Study On Sheep Production Strategy During Ecologically Fragile Period Of Grassland In Northeast Agro-pastoral Ecotone

In most parts of China, livestock production systems mainly depend on natural vegetation of grassland. However, the natural grassland shows great sensibility to grazing at certain phenological stage of pasture, such as early spring and late autumn. The strategy of livestock production during EFP should synchronize with the phenological stage of pasture; therefore, experiments were designed to meet the biological requirements for the grass and allow for higher yield of pasture and better subsequent performance of livestock. Hay-feeding strategy in early spring could help overcome this sensitive season. Every lamb could saved 24 kg herbage(DM) during the whole restriction period, and grassland without grazing could improve pasture production by 35～40% . After restriction, the refeeding lambs showed higher ADG than CK due to the high quality pasture and high feed conversion efficiency. Even in October, when pasture quality declined much, restricted lambs remained comparative high ADG. All restricted lambs reached full compensation at the end of the growth stage of pasture, whilst the female lambs attained the normal liveweight about a month earlier than male lambs did. During late autumn EFP, lambs supplemented with 150 g～300 g SFM/d/h could maintain high growing performance; consequently, the supplemented lambs gained 5 kg more liveweight than CK did. The crossbred lambs showed great variation to fluctuating quantity and quality of pasture; however, the Ujimqin lambs displayed amazing tolerance to roughage, featuring great utilizing efficiency to low quality pasture. Conclusion could be made that crossbred male lambs were more suitable for supplementation in autumn and could achieve standard market weight (46 kg) after supplementing SFM. However, it was more practical for the Ujimqin to continue extensive grazing. The grazing time of supplemented lambs were significantly less than CK, causing reduction in pasture DMI, and consequently save 500 kg pasture/ha. Meanwhile, the available pasture mass in the following spring increased 13.5% after regreening. Supplementation during late spring EFP not only improved production per unit grassland and achieved considerable amount of economical return but also saved large amounts of feed resources to allow for protection for fragile grassland.