Genetic and phenotypic differentiation of qualitative traits in Nigerian indigenous goat and sheep populations

Data from smallholder flocks of adult West African Dwarf (WAD) and Red Sokoto goats (n = 824) and Yankasa, Uda and Balami sheep (n = 636) were utilized to investigate the distribution and frequencies of certain qualitative traits. The animals were randomly sampled in Northern parts of Nigeria. They were scored for the presence or absence of wattle, beard, horn, coat colour [Phaeomelanic standard pigmentation, Eumelanic Standard pigmentation and Brown Eumelanin (goats); White, White and Black and White and Brown (sheep)] and hair type (smooth or coarse). Breed-dependence and sexual dimorphism were observed in the qualitative variables considered. In both WAD and Red Sokoto goats, the dominant genes for wattle (Wa(w)), beard (Br(b)), and polledness (H(o)(P)) were found to segregate at low frequencies (0.09 vs. 0.02; 0.05 vs. 0.12 and 0.00 vs. 0.00). The values were also much lower than the expected Mendelian value of 0.75. However, a different trend was observed for phaeomelanic standard pigmentation (A(wt)), where gene frequency was low in WAD (0.20); but high in Red Sokoto goats (0.63), conforming with the underlying assumption of complete dominance. Low gene frequencies were also recorded for wattle and beard in Yankasa, Uda and Balami sheep respectively (0.08, 0.02 and 0.09; 0.00, 0.00 and 0.00). Lower frequencies of wattle gene and variable coat colours obtained in both species are indicative of the fact that they have not been purified through artificial breeding. Estimates of genetic distance between WAD and Red Sokoto goats were, 0.005, 0.005 and 0.18 for wattle, beard and coat colour loci. In sheep, the estimates ranged from 0.0001 to 0.005 at the wattle locus. This shows that the two goat populations are more closely related at both the wattle and beard loci, thereby aiding in classical phylogenetic inference. The same is applicable to the sheep populations at the only estimated locus.