Abstract :
Information regarding morphology of indigenous sheep in South Africa is scant, and even
where data exist it is rarely presented using standardised methodologies. Principal component
analysis (PCA) was applied to 13 body measurements in order to provide an objective
description of the body shape and size of 1665 Zulu sheep, obtained from rural communities
of KwaZulu Natal. Data was analysed separate for young (no permanent incisors) and adult
sheep (≥2 pairs of permanent incisors). On average mature males measured higher than
mature ewes in most morphometric traits. The correlation coefficients between different
body measurements in young sheep were all significant except for correlation between ear
length and tail length whilst in adult sheep 79 out of 96 combinations showed significant
correlation. Body weight and heart girth had the highest correlations in both age groups. Ear
length and tail length related combinations had lower correlation coefficients in both age
groups. The PCA of morphometric traits extracted two components with a total variance of
66.85% in young sheep and four components in adult sheep which explained a total variance
of 62.13%. The first factor (PC1) in each case had high loadings for variables relating to body
size, whilst PC2 had high association with traits reflecting body shape. The PC3 had high
factor loadings for head length and head width, and thus defined head size. Tail length, ear
length and whither height on the other hand contributed least towards total variation. The
use of principal components was more appropriate than the use of original correlated variables
in predicting body weight of Zulu sheep. PCA was able to identify traits with greater
variability, these can be improved with greater success in breeding programmes and also
the number of variables was reduced to give a concise picture of morphological structure
(body size and shape) of a Zulu sheep. These components can as well be used in predicting
body weight of Zulu sheep.
