Annual analysis of nutritional quality of pasture in Haiyan County, Qinghai Province

In order to compensate for the problem of insufficient support for monitoring of the nutrient value of pasture in the Qinghai-Tibet Plateau, we examined the dynamic nutritional value of grassland pasture under grazing conditions in the Qinghai-Tibet Plateau. During the period September 2015 to August 2016, we selected typical Tibetan herdsmen and grazing pastures to track yak grazing, and simulated the collection of edible forage for sampling. The nutrient composition and total energy of the pasture were analyzed, and the dry matter digestibility of pasture was determined using a two-step in vitro method. The following results were obtained. 1) The contents of crude protein, ether extract, acid detergent fiber, ash, calcium, and phosphorus were 3.68%~19.21%, 0.86%~2.74%, 9.65%~43.83%, 44.70%~76.23%, 5.40%~9.62%, 2.13%~5.12%, and 0.027%~0.190%, respectively, and the contents of CP and ash in May were significantly higher than those in other months (P<0.01). 2) The digestibility of pasture was 42.72%~72.47%, which was significantly higher than that of other months (P<0.01). 3) Total energy (GE), digestive energy (DE), and metabolic energy (ME) were 17.76~19.67, 7.81~13.26, and 6.40~10.87 MJ·kg-1, respectively. There was no significant difference in the GE of forage in different months (P>0.05), although it was the highest in June, followed by November. DE and ME were significantly higher in May than in other months (P<0.05), and the lowest in December, followed by April and June. In conclusion, the natural forage of Haiyan County, Qinghai Province in May and June is of good quality, whereas in October to March, the nutritional value of forage is low. Therefore, in view of the different types of seasonal grassland grazing throughout the year, it is recommended that pastoralists and farmers use natural grassland to supplement feed for breeding yaks in October to March. In the future, we will conduct follow-up monitoring of forage grass, and determine the fine feeding of grazing yak.