Study On The Application Effect Of Replacing 50% Soybean Meal With Cotton Meal And Adding Compound Nutrition Additive In Yak Diet

As a unique plateau animal breed,the yak is the main economic source of herdsmen in some areas of our country.With the rapid development of the livestock and poultry breeding industry,the shortage of high-quality protein resources,high feed cost,low growth rate and low slaughter performance of the yak,seriously affect the development of feeding for the yak and economic benefits for the livestock farmers.Has gradually become the important factor to restrict the development of stock raising in our country.This experiment was conducted to study the effects of replacing 50%soybean meal with cotton meal and the addition of compound nutritionalcomplex additives in diet on growth performance,serum biochemical indexes,rumen fermentation parameters and microflora composition of yaks,so as to provide reference for the application of cotton meal and compound nutritional additive in yak diet.A 2X2 factor design was used in this study.The two factors were additive and cotton meal,and the two levels were whether 50%soybean meal was replaced by cotton meal cottonmeal replaced 50%soybean meal in the diet and whether the compound nutritive adiitive were added in diet.40 healthy male yaks（160.9±17.5kg）aged about 3 years old were randomly divided into one of 4 treatment groups with 10 replicates in each group and 1 yak per replicate.（D1:diet with cotton meal replacing 50%soybean meal with compound nutritional additive added,D2:diet with whole soybean meal with compound nutritional additive added D3:diet with cotton meal replacing 50%soybean meal without compound nutritional additive added,D4:Whole soybean meal diet withoutcompound nutritional additive added）,It took 10 d for adaptation and 90 d for the experiment.The results are as follows:1)Growth performance:substitution 50%soybean meal with cotton meal extremely significantly increased ADFI（P<0.01）and significantly increased ADG（P<0.05）of the yaks,but had no significant effect on F/G（P>0.05）;The ADFI and ADG of were elevated by supplementing compound nutritional additivein diet,but the difference was not significant（P>0.05）,and the F/G was not significantly affected（P>0.05）.The interaction of these two factors had no significant effectin ADFI,ADG and F/G of yaks（P>0.05）.2)Serum biochemical indices:the replacement of 50%soybean meal with cotton meal significantly increased the serum TC content（P<0.05）;The compound nutritional additive supplementation significantly decreased the UN content（P<0.01）,and the ALT content（P<0.05）;The interaction of the two factors had significant effects on serum TG content（P<0.05）,and the TG content of D1 group was significantly higher than that of D2,D3 and D4 groups（P<0.05）.There were no significant differences in other indexes（P>0.05）.3)Dietary cotton meal replacing 50%soybean meal significantly increased serum IGF-1 content（P<0.01）;Dietary compound nutritional additive significantly increased the contents of INS and GH in serum（P<0.05）,and extremely significantly increased the serum IGF-1（P<0.01）;The interaction of the two factors had no significant effectsin serum INS,GH and IGF-1 contents（P>0.05）.4)There were no significant effects on rumen MCP and NH₃-N concentrations of compound nutritional additives and cotton meal replacing 50%soybean meal and the interaction of the two factors（P>0.05）.replacing 50%soybean meal with cotton meal had no significant effect on rumen VFA（P>0.05）.Dietary compound nutritive additive significantly increased rumen propionic acid and TVFA（P<0.05）,and extremely significantly increased rumen butyric acid content（P<0.01）;The interaction of the two factors had significant effects on valerate and acetic acid/propionic acid in rumen（P<0.05）,and had extremely significant effects on isobutyric acid content（P<0.01）.The valerate in group D4 was significantly higher than that in D1,D2 and D3（P<0.05）,and the acetic acid/propionic acid in D4 was significantly lower than that in D2 and D3（P<0.05）.isobutyric acid content in group D1 was significantly higher than that in D2 and D3 groups（P<0.01）.5)The Ace,Chao Shannon and Simpson index of rumen microflora of yaks were not significantly affected by compound nutritional additive and cotton meal replacing50%soybean meal and the interaction of the two factors（P>0.05）.The relative abundance of Firmicutes and Bacteroidetes were both over 25%,which were the dominant groups of rumen microorganisms in all experimental groups.Prevotella＿1,Rikenellaceae＿RC9＿gut＿group,unclassified Norank＿f＿F802 were the dominant bacteria in each experimental group.The dominant flora at phylum and genus levels had no significant difference（P>0.05）.In conclusion,substituting50%soybean meal with cotton meal diet and the addition of compound nutritional additive in yak diet d improve the growth performance,optimize the serum biochemical indexes,and change the rumen fermentation parameters of yak,cotton meal can be used to replace 50%soybean meal in yak diet,and complex nutritional additives can be added,providing the possibility for further application of cotton meal and compound nutritional additive in yak diet.