Effects Of Adding Lysine To High-concentrate Diets On Performance And Rumen Fermentation Characteristics Of Hu Sheep

Lysine(Lys)is the first limiting amino acid in corn-soybean meal-based diets of ruminants,and therefore being the research focus of ruminant nutrition.This experiment took Hu sheep as the research object.Firstly,the optimal dosage of Lys was obtained by an in vitro test,and then the optimal dosage was selected to conduct an in vivo feeding test to explore the effects of Lys on the growth performance,nutrient digestion,serum biochemical indicators,rumen fermentation characteristics and rumen microbial community of Hu sheep.this study provided basic data for the application of Lys in high-concentrate diets of Hu sheep.The test is divided into two parts:Experiment 1: Effect of lysine supplementation level on in vitro rumen fermentation characteristics of high-concentrate diets.The purpose of the experiment was to explore the effects of different levels of Lys on the ruminal fermentation characteristics of high-concentrate diets with a grain-to-roughage ratio of 75:25.Five groups were set up in the experiment,0,0.05%,0.10%,0.20% and 0.40% Lys were added respectively,and each group had 5 repetitions,and no Lys was added as the control group.After 48 hours of in vitro fermentation,the fermentation broth was collected to detect the rumen fermentation parameters,and the multi-index comprehensive index(MFAEI)was used to comprehensively evaluate the addition effect.The results showed that: 1.The addition of Lys did not have a significant effect on gas production and organic matter digestion rate in all groups.The methane production in the 0.05%,0.10%,and 0.20% groups was significantly higher than that in the 0.40% group(P<0.05);2.The addition of Lys significantly increased the pH of the fermentation broth(P<0.05),and the contents of acetic acid,propionic acid,butyric acid,valeric acid and total volatile fatty acids(TVFA)in the0.05%,0.10% and 0.20% groups were significantly higher than 0.40 % group(P<0.05),the content of isovaleric acid in 0.10% and 0.20% groups was significantly higher than that in the control group and 0.40% group(P<0.05);3.MFAEI analysis found that adding 0.20% Lys could improve the rumen fermentation parameters in vitro best effect.the curve fitting of MFAEI at different Lys addition levels showed that the optimal Lys addition was 0.25%.Experiment 2: Effects of adding lysine to high-concentrate diets on growth performance,nutrient digestion,serum biochemical indicators,rumen fermentation characteristics and rumen microbial community composition of Hu sheep.The purpose of the experiment was to explore the effects of adding 0.25% Lys in highconcentrate diets with a grain-to-roughage ratio of 75:25 on the growth performance,nutrient digestion,serum biochemical indicators,rumen fermentation characteristics and rumen microbial community composition of Hu sheep.The experiment selected 24 healthy Hu sheep with similar weight(25±1.24 kg),and randomly divided them into two groups,12 in each group,and fed them with basal diet(control group)and basal diet+0.25% Lys(treatment group).The results showed that:(1)There were no significant differences(P > 0.05)observed in the daily weight gain,feed-to-gain ratio,crude protein,crude fat,neutral detergent fiber,acid detergent fiber,total protein,urea nitrogen,glucose,glutamic-pyruvic transaminase,and glutamic-oxaloacetic transaminase between the two groups.;(2)Rumen propionate,isobutyrate and the content and proportion of branched-chain volatile fatty acids were significantly higher than those in the control group(P<0.05),and the content of total volatile fatty acids was also higher than that in the control group(P<0.05);(3)There was no significant difference in α-diversity index(P>0.05);(4)The relative abundance of Bacteroidota,Prevotellaceae and Prevotella in the treatment group was significantly lower than that in the control group(P<0.05),while the relative abundances of Actinobacteriota,Desulfobacterota,Veillonellaceae and Dialister were significantly higher than those in the control group(P<0.05).In summary,adding 0.25% Lys had no significant effects on growth performance,nutrient digestion,and serum biochemical indicators of Hu sheep,but it could improve rumen fermentation,and alter the relative abundances of some bacterial genera.