Binary mixtures of alfalfa and birdsfoot trefoil with tall fescue: Herbage traits associated with the improved growth performance of beef steers

Abstract

Abstract High nitrogen (N) fertilizer costs and increased environmental stewardship have renewed interest in grass–legume pastures. This research compared herbage mass, nutritive value, steer growth performance and economics of binary mixtures of tall fescue ( Schendonorus arundinaceus [Schreb.] Dumort, nom. Cons.) (TF) with alfalfa (ALF) (TF + ALF, Medicago sativa L.) and birdsfoot trefoil (BFT) (TF + BFT, Lotus corniculatus L.), to tall fescue with (TF + N) and without N fertilizer (TF–N). Pastures were established in Lewiston, Utah, USA, and rotationally stocked by Angus beef steers for 112 days in 2012 and 2013. Herbage samples were collected prior to each 7‐day stocking period and analyzed for mass and nutritive value. Steers were weighed each 28‐day rotation cycle and cumulative average daily gain (ADG) calculated. Steer performance differed ( p = .05) among most treatments with ADG greatest for TF + BFT (0.73 kg/day) and TF + ALF (0.67 kg/day), followed by TF + N (0.61 kg/day) and the least for TF–N (0.40 kg/day). Multivariate analysis indicated that small inherent differences in herbage energy, fiber and digestibility were highly correlated with steer growth. Other variables associated with ADG included legume proportion and herbage mass. Fescue–legume mixtures had 29 to 33% legume proportion, and more ( p = .05) favorable energy and fiber concentrations than grass monocultures. Whereas herbage mass was greatest ( p = .05) for TF + N (2,956 kg/ha), followed closely by TF + BFT (2,741 kg/ha) and TF + ALF (2,623 kg/ha). Overall, TF + BFT and TF + ALF pastures had less herbage, but better nutritive value and increased steer growth performance compared to TF + N, without the added cost of fertilizer.