title: 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.
abstract: 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.
authors.affiliation: Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Shojaei
authors.forename: T
authors.initials: T
authors.lastname: Kroetsch
authors.forename: R
authors.initials: R
authors.lastname: Wilde
authors.forename: P
authors.initials: P
authors.lastname: Blondin
authors.forename: J P
authors.initials: JP
authors.lastname: Kastelic
authors.forename: J C
authors.initials: JC
authors.lastname: Thundathil
mesh_terms: D000818:Animals; D002417:Cattle / Q000033:anatomy & histology / Q000502:physiology*; D015925:Cryopreservation / Q000662:veterinary; D005298:Fertility / Q000502:physiology*; D006358:Hot Temperature; D007315:Insemination, Artificial / Q000662:veterinary*; D008297:Male; D012611:Scrotum / Q000033:anatomy & histology; D012661:Semen / Q000166:cytology*; D012662:Semen Preservation / Q000379:methods / Q000662:veterinary*; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology; D013737:Testis / Q000033:anatomy & histology