）摄入最低；5月份采食速度最快（1.15±0.16口/s）；6月份粗灰分摄入最高（18.29%±2.39%）、胎儿出生质量最大；9月份单口采食（1.97±0.27 g）、脂肪摄入量（3.77%±0.08%）、日增质量（97.43±5.18 g/d）、瘤胃甲烷气体排放最高（315.70±21.24 g/d）；10月份日采食总量（9749.40±2783.66g/d）、反刍速度最高（1.24±0.15团/min）；11月份半纤维素摄入最高（19.46%±2.58%）；12月反刍间隔最长（2.9±0.2h）。啃食模式的2月份单口采食量（0.95±0.14g）、采食速度（0.73±0.24口/s）、蛋白质（2.72%±0.49%）、粗灰分摄入（7.14%±3.25%）最低；3月份纤维素（39.25%±7.15%）、木质素（12.57%±0.46%）摄入量为最高，日采食量（4417.29±1114.56 g/d）、反刍速度（0.76±0.16团/min）、日增质量（?48.87±3.56 g/d）、瘤胃甲烷量排放（237.57±22.39 g/d）最低；该研究以解释牦牛生产过程中季节性甲烷排放节律。

Seasonal subtle alternation of yak foraging and its effect under pasturing condition

As the seasonal alternation of herbage height, yak regulates its foraging behavioral pattern to achieve the best matching. The grazing behavior of yak is the best foraging pattern in summer, the browsing and grazing combined pattern is the sub-optimal way in spring and autumn, and the browsing behavior, as the retained incisor in yak’s historical evolution, is adopted in winter. In order to find out how the foraging pattern adjustment caused by the incisors influenced the dry matter intake and enteric-fermentation methane seasonal micro-fluctuation, from September 2014 to September 2015 in Tianzhu County, Gansu Province, we tested 3 pattern (grazing, browsing, grazing+browsing combined pattern) alternation and their environmental influences. The analysis results showed that the yaks in July and August had the highest protein intake (10.70%±0.38%), the lowest crude fiber (18.68%±5.31%) and lignin intake (1.89%±0.49%), and the shortest ruminant interval (1.1±0.3 h), which adopted the grazing pattern. In April, the yaks adopted the grazing and browsing combined pattern, and hemicellulose (15.68%±5.17%) and crude fat intake (1.08%±0.09%) were the minimum; in May, the foraging ratio of yaks (1.15±0.16 bite/s) was the fastest;in June, the crude ash intake (18.29%±2.39%) was the highest and the fetal birth weight was also the biggest; in September, the foraging intake (1.97±0.27 g/bite), the fat intake (3.77%±0.08%), the average daily gain (97.43±5.18 g/d), and the enteric methane emissions (315.70±21.24 g/d) were the highest; in October, the total dry matter intake (9749.40±2783.66 g/d) and the ruminant ratio (1.24±0.15 chyme-mass/min) were the highest; in November, the hemicellulose intake (19.46%±2.58%) was the highest; in December, the ruminant interval (2.9±0.2 h) was the longest. In February, the yaks adopted the browsing pattern, the total intake (0.95±0.14 g/bite) was the lowest, and the browsing ratio (0.73±0.24 bite/s), the protein intake (2.72%±0.49%), and the crude ash intake (7.14%±3.25%) were the lowest;in March, the cellulose (39.25%±7.15%) and lignin (12.57%±0.46%) had the highest intake, and the daily browsing intake (4417.29±1114.56 g/d), the ruminant ratio (0.76±0.16 chyme-mass/min), the average daily gain (?48.87±3.56 g/d), and the enteric-fermentation methane emissions (237.57±22.39 g/d) were the lowest. The feed intake per chewing in October was the highest. The intake per chewing was the lowest in March. The speed of food intake reached the fastest in May and the browsing pattern was mainly adopted, with little“empty grazing”, then the yaks were regulating to the browsing and grazing combined pattern from October to December And then the intake speed was accelerated. The total daily intake reached the peak in October, and the daily body weight gain was the fastest;then the daily intake sharply declined in November. The daily intake reached the lowest in February and March. The highest ruminated efficiency was in October, and the slowest was in March. The shortest ruminant interval was in July, and the longest interval was in December. From June to September, there was the highest grass protein growth, and yaks regulated to the grazing pattern;and there was lower protein in winter grass, so yaks changed to the browsing pattern. From January to March, grass had the highest cellulose, and yaks changed to the browsing pattern;and in lower cellulose season, yaks used the grazing pattern. From January to September, yaks adopted the grazing pattern, and the enteric-fermentation methane emissions also reached the annual peak; the vitamin and nutrient declined in the milk during yak’s lactation;and for the browsing pattern from January to March, the methane emissions were the lowest.