暖季补饲矿物质盐砖对放牧牦牛生长性能、瘤胃发酵、血液和被毛矿物质含量的影响OA北大核心CSTPCD

To investigate the effect of supplementary feeding of mineral salt bricks on yak productivity under grazing conditions,two controlled grazing experiments were carried out. Twelve healthy male yaks,aged 2.5 years old with similar body weight[(139±6) kg],were randomly divided into two groups:a whole grazing group (CG Group) and a grazing group with supplementary feeding of mineral salt bricks (SG Group). Each group included six animals as replicates. The study focused on the effects of supplementary feeding of mineral salt bricks in the warm season on the growth performance,rumen fermentation,blood,and hair mineral content of grazing yaks. The total weight gain of yaks in the CG Group was 20.75 kg,with an average daily weight gain of 244 g·d-1. In contrast,the total weight gain of yaks in the SG Group was 39.45 kg,with an average daily weight gain of 464 g·d-1,which was 90.12％ higher than the CG Group. The dry matter digestibility of yaks in the SG Group was significantly higher than that of the CG Group (P<0.05). In contrast,the crude protein digestibility,ether extract digestibility,and neutral detergent fiber digestibility of the SG Group were significantly lower than those of the CG Group on the 30th and 90th day of the experiment (P<0.05). Similarly,the acid detergent fiber digestibility of the SG Group was also found to be significantly lower than that of the CG Group on the 30th and 60th day of the experiment (P<0.05). Furthermore,the yield of butyric acid,valeric acid,total volatile fatty acids and NH3-N in the rumen of the SG Group was significantly higher than that of the CG Group (P<0.05). On the 30th day of the experiment,there was no significant difference in rumen liquid pH between the CG Group and the SG Group (P>0.05). However,on the 60th and 90th day of the experiment the rumen liquid pH of the SG Group was significantly lower than that of the CG Group (P<0.05). The contents of Ca,P,K,Mg,and Fe in the serum of yaks in the CG Group were not significantly different from those in the SG Group on the 30th day of the experiment (P>0.05). Nevertheless,the contents of Na and Co in the CG Group were significantly higher than those in the SG Group (P<0.05). Conversely,the contents of Cu,Zn,and Mn in the serum of yaks in the SG Group were significantly higher than those in the CG Group (P<0.05). Moreover,the contents of Ca,P,and Na in the CG Group were not significantly different from those in the SG Group on the 60th and 90th day of the experiment (P>0.05). On the other hand,the contents of Fe,Cu,Zn,Mn,Mg,K,and Co in the SG Group were significantly higher than those in the CG Group (P<0.05). The hair mineral content analysis showed that on the 30th day of the experiment,the contents of Ca,Mg,Na,K,and Mn in the hair of yaks in CG Group were not significantly different from those in the SG Group (P>0.05). Nevertheless,the contents of Fe in the hair of yaks in the CG Group were significantly higher than those in the SG Group (P<0.05). Meanwhile,the contents of Cu,and Zn in the SG Group were significantly higher than those in the CG Group (P<0.05). On the 60th and 90th day of the experiment,the contents of Ca,Na,and K in the CG Group were not significantly different from those in the SG Group (P>0.05). However,the contents of Mg,Cu,Zn,Mn,and Fe in the SG Group were significantly higher than those in the CG Group (P<0.05). In conclusion,supplementation of mineral salt bricks in the warm season improved the body weight gain of yaks,nutrient digestibility of yaks foraging grass,rumen fermentation of yaks,metabolism of mineral elements in blood and deposition of mineral elements in hair. Additionally,mineral salt bricks also enhanced the mineral nutrition balance for grazing yaks during the warm season to more fully realize the growth potential of yaks.