Mitochondrial genetic variation in European, African and Indian cattle populations.

Mitochondrial DNA from representative animals of 13 different cattle breeds was assayed for restriction fragment length polymorphisms (RFLP) to determine phylogenetic relationships and levels of variation among breeds; 16 different mitotypes were found, described by 20 polymorphisms. Within these 16 mitotypes two major lineages were apparent: an Afro-European and an Asian type. These were found to differ at over 2.3% of sites surveyed. None of the mitotypes found in the Asian lineage was detectable in the Afro-European lineage and vice versa. Within each of the major mitotypes there were no further significant differences within or among breeds. Using rates of mitochondrial evolution estimated from other species, the two lineages were estimated to have diverged between 575,000 and 1,150,000 years ago; well outside the 10,000 years bp timeframe postulated by a single domestication hypothesis. The results presented are concordant with those generated in other studies and provide strong evidence for an independent domestication of Asian Bos indicus. Furthermore, the grouping of all African indicine populations within the clade containing all Bos taurus lineages points to the hybrid origins of the humped cattle of that continent.

Response of Nigerian zebu cattle to zeranol implants.

The effect of Zeranol, an anabolic agent, on the weight gains of Nigerian zebu fattening bulls was investigated over a period of 16 weeks. Implanted Sokoto Gudali and White Fulani bulls showed average daily weight gains of 0.5 and 0.49 kg respectively as compared to 0.47 and 0.41 kg by non-implanted counterparts. The anabolic effect of Zeranol was evident up to 8 to 9 weeks after implantation, after which there was no significant difference in weight gains of implanted and control animals.

Crossbreeding in tropical sheep: incidence of dystocia and parturition losses.

Studies were carried out on the incidence of dystocia and parturition losses during a crossbreeding experiment involving 96 West African Dwarf (WAD) ewes mated with rams of 4 breeds--WAD, Ouda, Permer and Yankassa. Results obtained indicated 8 (5.7%) cases of dystocia and 20 (10.64%) cases of stillbirths or death of lambs at birth. The WAD sires were not associated with dystocia or stillbirths but other sire groups were involved in both. All the difficult parturitions occurred during the rainy season while all stillbirths not associated with dystocia occurred during the dry season. The sires used and the level of feeding the ewes during pregnancy may be associated with the dystocia cases and parturition losses recorded. Eighty per cent of the dystocias involved ram lambs. The mean gestation period of the ewes that lambed during the dry season was significantly (P < 0.01) longer than that of the rainy season group. Application of traction and Caesarean operation were used in the treatment of dystocia cases.

Crossbreeding of exotic and indigenous cattle in Nigeria--haematological correlates.

The blood values of the German Brown, N'Dama and their three-quarter, half and quarter hybrids were studied to ascertain if and how some haematological parameters changed with crossbreeding. It was found that the red blood cell (RBC) and white blood cell (WBC) count and packed cell volume percentage (PCV) were significantly higher (P less than 0.01) in the N'Dama than in the German Brown; the crosses had values which were intermediate as compared to the two parent breeds. Generally, the changes in the mean blood values paralleled changes in the expected genotypes resulting from crossbreeding of the two parent breeds. The tendency of the blood values to change in direct proportion to the degree of N'Dama contribution was strongest for the WBC, followed by the PCV and RBC, respectively. A small random sample for leucocyte differential count did not reveal any differences amongst the genotypic groups.