More effective supplements for the northern beef industry

Abstract

A series of pen and metabolism experiments were carried out with young, growing cattle receiving tropical forages and a range of supplement types. The objectives were to establish growth response curves to these supplements and to investigate ways to reduce the substitution effects associated with their feeding. Growth responses to protein meals were higher at low intakes but comparable at higher intakes to those of ‘energy sources’ such as grains and molasses. Generic response curves to the different supplement types have been incorporated into simple spreadsheets for ration formulation. Of the
strategies investigated to reduce substitution, maintaining a higher protein/energy ratio in the supplement successfully reduced substitution at low intakes presumably through correcting an imbalance of nutrients in the rumen. Microbial protein production in the rumen was increased with the inclusion of all supplement types on low quality forage diets, but the largest increases occurred when a true protein source was included. The findings from this project can now be used by producers and their advisers as an aid to objective decision making in the feeding of young, growing cattle on low quality pastures. However, this decision making process will be enhanced through further research to include older, finishing cattle receiving medium quality forages and by inclusion of the response data in a decision support model.