Effect of Soybean Expeller Dietary Supplementation on the Antioxidant Status of Heifers during the Breeding Season

Abstract

This study evaluated the effect of soybean expeller (SBE) dietary supplementation on plasma antioxidant status inbeef heifers during a four-month natural breeding season. Thirty-two heifers were assigned into two groups over two consecutiveyears. One group grazed on Rhodes grass without SBE supplementation during the breeding season (LSBE; n = 16), while the otherreceived SBE supplementation at 0.6% of body weight (BW) during the breeding season (HSBE; n = 16). Plasma was analyzed fortotal phenolic compounds, flavonoids, antiradical activity, and overall antioxidant capacity. Oxidative stress was measured using thethiobarbituric acid reactive substances (TBARS) assay to assess malondialdehyde (MDA) levels. Heifers receiving SBE hadsignificantly higher antioxidant levels and lower oxidative stress, as indicated by reduced MDA levels, compared to the LSBE group.However, no significant differences were found on pregnancy rates, calving attributes, or postparturition recovery between thegroups. These findings suggest that SBE supplementation enhances plasma antioxidant capacity and reduces oxidative damage inbeef heifers without affecting reproductive outcomes.