Tall Fescue Mixtures with Birdsfoot Trefoil or Alfalfa Improve Forage Production, Beef Steer Gains, and Economic Returns.

High costs of nitrogen fertilizer and increased environmental stewardship necessitates a renewed interest in mixed grass-legume pastures, and past grass-legume research is not indicative of the irrigated, rotational grazing systems in the western U.S. This research compared the forage production, livestock performance, and economics of tall fescue-alfalfa (TF+ALF, Festuca arundinacea Schreb, Medicago sativa L.), and tall fescue-birdsfoot trefoil (TF+BFT, Lotus corniculatus L.) mixtures, to tall fescue with (TF+N) and without nitrogen fertilizer (TF–N). Pastures, comprised of four paddocks, were established in Lewiston, UT, and rotationally grazed by Angus crossbred beef steers for 112 days in 2012 and 2013. Forage samples were collected from each paddock prior to grazing to determine dry matter (DM) and nutrient content. Steers were weighed every 28 days to determine livestock performance. Forage yield was highest (P≤0.05) in TF+N (5164 kg ha^-1), followed by TF+BFT (4721 kg ha^-1) and TF+ALF (4463 kg ha^-1), whereas, the TF–N treatment had the lowest yield (2920 kg ha^-1). Average total digestible nutrients (TDN) were greater (P≤0.05) for TF+BFT (593 g kg^-1) and TF+ALF (593 g kg^-1) than for TF+N (558 g kg^-1) or TF–N (550 g kg^-1). Steer average daily gains (ADG) differed (P≤0.05) among all treatments with TF+BFT (0.73 kg d^-1) being the highest, followed by TF+ALF (0.67 kg d^-1), TF+N (0.61 kg d^-1), and lastly TF–N (0.40 kg d^-1). The TF+BFT treatment doubled the economic return ($1,133 ha^-1) when compared to TF+N ($572 ha^-1). Tall fescue-legume mixtures improve animal performance and economic returns as compared to traditional nitrogen fertilization.