天然羊草草地绵羊采食的季节变化

Seasonal changes of diet composition of sheep grazing on Leymus chinensis grassland

饱和链烷技术在国际上已被认为是估测家畜采食组分最为准确的方法,并且随着额外指示剂长链醇和长链酸的引入,进一步完善了该技术,使得对复杂采食组分的估测成为可能。本试验中利用饱和链烷与长链醇或长链酸的适当组合对绵羊在天然羊草(Leymus chinensis)草地的采食组分进行了测定。结果表明,在整个放牧季羊草、苔草(Carex duriuscula)和碱蓬(Suaeda heteroptera)为主要采食组分,但具有明显的季节性差异。6月,碱蓬所占比例最大,其次为羊草和苔草;7月,绵羊对苔草和碱蓬的采食出现大幅下降,而对羊草的采食出现大幅上升;8月,苔草成为最主要的采食组分,对羊草的采食降至放牧季最低,碱蓬的比例明显增加;其他草种如滨藜(Atriplex patens)、蒲公英(Taraxacum mongolicum)、芦苇(Phragmites communis)等为微量组分或采食比例不大。这种采食差异与草地植被的水平和垂直分布密切相关,而且采食植物的适口性在一定程度上也会影响家畜采食。另外,采食比例较大的植物组分,如羊草,择食指数并不高甚至表现为避食,而采食比例较低的植物,如芦苇、滨藜等,择食指数则较高。

N-alkane technique is considered to be the most accurate method to estimate diet composition of sheep,and the additionally introduced markers（long-chain alcohols and long-chain acids） further extended the range of available faecal markers,making it possible to estimate the diet with complex components.In this experiment,the dietary composition of sheep grazing on Leymus chinensis grassland was estimated using alkanes in combination with alcohols and/or acids during the grazing months.The results showed that L.chinensis,Carexdur iuscula and Suaeda heteroptera were the main diet components during the whole grazing seasons,but with evident seasonal changes.In June,the bulk of the diet was made up of S.heteroptera and L.chinensis,C.iuscula came after.In July,the consumption of S.heteroptera and C.iuscula faced a significant decline,but of L.chinensis increased obviously.In August,C.iuscula constituted the most proportion,and the consumption of L.chinensis and S.heteroptera decreased and increased,respectively.For the minor components,like Atriplex patens,Toraxacum mongolicum and Phragmites communis,non-significant changes were observed.The plant species distributed vertically and horizontally influenced on the grazing behavior of sheep heavily.In addition,palatability was another influencing factor.The analysis of selectivity index showed that the plant species,like L.chinensis,with high proportion in the diet presented low selectivity.Similarly the low proportion components,like P.communis and A.patens,might show high selectivity.