Exploratory principal components analysis of growth traits in Red Sokoto goats

Abstract

Growth traits of Red Sokoto goats were evaluated using 387records generated from goats raised under semi-intensive system of management at National Animal Production Research Institute (NAPRI), Shika, Zaria, Nigeria. Sex, type of birth, birth weight (BWT), weaning weight (WWT),12-month weight (WT12), adjusted weaning weight, season of birth and weaning were subjected to multivariate factor analysis with varimax rotation using IBM® SPSS® Version 21. Season of birth and weaning were classed into Season 1 (January-June) and season 2 (July-December). The factor scores and growth traits were subjected to stepwise regression procedure of SAS. The variables WWT, CWT, WT12 and sex combined to form the first principal component (PC1). Birth weight and season of birth formed the second component (PC2). Weaning season was the only outstanding variable in the third component. Predicted BWT of kids is expected to increase with increasing PC1 and PC2, but decrease with increasing PC3. Similar prediction pattern is obtained for CWT. However, predicted WT12 is expected to increase with increasing PC1, PC2 and PC3. Variability of growth traits of Red Sokoto goats at birth and thereafter up to 12 month of age are closely linked with season at which goats were given birth and weaned, respectively. The similarity of intercepts of regression equations and those of average values for growth traits in this study indicated the possibility of improvement of goat stocks through the principal components. Goat farmers and breeders are advised to increase efforts in improving the environmental conditions of their stocks because birth season is highly correlated with PC2 (birth characteristics). Also, weaning season (PC3) should be controlled to favour improved weaning weight of Red Sokoto goats.

Keywords: Exploratory PCA, Red Sokoto goats, growth traits, prediction equations