Journal of the Saudi Society of Agricultural Sciences (Apr 2022)
The Tunisian Barbary sheep: A look at the morphostructural characteristics of purebred ewes reared under arid conditions
Abstract
Fat-tailed Barbary sheep are well-adapted to Tunisian arid areas and extensive management. Multivariate morphometric characteristics of this important breed have not been investigated. Morphometric data, collected during February-April 2014, of 249 purebred redhead Barbary ewes, ranged into young (1–2 years) and adults (2–9 years), and reared in Sfax, southern Tunisia, were used to explore the breed morphostructural characteristics under harsh arid conditions (<200 mm of rainfall) through principal component analysis (PCA). As a result, 77% and 52 % of morphometric variance were shaped in young and adults respectively. Morphometric parameters linked to body size, particularly height at shoulder, body length, and height at rump, were heavily weighted to PC1 in both age categories, emphasizing a tight correlation between them. PCA scores into PC1 and PC2 show a great gradient of size plasticity from which small to medium-sized ewes were frequently seen, reflecting therefore a partial influence of arid conditions on the ewe's size. Measures, such as tail length (TL) and ear length (EL), were associated with component explaining weakest morphometric variance (PC3 in young, and PC2 in adults), which suggest their conservatory role in this morphostructure, interpreted here as an adaptive footprint to feeding resource scarcities and heat stress. Looking at morphometric differences in the large sample (229 ewes) of adults between the two locations, multivariate differentiation is globally assigned to PC defining the shape trends covering the body weight, heart girth, TL, and EL traits. A two-sample Hotelling's T squared test indicates that group centroids are statistically (P < 2.2 E-16) different, which has also been supported through permutation-based analysis of variance test, showing an influence (P = 0.001) of location on the multivariate morphometric data. Such morphometric contrast is explained to be originated from differences in the genotypic and environmental levels, without ignoring genotype by environment component. I hypothesize that the inclusion of HR trait in selection programs may enhance the ponderal performance and the adaptive capacity of the breed to heat stress of arid areas. This study advocates the usefulness of PCA in shaping the morphostructure rather than delineating the individual morphometric trends.
