Steer nutritional response to intensive-early stocking on shortgrass rangeland

Abstract

Steer nutritional response to vegetation conditions created by 4 grazing treatments was evaluated during the final 2 years (1987-88) of a 9-year grazing trial. Treatments were season-long stocking (treatment 1) at a moderate stocking rate and intensive-early stocking at 3 stocking rates: equal to season-long stocking by using twice as many steers for the first half of the season-long stocking grazing season (double-stocked-intensive-early stocking, treatment 2), and 2 rates greater than season-long stocking made by stocking at 2.5 or 3 times the stocking density or season-long stocking (2.5X- and triple-stocked-intensive-early stocking, treatments 3 and 4). Each treatment was replicated twice in a randomized-complete block. Three esophageally fistulated steers were placed in each pasture to collect diet samples for nutritional analyses, including crude protein and cell wall constituents. Total feces were collected from 3 steers in each pasture to estimate fecal output and calculate forage intake. Diet digestibility was estimated using alkaline-peroxide lignin as an internal marker. Three or 4 sampling periods were conducted during each grazing season. Herbage availability and dietary crude protein were similar among treatments in 1987, but both declined as stocking density increased in 1988. Cell wall constituents generally increased as stocking density increased in 1987, but were similar among treatments in 1988. Digestibility and forage intake were unaffected by grazing treatments in both years. Steer average daily gain declined as stocking density increased in both years. Seasonal changes in diet quality and forage intake reflected the precipitation pattern with improved nutrition whenever precipitation caused growth of the warm-season shortgrasses. Nutrient intake was reduced by stocking rates greater than that employed under season-long stocking, but was generally similar between season-long stocking and double-stocked-intensive-early stocking.