Métodos indiretos na predição da composição da carcaça de ovinos santa inês em crescimento

Abstract

The objective of this study was to evaluate in vivo and carcass measurements, as predictors of the physical and chemical compositions of the carcass; as well as listing the method and / or measurements that best fit the estimation of the composition of Santa Inês sheep carcasses in growth. For this purpose, (33; 39 e 42) male lambs, not castrated, Santa Inês, with average body weight (BW) of 19.43 ± 1.69 kg, and age between 6 and 7 months, fed a diet formulated to meet the nutritional requirements of sheep weighing 25 kg of body weight, aiming at an average daily gain of 200 g. The roughage was Tifton grass hay and the concentrate consisted of ground corn, soybean meal, mixture of the candy industry residue, gums and juices + corn gluten meal and mineral supplement. At the end of the experimental period, ultrasound measurements were performed to obtain the loin eye area - USM (Longissimus dorsi muscle) in the region between the 12th and 13th ribs; and biometric measurements. After fasting for 16 hours of solids, the animals were weighed to obtain body weight at slaughter (SBW), and slaughtered to obtain the carcass, which was weighed before and after cooling in a cold chamber at 4ºC, for 24 hours. At the end of the experimental period, ultrasound measurements were performed to obtain the loin eye area - USM (Longissimus dorsi muscle) in the region between the 12th and 13th ribs; and biometric measurements. After fasting for 16 hours of solids, the animals were weighed to obtain body weight at slaughter (SBW), and slaughtered to obtain the carcass, which was weighed before and after cooling in a cold chamber at 4ºC, for 24 hours. Morphometric measurements were performed on the cold carcass. To evaluate the physical and chemical compositions of the carcass, the dissection of the left half carcass was carried out, grinding, pre-degreasing and chemical analysis. The data were submitted to descriptive analyzes and Pearson's correlations. Subsequently, simple linear regressions and multiple regressions were applied, using a stepwise procedure in the selection of variables to compose the prediction models. All correlations between in vivo measurements and physical and chemical compositions, in kg, were significant, except for USM, which correlated with muscle tissue, protein and water. Biometric measurements and hot (HCW) and cold (CCW) carcass weights entered as predictors of the physical and chemical composition of the carcass, with high determination coefficients. The use of absolute weight (kg) was considered the best unit to estimate carcass composition using in vivo and morphometric measurements. The inclusion of variables in the models provided an increase in the precision of the estimation of the carcass components. SBW was the independent variable that most influenced the prediction equations of the physical and chemical components of the carcass in the evaluation of the in vivo measurements and HCW and CCW in the equations for the measurements in the carcass, however these variables should not be evaluated alone. Biometric measurements of growing Santa Inês sheep can be used together with slaughter body weight to estimate the physical and chemical composition of the carcass. Morphometric measurements can be used together with the carcass weight to estimate the physical and chemical compositions of the carcass. The HCW can be used, especially when it is not possible to obtain a cold carcass, without prejudice to the accuracy of the prediction model. To estimate the amount of fat in the carcass, the morphometric measures of the carcass compactness index, width of the rump and internal length of the carcass can be used.