| Subacute rumen acidosis(SARA)is a common nutritional metabolic disease in high-yielding ruminants.Among the individuals,there were significant differences in the risk of SARA due to different levels of roughage in the diet and variation among individual animals.Different SARA risk phenotypes cause rumen fermentation and rumen bacterial structure and content to change,especially the content of cellulolytic bacteria sensitive to pH in the rumen will decrease with the increase of SARA risk.Different fatty acids(especially OBCFA)contained in different types of bacteria species in the rumen and the hydrogenation of Butyrivibrio fibrisolvens on UFA in the rumen will eventually lead to the changes in the composition of the rumen contents and muscles fatty acids.However,at present,there are few studies on the interaction between rumen fermentation,rumen microflora,rumen contents and muscle fatty acid composition in sheep,and further researches are needed.Therefore,the main purpose of this study was to find out the individuals with different SARA risks through the differences between animal individuals and different dietary FNDF levels,which provides a theoretical basis and experimental basis for exploring the effect of SARA risk on the rumen health and muscle fatty acid composition of sheep.The first experience aimed to investigate the differences in production performance,rumen fermentation,rumen microflora,rumen contents and muscle fatty acid composition of Hu sheep with different SARA phenotypes.Forty-eight Hu lambs with the similar weights and ages were selected for this experiment and reared in individual units(0.75 m × 1.5 m × 1.0 m).After the transition for 14 days and adamption for 7days,the formal period will last for 63 days continously.All lambs were fed an identical diet.After the formal period,all animals were slaughtered through jugular vein bloodletting.Rumen fluid,rumen contents,and the longissimus dorsi were collected.According to the number of cellulolytic bacteria been sentive to the rumen pH,the lambs with the most or least cellulolytic bacteria were classified into lower SARA risk groups(LSR,n = 10)or higher SARA risk groups(HSR,n = 10),respectively.The results showed that:1.Rumen cellulolytic bacteria Fibrobacter succinogenes and Butyrivibrio fibrisolvens have a positive correlation with the ratio of acetate in the rumen,and a negative correlation with the ratio of propionate and valerate.There is no difference in the production performance(P > 0.05).The number of main amylolytic bacteria and cellulolytic bacteria in the HSR group were lower than those in the LSR group(P <0.05);there was no difference in TVFA content between the two groups(P > 0.05),but the ratio of acetate in the HSR group was lower(P = 0.018),the ratio of lactate(P = 0.042)and valerate(P = 0.002)was higeher.2.Compared to the LSR group,the proportions of C12:0,C14:0 and C16:0 in the rumen contents in the HSR group were lower(P < 0.05),the proportion of PUFA increased significantly(P < 0.05),the proportion of CLA decreased significantly(P = 0.011),the OBCFA ratio decreased significantly(P < 0.05);3.3.In the HSR group,the C17: 0 ratio in the muscle of Hu sheep increased significantly(P = 0.033),and the CLA ratio decreased significantly(P = 0.046),but there was no difference in the OBCFA(P > 0.05).The second experiment aimed to investigate the effects of dietary FNDF levels on rumen fermentation,rumen microflora,rumen contents,and the composition of muscle fatty acid of Hu sheepThirty male lambs purchased from Sanyang Jinyuan Agriculture and Animal Husbandry Co.,Ltd.,Jinchang City,Gansu Province were selected,and raised in a single pen.The experiment was designed using a single factor.Wheat straw was used as the source of dietary FNDF and the experimental animals were divided into 17%(H-FNDF,n = 10),12%(M-FNDF,n = 10),and 7%(L-FNDF,n = 10)according to the FNDF addition level.The entire trial period includes a 14-day transition period,a 7-day adaptation period and a 63-day formal period.After the formal period,slaughter was carried out and samples were collected.The results showed that:1.There was no significant difference in the effect of dietary FNDF level on TVFA in rumen fluid(P> 0.05),but with the decrease of dietary FNDF level,the proportion of acetate and acetate to propionate decreased significantly(P < 0.05),but the proportions of propionate and valerate decreased significantly(P < 0.05);2.With the level of FNDF in diet decreasing,the content of Streptococcus bovis significantly increased(P = 0.009),Butyrivibrio fibrisolvens significantly decreased(P = 0.010);the OTU,ACE,Chao1 and Shannon indices decreased significantly(P < 0.05),but Simpson increased significantly(P < 0.05),which showed that rumen microbial diversity decreased;3.Decreasing the level of FNDF in the diet,the octadecane unsaturated fatty acids increased significantly(P < 0.05),the proportion of CLA decreased significantly(P < 0.05);the increase of the propionate as the synthetic precursors of OCFA led to the increase of C15:0 and C17:0 in muscle(P < 0.05).Decreasing the amount of Butyrivibrio fibrisolvens led to the decreased proportion of CLA in muscle(P < 0.05).In summary,feeding the fattening Hu sheep with the same diet,due to the different content of cellulolytic bacteria in the rumen of different individuals,there is a difference in the risk of SARA in animals,which in turn affects rumen fermentation,rumen contents and muscle fatty acid composition.Compared with the LSR group,the proportion of valerate and lactate in the rumen of Hu sheep in the HSR group increased,and the proportion of OBCFA in the rumen contents was lower,but the proportion of PUFA increased significantly.Decreasing the level of FNDF in the diet decreased the production of acetate in the rumen of Hu sheep,but increased the proportion of propionate,valerate and lactate,and increased the risk of SARA.At the same time,it decreased the microbial diversity in the rumen and decreased the cellulolytic bacteria in the rumen.Reducing the number of Butyrivibrio fibrisolvens increased the ratio of PUFA in rumen digesta and muscle,but decreased the ratio of CLA. |
