Influence of inbreeding and some environmental factors on calving intervals in N'Dama cattle of Southwest Nigeria

Résumé

Records of 4184 N'Dama calves born between 1947 and 1984 at Fashola Stock Farm, Oyo State, Nigeria was used to compute inbreeding coefficient and determine its effects on calving intervals of cows. Only 273 of the 4184 calves (6.53%) were inbred with an average inbreeding coefficient of 9.71%, while five out of 293 sires had inbreeding coefficient of 9.25% and 43 out of 1849 dams had inbreeding coefficient of 9.95%. The inbreeding coefficient for the entire population was 0.63%, respectively 0.70% and 0.58% for male and female calves. The average calving interval was 445.34 ± 2.68 days within the herd while year of birth, parity of dam, age of dam and dam's age at first calving all significantly (P<0.05) impacted calving intervals of cows. Season of birth and inbreeding coefficient of dam did not exert statistical (P>0.05) influence on calving intervals of dams. Although the number of inbred animals in the population is relatively low, however the inbreeding level of these animals is high, which may be attributed to the fact that breeding policy on the farm was not strictly adhered to, and lack of proper and adequate registration system coupled with inconsistent animal identification system on the farm may be responsible for the inbreeding observed in the N'Dama population at Fashola Stock Farm.