Methods of Projecting Complete Lactation Production from Part-Lactation Yield

Abstract

Four methods of extending lactations-in-progress were compared: ratio, multiple regression, modified regression, and regression of the remainder of the lactation on the last test. Multiple regression estimates and regression estimates on the last test were about equally precise. Modified regression was intermediate while errors of ratio estimates were largest. Present use of ratio extension factors results in excessively large errors in projecting short-length lactation to a 305-day basis. © 1972, American Dairy Science Association. All rights reserved.