Protein requirements and responses: a United Kingdom perspective

Abstract

AbstractOnly as recently as 1992 was the digestible crude protein approach to the calculation of protein requirements for ruminants abandoned in favour of a scheme in which metabolizable protein (MP) became the nutritional currency (Agricultural and Food Research Council, 1992). Application of this scheme requires reliable methods to characterize foods in a number of ways and whilst there are deficiencies in current methodology for this purpose there is now a sufficient body of information available to sustain use of the scheme. Evaluation of the MP approach shows it to be a considerable advancement on what went before but still with some inadequacies. More attention needs to be given to the impact of food constituents on digestive processes within the rumen. Tests of the relationship between predicted MP supply and dairy cow performance show that rules are needed to predict partition of available MP between alternative routes of use. With such rules it will become more likely that a useful response prediction system can be developed. Ideas are put forward as to how some progress might be made to develop frameworks which will bring together ideas about responses to protein and energy yielding nutrients. Clarification of partition rules will be important in promoting improved feeding strategies for cows of different genetic index for milk production. However, it is felt that, given adequate partition rules, the MP approach applies equally to high genetic index and low index cows as regards calculation of requirements. A concern is expressed, however, that the current UK research environment may not be conducive to the open sharing of information which will be important to make rapid progress towards the development of nutrient response frameworks. A technology transfer system is needed which will enable advances in knowledge to be organized for translation into practice.