Integrative understanding and evaluation residual feed intake in dairy cattle

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Residual feed intake (RFI) is a liveweight and production corrected measurement of feed utilization. It has been recognized as a robust measurement of feed efficency in livestock. RFI is defined as the difference between the actual feed intake and that predicted on the basis of mean requirements for body weight maintenance and levels of production. Methods for evaluating RFI for meat producing animals during growth have been well studied in beef, swine and poultry, but there is no method available for evaluating RFI for female breeding stock. This is because the multifunctional energy requirements of breeding females, such as dairy cows, complicates the measure, but certainly does not diminish usefulness. Since feed reflects a large amount (40-50%) of the variable costs associated with milk production and conceptus' growth, genetic improvement of RFI can potentially be of great economic importance. Therefore, RFI research in the breeding female should be given a high priority. The proposed research will develop science based methods to evaluate RFI of breeding females accurately using the dairy cow as a model. I believe that genetic diferences of RFI exist in dairy cows and this can be used in the genetic improvement of feed utilization. Also high genetic correlation between RFIs obtained from a first lactation heifer (HRFI) and her life time RFI (CRFI) may exist and if so HRFI can be use to predict her CRFI. This proposed research is aimed to 1) develop an innovative science based methodology to evaluate RFI for dairy cow; 2) identify the genetic differences in RFI among individual cows for genetic improvement; and 3) investigate the possibility of using an animal's HRFI to predict her CRFI. Although the research project will use the dairy cow as a model, the theory and methodology will have broad applications across female breeding stock for other industries. This research program will present a major knowledge advancement in the field of agriculture sciences through better understanding feed utilizations. It will significantly benefit the dairy and other domestic animal industries of Canada and globally by improving feed utilization for milk and meat production.