轮牧方式对荒漠草原滩羊牧食特征、体重及繁殖性能的影响

【目的】合理的放牧方式对维持草地生态系统平衡具有重要意义。研究轮牧方式对滩羊牧食特性、体重及繁殖性能的影响可为草地放牧管理提供依据。【方法】以宁夏面积最大的荒漠草原为对象,在载畜率为0.75只/hm2水平下,设置连续放牧(CG)、二区轮牧(TG)、四区轮牧(FG)、六区轮牧(SG)4个处理。采用跟群全天观察法测定滩羊的牧食习性,利用差额法测定采食量,采用常规方法测定草群和滩羊摄入牧草营养成分,每个轮牧周期结束观测滩羊的体重,统计放牧期间繁殖性能等。【结果】放牧全天,滩羊采食时间占据了主体,比例达64%以上。随轮牧分区增加,滩羊采食、游走站立时间下降(P0.05),反刍卧息时间增加(P0.05);排泄、争斗、瘙痒、啃食异物等其他行为受个体行为影响更大,所占时间比例不到1.4%。草地牧草采食量表现为四区与六区轮牧无明显差异(P0.05),但均高于连续放牧和二区轮牧,连续放牧采食量最低(P0.05);草地采食率呈现连续轮牧二区轮牧四区轮牧六区轮牧的趋势,连续放牧达到39.06%,六区轮牧仅为27.9%;滩羊日采食量在二区、四区、六区轮牧方式下差异不大(P0.05),在连续放牧区最低(P0.05)。滩羊摄入的牧草的粗蛋白、粗脂肪、磷的含量总体高于草群相应养分含量,而粗纤维和钙低于草群养分含量,粗灰分和无氮浸出物比较接近,说明滩羊具有选食蛋白质含量高,粗纤维含量低牧草的能力;随轮牧分区增加,滩羊摄入的牧草粗蛋白含量呈下降趋势、粗纤维呈上升变化,但滩羊摄入干物质、粗蛋白和磷的总量增加;各处理下滩羊营养摄入量均超出了美国NRC绵羊饲养标准,说明暖季滩羊放牧不需要补饲。放牧期间,滩羊体重和日增重以连续放牧最低(P0.05),二区、四区及六区轮牧间无显著差异(P0.05);各处理下滩羊产羔率、羔羊平均初生重等繁殖性能接近,说明在适宜载畜率水平下,轮牧方式对滩羊繁殖性能影响不大。【结论】轮牧方式对滩羊牧食特征和增重产生了影响,相对于连续放牧,随轮牧分区增加,草地牧草采食率、滩羊采食时间和摄入的牧草粗蛋白含量下降,但草地采食量,滩羊日采食量及摄入的干物质、粗蛋白等营养物质总量增加。划区轮牧没有提高滩羊繁殖性能,但更有利于滩羊体重增加。若仅考虑滩羊牧食特征、增重性能以及生产中放牧管理的便利性,二区轮牧方式是宁夏荒漠草原滩羊暖季的最优放牧方式。

Effects of Different Rotational Grazing Ways on Grazing Characteristics,Weight and Reproductive Performance of Tan Sheep in Desert Steppe

【Objective】It is significantly important to maintain grassland ecosystem balance by reasonable grazing method. The study of the effects of rotational grazing on grazing characteristics, weight and reproductive performance of Tan sheep could provide a basis for grassland grazing management.【Method】The desert steppe in Ningxia was used as the research object, and under the stocking rate of 0.75·hm^-2, 4 treatments was designed which were continuous grazing (CG), two-area rotational grazing (TG), four-area rotational grazing (FG) and six-area rotational grazing (SG). The feeding habits, intake amount and nutrient intake of Tan sheep were studied by using all-day observation method, difference method and conventional nutrient determination method, respectively. Then the weight of tan sheep at the end of each rotational period was observed and the reproductive performance during grazing period was counted.【Result】The results are as follows: All the days of grazing, Tan sheep feeding time occupied the main part, the proportion of feeding time was 64% or more. With the increase of area number in rotational grazing, the ingestion time, standing and wandering time of Tan Sheep reduced（P＜0.05）, the rumination and resting time increased correspondingly（P＜0.05）. The differences of individual behavior had a greater impact on excretion, fighting, itching, eating foreign body and other acts , the proportion of time was less than 1.4%. The pasturing amount of four-area rotational grazing and six-area rotational grazing showed no significant differences and were both higher than the continuous grazing and two-area rotational grazing significantly, continuous grazing intake was the lowest among them（P＜0.05）. The grassland feeding rate showed a trend of CG＞TG＞FG＞SG , among them, the continuous grazing was 39.06%, and the six-area rotational grazing was 27.9%. The intake rate declined with the increase of rotational grazing area number; there was hardly significant difference in Tan sheep daily intake among three kinds of rotational grazing patterns（P＞0.05）, the continuous grazing was the last（P＜0.05）. The contents of crude protein, crude fat and phosphorus in grass taken by Tan sheep were higher than those in grass group, and crude ash and nitrogen-free extract were close, but crude fiber and calcium were lower. With the increase of area numbers in rotational grazing, the crude protein content of feeding forage had a downward trend, the crude fiber showed an opposite trend, but the total intakes of dry matter, crude protein and phosphorus were increased. The nutrient intakes of all the treatments were higher than that of NRC sheep feeding standards in the United States, which indicated that Tan sheep did not need supplementary feeding after grazing in the warm season. During grazing, the body weight and average daily gain of Tan sheep in continuous grazing area was lower than the other three areas which had hardly significant differences among them. The reproductive performance of Tan Sheep was not significantly affected by the differences of grazing patters. The reproductive performance of each treatment was similar, such as lambing rate, lamb average birth weight and so on, which indicated that the grazing method had little effect on the reproductive performance of Tan sheep at an appropriate stocking rate.【Conclusion】Rotational grazing patterns had an impact on the feeding characteristics and production performance of Tan sheep. Compared with the continuous grazing, with the increase of area number in rotational grazing, the pasture intake rate, feeding time and the intake of protein content were decreased, but the total amount of daily intake, dry matter, crude protein and other nutrients were increased. Rotational grazing did not improve the reproductive performance of Tan sheep, but more conducive to Tan sheep weight gain. The two-area rotational grazing is the best pattern for Tan sheep farming at warm season in Ningxia desert steppe if take consideration of the feeding characteristics, production performance of Tan sheep and convenience of production management.