RELATIONSHIP BETWEEN SCROTAL CIRCUMFERENCE AND ANDROGEN CONCENTRATION AS A PREDICTOR OF WHITE FULANI BULL’S FERTILITY

Abstract

The study implemented On-field Animal Research (OFAR) at three different locations within the Southern Guinea Savannah Agro ecological Zone of Niger State Nigeria in two seasons (dry and wet seasons). The experiment was conducted in a completely randomized design using a multifactorial arrangement; the factors are location, season and fertility status. The locations are three levels including Mokwa, Minna and Suleja, while the seasons are two levels including the dry and wet seasons. The experimental animals investigated were White Fulani bulls (n=1131) which are being kept under smallholder production system. The age was determined using dentition, the body weight of each bull was determined using Shaeffer’s formula and the scrotal circumference and testicular length were measured using a measuring tape. Testicular biometry was used to categorize bulls into high and low fertility bulls. Blood samples were collected from 24 bulls from each of the established fertility categories and for each of seasons (dry and wet seasons) for hormonal assay. Scrotal circumferences were significantly (p<0.05) higher in Mokwa (27.38 ± 0.18 cm) and during the wet season (30.03 ± 0.16 cm) compared to the dry season (23.59 ± 0.14 cm). There was significant influence of location, season and fertility status on testosterone concentration of the bulls (p<0.05). The level of testosterone was significantly (p<0.05) higher in bulls in Mokwa and during the wet season (3.98±4.65 ng/ml) compared to a lower level during the dry season (0.83±0.71 ng/ml). Testosterone hormonal concentration was higher in high fertile bulls (3.76±4.77 ng/ml) compared with low fertile bulls which had lower (1.06±0.87 ng/ml) testosterone level. Scrotal circumferences were significantly (p<0.05) higher in Mokwa (27.38 ± 0.18 cm) and during the wet season (30.03 ± 0.16 cm) compared to the dry season (23.59 ± 0.14 cm). Scrotal circumference was positively correlated (r = 0.62) with androgen concentration and could therefore be used as a field level fertility marker in selecting fertile White Fulani bulls for reproductive purpose. The study shows that scrotal circumference and androgen concentration can be used as a predictor of White Fulani fertility