AN EVALUATION OF VISUAL ASSESSMENT FOR FERTILITY IN BRAHMAN CROSS COWS USING THE BONSMA TECHNIQUE

A technique of visual assessment of cattle for reproductive efficiency , described by Professor Jan Bonsma of South Africa, was evaluated in two well-managed large herds of 1/2 to 3/4 Brahman cross heifers and c ows located in the dry tropics of north Australia. Individual lifetime performance records were available for all animals. Experienced cattl emen carried out the assessments. Higher scores were previously claime d to indicate higher fertility. The technique had high repeatability ( 0.7) and was quickly learned by the assessors. Scores from visual asse ssment had no useful predictive value for either heifer or cow fertili ty or for growth rate up to 27 mo of age, although 2.5-yr-old heifers which were scored as subfertile matured into 4% smaller cows than heif ers which had scored higher. Scores decreased as fatness increased (P< 0.05). Some biases in visual assessment occurred. Lactating cows score d higher than nonlactating cows (P<0.05), independently of their repro ductive record. Red and grey cows scored higher than brindle and black /brown cows (P<0.05). Bonsma scores were not influenced by the percent age of Brahman in the genotype. Significant, but apparently random, ag e effects on scores also occurred. It was concluded that the visual as sessment criteria described by Bonsma were of no practical value in as sessing potential productivity of breeding animals in well-managed Bra hman cross cattle in the dry tropics.