Causes of failure in British bulls in the breeding soundness evaluation.

Background: The breeding soundness evaluation is a method that is based on the evaluation of all factors that contribute to the reproductive function in bull, basically is constituted by the general clinical examination, examination of internal and external genital system, measurement of scrotal circumference, semen physical and morphological evaluation and sexual behavior. Most progress in improving the reproductive efficiency can be made by estimating the fertility of the males and by careful selection of the bulls. Reproduction will continue to depend mainly on the ability to manage all available information. The aim of this study was to determine the main causes of failure in British bulls in the steps provided for breeding soundness evaluation, as well as demonstrate the importance of the behavior examination as a norm and not just as a complementary test. Materials, Methods & Results: This study consisted in evaluating the records of breeding soundness evaluation of 10,407 British breeds of bulls (Abeerden Angus, Red Angus, Hereford, Polled Hereford, Shorthorn and Devon) in the State of Rio Grande do Sul. The animals evaluated were grouped into two age classes: young bulls (two years) and adult bulls (three to ten years). Breeding soundness evaluation consisted of four steps: a general clinical examination, special clinical examination; seminal examination and behavior examination. When the bull was not approved in one of the steps, did not perform the subsequent step. For the analysis of variance, the animals received a score 1 for approval or 0 for disapproval. Data were analyzed using the Statistical Analysis System (SAS ®). To investigate the failures in each steps of the breeding soundness evaluation, we used analysis of variance (PROC GLM) comparing the two age classes of bulls (young and adults). Means were compared by Tukey test at 5%. The pathologies of failures were subjected to multivariate cluster analysis (PROC CLUSTER and TREE). A multiple correspondence analysis (PROC CORRESP) was performed to identify characteristics associated with different breeds. The failure in the behavior examination of bulls of the six breeds, although it has been approved in other steps of breeding soundness examination, indicated that this step should be a norm and not just a complementary test. Discussion: In young bulls Polled Hereford and Aberdeen Angus and adults bulls Hereford eyes were the major causes of failure, probably due to infectious bovine keratoconjunctivitis affecting more animals no pigment around the eyes (Polled Hereford and Hereford), than other pigmented breeds. Physical causes of failures found in this study suggest that there is a greater predisposition for failure due the use of these bulls, which causes a constant physical and natural wear, to work at irregular and extensive fields, looking for cows in estrus, predisposing to physical conditions as the locomotor system. The behavioral evaluation of the bulls is not always done, only although there are reports of failure in adult bulls for libido and physical ability problems to perform the mounts. Although tests of libido and phisical ability may not be sufficient to accurately determine pregnancy rates, there is greater security for obtaining good pregnancy rates with the use of bulls that have been approved in all stages of the breeding soundness evaluation.