Comparison of mathematical models to estimate live weight through heart girth in growing Pelibuey sheep

38 Background: In traditional sheep production systems, the assessment of animal growth 39 based on live weight (LW) is limited by the high cost of livestock scales as well as the 40 sophisticated maintenance required. Objective: To develop and evaluate equations to 41 predict LW using heart girth (HG) in growing Pelibuey sheep. Methods: A dataset 42 (n=415) of clinically healthy male Pelibuey sheep from two months to one year of age, 43 with an average LW of 25.96 ± 10.25 kg and HG of 68.31 ± 10.53 cm, were used. Three 44 equations were evaluated: LW (kg) = −37.70 + 0.93 × HG (Eq. 1); LW (kg) = −1.74 + 45 0.19 × HG + 0.008 × HG 2 (Eq. 2); and LW (kg) = 0.003 × HG 2.68 (Eq. 3). Results: The 46 correlation coefficient between LW and HG was r = 0.94 (p<0.001). The three equations 47 showed a high concordance correlation coefficient (CCCs≥0.97). However, the random 48 error was the main component of the mean square partition of the prediction error 49 (≥82.78%) only for Eqs. 1 and 2. The test for parameter identity (intercept=0; slope=1) 50 was accepted only for Eq. 2 (p>0.05). On the other hand, for Eqs. 1 and 3, the intercept 51 was different from zero and the slope was different from one (p<0.05). Conclusions: The 52 second-degree equations accurately and precisely estimated the body weight of growing 53 Pelibuey sheep using the HG as a sole predictor variable.