Effects Of Dietary Different N/S Ratio On Meat Quality Of Tibetan Lamb

The alpine pasture area of Qinghai Province has a long dry grass period,low forage yield,and lack of nutrient supply in the grassland,which results in slow growth and low survival rate of lambs.The effects of nitrogen and sulfur ratio in diet on the quality of Tibetan lambs meat were studied by early weaning and precise supplementary feeding to accelerate the growth and survival rate of Tibetan lambs.This research adopts the single factor experiment design,the choice of similar weight,60 days of age in good health 150 weaned Tibetan lambs,the male and female halves were randomly divided into 5 groups(Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ),30 in each group,with five kinds of diets with different ratios of nitrogen and sulfur(4.5:1,6:1,7.5:1,9:1,10.5:1)were fed in limited amounts.The effects of different nitrogen and sulfur ratios on the quality of Tibetan lamb meat were deeply explored in the tests of the longest dorsal muscle at 180 days old for the determination of the muscle nutritional content,muscle tissue morphology,muscle long-chain fatty acids and muscle differential proteins,providing a theoretical basis for the determination of nitrogen and sulfur ratios in Tibetan lamb diet.The results were as follows:1.The effects of different dietary nitrogen-sulfur ratios on the nutritional content of longest muscle in lamb’s back and the determination of long-chain fatty acid content showed that there was no significant difference in the moisture content of sheep muscle between the five groups(P>0.05),group Ⅲ> groupⅤ> groupⅠ> group Ⅱ> groupⅣ;Crude fat content was not significantly different(P>0.05),group Ⅱ> groupⅤ> groupⅣ> groupⅠ> group Ⅲ;The crude protein content was highest in group Ⅱand the lowest in group IV,GroupⅡ and GroupsⅤwere significantly higher than those of groupⅠand Ⅲ(P< 0.05),and those of groupⅠand Ⅲ were significantly higher than Ⅳ(P < 0.05);the ash contentⅡwas the lowest,Ⅲ was the highest,and the difference was significant(P < 0.05);The content of various types of long-chain fatty acids in groupⅡwas higher than that in the group III,and the differences were significant(P<0.05).The content differences among the other groups were not significant(P>0.05),but the content in the group III was the lowest.2.The measurement results of different dietary nitrogen-sulfur ratios on the muscle fibers of the lamb’s longest muscle in Tibetan lambs showed that the muscle fiber diameter was the largest in groupⅡand the shortest in group Ⅲ,and the differences were significant in each group(P < 0.05),groupⅠ,Ⅳ,Ⅴ diameter less than groupⅡ,the difference was not significant;muscle fiber density was the smallest in group Ⅱ,the largest in group Ⅲ,the difference was significant.3.Determination of edible quality of Tibetan lamb’s longest back muscle with different nitrogen and sulfur ratios in diet results show that the p H,chromaticity,tenderness,hydraulic and cooked meat rate were all better in group Ⅲ,the difference in p H was significant(P < 0.05),the rest of the indicators were not significantly different(P > 0.05).4.Determination of differential proteins of Tibetan lamb’s longest back muscle with different nitrogen and sulfur ratios in diet results show that A(9:1),B(7.5:1),and C(6:1)groups identified 171 differential proteins,The results of subcellular localization analysis showed that the differential proteins were mainly located in cytoplasm,nucleus and mitochondria;The GO analysis results show that the results were based on analysis of the GO in the cell components,differential proteins were mainly enriched in mitochondria and cytoplasm,based on molecular functions,differential proteins were mainly expressed in redox,transport activity,and ion transmembrane transport protein activity Enrichment status,based on biological processes,differential proteins were mainly enriched during redox processes and protein phosphorylation;KEGG analysis showed that differential proteins were enriched in metabolic pathway and oxidative phosphorylation pathway.Among them,Cytochrome c oxidase subunit 5A,Cytochrome c domain-containing protein,Cytochrome b-c1 complex subunit 6,Cytochrome c oxidase subunit,NADH dehydrogenase [ubiquinone] 1 subunit C2 and other proteins were relatively active in the lamb longest muscle of Tibetan lambs with different nitrogen and sulfur ratios.The results showed that when the dietary nitrogen-sulfur ratio was 6:1,the content of various nutrients in the muscle of Tibetan lambs were higher.When the dietary nitrogen-sulfur ratio was 7.5:1,the various edible qualities of Tibetan lamb muscles were better.Therefore,the optimal n/s ratio for early-weaning Tibetan lambs should be 6:1 ~ 7.5:1.