Effect Of Low Protein Diet On The Meat Quality Of Xiangdong Black Goats

In this study,two diets with different protein levels were fed to explore the effect of low protein diet on the quality of goat meat,so as to provide theoretical reference for ruminant research and production practice.In this experiment,24 female goats in the growth period of about 19.6 ± 3.55 kg weighing about 8 months old were randomly divided into two groups,namely the normal protein group(crude protein content 10.77%)and the low protein group(crude protein The content is 5.22%).Each group contained 12 goats,and each goat raised in a single cage.All goats were dewormed before the experiment,with a test period of 70 days,including a pre-feeding period of 25 days and a normal feeding period of 45 days.Blood samples at day1,day4,day7,day16,and day36 was collected by venipuncture from jugular vein during the normal feeding period,and the serum amino acid and fatty acid compositions were measured.Slaughter was carried out at the end of the normal feeding phase test,and the right side of the trunk longissimus dorsi,vastus lateralis and semitendinosus muscles were collected.The contents of rice,amino acids and fatty acids as well as the gene expression of skeletal muscle growth factor were determined.The results showed that:(1)Effects on the growth performance and carcass quality of Xiangdong black goats:Low-protein diet had no difference on the initial body weight,final body weight,average daily weight gain,total weight gain,etc.(P> 0.05)However,the total weight gain and average daily weight gain of the low protein diet group showed negative values;the feed conversion rate of the low protein diet group also showed negative values.The feed conversion rate of lowprotein group had the trend to be decreased(P= 0.09).The low-protein diet increased the L*value of meat color of the muscles of the longest dorsal muscle after slaughter(P< 0.05),but did not affect the p H value of the muscles of the longest dorsal muscle,eye muscle area,water loss rate,slaughter rate,carcass weight and other indicators(P> 0.05).(2)Effect of low-protein diet on amino acid and fatty acid composition in blood and skeletal muscle of Xiangdong Black Goat.Low-protein diet significantly(P <0.05)reduced the content of serine,methionine and lysine in blood.Low protein diets reduce the content of valine,leucine,lysine,phenylalanine,and total essential amino acids in lateral femoral muscle(P <0.05)and glutamic acid in semitendon muscle(P <0.05).Low protein diets significantly(P <0.05)reduced the content of eicosadienoic acid and docosaenoic acid in the semitendinosus muscle and polyunsaturated fatty acids,oleic acid,and arachidonic acid in the lateral femoral muscle,Low-protein diets also significantly(P <0.05)reduced oleic acid content in the longest muscles of the back.(3)Effect on the m RNA expression of growth regulatory factorgenes: low-protein diet down-regulated the expression of Myf6 gene in the longissimus muscle(P< 0.05),but had no effects on the m RNA expression of My OD,Myf5,My OZ1,My LPF,Six1 and other genes(P>0.05).In semitendinosus muscle,the m RNA levels of My OD and My LPF were decreased in the low-protein group(P< 0.05),but the m RNA expression of Myf5,Myf6,My OZ1 and Six-1were not changed(P> 0.05).In the vastus lateralis muscle,low-protein diet didn’t change the m RNA expression of My OD,Myf5,Myf6,My OZ1,My LPF,six-1 and other genes(P> 0.05).In summary,(1)reducing the crude protein level in the diet of Xiangdong Black Goat does not affect its growth performance,but it will increase the L * value of the meat color 24 hours after slaughter,and reduce the glutamic acid in the lateral femoral muscle and semitendon Content,while reducing the content of polyunsaturated fatty acids in the lateral femoral muscle.(2)Low-protein diets down-regulated the expression of the MYF5 gene of the longest muscle of the back and the My OD and My LPF genes of the semitendinosus muscle,hindering the growth of skeletal muscle fibers.