Moribund sperm in frozen-thawed semen, and sperm motion end points post-thaw and post-swim-up, are related to fertility in Holstein AI bulls

• Published in: Theriogenology Vol. 77; no. 5; pp. 940 - 951
• Main Authors: Shojaei, H, Kroetsch, T, Wilde, R, Blondin, P, Kastelic, J.P, Thundathil, J.C
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.03.2012
• Subjects: Animals; bulls; Cattle; Cattle - anatomy & histology; Cattle - physiology; Computer assisted sperm analysis (CASA); correlation; Cryopreservation - veterinary; Fertility - physiology; Fertility markers; Holstein; Hot Temperature; Insemination, Artificial - veterinary; Male; Moribund sperm; Scrotum - anatomy & histology; semen; Semen - cytology; Semen Preservation - methods; Semen Preservation - veterinary; Sperm Motility; Sperm viability; spermatozoa; Spermatozoa - physiology; Testis - anatomy & histology; thawing; Fertility markers; Moribund sperm; Sperm viability; Cattle; Computer assisted sperm analysis (CASA)
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/j.theriogenology.2011.09.026

The objectives were to compare testicular physical characteristics and post-thaw sperm characteristics and their associations with fertility in Holstein bulls used for AI. Ten Holstein bulls (4–5 y old) were classified as either high-fertility (HF) or low-fertility (LF; n = 5 each), based on adjusted 56-d non-return rates [non-return rate (NRR); range (mean ± SD): 55.6 ± 4.6 to 71.8 ± 1.3%). Testicular physical characteristics were not significantly different between the two groups. Four ejaculates were collected from each bull and cryopreserved. Several indexes of sperm motion (based on computer-assisted sperm analysis) at post-thaw and post-swim-up were correlated with NRR. Sperm from HF bulls were in transition to a hyperactivated motility pattern, whereas those from LF bulls had only a forward progressive motility pattern. In HF vs LF bulls, there was a greater percentage of viable sperm after thawing (60.6 ± 9.7 vs 49.5 ± 8.0%, P < 0.05) and after swim-up (70.9 ± 11.0 vs 63.0 ± 8.8%, P < 0.01); these two end points were positively correlated with fertility (r = 0.45, P < 0.01 and r = 0.78; P < 0.01, respectively). Furthermore, in HF vs LF bulls, the ratio of sperm recovered after swim-up to viable sperm in post-thaw semen was higher (P < 0.001), and the proportion of moribund sperm expressed as a percentage of live sperm differed (12.6 ± 3.4 vs. 16.4 ± 3.1%, P < 0.001) and was negatively correlated (r = −0.33, P < 0.05) with fertility. In conclusion, fertility of Holstein bulls maintained in a commercial AI center was not predicted by testicular physical characteristics, but it was associated with differences in moribund sperm in the inseminate, as well as characteristics of sperm post-thaw and after swim-up.