2007 Annual Report 1a.Objectives (from AD-416) To determine if adjustment of lifetime income for premature or delayed culling reduces the economic importance of PL uniformly under different patters of net income; to determine if the frequency and magnitude of production beyond 305d varies over time, across breeds, and with the age of the cow; to determine an economically sound method to expand the measure Productive Life (PL) to include productive days beyond 305; to determine an optimum method to predict the estimate of the new expanded measure of Productive Life for cows that are still alive; and to re-evaluate the economic weights for the traits in the merit indexes with the inclusion of the new measure of Productive Life. 1b.Approach (from AD-416) The estimate of the economic weight for the current measure of productive life in our initial work using lifetime RNI was exaggerated. The impact of adjustment of RNI for opportunity cost on the economic importance of traits in the merit indexes will be examined under different economic conditions (High and low average profit resulting from different costs per day and replacement costs); the proportion of total lactation production after 305d will be analyzed to determine the impact of breed (Holstein and Jersey), level of production, and trends over time; the value of days beyond the 305d currently included in the measure of PL will be determined using the Relative Net Income (RNI) method originally developed at AIPL and the form of the measure adjusted for opportunity developed at VA Tech under different economic conditions (High and low average profit). 3.Progress Report This report documents research conducted under a specific cooperative agreement between ARS and Virginia Polytechnic Institute and State University (Blacksburg, VA). Additional details of research can be found in the report for the parent project 1265-31000-085-00D, "Improving Genetic Prediction of Economic Merit of Dairy Animals". Research conducted under the agreement is related to objectives 4 (improved rankings for overall genetic merit) and 5 (characterization of dairy industry programs and practices). Monitoring activities for the project included meetings in Raleigh, NC, and San Antonio, TX, between three Animal Improvement Programs Laboratory research geneticists and Cooperator researchers to discuss future research plans, fund uses, and project extension. Additional phone calls were made regarding project status, and research publications were drafted via several iterations of e-mail exchange. The ability of nine widely used lactation curves to predict 305-day as well as 999-day lactations was compared. Some of the simple formulas were found to be more favorable than the complicated ones because the computational difficulties associated with complicated formulas outweighed their marginal superiority in prediction accuracy. Group-average lactation curves, which represent the average performance of a whole herd during a lactation with varying levels of individual contributions, were investigated for their usefulness in modeling group performance for diagnostic purposes and as a weighting factor in calculating a useful measure of productive life. Computer programs were reorganized to output better graphics, to give users simpler access to options, and to provide additional output, such as best prediction of daily yields; the revision provides a flexible tool for modeling lactation records of any length. An oral presentation on estimation of yields for long lactations using best prediction was given at the annual meeting of the Federation of Animal Science Societies, and an abstract was prepared and published in the meeting proceedings. A scientific paper on modeling group-average lactation curves for milk, fat, and protein yields of Holsteins with extended lactations was prepared and submitted for the peer-reviewed proceedings for the Conference on Mathematical Modeling in Nutrition and the Health Sciences. A scientific paper on modeling extended lactations was prepared, submitted to the Journal of Dairy Science, and published.