**5. Effect of Polyunsaturated Fatty Acids (PUFAs)**

Linoleic acid or omega-6 fatty acid is the only FA for which NRC has established require‐ ments at least 0.1% of diet for sexually active boars. However, the effect of various fatty acids (FAs) top on diet, particularly the omega-3 fatty acids, on semen quality and libido characteristics in boars are more interesting. Nowadays, there are 3 types of omega-3 fatty acids that are linolenic, eicosapentaenoic (EPA) and docosahexaenoic (DHA). The boar feed commonly consist of the large amounts of crops, with source of protein added in the form of soya-bean, fish powder, bone powder, etc. Thus, dietary fatty acids have a (n-6):(n-3) normal ratio of greater than 6:1 and do not contain long chain n-3 PUFAs. If 22:6(n-3) is essential for optimal fertility in pig spermatozoa, as being in human sperm [28,36,37], then it is possible that supplement 22:6(n-3) PUFAs on boar diets to improve the spermatogenesis. This sup‐ plementation may increase from either a deficit of (n-3) fatty acids or an increasing synthesis of 22:6(n-3) from 18:3(n-3) to competition between (n-6) and (n-3) fatty acids [38]. The tuna oil supplementing on the boar diet can increase the percentages of sperm cells with progres‐ sive motility, the proportion of live sperm, normal acrosome head, and normal morphology [39]. It was found that boars fed withcommercially available product containing DHA, vita‐ min E and selenium (PROSPERM®, Minitube America, Inc., Minneapolis, MN) for 16 weeks had a higher sperm concentration, number of sperm/ejaculate, and sperm motility compar‐ ing with control group [40]. In many experiments, 8-week period was used as the control period because spermatogenesis in boars requires 34–39 d and epididymal transport in‐ volves another 9–12 d [41]. It is not surprising that a 7–8 week period may be necessary after dietary supplementation [40,42].
