Effects of bull exposure and body growth on onset of puberty in Bunaji andFriesian x Bunaji heifers

A total of ninety seven pre-pubertal Bunaji (BJ) and Friesian-Bunaji (FR x BJ) heifers were allotted randomly to two treatments groups for a period of 15 months. The treatment groups consisted of the followings: Mature Bull E xposure (MBE) and No Bull Exposure (NBE). Heifers were body condition score d and their live weights recorded on 28 days consecutive intervals. A heife r tactile stimulation in bull bio-stimulation. was considered to have attai ned puberty if she displayed oestrus, had a palpable corpus luteum with an associated P4 concentration > 1 ng.mL(-1). The onset of puberty was signifi cantly earlier in MBE heifers (23.1 +/- 0.4 months) than NBE heifers (26.4 +/- 0.4 months). The mean ages at puberty for MBE-BJ, NBE-BJ, MBE-FR x BJ, NBE-FR x BJ were 24.3, 27.8, 22.1 and 25.0 months respectively. More MBE he ifers (70.8%) attained puberty between 17 and 24 months of age than NBE hei fers (18.3%) and on the same ages, more FR x BJ heifers (62.0%) than BJ hei fers (25.5%). The mean live weight of MBE heifers at puberty (224.4 +/- 4.2 kg) was significantly lower than that of the NBE heifers (255.8 +/- 4.2 kg ). The FR x BJ heifers attained puberty at a significantly higher live weig ht (270.2 +/- 4.2 kg) than the BJ heifers (228.6 +/- 4.2 kg). The use of a vasectomised bull especially in some elite farms that rely on artificial in semination services may be an effective management tool that can decrease a ge at puberty. More work is required to determine the relative contribution of visual, auditory, olfactory, pheromonal and tactile stimulation in bull biostimulation.