Effects of rumen lysine supplementation in diets with different protein levels on growth performance,nutrient digestion,serum biochemistry and rumen fermentation parameters in yaks
This experiment was conducted to investigate the effects of rumen-protected lysine(RPLys)supplementation in diets with different protein levels on growth performance,apparent nutrient digestibility,serum biochemical parameters and rumen fermentation parameters of yaks,in order to provide a technical reference for the application of RPLys in yak breeding.The experiment was conducted in a 2×3 factorial design with 2 ration protein levels(low protein ration:12.98%,high protein ration:14.99%)and 3 RPLys supplementation levels(0%,0.15%and 0.30%,dry matter basis).Thirty-six healthy male yaks with(237.00±35.96)kg,approximately 4 weeks old,were randomly divided into 6 groups(groupⅠ:low protein basal diet,group Ⅱ:low protein diet with 0.15%RPLys,group Ⅲ:low protein diet with 0.30%RPLys,group Ⅳ:high protein basal diet,groupⅤ:high protein diet with 0.15%RPLys,group Ⅵ:high protein diet with 0.30%RPLys).6 replicates per treatment group,1 yak per replicate.Pre-feeding period 7 days,regular feeding period 60 days.The results were as follows:(1)In the main effect of RPLys supplementation,the average daily gain was best in the 0.30%group,which was significantly higher than that in the basal diet group(P<0.05);in the interaction of the two factors,the highest value was found in the group Ⅲ,which was significantly higher than that in the group Ⅰ(P<0.05).In the main effect of RPLys supplementation,the feed to gain ratio was best in the 0.30%group,which was significantly lower than that in the basal diet group and the 0.15%group(P<0.05).In the interaction between the two factors,the ratio of feed to gain was best in the groupⅢ,which was significantly higher than that in the group Ⅰ(P<0.05).(2)In the main effect of protein level,the apparent digestibility of organic matter(OM)in the high protein diet group was significantly lower than that in the low protein diet group.Crude protein(CP),neutral detergent fiber(NDF)and acid detergent fiber(ADF)in the high protein diet group were significantly lower than those in the low protein diet group(P<0.01).In the interaction of the two factors,group Ⅲ was the best,and its OM,CP,NDF and ADF were significantly higher than those in group Ⅰ(P<0.05).(3)In the horizontal main effect of RPLys supplementation,the levels of alanine aminotransferase,glucose,urea,total protein,aspartate aminotransferase,albumin,globulin,creatinine,insulin(INS)and insulin-like growth factor 1(IGF-1)were significantly increased in the 0.15%and 0.30%groups compared with the basal diet group(P<0.05).The highest INS in groupⅥwas significantly higher than that in group Ⅰ(P<0.05).(4)In the main effect of RPLys supplementation level,free amino acids in the 0.15%and 0.30%groups were significantly lower than those in the basal diet group(P<0.05),and in the interaction of the two factors,groupⅤ was the lowest,which was significantly lower than that in group Ⅰ(P<0.05).(5)In the main effect of protein level,the contents of ammonia nitrogen and volatile fatty acids of each component in the high protein diet group were significantly higher than those in the low protein diet group,the ratio of acetic acid to propionic acid was significantly lower than that in the low protein diet group(P<0.05),and in the main effect of RPLys supplementation level,microbial protein in the 0.15%and 0.30%groups was significantly lower than that in the basal diet group(P<0.05).In conclusion that the addition of 0.30%RPLys in the low protein basal diet group had the best effect and could significantly improve the production performance of yaks.
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