Date of Award
Master of Science
Frank Neal Schrick
J. Lannett Edwards, Ky G. Pohler, Lewrell G. Strickland
To determine the occurrence of proximal droplets in performance-tested bulls, parameters related to breeding soundness examination (BSE) classification were evaluated. Bulls (542 Angus bulls) were classified as satisfactory (BSE guidelines; Society for Theriogenology) or deferred. On-test risk factors were identified, associated with increased probability for bulls to be deferred due to proximal droplets. On-test weight (P = 0.019), on-test scrotal circumference (P = 0.018) and the covariate of age (P = 0.007) were all associated with the probability for a bull to be deferred on test due to proximal droplets. Accounting for the covariate of age and the effect of on-test SC, bulls in weight category 5 (>500 kg on-test weight) had 12.5 times the odds of deferral due to proximal droplets compared to bulls in weight category 2 (350 – 400 kg) (OR: 12.5, 95% adj. CI: 1.47, 111.11; adj. P = 0.017). Accounting for the covariate of age and the effect of on-test weight, bulls that were categorized as SC on-test 1 (< 30 cm) had 7.9 times the odds for deferral due to proximal droplets compared to bulls categorized as SC 3 (33 – 36 cm; OR: 7.9, 95% CI: 1.4, 44.4; P = 0.012). Additionally, bulls that were categorized as SC 2 (30 – 33 cm) had 4.7 times the odds for deferral due to proximal droplets compared to bulls categorized 3 (33 – 36 cm; 95% CI: 1.1, 20.0; P = 0.03). After accounting for age and bull on-test weight, bulls that were categorized as SC growth 3 (> 6.2 cm growth) had 3.7 times the odds for deferral due to proximal droplets compared to bulls categorized 2 (3.4 to 6.2 cm growth; OR: 3.7, 95% CI: 1.69, 8.26; P = 0.001. In summary, bull on-test weight, on-test scrotal circumference, scrotal circumference growth and age are important factors associated with unsatisfactory classification due to proximal droplets. Occurrence of proximal droplets have been previously associated with bull maturity; however the cause of its relationship to on-test weight, on-test scrotal circumference and rapid scrotal circumference growth in performance-tested bulls remains unclear.
Bartenslager, Zachariah Johnson, "Occurrence of proximal droplets in performance-tested beef bulls. " Master's Thesis, University of Tennessee, 2018.