| Based on the production practice of the experimental area,the present study was carried out including of three aspects to explore the sheep grazing production mode of efficient utilization of cultivated grassland in the loess hilly-gully region of central Gansu,and the response mechanism of mutton sheep production performance and meat qualities.In experiment 1,two sheep breeds,Hu sheep and small-tailed Han sheep,were used for grazing comparison test,and their production performances and meat qualities were measured to select the sheep breed more suitable for grazing in the agricultural areas.In experiment 2,the rotation grazing experiment of more suitable breed of mutton sheep was carried out under different grazing intensities(light grazing LG,1.19 sheep unit / mu;medium grazing MG,1.58 sheep unit / mu;heavy grazing HG,2.39 sheep unit / mu),and the growth performance,slaughtering performance and meat quality were monitored;In experiment 3,the fattening performance and meat quality parameters of mutton sheep fed in two different ways were compared under suitable grazing conditions(MG).The research results showed that:1.Longzhong sainfoin grassland was harvested and stored in the first stubble and grazed by sheep in the second stubble.Under the grazing condition for three months without supplementary feeding,the average daily gain of small-tailed Han sheep can reach 100 g,the dressing percentage can reach 43%,and relatively high-quality mutton can also be produced.Under the present experimental conditions,there was no significant difference in crude protein 、water and ether extract between Hu sheep and small-tailed Han sheep(P > 0.05).The contents of glutamate,alanine,aspartic acid,leucine and lysine in longissimus dorsi muscle of Hu sheep were significantly higher than those of small-tailed Han sheep(P < 0.05),while the contents of valine was lower(P < 0.05),and there was no significant difference in the contents of other amino acids(P > 0.05).The contents of non-essential amino acid(NEAA,58.89%),functional amino acids(31.37%)and delicate amino acids(53.35%)in Hu sheep were also higher than those in small tailed Han sheep,while essential amino acid(EAA,41.11%)and E/N(0.7)were higher in small tailed Han sheep.There was no significant difference in the characteristic parameters of the longissimus dorsi muscle between Hu sheep and small tailed Han sheep(P > 0.05).2.The average daily gain and average daily gain weight of unit area of mutton sheep grazing(MG group)on the stubble of sainfoin grassland are 191.46 g and 1254.10g/hm2 respectively,which were significantly higher than HG group(P < 0.05),but no significant difference with LG Group(P > 0.05).Different grazing intensities have significant effects on the ether extract content of lamb muscle(P < 0.05).3.Different feeding methods(grazing condition-MG group vs house feeding)had significant effects on the meat color L* of mutton sheep(P < 0.05).The L* of lambs under grazing condition was 36.67,significantly lower than these under house feeding condition,which was 44.18.Meat color L* and lipid oxidation degree of raw meat were significantly affected by the interaction of feeding mode and time(P < 0.01).The feeding mode had significant effects on the content of total phenolic compounds and Fe2+(FRAP)in the longissimus dorsi muscle of mutton sheep(P < 0.05).MG group α-tocopherol content was 3.01 μg/g,which was significantly higher than that in the house feeding group(0.37 μg/g)(P < 0.01).C19:0、docosahexaenoic acid(C22:6n3)、eicosapentaenoic acid(C20:5n3)and n-3 polyunsaturated fatty acids contents of muscle were significantly affected by feeding methods(P < 0.01).The content of n-3polyunsaturated fatty acids in muscle of lambs in MG group was 176.64 mg/100 g,whichwas significantly higher than house feeding group(65.81 mg/100g).And α-Linolenic acid(C18:3n3)content had a tendency to be higher than that in the house feeding group(P = 0.05).The content of PUFA in MG group was 800.04 mg/100 g,which was 3.2% higher than house feeding group(775.04 mg/100g).From day 0 to day3 and from day 3 to day 6,the content of thiobarbituric acid reactants(TBARS)in lamb meat of house feeding group further increased,while the TBARS value in MG group tended to be stable;In addition,the content of malondialdehyde(MDA)in muscle of lambs in MG group was 0.81 mg/kg,which was significantly lower than house feeding group(1.46 mg/kg)(P < 0.05).The content of n-6 PUFA/n-3 PUFA in mutton sheep was significantly different under different feeding methods,and the content of n-6PUFA/n-3 PUFA in MG group was significantly lower than that in house feeding group after 6 days of refrigeration(P < 0.05).The atherogenic index and thrombogenic index in mutton were 0.47 and 1.86 respectively under grazing conditions,while those in house feeding group were 0.65 and 3.53.The results indicated that grazing can reduce the atherogenic index and thrombogenic index in the muscle of mutton sheep.To sum up,the 1.58 sheep unit / mu may be suitable for small tailed Han sheep grazing on sainfoin stubble land in Central Gansu.Under this production mode,mutton unsaturated acids fatty and the content of α-tocopherol and other antioxidant substances was also higher.And more,the antioxidant performances of mutton were also improved,which can slow down the lipid oxidation degree of mutton. |
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