Effects of Linoleic and Linolenic Acid Supplementation on the in Vitro Production of Pig Embryos in a Heat-Stressed Environment

Elevated environmental temperatures induce heat stress which cause depresses fertility and early embryonic development. Fatty acids initiate an endergonic reaction that is able to absorb cellular heat, thus causing a decrease in temperature. The objective of this study was to minimize heat stress-induced damage by supplementing oocytes (n = 4570) with linoleic and linolenic acid during maturation at either 38.5 or 41.5 °C. Oocytes were supplemented with 50 μM linoleic acid, linolenic acid, or both (25 or 50 μM) during 40-44 h of maturation and then evaluated for the formation of reactive oxygen species during maturation, fertilization characteristics, and rates of embryonic cleavage and blastocyst development were observed at 48 h and 144 h after IVF, respectively. There were no significant differences between the treatment groups matured at 38.5 °C when comparing reactive oxygen species generation. Supplementation of linoleic or linolenic acid significantly decreased (P < 0.05) reactive oxygen species generation in oocytes matured at 41.5 °C compared to no supplementation. There were no significant differences between the treatment groups matured at 38.5 °C when comparing penetration rates, polyspermic penetration and male pronuclear formation (MPN). Maturation at 41.5 °C produced significantly higher (P < 0.05) penetration and MPN rates in oocytes matured with 50 μM linoleic and linolenic acid compared to all other treatment groups. There were no significant differences between the other treatment groups comparing penetration rates, polyspermic penetration or MPN. Penetration and MPN rates were significantly higher (P < 0.05) in oocytes matured at 38.5 °C compared to 41.5 °C. There were no significant differences between groups when supplementing maturing oocytes at 38.5 °C when observing the percentage of cleaved embryos by 48 h after IVF and the percentage of those reaching the blastocyst stage by 144 h after IVF. Supplementing either 25 or 50 μM linoleic and linolenic acid to maturing oocytes at 41.5 °C significantly increased (P < 0.05) the cleave rates by 48 h after IVF and the blastocyst formation rates by 144 h after IVF compared to all other treatment groups. All treatment groups of maturing oocytes at 38.5 °C had significantly greater (P < 0.05) embryonic development compared to those matured at 41.5 °C except for those supplemented with 50 μM linoleic and linolenic acid. These results indicate that supplementing 50 μM linoleic and linolenic acid to the maturation medium of pig oocytes at an elevated temperature reduces the effects of heat stress-induced damage.