Abstract
Dietary supplementation is the most feasible method to improve oocyte function and developmental potential in vivo. During three experiments, oocytes were collected from maturing, dominant follicles of older mares to determine whether short-term dietary supplements can alter oocyte metabolic function, lipid composition, and developmental potential. Over approximately 8 weeks, control mares were fed hay (CON) or hay and grain products (COB). Treated mares received supplements designed for equine wellness and gastrointestinal health, flaxseed oil, and a proprietary blend of fatty acid and antioxidant support (reproductive support supplement (RSS)) intended to increase antioxidant activity and lipid oxidation. RSS was modified for individual experiments with additional antioxidants or altered concentrations of n-3 to n-6 fatty acids. Oocytes from mares supplemented with RSS when compared to COB had higher basal oxygen consumption, indicative of higher aerobic metabolism, and proportionately more aerobic to anaerobic metabolism. In the second experiment, oocytes collected from the same mares prior to (CON) and after approximately 8 weeks of RSS supplementation had significantly reduced oocyte lipid abundance. In the final experiment, COB was compared to RSS supplementation, including RSS modified to proportionately reduce n-3 fatty acids and increase n-6 fatty acids. The ability of sperm-injected oocytes to develop into blastocysts was higher for RSS, regardless of fatty acid content, than for COB. We demonstrated that short-term diet supplementation can directly affect oocyte function in older mares, resulting in oocytes with increased metabolic activity, reduced lipid content, and increased developmental potential.
Highlights
Oocyte viability is essential for female fertility
Lipid content, and metabolism vary among species, with oocyte lipid content affecting its reliance on the oxidation of carbohydrates or fatty acids (Dunning et al 2014, Dalbies-Tran et al 2020)
Studies have reported some success with dietary supplementation (Nehra et al 2012, Ben-Meir et al 2015), no specific recommendations are available for women undergoing assisted reproductive technology (ART) procedures (Cecchino et al 2018, Gaskins & Chavarro 2018), and less guidance is available for mares
Summary
Oocyte viability is essential for female fertility. Maternal factors can affect oocyte quality, potentially by causing alterations in oocyte metabolism (Babayev & Seli 2015). Energy needed for oocyte development and maturation is primarily produced through aerobic mitochondrial metabolism (Ben-Meir et al 2015, Cecchino et al 2018). Mitochondria do not replicate until after blastocyst formation in several species, including the horse and human; mitochondria within the oocyte are responsible for providing energy during early embryo development (May-Panloup et al 2007, Spikings et al 2007, Wai et al 2010, Hashimoto et al 2017, Hendriks et al 2019). After the initiation of antral formation, approximately 2 months are required for the growth of the human oocyte and the development of the follicle to the ovulatory stage (Williams & Erickson 2012). Specific treatments or nutraceuticals can be used to target the follicle and oocyte during this growth phase. Granulosa cells line the ovarian follicle and have an essential role in metabolism and transport of nutrients
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