Evaluation of bull breeding soundness examination

Abstract

Records from 2,887 bull breeding soundness examination conducted at Michigan State University from 2007-2017 were analyzed to validate, verify, and evaluate the process. All bulls were examined using Society for Theriogenology Bull Breeding Soundness guidelines. With a conservative α of .001, nominal logistic regression was used to identify influential factors and potential sources of bias, and determine predictive accuracy of the breeding soundness examination itself in classifying reproductive potential. Of 2,887 records evaluated, 82% of bulls were classified as satisfactory potential breeders, 3% unsatisfactory, and 15% deferred. Factors identified as influential in final classification of bulls included season, veterinarian bias, presence of white blood cells, and percent morphologically normal sperm. Season of year and presence of white blood cells in ejaculate significantly affected the outcome. Routine and consistent evaluation of bulls is important for economic success of beef cow-calf operations. Further studies are needed to determine if the seasonal effect is related to ambient temperature or underlying physiology of spermatogenesis in the bull. Some components of the breeding soundness examination may be unnecessary. We concluded that veterinarians and farmers could save time and money by reducing the number of data collection points while increasing reproductive potential of the herd by using only influential factors in the process. Breeding soundness examination has been useful in evaluation of reproductive potential in bulls; however, alternate formulas of reproductive potential may have higher predictive accuracy and validity and may be more cost effective.