三种放牧率对高山禾草—嵩草型草地和羔羊生长的影响

EFFECTS OF THREE STOCKING RATES ON SWARD AND LAMB GROWTH IN ALPINE GRASS-KOBRESIA RANGELAND

作者于1987～1988年在甘肃农大天祝高山草原试验站进行了三种放牧率对高山禾草—嵩草型草地和羔羊生长影响的研究。试验地为经过改良的天然草地。供试羔羊为2或3月龄断奶的甘肃高山细毛品种和边甘杂种(FI)去势羔羊。分别以高、中和低三种放牧率实行划区轮牧。小区面积和放牧天数根据实测采食量和利用率确定。放牧频率为2,轮牧周期40天。结果表明,放牧率的变化对当年的草地植被成分、地下植物量及土壤含水量均无显著影响,但对可食牧草产量影响较大。随着放牧率增大,牧草产量明显降低(P<0.05),毒草产量变化较小。放牧率的增大,使甘肃高山细毛品种羔羊个体生长速度显著降低(P<0.01);而边甘杂种羔羊生长发育良好。在甘高品种羔羊中,2月龄断奶羔羊的平均日增重随放牧率增加明显降低(P<0.01);而3月龄断奶羔羊受其影响较小(P>0.05)。放牧羔羊的日增重、在放牧初期与羔羊采食量呈显著正相关(r=0.72),其体重下降的临界期为9月下旬。

The effects of three stocking rates(SR) at 26, 39 and 52 lamb / ha on the sward and growth of grazing lambs were studied with two type lambs of GF(Gansu Fine Wool) and BG(crossbred of Border Leicester and GF) at the Alpine Grassland Experiment Station of Gansu Agric. Univ., Tianzhou county, during 1987-1988. The swards were grazed rotationally with 7 paddocks for each SR treatment, and the herbage yield, botanical composition, animal intake and daily liveweight gains(DLG) were measured. The results show that the herbage yields reduced significantly(P<0.05) by increasing SR to a high level, but no much changes in botanical composition, underground phytomass and soil moisture. There was no significant difference between the two type lambs at the medium SR, however, lambs weaned at 2 months decreased their DLG very significantly (P<0.01). It was found that lamb DLG correlated with their intakes positively(r = 0.72) and the critical period of reducing DLG for grazing lambs would be in late September.