Comparative Study On The Growth Performance,rumen Microecology And Meat Quality Of Different Production Types Of Sheep Grazed On Sainfoin Pasture

The selection of livestock species suitable for grazing is an ideal way to achieve efficient use of Sainfoin and improve the quality and efficiency of livestock production,which is an inevitable requirement for the connotative development of its stubble grazing mode.Alpine Merino sheep is a new breed of grazing-type wool and meat production,and it is unknown whether it can achieve its high-quality production performance in semi-arid areas.In this study,we proposed to conduct a comparative study on the production performance,rumen microecology and meat quality of sainfoin pasture under grazing and supplemental feeding conditions,with the aim of providing theoretical and technical support for the grazing production of Alpine Merino Sheep in rainfed agricultural areas.Twelve male lambs of the Alpine Merino Sheep（AM;BW:24.10±2.25 kg）and Small-tailed Han Sheep（SM;BW:23.16±1.96kg）male lambs in good health and similar body condition were selected as experimental animals for a 115d trial with Sainfoin second crop grazing and supplemental feeding.The experiment was conducted for 115 d with grazing of sainfoin pasture and supplemental feeding.The results of the study showed that:1.There was no significant difference（P>0.05）in final body weight（40.22 kg vs.38.30 kg）and mean daily gain（142.05 g vs.137.73 g）between AM and SM under grazing and supplementary feeding conditions on Sainfoin Stubble;Ruminal fluid pH（7.31 vs.7.63）,NH₃-N（18.21 mg/dL vs.16.83 mg/dL）,and each component of the rumen environment volatile acids acetic（71.80%vs.71.03%）,propionic（15.00%vs.15.62%）,isobutyric（1.33%vs.1.26%）,butyric（10.14%vs.9.93%）,isovaleric（1.14%vs.1.08%）,valeric（0.99%vs.1.09%）and acetic/propionic（4.85 vs.4.64）and total volatile fatty acids（40.12 mmol/L vs.34.29 mmol/L）were not significantly different（P>0.05）.2.The ACE,Chao1 and Shannon indexes were significantly higher in AM than in SM（P<0.01）,and the number of OTUs was also significantly higher in AM than in SM（P<0.01）.In terms of relative abundance at the level of rumen microflora level,Synergistota was significantly higher than SM（P<0.01）and Proteobacteria was significantly lower than SM（P<0.05）in AM.In terms of relative abundance at the genus level,Prevotella and Succinivibrio were significantly lower than SM（P<0.05）,while Prevotellaceae＿UCG＿003 was significantly higher than SM（P<0.05）.The correlation analysis revealed that the relative abundance of Prevotella in AM rumen was significantly negatively correlated with acetic,the relative abundance of unclassified＿Selenomonadaceae was significantly positively correlated with acetic,the relative abundance of Rikenellaceae＿RC9＿gut＿group was significantly positively correlated with propionic,the relative abundance of Butyrivibrio was significantly negatively correlated with isovaleric,and the relative abundance of Succiniclasticum was significantly positively correlated with NH₃-N,and the relative abundance of Succinivibrio was significantly and positively correlated with isovaleric.The relative abundance of Prevotella in SM rumen was significantly and negatively correlated with valeric;the relative abundance of Succinivibrio was significantly and negatively correlated with pH,the relative abundance of Rikenellaceae＿RC9＿gut＿group was significantly and positively correlated with total volatile fatty acids,the relative abundance of Succinivibrio was significantly and positively correlated with pH and significantly and negatively correlated with isobutyric acid and valeric acid,and the relative abundance of Prevotella＿UCG＿003 was significantly and negatively correlated with pH and significantly and positively correlated with valeric acid.KEGG functional predictions showed that the relative abundance of functional genes for microbial metabolism in diverse environment as well as carbon metabolism was significantly higher（P<0.05）and the relative abundance of functional genes for biosynthesis of secondary metabolite,biosynthesis of antibiotics and biosynthesis of amino acid was lower（P<0.05）in AM compared to SM.3.There was no significant difference between AM and SM in hot carcass weight（15.70 kg and 15.95 kg）（P>0.05）;there was a tendency for AM to have better eye muscle area and marbling than SM;carcass grading of sheep showed no significant difference between AM and SM in the weight and proportion of primary,secondary and tertiary meat（P>0.05）.The differences in pH,shear force,cooked meat percentage,drip loss and meat color between AM and SM groups were not significant（P>0.05）,and the crude fat content of the longest back muscle was significantly higher in AM than in SM（P<0.05）.The proportions of C12:0,C13:0,C14:0,C15:0,C16:0,C17:0,C18:1n9t,C20:1,C18:3n3,C22:1n9 and saturated fatty acids were significantly higher in AM lamb than in SM（P<0.05）,and the proportions of C18:2n6c,C20:3n3,C20:5n3,C18:1n9c and the ratio of n-6/n-3 PUFA,C18:2n-6/C18:3n-3,Polyunsaturated fatty acids/saturated fatty acids and Monounsaturated fatty acids/saturated fatty acids were significantly lower in AM than in SM（P<0.05）.atherogenic index,thrombogenic index were significantly lower in SM muscle than in AM（P<0.05）.In addition,the malondialdehyde content in raw meat was significantly higher in SM than in AM when left for 7 days（P<0.05）.In conclusion,Alpine Merino sheep,as a sheep breed for grazing farming in alpine areas,were introduced to semi-arid rainfed agricultural areas and showed excellent growth performance under grazing and supplemental feeding conditions in stubble pastures.Based on their ruminal microecology and meat quality parameters,it is shown that Alpine Merino sheep can be studied in depth as a sheep selection breed for local grass-fed production to achieve efficient use of grass and production of high quality livestock products.