FORAGE AVAILABILITY FROM A TEMPERATE PASTURE MANAGED WITH INTENSIVE ROTATIONAL GRAZING

Successful integration of rotational grazing into livestock production systems requires estimates of pasture growth rates for feed budgeting of daily animal intake. By matching livestock nutrient demand with fo rage availability, over-feeding of supplements can be minimized, which reduces feed costs and the need to manage surplus nutrients. A three- year grazing study was carried out on a Kentucky bluegrass (Poa praten sis L.)-dominant pasture to estimate the daily quantity of herbage ava ilable to cattle in an intensive, rotational grazing system. Herbage p roduction, species composition, and forage quality were determined in each of the six grazing cycles in a year, from April until September. The average length of a grazing cycle was 28.6 d, with 2.7 d for durat ion of grazing on a paddock. Pre-grazing and post-grazing sward height s, measured with a plate meter, were 14 and 7 cm, and the correspondin g herbage masses were 1955 and 775 kg DM ha(-1) respectively. Under ad equate soil moisture during 1989, herbage available for daily intake w as 53 kg ha(-1) from April until mid-August, declining to approximatel y 32 kg ha(-1) d(-1) by the end of September. Distribution of this her bage was fairly uniform until the end of August. However, a dry summer in 1991 reduced herbage availability to 15 kg ha(-1) d(-1). Bluegrass and white clover (Trifolium repens L.) formed 70% of the herbage yiel d during the period April-June. Later in the season, dead matter and o ther species increased, reducing the contribution of bluegrass and clo ver to approximately 60% of total dry matter. While these pastures hav e the potential to provide significant amounts of forage for 5-6 month s in a year, additional on-farm forage reserves are needed during peri ods of water stress.