Effect of Winter Grazing Management Strategies on Average Daily Gain of Yearling Steers.

Winter grazing can help reduce the need for purchased feeds in a livestock production system to finish beef cattle on pasture. Our objective was to evaluate how stocking density, pasture and stockpiled forage influenced performance of yearling steers during winter grazing. Four grasslands of different botanical composition were grazed in sequence from November through January for two consecutive years as follows: I. naturalized grazingland; II, III and IV that were sown and managed for hay production during the growing season. Two stocking densities were compared: low 8.23 steer ha^-1; high 11.5 steer ha^-1. Forage mass was estimated using a falling plate meter before each grazing event. Residual measurements were made at the end of each grazing event with data used to estimate herbage disappearance. Disappearance relative to days of occupation was considered forage utilization. Pre-grazing samples were clipped at ground level and separated into grasses, legumes, forbs and dead, samples were dried, weighed and analyzed for nutritive value. Soils at the grasslands were characterized for physical and chemical properties. Pre-graze stockpiled forage mass averaged 2892 kg ha^-1. Forage mass differed by year (P < 0.0001) and grassland (P = 0.0004). In general, soil pH (±5.4), organic matter (±8 g/kg) and penetration resistance (±1700 kPa 0-20 cm depth) were not limiting for forage production, however soil channery and drainage characteristics could be related to observed differences in forage mass between years and grasslands. Residual herbage differences occurred between stocking density (P = 0.0015), but no differences were found for disappearance or forage utilization. Botanical composition differed for all components as a function of year and grassland, but legumes differed only by year. Stocking densities did not influence grassland botanical composition. Year affected all of the herbage nutritive constituents except crude protein which differed with grassland (P = 0.0009). Steer performed differently in both years (P< 0.0001), but average daily gain was not influenced by stocking density (P= 0.4820). Average daily gain was 0.11 kg in 2011 and 0.50 kg in 2012. Acceptable gains in 2012 may be a product of soil-weather conditions during stockpile influencing pasture quantity and quality and animal behavior during winter grazing interacting with environment.