High-Performance Short-Duration and Repeated-Seasonal Grazing Systems: Effect on Diets and Performance of Calves and Lambs

Abstract

Diet composition, performance, and production of calves and lambs grazing in combination were contrasted between a repeatedseasonal (RSG) (May-Sep.) and a 16-subunit, 1-herd high-performance short-duration grazing (HPSDG) system during 1983 and 1984. Animal numbers were adjusted with put-and-take sets of livestock to attain planned forage use levels for each cycle in HPSDG and comparable end-of-season use levels in both treatments. Diet quality, as estimated from fecal nitrogen (N), was better (P<0.05) for the RSG livestock especially during the first 2 grazing periods. Similarity indices of lamb and calf diet composition indicated compatibility of the lamb and calf mix in both grazing systems treatments. Calves primarily selected western wheatgrass (Agropyron smithii Rydb.) and annual grasses and lambs selected buffalograss (Buchloe dactyloides [Nutt.] Engelm.) and blue grama (Bouteloua gracilis [H.B.K.J Lag. ex Griffiths). Average daily gain (ADG) of RSG calves was greater in both 1983 and 1984 (0.52 and 0.68 kg/d) compared to HPSDG calves (0.39 and 0.62 kg/d,P<0.05). RSG lamb ADG (72.6 g/d) was greater in 1983 compared to HPSDG (45.4 g/d, P<0.05). Attained stocking rates were 35 and 25% higher in HPSDG during 1983 and 1984, respectively. Gain/ha, however, was greater for the HPSDG calves and combined livestock (calves + lambs) only during 1984 (P<0.05).