Bovine haemoglobin polymorphism of 75 Bunaji cattle and their crosses with Friesian cattle in the Dairy Research farm of National Animal Research Institute (NAPRI), Shika, Zaria was studied by horizontal starch gel electrophoresis. The gene frequency of HbA and HbB was observed as 0.64 and 0.36, respectively, for pure Bunaji and 0.86 and 0.14 for the crosses. The frequencies of Haemoglobin AA, AB and BB genotypes were 0.407, 0.462 and 0.131, respectively in the Bunaji, and 0.735, 0.245 and 0.020 in the Friesian X Bunaji cross. The rare presence of Hb BB in the Friesian-Bunaji crosses population suggested some adaptive superiority of the Hb AA over Hb BB. Also, the preponderance of heterozygotes (HbAB) against homozygotes of both types (HbAA and Hb BB) in the pure Bunaji probably suggested that the heterozygotes were favoured by natural selection. There was no statistically significant association (P<0.05) between Hb genotype frequency and the two variables: breed and sex being studied. Breed and sex had no significant association (P> 0.05) with Hb polymorphism in the cows, indicating that breed and sex of the cows were independent on the occurrence of Hb types. The Hb type AA in the Nigerian Friesian-Bunaji cattle crosses of Zaria environment was favoured by natural selection, possibly for adaptation against the hot tropical weather and tolerance of tick and helminthic infections which is not achievable with exotic cattle breeds.
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