Effects of different energy levels diets on growth performance,rumen metabolic parameters and economic benefits of yaks
This experiment was conducted to investigate the effects of energy level on growth performance,rumen metabolic parameters and economic benefits of yaks.A total of 120 male yaks of 36 months of age with similar body weight(198.46±18.67 kg)were divided into 3 groups with 8 replicates per group and 5 yaks per replicate.The diets were supplemented with(9.41 MJ/kg),medium(10.44 MJ/kg)and high(11.37 MJ/kg)energy diets.The experiment consisted of 2 weeks of preliminary experiment and 13 weeks of formal experiment.The results showed as follows:energy level had significant effect on male yak growth,FBW in medium and high energy groups was significantly increased by 5.87% and 5.03% compared with that in low energy group(P＜0.05);The total weight gain and ADG were significantly increased by 30.26% and 28.02% (P＜0.05),respectively.ADFI was significantly decreased by 5.62% and 12.13% (P＜0.05),respectively.The ratio of feed to gain was significantly decreased by 27.39% and 31.35%,respectively(P＜0.05).Rumen pH in high energy group was significantly lower than that in low energy and medium energy groups(P＜0.05).The rumen NH3-N levels in the high-energy group of male yaks were significantly higher than those in the low-energy and medium energy groups(P＜0.01);The rumen MCP content of male yaks in the medium energy group was significantly higher than that in the low energy and high energy groups(P＜0.05).With the increase of dietary energy level,the acetic acid content in the rumen of male yaks significantly decreased linearly(P＜0.01),and the propionic acid content significantly increased linearly(P＜0.01).The contents of butyric acid,valeric acid,isobutyric acid,isovaleric acid and total VFA in medium and high energy groups were significantly higher than those in low energy group(P＜0.05).The feed unit prices of each group were 1.79,2.47 and 3.16 yuan/kg,respectively.Combined with feed intake,the feed cost was 1101.14,1434.03 and 1708.11 yuan per head,respectively.The price of live cattle was 34.87 yuan,and the gross profit of each group in this experiment was 831.36,1078.70 and 765.92 yuan,respectively.In conclusion,the energy level had significant effects on the growth and rumen metabolism parameters of yak calves,and the growth performance and gross profit of male yaks in the medium energy group were the best.
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