Extending grazing into the winter, as opposed to feeding of harvested forages, can increase the sustainability of ranching in the western US. This study was conducted to determine the economic value of grazing stockpiled forage kochia (Kochia prostrata [L.] Scrad.) and crested wheatgrass (Agropyron desertorum [Fisch. Ex Link] Schultes) during the fall and winter. Changes in cow body weight, body condition score, and ultrasound backfat were compared for late-gestation cows grazing forage kochiacrested wheatgrass pastures vs. those fed alfalfa (Medicago sativa L.) hay in drylot. The study was conducted from early November to late January for 2 consecutive years near Promontory, Utah. Forage availability and nutritional quality were monitored throughout the experiment. Cows grazing stockpiled forages did not receive any protein or energy supplements. Forage kochia comprised approximately 70% of available forage, with November crude protein content of 116 and 76 g kg À1 in years 1 and 2, respectively. Nutritional quality declined throughout the season, presumably mostly because of removal of higher-quality forage by preferential grazing as opposed to weathering. Averaged over years, cows grazing forage kochia-grass gained body weight (19 kg), increased in body condition (0.3 points), and maintained backfat thickness, finishing well within the range considered optimum for onset of calving and return to estrus. Pasture-vs. drylot-fed cows did not differ with regard to changes in body weight or body condition score. Both treatments increased backfat in year 1, when initial backfat was less than 0.5 cm, but both treatments resulted in loss of backfat in year 2, when initial backfat was greater than 1.0 cm. Grazing was more economical, costing $0.24 cow À1 d À1 less than feeding alfalfa hay in drylot. Forage kochia can be used on western rangelands to extend grazing into the fall and winter, thereby improving the profitability of beef production.
ResumenExtender el apacentamiento hasta el invierno, como estrategia opuesta a la alimentació n con forrajes cultivados, puede incrementar la sostenibilidad de las operaciones ganaderas del oeste de Estados Unidos. Este estudio se condujo para determinar el valor econó mico de apacentar forraje acumulado en pie de ''Kochia'' (Kochia prostrata [L.] Scrad.) y ''crested wheatgrass'' (Agropyron desertorum [Fisch. Ex Link] Schultes) durante el otoñ o e invierno. Cambios en el peso corporal, la condició n corporal y grasa del lomo medida con ultrasonido fueron comparados entre vacas en estado final de gestació n apacentando praderas de ''Kochia''-''Crested wheatgrass'' versus vacas alimentadas en corral con heno de ''Alfalfa'' (Medicago sativa L.). El estudio se llevo a cabo cerca de Promontory, Utah de inicios de Noviembre a fines de Enero durante dos añ os consecutivos. La disponibilidad de forraje y la calidad nutricional fueron monitoreadas a lo largo del experimento. Las vacas apacentando los forrajes acumulados en pie no recibieron ningú n suplemento ni proteico ni energ...