Genetic and Non Genetic Sources of Variation for Linear Body Conformation Traits in Bunaji and Friesian X Bunaji cows
The effects of Age of dam at calving, Sex of calf, Breed, Sire, month of calving and season of lactation on linear body conformation traits was investigated in the dairy herd of the National Animal Production Research Institute, Shika Zaria, Nigeria. Seven linear body conformation traits of 25 Bunaji and 25 crossbred (Friesian x Bunaji) cows were measured. The measurements were taken monthly by 3 evaluators for the complete lactation length of the cows, this resulted in 1275 cumulative records, (with 750 records from Friesian x Bunaji and 525 records from Bunaji). The 7 body conformation traits (stature, chest width, wither height, heart girth, body length, body depth and rump width) were measured in centimeter using flexible tape. The results showed that all the genetic and non genetic factors considered had significant effect (P<0.05) on the linear body conformation traits. However, there was no significant (P>0.05) variation amongst the evaluators in their measurements, except RW. The body size characteristics increased with age. The male bearing cows were relatively broader (CW, HG) and longer (BL) than the female bearing cows, though there was no significant difference (P>0.05) in their statures (ST) and the body depth (BD). The crossbred cows were taller (ST, HW) longer (BL), broader (CW, HG), but less deep (BD) than the pure Bunaji. The animals of season 1 were taller (ST, WH), deeper (BD) and longer (BL) than the others. However, animals of season 2 and 3 had similar body sizes (ST, CW, BD, WH, HG, BL and RW). It is therefore suggested that in selecting for body conformation these genetic and non genetic factors should be taken into consideration.
Key words: Friesian x Bunaji, linear body conformation, evaluators, breed, sire