Methods for improving boar and stallion semen quality

Handling of semen is a very important tool for a successful artificial insemination in both pig and horse farming. One of the main problems during liquid and frozen semen storage is the loss of fertilizing potential mainly due to a sudden reduction of temperature, an excessive production of reactive oxygen species and alterations in the antioxidant defense systems. Supplementation of sperm preparation with different antioxidants gave interesting and promising results and, during recent years, use of plant antioxidants has been gaining the attention of several research groups. Moreover, an increase in the fertilising ability of boar sperm has been demonstrated after photo-stimulation. On these bases, the objective of the present thesis was to assess whether: 1) Resveratrol (RESV) or Epigallocatechin-3-gallate (EGCG) supplementation of thawing boar semen extender is effective in influencing sperm quality parameters and in vitro fertilization ability; 2) EGCG and green tea extract polyphenols improve stallion semen parameters during cooling at 4°C; 3) Photo-stimulation improves frozen-thawed boar semen quality. The results obtained demonstrate that the addition of RESV or EGCG, alone or in combination, to thawed boar semen positively affects in vitro penetration rate while no positive effects were registered in cooled stallion semen up to 48 h storage; as a consequence, the addition of these substances in cooling medium for stallion sperm storage is not useful. Therefore, it is evident that the effects of antioxidants may vary depending on species as well as on the way semen is processed for preservation (cooled vs frozen-thawed). Moreover, photo-stimulation may be considered as a potential tool to increase the cryotolerance of poor freezability ejaculates (PFE) but more researches on the mechanisms underlying the detrimental effects on sperm motility are required; they may allow to understand whether such increase in cryotolerance has a significant impact upon the fertilizing ability of PFE.