Effect Of Rumen-protected Methionine On Growth Performance,Nutrient Digestion And Rumen Microorganisms Of Yak

The purpose of this experiment was to study the effects of diet supplemented with different level rumen-protected methionine(RP-Met)on growth performance,nutrient apparent digestibility,blood prarmeter and rumen microbes of Maiwa yak,to provide basic data for rational use of RP-Met,and provide a theoretival basis for the development and efficient utilization of yak feed resources.Twenty-four healthy yaks with an initial body weight of(252.79 ± 15.95 kg)were randomly divided into four groups,with six yaks in each group,yaks in each group were respectively fed total mixed rations supplemented with RP-Met at the level of 0 g/d(CON),5 g/d(RPM1),10 g/d(RPM2),15 g/d(RPM3).The experiment lasted for 80 d,with10 d of adaptation period and 70 d of trial period.Trial 1: Effects of RP-Met on growth performance,nutrient apparent digestibility,and serum parameters of yakThis experiment was to investigate the effects of different supplemented level of RP-Met in diets on growth performance,nutrient apparent digestibility,serum biochemical parameters and serum free amino acids of yak.The results showed as follows:(1)In the term of growth performance,with the increase of dietary RP-Met supplemented levels,the average daily gain(ADG)increased linearly with the increase of the supplemented levels(P < 0.05);(2)There is no significant effect on nutrients apparent digestibility of yak by supplemented RP-Met in diets(P > 0.05);(3)In terms of economic benefit,with the increase of dietary RP-Met supplemented levels,the growth benefit of yak showed a tendency increased linearly(P = 0.09);(4)The content of ALP in the serum increased linearly with the increase of the supplemented levels(P< 0.05),RPM3 group was significantly higher than other treatment groups(P < 0.05),the content of GLU showed a tendency increased linearly(P = 0.09),the content of MDA showed quadratic curve(P < 0.05),firstly increased and then decreased,RPM3 group was significantly higher than other treatment groops(P < 0.05).(5)The Met in the serum show a tendency increased linearly with the increased of the supplemented levels(P = 0.051),and the RPM3 group was tend to higher than CON group and RPM1(P = 0.078).In summary,the supplementation of RP-Met in diet can improve the performance of yaks,significantly improve the utilization efficiency of amino acids.In conclusion,the RP-Met supplemental 15 g/d of yak increased the performance and economic benefit.Trial 2: Effects of RP-Met on rumen fermentation and metagenomics of yakThis experiment was to investigate the effects of different supplemented level of RP-Met in diets on rumen fermentation parameters,rumen microbial species,microbial carbohydrate active enzyme(CAZy)and protein metabolic composition and relative abundance of yak.In the result,the content of MCP in the rumen increased linearly with the increase of the supplemented level(P < 0.05),RPM3 group was significantly higher than other treatment groups(P < 0.05),the value of acetate to propionate ratio in RPM2 grouop was significantly lower than those in CON group and RPM1 group(P< 0.05).At the phylum level,the relative abundance of Lentisphaerae showed quadratic curve,firstly decreased and then increased(P < 0.05),RPM1 group was significantly higher than other treatment groups(P < 0.05).At the genus level,the relative abundance of Prevotella in the rumen decreased linearly with the increased of the supplemented RP-Met level(P < 0.05),RPM2 and RPM3 group was trend higher than CON group and RPM1 group(P = 0.068).The supplementation of RP-Met had no singnificant effect on the the relative abundance of rumen CAZy enzymes and functional protenis in yaks.In conclusion,the supplemention of RP-Met in diet does not affect the composition and function of rumen microorganisms,and the supplementation of 10 g/d and 15 g/d can optimize the structure and function of rumen microorganisms in yaks.Summary: Overall consideration,under this condition of experiment,supplementation of 15 g/d RP-Met in the diet was recommendation to improve utilization efficiency of amino acids and economic benefit.