Does adaptive grazing management influence dietary quality of yearlings during the grazing season on western Great Plains rangelands?

Abstract Text: Grazing management decisions, such as timing of herd movements, can have a direct impact on the diet quality and nutritional plane of cattle. The variation in diet quality relative to adaptive versus continuous grazing strategies can lead to differences in cattle weight gains which directly impacts the profit margin for livestock producers. Near Infrared Reflectance Spectroscopy (NIRS) was used on fecal samples collected weekly from yearlings during the 2015 grazing season (May-October) to evaluate if differences occurred in measurements of dietary quality (crude protein and digestible organic matter) between adaptive grazing and continuous, season-long grazing in 2 rangeland ecosystems of the western Great Plains: shortgrass steppe and northern mixed-grass prairie. Yearling cattle under traditional grazing management at a moderate stocking rate had a 1.2 to 2.4% higher dietary crude protein (p < 0.003, p < 0.001) and a 0.5 to 1.4% higher digestible organic matter (p < 0.1, p < 0.001) than yearling cattle under adaptive grazing management across the season at HPGRS and CPER respectively, with maximum differences for both protein and digestibility exceeding 5% at times. At CPER, adaptive grazing management caused a 2 to > 4 fold steeper decline in digestibility between rotations compared to traditional grazing management.

Keywords: beef cattle, diet quality, grazing management