| The present study was carried out to research the relationship between yak soil ingestion and grassland vegetation characteristics,and to discuss the potential effect of soil ingestion on yak mineral nutrition,and also to supply a theoretical basis for estimate the soil ingestion amount of yak and the regulation of mineral nutrition in grassland grazing systems.The study site lies in east Qilian Mountains,and two blocks of enclosed grassland occupied 1667 m3 and 5 yaks with 3 years old were selected for experiment,including warm(August)and cold(December)seasons.The vegetation height,coverage and biomass of grazing grassland were measured during trial,and trial samples from soil,forage,blood,and rumen liquid were collected,and yak fecal samples were gathered through video,then the amount of soil ingestion was calculated using titanium as endogenous marker.The following major results were obtained:1?The vegetation height,coverage and biomass of grazing grassland decreased significantly with grazing during both warm and cold seasons(P<0.01).Seasonal change was showed that the vegetation coverage in former trial stage during warm season was higher than that in cold season,and vegetation height and biomass were higher in cold season,however,vegetation biomass decreased faster in cold season.2?The daily soil ingestion amount for the proportion of diets were 2.80%~10.11%and 2.13%?13.42%respectively in warm and cold,and there were significant seasonal change in soil ingestion with higher in the pre-grazing of warm season,and lower in the end-grazing of cold season.3?It was found that the daily soil ingestion amount for the proportion was significantly negatively correlated(P<0.05)with Stipa capillata height and coverage.Polygonum viviparum height and coverage and Total biomass,was significantly negatively correlated(P<0.01)withKobresia humilis coverage.Kobresia capillifolia coverage and Melissitus ruthenica coverage by analysisingthe correlation between soil fertility and vegetation characteristics of grassland.The model of soil ingestion for yak grazing can be established.Warm season:%SI=16.419+1.524 KHH-0.205 SCC+0.067 PVC-0.225 KHC-0.032 TB(RZ=0.996,P<0.010 and%SI=4.632+0.684 SCH-1.302 KCH-3.259 MRH+1.199 SCC+0.019TB(RZ=0.985,JP<0.O0)o(KHH:Kobresia humilis height;SCC:Stipa capillata coverage;SCH:Stipa capillata height;PVC:Polygonum viviparum coverage;KHC:Kobresia humilis coverage;MRH:Melissitus ruthenica height;KCH:Kobresia capillifolia height;%SI:%soil ingestion;TB:Total biomass).However,the present models of soil ingestion for yak were established in the special grassland condition,and the application of model was need to study further..4?With the increase in soil ingestion,yak serum Na,K,Pi content were improved in cold season and warm season,and the effect for serum K was significant(P<0.05),and the contents of Cu,Fe,Zn,Ca,Mg were decreased,but Fe decrease was significant(P<0.05),meanwhile serum Ca and Cu content was below the critical level with element deficiency phenomenon.5?The contents of acetic acid,propionic acid,butyric acid,isobutyric acid,valeric acid and isovaleric acid were decreased significantly(P<0.01),and shortage of forage for yak should be a major reason. |
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