| In order to study the effects of polyunsaturated fatty acid combination on digestion and metabolism,rumen fermentation parameters,blood biochemical indexes,antioxidant function,immune function,growth performance,and slaughter performance,meat quality,and the content of conjugated linoleic acid in body tissues of the Tan sheep through feeding experiments,digestion and metabolism experiments,and slaughter experiments.Twenty-seven male Tan sheep lambs with good body condition and about 4 months of age were selected and divided into 3 groups by completely random grouping design,named control group(basic diet)and test group Ⅰ(basic diet+1%Soybean oil+1%Schizochytrium powder),test group Ⅱ(basic diet+1%linseed oil+1%Schizochytrium powder),in which the oil combination replaced the same proportion of corn on the basis of dry matter.The pre-feeding period was 15 days,and the formal period was 60 days.All sheep were given free access to water during the experimental period.Experiment 1:Effects of polyunsaturated fatty acid combination on digestive metabolism and rumen fermentation function of Tan sheep.The results of digestion and metabolism showed that the combination of dietary polyunsaturated fatty acids had no significant effect on the apparent digestibility of nutrients,nitrogen metabolism and energy metabolism.The results of rumen fermentation function showed,after adding the combination of linseed oil and Schizochytrium powder for 60 days,the contents of NH3-N,TVA in the rumen of Tan sheep was extremely significantly higher than that of the control group(P<0.01),and significantly higher than that of adding the combination of soybean oil and Schizochytrium powder(P<0.05).Adding the combination of polyunsaturated fatty acids to the diet significantly increased the contents of C20:5n3(EPA)and C22:6n3(DHA)in the rumen of Tan sheep(P<0.05).This indicated that adding the combination of polyunsaturated fatty acids to the diet could increase the contents of NH3-N,EPA and DHA in the rumen,and also increase the content of TVA,a substrate for synthesizing CLA,without affecting the digestion and metabolism of Tan sheep.Experiment 2:Effects of polyunsaturated fatty acid combination on blood biochemical indexes,immune function and antioxidant capacity of Tan sheep.The results of blood biochemical indexes and immune function showed,the combination of linseed oil and Schizochytrium powder on the 60th day could significantly increase the contents of plasma total protein(TP),and the combination of linseed oil and Schizochytrium powder on the 30th day can significantly increase the contents of IgG and IgM(P<0.05).It showed that adding the combination of linseed oil and Schizochytrium powder can improve the immune function of Tan sheep.The results of antioxidant capacity showed that:on the 30th day,the concentration of Malondialdehyde(MDA)in the plasma by adding the combination of polyunsaturated fatty acids was extremely significantly lower than that of the control group(P<0.01).The concentration of T-SOD of adding the combination of soybean oil and Schizochytrium powder was significantly higher than that of the other two groups(P<0.05).It showed that the combination of polyunsaturated fatty acids can enhance the body’s ability of the Tan sheep to resist oxidative stress.Experiment 3:Effects of polyunsaturated fatty acid combination on production performance,meat quality and fatty acid composition of body tissue of Tan sheep.The production performance results showed that the average daily weight gain of Tan sheep with the combination of linseed oil and Schizochytrium powder,and the combination of soybean oil and Schizochytrium powder increased by 17.60%and 18.82%,respectively,compared with the control group,and the feed-to-weight ratio decreased by 2.60%and 2.60%.The daily weight gain was 17.35%and 18.62%higher than the control group,and the daily net profit was 0.36 yuan and 0.34 yuan higher,respectively.The results of meat quality showed that the net meat rate of Tan sheep carcass was extremely significantly higher in adding the combination of polyunsaturated fatty acids than the control group(P<0.01),and the combination of linseed oil and Schizochytrium powder was more significantly improved Slaughter rate(P<0.05)than the combination of soybean oil and Schizochytrium powder.The combination of adding polyunsaturated fatty acids significantly decreased the shear force and L*value of meat color(P<0.05),and significantly increased a*value of meat color(P<0.05).The marbling score of the two experimental groups was higher than that of the control group.The results indicated that adding the combination of polyunsaturated fatty acids in the diet did not affect the production performance of Tan sheep,and could improve economic efficiency,meat tenderness,and meat color,as well as make the distribution of intramuscular fat more abundant and uniform.In contrast,the combination of linseed oil and Schizochytrium powder could improve the slaughter performance of Tan sheep.The results of fatty acid composition of the longissimus dorsi muscle showed that adding the combination of polyunsaturated fatty acids significantly increased the contents of the total PUFA and DHA and the P/S ratio(polyunsaturated fatty acid/saturated fatty acid)in the longissimus dorsi muscle of Tan sheep(P<0.01),significantly increased the content of c9,t11CLA(P<0.05),and the combination of linseed oil and Schizochytrium powder had better effect.In addition,the combination of soybean oil and Schizochytrium powder significantly increased the content of n-3PUFA and LNA in the longissimus dorsi of Tan sheep(P<0.01),and the combination of adding linseed oil and Schizochytrium powder significantly increased the contents of n-3PUFA,LNA,EPA and TVA in the longissimus dorsi muscle of Tan sheep(P<0.05).The results of fatty acid composition of subcutaneous fat showed that adding the combination of polyunsaturated fatty acids significantly increased the content of t10,c12CLA of Tan sheep subcutaneous fat(P<0.01),significantly increased the content of DHA(P<0.05),and to a certain extent increased the content of c9,t11CLA,the combination effect of linseed oil and Schizochytrium powder was slightly better.The contents of TVA,t10,C18:1 in subcutaneous fat of tan sheep with soybean oil and Schizochytrium powder were extremely significant(P<0.01)and significantly higher than those with linseed oil and Schizochytrium powder(P<0.05).It indicated that adding the combination polyunsaturated fatty acid could increase the contents of TVA,CLA,DHA,EPA and other beneficial polyunsaturated fatty acids in the longissimus dorsi and subcutaneous fat of Tan sheep to varying degrees.All in all,adding a combination of polyunsaturated fatty acids to the diet can increase the NH3-N concentration and the EPA and DHA content in the rumen fluid of Tan sheep without affecting the digestion,metabolism and production performance of Tan sheep,and can also increase the content of TVA,the substrate for synthesis of CLA.The combination of linseed oil and Schizochytrium powder can improve the immune function of Tan sheep.Adding a combination of polyunsaturated fatty acids can enhance the body’s ability of the Tan sheep to resist oxidative stress,improve the clean meat rate,meat tenderness,and meat color of Tan sheep carcasses,and can also make the distribution of intramuscular fat more abundant and uniform.The combination of linseed oil and Schizochytrium powder can improve the slaughtering performance of Tan sheep.Adding a combination of polyunsaturated fatty acids can significantly increase the content of beneficial polyunsaturated fatty acids in body tissue,and the combination of linseed oil and Schizochytrium powder can increase the content of CLA in Tan sheep body tissue more than the combination of soybean oil and Schizochytrium powder.Therefore,in this experiment,the combination of linseed oil and Schizochytrium powder was the best for producing Tan mutton rich in CLA functionality. |
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