Vol. 8, Issue 4, Part G (2023)

Coat colour mediates and determines the extent of heat load on the animal with light coloured animals reflecting back most of the sun’s heat hence less heat load and stress. On the other hand, dark coloured coats absorb more energy than the light coloured coats hence the former are likely to have higher thermal stress. The Kenyan Boran breed of cattle is characterized by a wide range of colours which include white, grey, golden, brown and red coat colours. However, the performance of different coat colour in terms of early growth and male fertility traits has not been determined. The objective of this study was therefore to assess coat colour variation and evaluate their effects on early growth and male fertility traits. The research was conducted on Kenyan Boran breed kept at Beef Research Institute (BRI) Lanet. Data collected included information on the animal’s identity, coat colour, pedigree, parity, date of birth and weaning, birth weight, weaning weight, pre-weaning average daily gain and scrotal circumference, length and width. Genetic variance and heritability estimates were determined using probit mixed model and generalized linear mixed model. Variation in coat colour was evaluated using general linear model. Results revealed mean birth weight, weaning weight, average daily gain, scrotal circumference, width and length of 24.51 kg, 138.37 kg, 0.51 kg/day, 14.45 cm, 7.65 cm and 8.52 cm, respectively. Year of birth was significant for growth and male fertility traits (p<0.001) Season of birth had a significant effect on weaning weight and average daily gain (p<0.05). Colour of calf had a significant effect on average daily gain and scrotal circumference (p<0.05). Brown and white calves had faster growth rates compared to red calves whereas brown calves had larger scrotal circumference than white and mottled calves. Colour of dam of calf influenced birth weight, weaning weight and average daily gain significantly (P<0.05) where red dams gave birth to light calves but had higher weaning weight and pre-weaning daily gain compared to brown and white dams. Dam weight at birth significantly (p<0.05) influenced birth weight and average daily gain whereas weaning age had a significant effect on weaning weight. The significant effect of coat colour of calf or dam on growth and male fertility traits should be accounted for when estimating performance of animals in beef cattle.