Salmate DHA+® fish oil supplement fed to boars and impact on sperm production

Abstract Omega-3 fatty acid supplementation can increase sperm production in boars, but the mechanism has not been demonstrated. The current study was to determine if the increase in sperm production was due to a reduction in germ cell apoptosis during spermatogenesis. Duroc boars (438–686 days of age) were fed either a control diet of corn, soybean meal, 5% fiber, plus vitamins and minerals per NRC requirements or the control diet plus a proprietary blend of fish oil, Salmate DHA+® supplemented diet with 1.83 g DHA (Docosahexaenoic Acid, C22:6) and 0.78 g EPA (Eicosatetraenoic acid, c20:5) omega-3 fatty acids from 26 g Salmate DHA+® (The Ballard Group, Inc. and Feedworks USA, Ltd.) per day per head added to the control diet. The control diet was fed to all boars (n=10) for 62 days and then Salmate DHA+® was added to the diet of 5 of the boars while the other 5 continued the control diet for another 62 days. At the end of the experiment all boars were harvested, the testes collected, fixed with Karnovsky’s fixative, post-fixed with 70% ethanol, embedded with acrylic resin, 2-micron sections taken, and sections stained with Toluidine Blue. During the study, boars were on routine semen collection. Semen data were evaluated for all boars on the first 62 days of the control diet (before period) and then for control and Salmate DHA+® boars from day 22 to 62 after Salmate DHA+® feeding started (after period). A total of 107 ejaculates were evaluated in the study. The control boars’ total sperm per ejaculate (X 109) was 105.7±7.3 vs. 110.9±10.4 in the before vs. after period (p>0.05). The Salmate DHA+® boars’ total sperm per ejaculate (X 109) was 103.4±5 vs. 122.8±7 in the before vs. after period (1.18-fold increase, p<0.05). To examine apoptosis via histology, the number of round spermatids (RS) and Sertoli cells (SC) were counted in 10 stage 1 seminiferous tubules for each boar with adjustments made for cell nucleoli or nuclei size and thickness of the histology section. The ratio of RS/SC or Sertoli Cell Index was then determined to estimate how many RS survived apoptosis in spermatogenesis. The Sertoli Cell index was 9.46±0.84 vs. 15.03±0.97 respectively for Control and Salmate DHA+® boars (p<0.01). The number of RS/SC increased 1.59-fold due to Salmate DHA+® treatment and demonstrates a reduction in apoptosis. The increased number of RS may explain the increased sperm per ejaculate after Salmate DHA+® treatment.