Nutrient Content, Dry Matter Yield, and Species Composition of Cool-Season Pasture with Management-Intensive Grazing

The objective of this study was to determine changes in the nutrient content, available pasture, and species stand counts of cool season pastures during the grazing season. Four replicated pastures were flexibly subdivided into 18 to 36 paddocks and grazed rotationally from late April to November in each of 2 yr. Steers were grazed with fresh pasture offered each 1 to 2 d, which resulted in rest periods for paddocks of 17 to 35 d. Samples used to determine the nutrient content of pasture forage dry matter (DM) were collected from two grazing rumen-fistulated heifers that had empty, clean rumens at initiation of the sampling period. Mean stand counts in long-term established pastures for the grazing season were 24% legumes, 45% grasses, 8% grassy weeds, 10% bare ground, 11% broadleaf weeds, and 1% dung piles. Stand counts did not differ between years. Mean DM utilization of pasture per grazing cycle was 1103 kg/ha, and total DM temporal utilization per season was 6624 kg/ha, which was 35% of the pasture available for each grazing. Pasture content of neutral detergent fiber, crude protein, in situ digestible DM, and net energy for lactation did not differ between years but did differ among months of harvest: neutral detergent fiber decreased, crude protein and in situ digestible DM increased, and acid detergent fiber and estimated net energy for lactation remained relatively constant over the grazing season. The content of measured nutrients in ingested herbage did not differ among heifers sampled. These results indicate that individual cattle select similar quality diets from given pastures and nutrient differences occurred among months of sampling. Even though differences among months of season were statistically different, actual differences were small. Management-intensive grazing of pastures was uniform enough over season, and animal selectivity was strong enough over season to result in constant quality of consumed pasture.