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PSXI-18 Effect of beef bull fertility on conceptus attachment and pregnancy loss in multiparous lactating dairy cows.

Year: 2025
Type: article
Abstract: Fertility varies significantly among service sires (SS), but the factors underlying these differences remain poorly understood. The increase in pregnancy-specific protein B (PSPB) during the critical period of conceptus attachment (CA) may provide insight into how sperm fertility affects embryonic survival in lactating dairy cows. This study investigated whether CA rates and subsequent pregnancy losses differ between SS classified as high- or low-fertility. We hypothesized that high-fertility SS (H) would increase the chances of CA and reduce pregnancy loss in multiparous lactating dairy cows compared with low-fertility SS (L). Multiparous dairy cows (n = 408) were synchronized with Double Ovsynch and received AI at 76 ± 3 DIM. Cows were assigned randomly by parity (2nd, 3rd, or ≥ 4) to receive AI from either n = 5 high- or n = 5 low-fertility beef bulls selected based on pregnancy rates adjusted for environmental and management factors using Beef InFocus data (ABS Global US). Timed-AI was performed 16 h after final GnRH of Double Ovsynch. AI was performed by three technicians blind to treatment. Conceptus attachment was defined as an increase of ≥10% from d 18 to 26 post-AI. Pregnancy was diagnosed at 35 days post-AI using transrectal ultrasound. Data were analyzed using the FREQ and GLIMMIX procedures in SAS® 9.4. There was no difference in CA percentage between H and L (58% vs. 55%, P = 0.6) nor a treatment-parity interaction (63% vs. 56%, 66% vs. 51%, 49% vs. 58%, for 2nd, 3rd, or ≥ 4 parities, respectively; P > 0.2). Pregnancy loss from CA to 35 days post-AI did not differ between H and L (27% vs. 19%; P = 0.2) with no treatment-parity interaction. No significant differences were observed in serum PSPB concentrations on day 26 post-AI (10.9 ± 0.5 vs. 11.0 ± 0.5 SEM ng/mL; P = 0.9). However, 2nd parity cows had greater concentrations of PSPB 26 d post-AI compared with 3rd or 4th+ parity cows (P = 0.01). SS ranged from 41% to 68% CA. PSPB concentrations ranged from 8.9 ± 1.3 to 12.3 ± 1.0 SEM ng/mL across SS. The average increase in PSPB from day 18 to 26 post-AI ranged from 3909% to 5506% among SS. A greater increase in PSPB was associated (P < 0.001) with a lesser likelihood of pregnancy loss between CA and 35 d post-AI. In summary, high fertility SS did not increase the likelihood of CA or reduce subsequent pregnancy loss as hypothesized. However, fertility and average concentrations of PSPB on d 26 post-AI varied significantly amongst all bulls.
DOI: 10.1093/jas/skaf300.652
Language: English
Open Access status: bronze
OpenAlex ID: W4414830846
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