| Sixteen Qinchuan steers after fattening were used in this study and devided into 4 groups according to the age(Group:Ⅰ,Ⅱ,Ⅲ and Ⅳ.Age:18,24,30 and 36 age in month) were measured some items as follows:slaughter and carcass traits,phisical and chemical traits of muscle and histological properties of muscle fibre.The disparity in each trait were studied using variance analysis.Some detail analysis were made for the ralation of each trait,and predicted models to beef yield were established by regression analysis.The results were follows:Traits of carcass and meat ｑuality at the various age had significant differences(P＜0.05 or P＜0.01).Dressing percentage of steers of 18 and 24 age in month had significant differences(P＜0.05),but not in the steers of 24,30 and 36 age in month(P＞0.05).Net meat percentage,carcass percentage and meat-bone ratio at 4 age groups had not significant differences(P＞0.05),but these items of 24 age in month were the highest of the groups,amount to 45.24%,83.35% and 5.17.The difference of ralative values at the various age was not significant for muscle colour.Marbling between 18 and 24 or more 24 age in nonth had significant differences(P＜0.01),and the differences were not significand at the age of 24 and 30 months but at the age of 24 and 36 months,which indicated:fat deposition appeared after 24 age in month,and its ｑuality became higher with growth of age.Tenderness at 24 to 30 age in month was the best of the groups.The chemical analysis of muscles shown that the content of crude protein,oleic acid and unsaturated fatty acid inereased significantly with age (P＜0.05),but the content of water,crude fat,crude ash and amino acid in muscle had not significant differences at 4 age groups (P＞0.05).In addition,the diameter and area of muscle fibre increased significantly with age (P＜0.05).Phenotype correlation analysis shown that the traits of carcass and meat ｑuatily had very close relationship.There were significant relationship between live weight and other traits,including meat weight,carcass lenght,rear leg of carcass lenght,lion-muscle thickness,back-fat thickness,ribeye area,muscle colour,marbling,crude fat,the content of amino acid and histological traits of muscle fibre(P＜0.05 or P＜0.01),which suggested that live weight has influence on the proterties of carcass and meat ｑuality.The significant relationship between shear forc and marbling shown that the more rich marbling were,the more tender meat were,and the density of muscle fibre & the mount of muscle fibre indicated that the meat became older with decrease of them.Futhermore,marbling and fat thickness & ribeye area all had significant relationship (P＜0.05).The traits of carcass and meat ｑuality were classified respectively into six major characteristic groups which could reflect rather comprehensively the properties of carcass and meat ｑuality on the lever of threshold T=0.7997 and T=0.3461 by using cluster analysis.The typical traits were selected to make principal component analysis from major characteristic groups obtained by cluster,and about 87.76% total variance information was synthesized through the former 4 principal components which could provide some referance for multi-objective selection of the traits of carcass and meat ｑuality in Qinchuan Cattle.It was important that carcass were cut into different portion of meat whose percentage were used to evaluate beef performance in the product of high ｑuality beef.The studies shown that beef performance can be reflected by the retail cuts percentage which had significant relationship with carcass weight,meat weight,dressing percentage,net meat percentage and meat-bone ratio(P＜0.05 or P＜0.01).Six items,live weight,age,carcass weight,fat thickness,ribeye area and marbling were selected to predict the percentage of different retail cuts weight to carcass wetght.On the basis of this study,four eｑuations were obtained as follows:the percentage of superior ｑuality beef=13.4893-0.0244×live weight-0.1043×ribeye area+7.9556×fat thickness,... |
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