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A review of the energy, protein and phosphorus requirements of beef cattle and sheep. - WQ0133

Energy, protein and phosphorus are essential nutrients for beef and sheep, and both the amounts consumed and the forms in which they are provided can have major impacts on the productivity of livestock. This project will provide standards for the energy, protein and phosphorus in diets of cattle and sheep in the UK.

UK standards for beef and sheep have not been revised for over a quarter of a century, but in that time there have been considerable developments in the genetics of beef and sheep breeds, feedstuffs available and knowledge of the way in which ruminants digest and utilise feed. Fifteen years ago the concept of metabolisable protein was introduced to ruminant rations in the UK as a means of describing the available and utilised protein-N, and this was successfully incorporated into the Defra-funded LINK “Feed into Milk” rationing programme for dairy cows. However, there has been no similar co-ordinated approach to establishing the metabolisable protein requirements of beef cattle and sheep.

The extent to which the protein nitrogen (N) in feed is utilised for protein synthesis in ruminants is variable but generally low (typically <30%). Unutilised N is excreted, predominantly in urine as urea-N, and is rapidly hydrolysed to ammonia, causing acidification and N eutrophication after deposition to soils. Ammonia emissions from ruminants account for more than half of total ammonia output in the UK.

The UK government has signed up to a number of initiatives to improve water and air quality. The Water Framework Directive requires the UK to set in place measures that will ensure that all inland and coastal waters achieve `good ecological and chemical status` by 2015. Recent estimates have suggested that agricultural activities contribute up to 60% of diffuse nitrate entering river systems, with much of this coming from unutilized feed N in the livestock sector. Feeding recommendations, based on improved definitions of the requirements of cattle and sheep for dietary protein N and the supply of metabolisable protein from feeds, may be expected to result in a reduction in N excretion.

In the context of air quality, the UK is a signatory to the Thematic Strategy on Air Pollution, the Kyoto protocol, the Gothenburg protocol and the EU directive on acidification, all of which aim to reduce the production of a range of gases, including ammonia. It is widely accepted that the N excreted in the urine of ruminant livestock is the primary source of ammonia emission by UK agriculture. Furthermore, there is clear evidence that both the amount and nature of protein in the diet have major effects on the amount of N excreted and the route of excretion (in faeces or urine), and improvements in ruminant diet formulation have resulted in reductions in both total N excreted and ammonia production. This study would therefore include a review of the nutrient standards for cattle and sheep published in other countries, and draw on recent research undertaken in the UK and elsewhere to develop recommendations for energy and protein concentrations in rations for UK beef and sheep.

Phosphorus (P) is another essential nutrient for cattle and sheep, but P supplied in excess of requirements is excreted in manure – predominantly in faeces. It is generally accepted that P excreted by livestock and which enters watercourses via manures applied to land makes a major contribution to eutrophication of inland waters. As a result of the adoption of the Water Framework Directive, Defra`s water policy has made tackling diffuse pollution a top priority. This project will include a review of the requirements for P by beef cattle and sheep and identify the scope for reducing P excretion by these livestock.

The project would identify critical areas where further research may be necessary to refine the recommendations for energy, protein and phosphorus. Finally, the results of the review would be published in the form of recommendations that could be used as the basis of ration formulation for beef cattle and sheep in the UK.
7. (b) Objectives

Because the energy, protein and phosphorus requirements of cattle and sheep have not been reviewed in the UK for many years, a range of different standards are used by livestock farmers, feed manufacturers and consultants to formulate rations. As a result, intakes of nitrogen (N) and phosphorus (P) frequently exceed requirements for the level of production required. The excess N and P is excreted, with adverse environmental effects. This project will attempt to identify the requirements for energy, N and P by beef cattle and sheep in the UK, providing farmers and their advisors with the information necessary to formulate diets to meet requirements but minimise excretion. Because N cannot be considered in isolation, the project will also include a review of the energy requirements of cattle and sheep. The overall objectives of this project therefore are:

1. To review current information on the energy, protein and phosphorus requirements of beef cattle and sheep. This will include standards and models published in other countries, and will assess the extent to which the information they contain may be applicable to UK beef and sheep producers;
2. To review factors affecting intake by beef cattle and sheep, and to develop predictive relationships to estimate feed intake;
3. To review the requirements for phosphorus, and assess the extent to which current practice meets the requirements, and strategise for reducing intake where it exceeds requirements
4. To produce a feed database for use in beef and sheep rations;
5. To update estimates of the energy, protein and phosphorus requirements for cattle and sheep, and produce these in form that may be readily understood and used by beef and sheep farmers and their advisors.

Project Documents
• Abstract : Final report   (174k)
• Final Report - Annex : Final report   (992k)
Time-Scale and Cost
From: 2008

To: 2008

Cost: £55,000
Contractor / Funded Organisations
Sustainable Farming and Food Science              
Water Quality              
Water Quality and Use              
Fields of Study
Water Quality