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 in beef heifers during a four-month natural breeding season. Thirty-two heifers were assigned into two groups over two consecutive years. One group grazed on Rhodes grass without SBE supplementation during the breeding season (LSBE; n = 16), while the other received SBE supplementation at 0.6% of body weight (BW) during the breeding season (HSBE; n = 16). Plasma was analyzed for total phenolic compounds, flavonoids, antiradical activity, and overall antioxidant capacity. Oxidative stress was measured using the thiobarbituric acid reactive substances (TBARS) assay to assess malondialdehyde (MDA) levels. Heifers receiving SBE had significantly 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 the groups. These findings suggest that SBE supplementation enhances plasma antioxidant capacity and reduces oxidative damage in beef heifers without affecting reproductive outcomes.