Multivariate analysis of body weight, morphometric and thermo-physiological traits of indigenous pigs under tropical conditions

Abstract

The study aimed at describing objectively the interdependence among the morphological and heat tolerance traits of Nigerian indigenous pigs and to predict body weight from conformation traits. Data on body weight, eight linear body measurements (BL, CG, CD, WH, RH, EL, SL and TL) and three thermo-physiological parameters were measured on 150 randomly selected pigs of three growth stages (piglets, growers and finishers) from February to December, 2020. The animals were managed in an extensive system in Plateau State, north central Nigeria. General linear model was used to study growth stage and sex effects including their interaction. Multivariate principal component analysis was used for the size, shape and heat tolerance determination while the animals were classified using canonical discriminant analysis.  The stepwise regression was used for body weight prediction. The results showed that finishers had significantly higher (P<0.05) body weight, body length, chest girth, chest depth, withers height, rump height, ear length, snout length and tail length, followed by growers while the least values were recorded in piglets. Pulse rate was not significantly different (P>0.05) between piglets and finishers, although the latter had higher respiratory rate (39.48±0.53 vs. 39.90±0.53 vs. 36.77±0.75). However, rectal temperature was similar (P>0.05) among the three pig categories. With the exception of tail length, sexual dimorphism was observed in all the morphometric traits with higher values recorded for males. However, the three thermo-physiological traits were not affected by sex (P>0.05). BW was highly and positively correlated with most biometric traits (r = 0.80-0.93, 0.66-0.80 and 0.83-0.93; P<0.01 for piglets, growers and finishers, respectively). Three principal components (PC1, PC2 and PC3) were extracted for optimal balance of the animals.  Withers height, ear length and body weight were found to be the most discriminating variables to separate the pig categories. Classification results showed that 100% of piglets, 96.7% of growers and 96.7% of finishers were correctly assigned to their distinct populations. The present Information could be exploited in devising appropriate management and breeding programs for tropically adapted pigs in Nigeria.