Fitting of univariate and multivariate regression equations to predict weight of fat-tail and carcass parts from physical characteristics

Awareness of the animal carcass parts and fat-tail weight، in live animal can help to select and determine the optimum slaughtering age. For this purpose، live weight، phenotypic dimension of fat-tail as well as back fat thickness and eye muscle area were measured by ultrasound in 38 Moghani male lambs. Then، all sheep were slaughtered and after removal of their internal organs، carcasses were stored in cold temperatures for 24 hours at 4 °C. Then، each carcass was divided into two equal parts. Right sides of each carcass were cut in to، leg، shoulder، brisket، rack and neck and were weighed. Data analysis showed that body weight alone explains the 0. 85، 0. 43، 0. 56، 0. 70، 0. 52 and 0. 50 of the variations of half-carcasses، neck، shoulder، leg، rack and brisket، respectively. Residual standard deviation (RSD) in these equations was also very low and range from 0. 10 to 0. 50. Coefficient of determination of all equations were increased with adding variables measured by ultrasound in multivariate models except for neck weight، and were increased to 0. 86، 0. 43، 0. 59، 0. 73، 0. 58 and 0. 57، respectively. Coefficient of determination was 0. 78 for estimated fat-tail weight with the use of circumference، width and diameter of the fat-tail in step wise procedure. While، coefficient of determination with using full model increased to 0. 81. Based on results of this research، prediction of carcass cuts and fat tail weight is possible with high accuracy by using some phenotypic and ultrasound measurements.