Developing equations for predicting internal body fat in Pelibuey sheep using ultrasound measurements

The objective of the present study was to to develop equations for predicting internal body fat in Pelibuey sheep using ultrasound measurements (USM). Twenty-four hours before slaughter, USM were obtained for 35 male fattening Pelibuey sheep with a bodyweight (BW) of 39.22 +/- 7.01 kg. The back-fat thickness (cm) and longissimus thoracis and lurnborum muscle area (cm(2)) were measured between the 12th and 13th thoracic vertebrae (TFT and TLDA) and the 3rd and 4th lumbar vertebrae (LFT and LLDA). Additionally, ultrasound kidney-fat thickness (uKFT) was measured behind the 13th right rib. After slaughter, data on both carcass and non-carcass components were recorded. Internal fat (IF, internal adipose tissue) was dissected, weighed and grouped as mesenteric (MF), omental (OM) or kidney and perirenal fat (PRF). Correlation coefficients among variables were calculated, and regressions were carried out according to SAS procedures. Only the LLDA was poorly correlated (r = 0.38, P < 0.05) with MF, and the other internal body fat depots only had non-significant correlations (P > 0.05). The uKFT was highly related with internal body fat depots (0.78 <= r <= 0.91, P < 0.001). Regression equations developed to predict OM and MF had an r(2) ranging from 0.61 to 0.87, respectively, while those developed to predict PRF and IFAT had an r(2) ranging from 0.66 to 0.77, respectively. The equations presented a moderately high precision (r(2) > 0.69 <= and <= 0.83), high accuracy (bias correction factor > 0.93) and good reproducibility index (concordance correlation coefficient > 0.81 and <= 0.90) along with a moderate to high efficiency of prediction (from 0.71 to 0.82). In conclusion, our results indicated that the use of ultrasound measurements could accurately and precisely be used as alternatives to predict the internal fat depots of Pelibuey sheep.