Grazed grass is currently the cheapest feed source available for beef cattle in Ireland, with an estimated cost of £38/tonne digestible dry matter. Corresponding digestible dry matter (DM) costs for silage and purchased concentrates are £98 and £155/t respectively. The intake of grass, or its contribution to total intake, needs to be increased if the cost of animal carcass gain is to be reduced. This can be achieved by producing a high yield of grass and utilising it efficiently throughout a long grazing season, while maintaining high levels of animal performance. Critical to this strategy is maintaining good animal performance at grass in the autumn. Acceptable liveweight gains are generally achieved on commercial farms until mid-summer. 

However, animal performance is often poor later in the season. Grass growth varies widely throughout the year and as grass growth declines in the autumn, herd demand often exceeds feed supply. The shortage of feed can be corrected by appropriate and judicious supplementation. Figure 1 shows a typical grass growth curve and a feed demand curve for a drystock farm stocked at 2 L.U./ha. Furthermore autumn grass has a lower dry matter digestibility (DMD) than grass in spring. Also, at similar DMD values, autumn grass has a lower feeding value, and lower intake characteristics, in comparison with grass available in early and mid-season. The nutritional value of autumn grass may thus be insufficient to support satisfactory levels of animal liveweight gain, thereby necessitating the need for supplementary feeding. 

Beef farmers must no longer consider themselves as producers of live or carcass weight but as providers of a quality food product if they are to sell beef onto the high value markets of the world. Scientific evidence is available (Larick et al., 1987) from some countries to show that beef produced from feedlot cattle can be more tender and have better flavour than pasture-finished beef. This information is used to gain a marketing advantage by countries such as Australia and the United States where feedlot finishing is the norm. If Irish beef is to gain a share of the quality consumer market then its strengths must be identified and sold.

The presence of certain polyunsaturated fatty acids (PUFA) in the human diet has been shown to be beneficial. Decreasing the ratio of n-6 (primarily linoleic acid) to n-3 (primarily linolineic acid) PUFA has been shown to reduce the incidence of cardiovascular disease (Wood and Enser, 1997). Despite a hydrogenation effect in the rumen, some dietary unsaturated fatty acids bypass the rumen intact for absorption and deposition in body fat (Wood and Enser, 1997). Ruminant tissue fat of concentrate-fed animals has been shown to contain a higher ratio of n-6 to n-3 fatty acids than grass-fed animals. A number of experiments have been conducted at Grange Research Centre, in collaboration with the National Food Centre, to quantify the animal production and meat quality responses of supplementing autumn grazed grass with concentrates.