343 Frequency of semen collection impacts semen quality and physiological parameters in yearling Rambouillet Rams.

Abstract Artificial insemination (AI) holds promise for rapid genetic improvement in sheep, but the successful use of this technology is highly dependent on the quality of the semen utilized. Semen collected from rams with desirable genetics may be used fresh or stored via cryopreservation for later AI applications. In cattle, associations between ejaculate collection frequency and semen characteristics have been described, with initial ejaculates serving as a “clean-out” of the epididymis and a secondary ejaculate collected for breeding. The objective of this study was to evaluate the impact of semen collection frequency (first ejaculate [EE1] vs second ejaculate [EE2]) on semen quality and physiological parameters in yearling Rambouillet rams. Semen was collected from twenty (n = 20) single-sourced rams (BW = 80.6 ± 3.1 kg) in late February. Prior to collection, health and physiological measurements were collected including heart rate (HR) and rectal temperature (RT). Ejaculates were collected using a handheld rectal EE probe twice; initial ejaculates and secondary ejaculates collected 5 hour later. Semen was diluted with a commercially available extender (10 extender:1 semen). Semen volume, sperm concentration and motility were evaluated immediately following collection utilizing a portable Computer Aided Sperm Analysis (CASA) system. Sperm morphology was conducted utilizing CASA with the aid of SpermBlue staining. To evaluate the impact of semen collection technique on physiological status of the rams, HR and RT were collected immediately following each ejaculate collection. Semen and physiological measures were analyzed using a paired t-test using JMP (JMP Pro v. 17.0). Heart rate was not impacted by EE frequency (P ≥ 0.54); however, baseline heart rate was 37% lower prior to EE (P ≤ 0.01). Rectal temperature was greater (P ≤ 0.01) for EE2 vs EE1. Semen volume (mL) and total motility (%) were greater (P ≤ 0.01) for EE2 compared to EE1 (1.1 vs 0.5 mL; 87.7 vs 47.3%, respectively). Additionally, semen concentration (106 sperm/mL) was 54% greater (P = 0.03) for EE2 compared to EE1. The percentage of sperm with fast motility was not different between EE1 and EE2 (P = 0.14). However, the percentage of sperm with circular motility was greater (P ≤ 0.01) for EE2 compared to EE1 (61.9 vs. 28.1%, respectively). The percentage of sperm with abnormal heads tended to be greater (P = 0.07) for EE2. Ultimately, the secondary ejaculate collection showed advantages in terms of semen quality, specifically in volume, motility, and concentration. This study indicates an advantage to performing multiple collections when attempting to utilize or store ram semen for artificial insemination. Further investigation is needed to evaluate long-term effects of increased electroejaculation on sheep welfare.