119 Award Talk: The effect of grass-legume mixtures on cattle in the Southeastern U.S.

Abstract Forage systems in the Deep South face seasonal challenges that limit cattle productivity, particularly due to poor summer forage quality and the widespread presence of toxic tall fescue (Schedonorus arundinaceus). This study evaluated the integration of leguminous species— alfalfa (Medicago sativa L.) and red clover (Trifolium pratense) into traditional forage systems to enhance forage nutritive value, mitigate toxicosis-related issues, and improve beef cattle performance under regional production constraints. Three studies were conducted to address complementary objectives. First, the digestibility and microbial responses of beef steers to conserved forages—bermudagrass hay, alfalfa baleage, and an alfalfa-bermudagrass baleage—were evaluated using four ruminally fistulated steers in a completely randomized design. Second, a metabolism trial conducted in a Latin square design assessed the effect of increasing red clover hay inclusion (0%, 10%, 20%, and 30%) in ‘KY31’ tall fescue diets on digestive kinetics and symptoms associated with fescue toxicosis. Third, a grazing study using 20 replicated tall fescue pastures grazed by stocker steers (267 ± 35.8 kg BW) investigated the efficacy of interseeded red clover and byproduct supplementation (0.5% and 1.0% body weight; 50/50 soybean hulls/corn gluten feed) as cost- effective interventions to sustain cattle growth and mitigate the effects of fescue toxicosis. Conserved forages with the inclusion of alfalfa significantly improved crude protein concentration (P < 0.01) and dry matter digestibility (P < 0.01), with distinct microbial profiles observed among forage types (P < 0.01). In the second study, increasing red clover inclusion in fescue diets reduced rumen temperature (P < 0.01), suggesting mitigation of vasoconstriction linked to fescue toxicosis. Additionally, clover inclusion increased dry matter digestibility (P < 0.04) and crude protein content (P < 0.01). The grazing trial confirmed that red clover in the diet improved average daily gain (ADG) over non-supplemented control pastures and performed comparably to the 0.5% supplementation group (P < 0.05). Gain per hectare followed a similar trend (P=0.03). These findings influenced cattle marketing schedules; the supplemented steers were sold soon after the study while the control steers were held the longest before they were ready to sell. Collectively, these studies demonstrate the agronomic and economic value of integrating legumes into Deep South forage systems. Alfalfa improves the nutritional quality of conserved forages, while red clover offers dual benefits of enhanced digestibility and potential mitigation of fescue toxicosis. Moreover, interseeding legumes served as a low-input, sustainable alternative to feed supplementation. These findings support the broader adoption of legume-inclusive systems as a practical strategy to improve forage quality and cattle performance in the Southeastern U.S.