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Quantification of nutrient supply in forage-based diets for beef cattle.
McGee, Michael Owens, David O'Kiely, Padraig
McGee, Michael
Owens, David
O'Kiely, Padraig
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2009-12-01
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McGee, M., Owens, D., O'Kiely, P. Quantification of nutrient supply in forage-based diets for beef cattle, End of Project Reports, Teagasc, 2009.
Abstract
Cattle rearing systems in Ireland are predominantly grass-based as 80% of agricultural land is dedicated to
grassland (silage, hay and pasture) (CSO, 2007). Feed costs represent the largest single variable cost in beef
production in Ireland.
Grazed grass is generally the cheapest source of food available for beef (and milk) production provided that the
environment and management permit high yields of high quality herbage to be utilised (McGee, 2000).
Environmental legislation and the rules of environmental schemes such as the European Union (EU) Rural
Environmental Protection Scheme are progressively restricting the application of fertilizer Nitrogen (N), and
many grazing systems are becoming more extensive.
Over 80% of all farms in Ireland make grass silage (O’Kiely et al., 1998) and it accounts for 87% of total grass
conserved (Mayne and O’Kiely, 2005). The deficiencies in nutrient supply to beef cattle from grass silage are
usually overcome by supplementing with concentrates (McGee, 2005), which are primarily cereal-based
(Drennan et al., 2006). However, diverse types of concentrates containing a variety of feed ingredients,
particularly non-cereal by-products are available and frequently fed as supplements to grass silage or as highconcentrate
diets. The relatively small amount of information available on feeding these contrasting
concentrates to beef cattle is inconsistent. Moreover, there has been an increased use of other ensiled forages
such as maize and whole-crop cereals. These forages have high intake potential and can reduce the concentrate
feeding level, while maintaining or increasing performance of beef cattle (Keady, 2005).
With increasing costs of beef production and increasing constraints of environmental regulations, efficient
utilisation of consumed nutrients by cattle is imperative in providing sustainable production and income to
farmers.
Feed evaluation systems are used to match the dietary nutrient supply with animal requirements for a specific
level of production (Dijkstra et al., 2007). These systems are important in order to optimise the efficiency of
feed utilisation, to improve animal performance and to reduce nutrient losses to the environment (Dijkstra et al.,
2007). Although the reticulo-rumen is central to the profile of nutrients available for absorption, yet quantitative
knowledge of the rates of passage and the digestion of nutrients in the rumen is limited compared with that on
degradation rates (Dijkstra et al., 2007). There is a lack of information that adequately characterises the supply
of nutrients from forages and feedstuffs specific to Ireland, especially for fresh grass-based diets of which, there
are very few studies reported in the literature. This shortcoming impedes our ability to capitalise on the merits of
evolving feeding systems.
This project aimed to:
1. Increase the knowledge and advance the understanding on rumen digestion and nutrient flow from the
rumen of the main forages / forage-based diets offered to beef cattle in Ireland.
2. Evaluate strategies for optimal utilization of nutrients consumed by cattle.