170 Impact of l-carnitine dietary supplementation on the quality of ram semen collected during the non-breeding season

Systems for producing sheep are dependent on seasonal cycles of reproduction, which are controlled by photoperiod. It is believed that testicular function and semen quality are decreased during the non-breeding season. Ram spermatozoa are highly susceptible to oxidative damage mainly due to the high levels of polyunsaturated fatty acids in their plasma membranes and production of high amount of reactive oxygen species. l-Carnitine (LC) has potential impacts on sperm metabolism by supplying energy through β-oxidation to enhance sperm motility. LC is also critical for fatty acid metabolism and has antioxidant capacity. Positive impacts of dietary supplementation with LC on sperm quality and fertility have been reported in many species; however, little is known about its effect on sheep spermatozoa. The objective was to evaluate the effects of LC dietary supplementation on the quality of ram semen collected during the non-breeding season. Ten mature Katahdin rams were randomly assigned into treatment (n = 5; fed LC added to a commercial sheep feed at 0.0022 g kg⁻¹ of bodyweight; Brown et al. 2022, J. Anim. Sci. 100, suppl. 3, 26), and control (n = 5, commercial sheep feed only) for 8 weeks during the non-breeding season (June–July). Semen was collected from the rams once per week by electroejaculation and then diluted with Tris buffer extender. Sperm cell concentration and motility were evaluated by CASA. Sperm viability was evaluated by eosin-nigrosin stain. Data were analyzed by independent t-test, and significant differences were set at P < 0.05. No significant differences (P > 0.05) were observed in sperm concentration (2.4 vs. 2.7 × 10⁹ sperm mL⁻¹), sperm motility (62.9% vs. 63.4%), or percentage of live spermatozoa (64.8% vs. 66.8%) between LC and control groups, respectively. In conclusion, under our experimental conditions, results showed that feeding rams with LC during the non-breeding season had no significant impact on their semen quality compared with the control group. Further experiments are in progress to evaluate the effects of LC on semen quality collected during the breeding season, reproductive parameters, and the levels of reproductive hormones such as testosterone.

This work was supported by a USDA/NIFA 1890 Capacity Building Grant (Award 2022-38821-37343).