Incorporation of Testicular Ultrasonography and Hair Steroid Concentrations in Bull Breeding Soundness Evaluation

SIMPLE SUMMARY: Bulls’ subfertility has a major impact on the efficiency of production and profitability of cattle enterprises. Bulls typically undergo a bull breeding soundness evaluation (BBSE) to predict potential fertility. The present study investigated if a more comprehensive index of indicative fertility could be developed in bulls by including testicular ultrasonography and hormonal status in the BBSE. Bulls with homogeneous testicular parenchyma showed a higher percentage of motile sperm post-thawing compared with bulls with heterogeneous parenchyma. In bulls with homogenous parenchyma, the percentage of motile sperm, progressively motile sperm, and motility yield were positively correlated with hair DHEA-S concentration. The use of testicular ultrasonography and DHEA-S status in the BBSE would provide a more comprehensive assessment of potential fertility in bulls. In addition, ultrasonography can be used in the BBSE when the evaluation of semen parameters is not available. ABSTRACT: Testicular ultrasonography and steroid concentrations (cortisol, dehydroepiandrosterone sulfate (DHEA-S), cortisol/DHEA-S ratio, testosterone) in hair were examined for their utility in the bull breeding soundness evaluation (BBSE). Beef and dairy bulls (n = 16; 2.7 ± 0.4 years old; body condition score 3.2 ± 0.1) of five breeds were maintained under the same conditions at an accredited semen collection center. Bulls underwent routine semen collection twice weekly for 12 weeks and semen was processed and cryopreserved. Ultrasonography and hair sampling were undertaken at the last semen collection. Bulls with homogeneous testicular parenchyma (n = 8) had a higher (p < 0.05) percentage of motile sperm post-thawing compared with bulls with heterogeneous parenchyma (n = 8). There were no differences (p > 0.05) in the hair concentrations of cortisol, DHEA-S, and testosterone between bulls with homogeneous and heterogeneous parenchyma. In bulls with homogeneous parenchyma, hair DHEA-S concentration was positively correlated with percentage motile sperm (R(2) = 0.76), progressively motile sperm (R(2) = 0.70), and motility yield (R(2) = 0.71). The findings indicate that the integration of testicular ultrasonography and hair DHEA-S status in the BBSE could provide a more comprehensive assessment of indicative fertility in bulls. Additionally, ultrasonography can be used in the BBSE when the evaluation of semen parameters is not available.