| Soil ingestion behavior of livestock is an important way to obtain mineral elements to meet its nutrition requirement, so it is of great significance to study the soil ingestion behavior of grazing livestock. Little research about soil ingestion for yak has been reported so far. This study revealed the soil ingestion behavior features of yak and nutrition mechanism of mineral elements through systematic research on the mineral nutrients of grazing pasture and feed intake, amount of soil, serum mineral index and soil ingestion behavior features in different seasons. To provide a theoretical basis and technical support for livestock management in alpine grassland grazing systems, this study conducted in the pasturing area of Tianzhu Wushaoling selected4yaks (3～5years old,190～240kg) as experimental objects. The0～5cm topsoil samples, edible forage and livestock blood samples were collected in January (cold season), May (seedling period), August (warm season) and October (hay period), respectively. The total fecal method was used to collect yak faeces and titanium as endogenous marker to estimate soil ingestion amount and grass feed intake amount for yak in each season. The following results were obtained:1. The grass feed intake of yak in January, may, August, October, were5.10kg,6.62kg,6.84kg,5.83kg per day respectively. There is no significant difference between may and August, and significant differences between each other month.2. The soil ingestion amount in January May, August and October were747.86g,724.83g,445.34g and445.34g per day respectively. The proportion of soil with respect to the total diet were12.87%,10.13%,6.26%and10.13%, respectively. The average daily soil ingestion amounts had no significant difference between January and May (P>0.05), but they had significant difference between samples from August and October. The proportion of soil with respect to the total diet had significant differences between samples from each period.3. The proportion of average daily intake of mineral elements, i.e. K, Ca, Na, Mg, Fe, Mn, Zn, Cu, Co, with respect to the total amount of grain were49.20%, 33.35%,70.25%,33.35%,74.07%,55.45%,14.53%,55.45%and74.37%, respectively. There were positive correlations between proportions of K, Ca, Na, Mg, Mn, Zn, Cu, Co and the soil ingestion amounts. It was extremely significant for K and soil ingestion amounts (P<0.01), significant for Mg and soil ingestion amounts (P<0.05), while not significant for the rest elements.4. Soil ingestion amount and mineral element levels were positively correlated, but not significant.5. Annual Ca (4416～8802mg/kg), Mg (1268～1532mg/kg) element content of grasses could meet the demands for Ca (0.1%～0.5%), Mg (0.1%) as recommended. The content of Na (618.6mg/kg) could barely meet the demands (600～800mg/kg) recommended in January, but it was below the recommended value in May (335.8mg/kg), August (483.3mg/kg) and October (261.1mg/kg). K (1357～1598mg/kg) levels of annual grasses were far below the recommended value. Co (0.14～1.54mg/kg), Fe (581～1657mg/kg), Mn (43-109mg/kg), Zn (37.03～67.02mg/kg) levels could meet the recommended demands for yak (Co, Fe, Mn, Zn were0.1mg/kg,50mg/kg,20mg/kg,30mg/kg). Cu content in January (9.1mg/kg) and October (4.72mg/kg) were below the recommended value (10mg/kg), while the content in May (10.09mg/kg) and August (15.19mg/kg) could meet the recommended values. |
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