Reducing Dietary Protein in Dairy Cow Diets: Theoretical Considerations and Practical Constraints in Relation to Cow Productivity Welfare and Fertility

摘要

The combined effects of increased global protein prices and legislation introduced on the storage and application of cattle manure and slurry has resulted in renewed interest to reduce protein levels in dairy cow diets. Only around 25-35% of dietary protein is captured and secreted in milk, with the majority of the remaining nitrogen (n) being lost in urine and faeces (e.g. Colmenero and Broderick, 2006). This is costly in terms of feed use and represents a potential environmental hazard. Systems, including the current Metabolisable Protein (MP) system adopted within the UK (i.e. MPFlM), have been developed to predict the protein requirements of dairy cows but are based on a rather limited range of feeding regimens that offer conventional (typically 170 to 200 g crude protein/kg DM) levels of dietary protein. Uncertainty, therefore, surrounds the ability of these systems to predict animal requirements accurately and to model animal performance at lower dietary protein levels.