Manipulation of Grass Supply to Meet Feed Demand

Abstract

Grazed grass is generally the cheapest form of feed available for beef and milk production in Ireland. Grass growth is variable during the year with a peak in May/June and a secondary peak in August. There is little net growth from December to February. Grass growth is also variable across the country with higher grass growth in the south and south-west (14 to 15 t DM/ha/year) compared with approximately 11 t DM/ha/year in the north-east (Brereton, 1995). There is poor synchrony between grass supply and feed demand on beef and dairy farms. The feed demand curve for a calf to two year old beef system shows feed demand decreasing as grass supply increases, and grass supply decreasing as feed demand increases. Similarly, the feed demand curve of a spring calving dairy herd shows poor synchrony with grass supply, with a surplus of grass from about mid-April to mid-August, and a deficit for the rest of the year. Traditionally surplus grass produced during May and June is conserved as silage or hay and fed back to cattle and dairy cows during the deficit times of the year. This project examined the possibility of reducing the grass growth peak in May/June and increasing grass supply later in the year by altering nitrogen application pattern and extending autumn rotation lengths.