Effect of grazing strategies and pasture species on irrigated pasture beef production

Abstract

Irrigated cool-season grasses can be used as complementary forages with other forage resources. Improved efficiency of animal production from irrigated pasture could increase their utility as a complementary forage. The factors of species composition, grazing management, irrigation, and fertilization all have the potential to affect efficiency of irrigated pasture production. Specific objectives of this study were: (1) to determine the effect of deferring irrigated pasture and restricting irrigation water and fertilization during mid-summer on pasture and livestock production; and (2) to evaluate different pasture stands for adaptability to different grazing strategies. Eight, adjacent 1.25-ha pastures were established as 2 replications of 2 different pasture stands grazed under 2 grazing management strategies. Pasture stands consisted of intermediate wheatgrass (Agropyron intermedium Host. Beauv.) as a monoculture (IWG) and a 4-species mixture (MIX) of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leyss.), meadow bromegrass (Bromus biebersteinii R. & S.), and Garrison creeping foxtail (Alopercurus arundinaceus Poir.). Grazing treatments with yearling steers consisted of season-long grazing (SLG) and a graze-defer-graze (GDG) strategy. For the GDG pastures, 38% less fertilizer and 34% less irrigation water were applied, but animal days of grazing were reduced only 16% over the 3-year study. Animal weight gains were comparable between pasture types when considered over the entire grazing season but were higher for IWG early in the growing season and for MIX late in the season. Persistence of pasture stand was better for the MIX pastures than IWG pastures which were invaded by annual weeds after the first grazing season. Highest gains ha-1 were from the SLG pastures because of more days of grazing, but animal productivity was not proportionally reduced for the GDG strategy. The MIX pastures were suited for either grazing strategy.