Daily and seasonal forage availability under rotational grazing of a mixed-species temperate pasture

Sustainable use of mixed species pastures under management intensive rotational grazing requires information on forage dry matter availability on a daily basis for feed budgeting purposes. Forage availability, forage nutritive quality, and species composition were measured during May to September in 1994 and 1995. Forage available for daily consumption declined in both years as the season progressed. However, the magnitude of this decline varied between years during summer (July to September), which was attributed to differences in soil moisture availability. Under adequate moisture conditions observed in 1994, forage was available at an average rate of 70, 68, 51, 66, 24, and 11 kg dry matter ha(-1) d(-1) during May, June, July, August, September, and October, respectively. Due to extended periods of dry weather in the summer of 1995, forage availability during the months of July, August and September was reduced to 26, 47, and 11 kg ha(-1) d(-1), respectively. Total forage consumed during 1994 and 1995 was 8580 and 6460 kg dry matter ha(-1), respectively. Averaged over the two years, forage dry matter consumed during the grazing season contained 22% crude protein (CP), 45% neutral detergent fiber (NDF), and 24% acid detergent fiber (ADF). Averaged over the two years, forage cut at ground level was composed of 22% Kentucky Bluegrass (Poa pratensis L.), 33% of mostly smooth bromegrass (Bromus inermis Leyss.) and quackgrass (Elytrigia repens [L.] Nevski), 13% legumes (mostly white clover, Trifolium repens L.), 27% dead matter, and 5% of all other species. These fractions remained stable during the season, except under intense drought when dead matter increased as the bluegrass and white clover fractions declined. However, bluegrass and clover recovered quickly upon return of favorable moisture conditions. The results indicate that these pastures can provide significant amounts of forage under management intensive rotational grazing, but additional feed may be needed for a month or two under extended periods of water stress. While more years of data are needed to accurately assess the effects of rotational grazing on species composition, the limited set of data presented suggests that the pasture composition, a measure of pasture persistence, may remain fairly stable from year to year under the system of grazing management imposed, even though significant but transient changes were observed within a grazing season.