Main report — E.A.A.P. working group on: Efficiency in the dairy cow

Abstract

In both scientific work and in the planning of breeding programmes, feeding schemes etc., the definitions of biological and economic efficiency and optimization procedures are important. So too is knowledge and understanding of the relationships between the variables involved. Therefore, the Commission on Animal Genetics and the Commission on Animal Nutrition within the European Association of Animal Production set up a working group with the purpose of stimulating the development and use of a common language (definitions etc.) among animal geneticists and nutritionists working on increased efficiency in the dairy cow for production of milk, milk fat, milk protein, and the connected beef production. Efficiency can be defined as the ratio of output/input, with output and input given in a variety of units, biological, physical or financial. Using the term “efficiency” requires a clear definition, both of the term chosen and of the system studied. Definitions concerning nutrition and breeding are given and recommended with respect to primary and secondary traits as well as an overall selection index. A few examples are: (1) residual food intake, a minus b, estimated energy in feed intake, minus estimated energy in products (milk, gain and foetus) and for maintenance; (2) feed efficiency, b/a; (3) economic efficiency, the net income per unit of product (e.g. milk). The improvement in biological efficiency is important, and research has to be focused on the underlying processes such as rumen function, utilization of digested and metabolized energy and the partitioning of feed energy between milk and body tissue. Knowledge about genetic variation between animals for these different biological processes is very limited, and should be studied in relation to the composition of feed ration, the feeding strategy and the physiological state of the animal. One-sided genetic selection for milk yield capacity is seen to have a negative effect on feed efficiency, reproduction and health, while the feed intake capacity does not keep step with the requirements for the increasing yield. Under these circumstances the net income per kg milk is decreasing, when calculating according to the overall economic efficiency. Therefore it seems essential to include secondary traits in dairy-cattle breeding programmes. This, however, requires extensive and demanding field data recording, and more research is needed to explore the effect of direct selection for improved feed efficiency and feed intake capacity and to develop a consistent approach to indexing for multiple trait selection. The issue is complex, and there is a great need for cooperation between countries and institutes.