Evaluation of 3 bromegrass species as pasture: Herbage nutritive value, estimated grass dry matter intake and steer performance

Abstract

A 2 year grazing study was conducted to evaluate the effects of grazing meadow bromegrass (Bromus riparius Rehm.; cv. Paddock), smooth bromegrass (B. inermis Leyss.; cv. Carlton), and hybrid bromegrass (B. riparius×B. inermis.; cv. AC Knowles) on herbage nutritive value, dry matter (DM) intake and grazing beef steer performance. Each year, 36 crossbred beef steers (297±6kgBW) (15 month initial age) were randomly allocated to 1 of 3 replicated (n=2) paddocks of each bromegrass species in a “put and take” stocking system from May to July. Herbage samples were collected at start, middle, and end of each grazing period and analyzed for DM, crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), in vitro dry matter digestibility (IVDMD) and in situ rumen degradation kinetics. Herbage DM intake was estimated by combining fecal output with herbage in vitro dry matter digestibility. Fecal output was estimated using chromium sesquioxide (Cr2O3) as an external marker. Herbage CP (138±4.2g/kg), NDF (574±5.3g/kg), ADF (340±5.3g/kg), IVDMD (628±3.5g/kg), and effective degradation of herbage DM (35.87±1.07% of DM) did not differ (P>0.05) among the bromegrasses. In all 3 bromegrasses, CP and IVOMD decreased (P<0.05) and NDF and ADF increased (P<0.05) as the grazing season progressed. Over the 60d grazing season, DM intake (10.0±1.7kg/d), ADG (1.0±0.24kg/d), and final BW (329.0±9.2kg) were similar (P>0.05) among steers grazing either bromegrass pasture. The results of this study suggest that meadow bromegrass, smooth bromegrass and hybrid bromegrass are suitable species for grazing providing suitable nutritive value and steer performance for pasture in western Canada.