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The metabolic demands of reproduction, specifically late gestation, parturition, and lactation, may trigger an upswing in oxidative stress in mares.

“Oxidative stress signifies an imbalance between the normal production of oxidative products within a body and the ability of the body to neutralize those agents and repair the damage caused by them,” said Catherine Whitehouse, M.S., a nutrition advisor with Kentucky Equine Research. “When the system works as it should, it is a harmonious give and take.”

Everyday life events, like advancing pregnancy or an escalation in athletic intensity, can disrupt this well-oiled antioxidant mechanism, according to Whitehouse.

Researchers recently theorized that a deluge of oxidative products may be generated in response to the metabolic changes inherent to pregnancy and foaling, though these changes may be different in maiden mares and those mares that had previously foaled, also known as multiparous mares. To study this, they evaluated changes in antioxidant enzymes during the last third of pregnancy, at parturition, and postpartum in both sets of mares. In addition, they also measured lipid peroxidation and protein oxidation during these same periods.*

According to the researchers, “lipid peroxidation and protein oxidation were quantified as parameters of oxidative processes, while antioxidant enzymes, specifically glutathione peroxidase (GPx) and superoxide dismutase (SOD), were used to evaluate the antioxidative defense.”

Fifteen mares were used in the study, seven maiden and eight multiparous. Blood samples were collected weekly, beginning about four months prior to their due date. Blood was collected 12 hours after foaling and weekly until the second ovulation after foaling.

Results of the study showed a significant change in oxidative indicators and the antioxidative defense close to parturition. This mirrors the findings of other researchers.+,○ Parity, or the number of times a mare has previously given birth, did not influence the parameters analyzed.

Elevation of antioxidant enzymes can signal the need for an effective, body-wide antioxidant during periods of stress, such as the time surrounding foaling. As an antioxidant, vitamin E helps protect the body against oxidative stress. In horses, the form of vitamin E offered is important, as natural-source supplementation is more successful in raising blood alpha-tocopherol levels in the horse. Choose a research-proven vitamin E supplement from a reliable company.

*Rohof, J.E., M.A. Alonso, D.F. Souza, K.M. Lemes, M. Nichi, and C.B. Fernandes. 2020. Influence of parity on the oxidative balance in pregnancy and postpartum mares. Journal of Equine Veterinary Science 89 (Abstract).

 +Cecchini, S., F. Fazio, M. Bazzano, A.R. Caputo, C. Giannetto, and G. Piccione. 2019. Redox status and oxidative stress during late pregnancy and postpartum period in mares. Livestock Science 230:103821.

 Sgorbini, M., F. Bonelli, A. Rota, P. Marmorini, G. Biagi, M. Corazza, and A. Pasquini. 2015. Maternal and neonatal evaluation of derivated reactive oxygen metabolites (d-ROMs) and biological antioxidant potential in the horse. Theriogenology 83:48-51.

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