PSIII-19 Effects of insemination time and semen sorting on conception rate to AI in beef cattle

Abstract Sex-sorted semen can provide an opportunity for beef cattle producers to reach production goals by targeting sex-specific calving. Previous research in dairy cattle suggested that conception rate to AI (CRAI) increases if insemination occurs late with respect to estrus. The objective of this study was to determine if CRAI differed between sex-sorted (SS) and conventional (CON) semen based on the timing of insemination. We hypothesized that CRAI would be impacted by semen sorting and may vary over time. Both male (n = 621) and female (n = 262) sex-sorted and non-sorted conventional semen (n = 232) from two different AI companies were used. From 2017 to 2021, 1,115 inseminations occurred on a single beef cow-calf operation (n = 247 females), performed by one inseminator. Inseminations occurred at various timepoints following estrous detection. The precise time of onset of estrus was determined using an ear-tag sensor (CowManager SensOor, Agis Automastering BV, Harmelen, the Netherlands). Based on previous research, CowManager precisely and accurately determines the onset of estrus in cattle. The inseminator was instructed to breed randomly from 0 to 24 h after an estrus alert was received by CowManager and during normal hours of operation to replicate a commercial operation. CRAI was determined by rectal palpation performed by a single technician approximately 60 d following AI for females that did not return to estrus and was validated by subsequent calving date. Data were analyzed with the GLM procedure of SAS (v.9.4, SAS Inst. Inc., Cary, NC). To aid in analysis, insemination times following estrous detection were grouped into six categories: less than 8 h (< 8), 8 to 11 h (8-11), 12 to 15 h (12-15), 16 to 19 h (16-19), 20 to 23 h (20-23), and greater than 24 h (>24). CRAI was less (P < 0.05) for SS (59%) than CON (68%) semen. No difference was observed (P > 0.1) between SS male (58%) vs SS female (62%) semen. Time affected CRAI (P < 0.05) as fewer females conceived when inseminated late (> 24h) than at any other time regardless of semen sorting. Time also impacted (P <.05) CRAI for all sex-sorted semen. More (P < 0.05) females conceived early (< 8 h and 8 to 18 h) and fewer (P < 0.05) females conceived when inseminated late (> 24h) with respect to the onset of estrus. Although significant effects of semen sort and time were observed, no significant semen sort by time interaction (P > 0.1) was observed. These data suggest that CRAI is less for females inseminated with sex-sorted semen than for those inseminated with conventional semen. Also, CRAI is similar for male- and female-sorted semen. The ability to AI with SS semen at similar timepoints as CON semen, could increase the adoption of SS semen and increase reproductive efficiency.