PREDIÇÃO DO PESO CORPORAL DE SUÍNOS “TIPO BANHA” POR MEIO DE MEDIDAS MORFOMÉTRICAS

Abstract

Mixed breed lard-type pigs play an essential role in subsistence pig farming in developing regions, as they are raised extensively or semi-extensively by rural producers with low purchasing power, with low implementation costs. Most of these producers do not perform zootechnical control of their herds and do not periodically monitor the animals' body weight, as the acquisition of scales is unfeasible due to their high cost. In view of this, the present study aimed to develop mathematical models for predicting the body weight of "lard-type pigs" raised extensively or semi-extensively based on their morphometric measurements. Data on body weight (BW), carcass length (CW), thoracic circumference (TW), hip circumference (HW), and withers height (HH) were collected from 240 animals, 122 males and 118 females, with BW between 4.7 and 68.0 kg, raised on small rural farms with a family profile, located in the municipality of Chapadinha-MA and adjacent municipalities. The means, standard deviations, coefficients of variation, and maximum and minimum values ​​of all measurements were calculated, and then Pearson's correlation coefficients (r) were calculated, showing that the characteristics analyzed presented strong correlations (r ≥ 90) with BW, both in males and females. The variable with the highest correlation with PC in both sexes was CT (r = 0.96) and the one with the lowest correlation was AC (r = 0.91) for males and AG and CC for females (r = 0.90). Afterwards, the data were subjected to the normality test (Cramer-von Mises) and the data from males and females were separately subjected to multiple linear regression analysis using the Stepwise selection method. Subsequently, the equations for males and females were compared using the F test, with no difference between sexes (P = 0.376). This showed that only one equation is sufficient to explain the variation in body weight of males and females, being: BW: -35.51 (± 1.03) + 0.80 (± 0.04) × TC + 0.11 (± 0.04) × CC (R2=0.93; P<0.0001). Next, the CC and CT data of 53 pigs weighing between 6.5 and 42.8 kg that did not participate in the parameterization of the equation were used to estimate BW, in order to evaluate the practical applicability of the general equation. A high correlation was observed between predicted and observed values ​​(r = 0.96), suggesting good predictive capacity of the equation. This result shows that CC and CT are sufficient morphometric measurements to accurately predict the BW of lard-type pigs, which may benefit small pig producers who do not have scales on their properties.