Repeatability of Objective Measurements of Linear Udder and Body Conformation Traits in Frisian X Bunaji Cows
The objective of this study was to estimates the repeatability of objective measurements on linear udder and body conformation traits and to evaluate the objectivity of the measurements in Friesian x Bunaji cows. Data from 50 (F1) Frisian X Bunaji cows collected between 2007 and 2008 at the Dairy Research Farm of the National Animal Production Research Institute (NAPRI), Shika, Zaria, Nigeria, were used for the study. Analyzed conformation traits were seven body conformation traits: stature (ST), chest width (CW), withers height (WH), heart girth (HG), body length (BL), body depth (BD) and rump width(RW) and seven udder conformation traits: rear udder height (RUH), rear udder width (RUW), udder depth (UD), udder cleft (UC), fore teat position (FTP), rear teat placements (RTP) and teat length (TL). Both were measured in centimeter (cm) using a flexible meter tape. Three novice evaluators participated in the experiment. The frequency of measurements was once a month, commencing 3-4 days post-partum. Each of the three evaluators was able to take 10 repeated records on each of the 50 cows within the lactation length, resulted in 1500 cumulative records. Number of lactations and evaluators were included in the model as fixed factors. The objectivity of the method, measured by repeatability among the three evaluators was satisfactory: 0.940, 0.873, 0.954, 0.892, 0.941, 0.955, 0.899 for the seven body conformation traits (ST, CW, BD, HW, HG, BL and RW, respectively), and 0.938, 0.935, 0.674, 0.829, 0.38, 0.847, 0.827, for the seven udder conformation traits (RUH, RUW, UC, RTP, FTP and TL, respectively). The variation due to evaluators’ effect was significant (p<0.01) on all the udder measurements except UC and TL, but not significant (p>0.05) on the body measurements except RW. Number of lactation had significant effect (p<0.01) on all the udder and body conformation traits except UC, ST, WH and BL. Although novices took the measurements, the objectivity of the method was satisfactory and sufficiently reliable to be used as an alternative method of evaluating linear udder and body conformation traits in dairy cows.