Genetic variability of Nigerian sheep breeds at the insulin-like growth factor-1 (IGF- 1) gene locus

Abstract

The genetic variability of some Nigerian breeds of sheep at the IGF 1 locus was investigated. Blood samples from 150 sheep (50 each of Yankasa, Balami and Uda sheep) were collected from the Maiduguri abbatoir and analysed at the Biotechnology centre of the University of Maiduguri. A relatively high level of genetic variability was detected in Nigerian sheep; the mean observed heterozygosity (Ho) and expected heterozygosity (He) values were 0.433 and 0.476, respectively. Comparison of expected heterozygosity of alleles between the populations showed that yankasa was the most heterozygous of the sheep populations though the unbiased expected heterozygosity (0.503) for the Yankasa was the same as that of the Balami. All populations were 100% polymorphic at the IGF 1 locus with fixation index ranging from -0.169 to 0.378 and a mean of 0.093, which suggests a general pattern of random mating. Similarly, low mean values for Fis (0.093), F (0.089), Fis (0.089), Fit (0.130) and Fst (0.045) supports the assertion that inbreeding was limited due to outcrossing with relatively high level of gene-flow (Nm = 5.292). The analysis of molecular variance (AMOVA) revealed that only 1% of the total variations observed in the sampled populations is accounted for by the population differences while individual differences accounted for 85%. The UPGMA phylogenetic tree revealed that the Uda and Yankasa populations are closer to each than each is to Balami. Thus, it can be concluded that sufficient genetic variation exist in the studied Nigerian sheep breeds and these populations are unlikely to decline due to inbreeding.