Effects of isoflavone supplementation, via red clover hay, on the growth and postgraze physiological recovery of beef steers grazing endophyte-infected tall fescue pastures

作者：Davis BE, Jacobs AA, Flythe MD, Hamilton TA, Ji H, Schrick FN, Goodman JP · 发表于：Journal of animal science · 年份：2025 · DOI：10.1093/jas/skaf304 · 被引用次数：85 · 研究领域：Trifolium、Isoflavones、Festuca、Animals、Cattle、Male、Animal Feed、Diet、Dietary Supplements、Endophytes、Animal Nutritional Physiological Phenomena

Livestock grazing endophyte-infected (E+) tall fescue can exhibit persistent systemic vasoconstriction and fescue toxicosis. Isoflavones in legumes, most notably red clover (RC), are known hypotensive agents. The objective of the experiment was to evaluate the effect of isoflavone supplementation via RC hay, every day or every other day (QOD), on average daily gain (ADG) of steers grazing E+ tall fescue pastures and their physiological recovery after grazing when managed on a non-toxic diet (28 d). In Spring 2018 (62 d) and 2019 (65 d), 36 Angus× steers were blocked by initial body weight (BW) into pastures (n = 6 pastures year-1) assigned to one of three supplement treatments: Dried distillers' grain with solubles (DDGS) only (CON; pasture + DDGS), 7.5% RC hay daily (based on 300-kg steer consuming 2.5%-BW; 7.5%-RC; pasture + DDGS + RC hay), or 7.5% RC hay QOD (7.5%-RC QOD; daily rotation of either: CON or 7.5%-RC). All supplements were isonitrogenous, and shrunk BW was collected at the start and end of the grazing period for determination of ADG. Each year, immediately after the grazing period, three steers were randomly selected from each pasture and moved to outdoor partially covered pens where they were fed a non-toxic diet for a recovery period of 28 d. The caudal artery of each steer was imaged immediately after grazing and then every 7 d over the recovery period using Doppler ultrasonography to monitor artery luminal areas (CAA). Jugular blood samples were collected i...