Short communication: performance of beef cows fed Kernza intermediate wheatgrass straw mixed with alfalfa haylage.

Abstract

Kernza intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth & D.R. Dewey) is a novel dual-use perennial grain and forage crop with environmental and economic benefits for farmers. Perennial crop byproducts, such as Kernza straw, have been suggested as an alternative forage source in livestock systems. However, there is limited information on cattle performance offered Kernza straw. Therefore, our study assessed the performance of mature beef cows fed Kernza straw mixed with a haylage composed of alfalfa (Medicago sativa L.) and cool-season grasses. Grasses included orchardgrass (Dactylis glomerata L.), meadow fescue (Festuca pratensis L.) and Kentucky bluegrass (Poa pratensis L.). Two feeding trials conducted in two different years were performed with 36 pregnant Angus cows (Bos taurus) in six pens of six animals each in a completely randomized design with three replications. Dietary treatments included: (i) a 100% grass-alfalfa haylage (control), and (ii) a 50% Kernza straw - 50% grass-alfalfa haylage. Average daily gain was lower in the Kernza straw cows than in the control group (0.41 vs 0.92 kg day^-1) in Trial 1 (P = 0.02) with no differences in Trial 2 (P = 0.13). Daily dry matter intake did not change in Trial 1 (P = 0.08), while for the cows offered Kernza straw it was reduced from 12.9 to 11.3 kg cow^-1day^-1 in Trial 2 (P < 0.01). There were no changes in body condition among cows fed different diets in both trials (P > 0.05). Therefore, 50% Kernza straw can be successfully used in beef cow diets at least for 60 days without negative impacts on animal performance and potential economic and environmental benefits.