内蒙古典型草原放牧绵羊体增重与放牧率之间的关系

Relationships between body gains and stocking rates of grazing sheep on typical Inner Mongolian grassland

实验于 1990～ 1993年在中国科学院内蒙古草原生态系统定位研究站进行。实验设计为不同放牧率下的划区轮牧 ,包括 1.33、2 .6 7、4 .0 0、5.33和 6 .6 7羊 / hm2 (1990年为 1.33、2 .0 0、2 .6 7、3.33和 4 .0 0羊 / hm2 ) 5个放牧率等级和 3个轮牧小区 ,轮牧周期为 4 5天或 4 6天 ,共放牧 138天。结果表明 ,整个暖季放牧期间 ,相邻 3种放牧率间体重差异很少达显著性水平 ,间隔 2个放牧率或以上的处理间 ,差异显著或极显著 ,且随着实验年数的增加 ,出现体重显著性差异的日期有所提前 ,但降水量等因素对此趋势有些影响。与放牧率高的处理相比 ,放牧率低的处理一般出现日增重峰值的日期早、峰值数多、峰值高和持续时间较长。绵羊日增重模式 ,依不同年份和不同放牧率而有些差异 ,但一般可划分为 :1快速增重期 (5月 2 0日～ 7月 2 0日 ) ,平均日增重达 150 g左右或以上 ;2增重缓慢期或平台期 (7月 2 0～ 8月 2 0日 ) ,平均日增重为 0～ 50 g;3较快增重期 (8月 2 0日～ 9月 5日或 9月 2 0日 ) ,平均日增重为 50～ 150 g;4开始减重期 (9月 5日或 9月 2 0日～ 10月 5日 )。同时每只羊个体增重与放牧率呈高度负相关 ;而公顷增重先随放牧率的增大而增加 ,但放牧率增大到一定程度时 ,分顷增重不再增加 。

The experiment was carried out at the Inner Mongolia Grassland Ecosystem Research Station during 1990～1993, with 5 stocking rates (1.33,2.00,2.67,3.33 and 4.00 sheep/ha in 1990 and 1.33,2.67,4.00,5.33 and 6.67 sheep/ha in the following two years) and 3 paddocks of one hectare each for a complete rotational grazing circle of 45～46 days. The total grazing period each year consisted of 138 days from May 20 to October 5. The results indicated that there were no significant differences in body gains between a stocking rate and that in its close neighbourhood, except for the case between the highest and the lowest stocking rates. At a lower stocking rage the time of obvious body gains usually came earlier, with multiple peaks of higher value and longer persistence, than the case of a higher stocking rate. The body gain of individual sheep appeared to be highly and negatively correlated with the stocking rate, while the total body gain per hectare increased first with an increase in the stocking rate, but started to decline when a certain level of stocking rate had been reached.