PSII-33 Mitigation of testicular heat stress in boars with PG600

Abstract Testicular heat stress due to increasing summer temperatures negatively impacts spermatogenesis reducing semen quality in boars. Scrotal insulation (SI) can mimic summer heat stress. Our hypothesis is that PG600 can mitigate heat stress in boars. PG600 is human chorionic gonadotropin (HCG) and equine chorionic gonadotropin (ECG) which have LH- and FSH-like effects respectively. During spermatogenesis, LH impacts testosterone production by Leydig cells and FSH impacts Sertoli cells to produce androgen receptors, inhibit apoptotic signals and sustain spermatogenesis. Eight boars (8–12 months of age) were randomly assigned to two treatment groups: SI + saline or SI + PG600. The SI was applied for 48 hrs. Injections were administered 24 hrs prior to SI application and again at onset of SI. PG600 was given at a standard gilt dose to induce puberty. Semen was collected every M-W-F for two weeks prior to treatment and 44 days post-treatment. Semen was evaluated for nuclear head shape via Fourier harmonic analysis (FHA) described as Harmonic amplitudes 0–5 (HA0-5). Semen for each collection day post-treatment was compared to the average of the semen collection days pre-treatment, described as day 0. Scrotal insulation produced a 3.7°C increase in average scrotal temperature for 48 hrs. Post-SI + saline, HA0 decreased on days 21–33 (P < 0.05), HA1 increased on day 30 (P < 0.05), HA2 decreased on day 35 (P < 0.05), HA3 increased on days 21–33 (P < 0.05), HA4 increased on days 21–26 (P < 0.05), and HA5 increased on days 21–30 (P < 0.05). Post-SI + PG600, decreased the number of days post-SI when changes in harmonic amplitudes were seen (P < 0.05) as well as the magnitude of the response (P < 0.05). PG600 was for the first time shown to significantly mitigated the response of boars to SI and testicular heat stress. Increased doses of PG600 may improve results.