Temporal Composition of Alfalfa–Grass Pastures and Productivity Response of Holstein Steers

Abstract

Core Ideas Bloat incidence was less when grass proportion was 40% or more of grass–alfalfa sward. Alfalfa masked differences among grasses in grazed forage amount and nutritive value. Holstein steer growth rate was highest when sward alfalfa proportions were greatest. Alfalfa–meadow fescue maintained the greatest alfalfa proportion after three seasons. This study compared forage productivity and animal performance in three alfalfa (Medicago sativa L.)–grass mixtures: alfalfa–meadow fescue [Schedonorus pratensis (Huds.) P. Beauv] (A–MF), alfalfa–orchardgrass (Dactylis glomerata L.) (A–OG), and alfalfa–tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] (A–TF). Mixtures were rotationally grazed with Holstein (Bos taurus, initial weight 242 kg, annually n = 180) steers from 2014 to 2016. Steer performance data from 2014 were excluded due to several incidences of bloat. Grass proportions increased over the 3‐yr study from 23% in 2014 to 40% in 2015 to 71% in 2016 (P < 0.01). Relationships (P < 0.001) between grass proportion and nutritive variables were detected with neutral detergent fiber (NDF) (R2 = 0.40) and NDF digestibility (R2 = 0.13) increasing with grass proportion, and crude protein (CP) decreasing (R2 = 0.29) with grass proportion. No relationship (P = 0.82) existed for in vitro true digestibility (IVTD). Grass proportions were lower, 60% grass, (P < 0.05) in A–MF pastures in 2016, compared to 77% for A–TF and A–OG causing higher average daily gain (ADG) for A–MF (P < 0.01) (0.81, 0.56, and 0.57 kg d−1 for A–MF, A–OG, and A–TF, respectively) and a tendency (P = 0.10) for greater gain per hectare for A–MF (P = 0.08) (994, 752, and 765 kg ha−1 for A–MF, A–TF, and A–OG, respectively). Cattle ADG was greatest when alfalfa sward proportions were high. By 2016, A–MF pastures had the highest alfalfa proportion, and therefore, the highest levels of ADG and gain per hectare.