Effects of a polycrop or oat monocrop on forage yield, nutritive value, utilization and weaned steer performance for winter swath grazing

This 3-year study assessed winter beef cattle performance swath-grazing either (i) polycrop system (PC) comprising CDC-SO1 oat (Avena sativa L.), Golden Globe turnip (Brassica rapa L.), Hunter turnip (Brassica rapa L.), Goliath forage rape (Brassica napus L.) and 4010 forage pea (Pisum sativum L.) or (ii) a monocrop system (OMC; CDC-SO1 oats). Other evaluations included dry matter (DM) yield at oat’s soft dough (SD) and hard dough (HD) stages, nutrient composition, estimated DM intake and economics. A 12-ha field was subdivided into six, 2-ha paddocks. Each paddock was assigned to PC or OMC treatment. Crossbred beef steers’ initial body weight (BW) averaged 267 ± 14.1 kg at allocation to each forage system. The OMC had a greater (P < 0.01) DM yield than PC. Compared to the SD stage, NDF at HD decreased (P = 0.03) by 5.9%, starch increased (P < 0.01) by 36.8%, and TDN increased (P = 0.01) by 2.5%. The ADG of steers grazing the OMC or PC were similar (P = 0.47). Swath cost per kg steer gain was lower (P = 0.04) for OMC ($0.62 kg⁻¹) than PC ($0.91 kg⁻¹). The PC retained higher post-graze swath CP and lower NDF than OMC.