Title: Age, Live Weight and Milk-Energy Yield in Illinois Cows
Abstract: In a previous article it was mentioned (1, footnote 6) that a plan of using live weight in connection with Dairy Herd Improvement Association records was under trail.This paper reports some of the results of that trial, dealing with all the Holstein (957) and Jersey (195) records available covering the first 8 monthly tests of the lactation without interruption.The records were all made under farm conditions, milking twice daily.It is impossible to deal with the records beyond the 8th month without in many cases encountering serious disturbances associated with advanced pregnancy and with management practice.Comparisons are simplified and biological meanings are clarified by dealing with the first 8 months of lactation (when the usual calving interval is 12 months) as compared with trying to deal with the whole lactation, or with fiscal year records.This fact was recognized by Gowen (2) as early as 1920, but the merits and advantages of the system are not yet generally appreciated. ~STIMATE OF LIVE WEIGHTLive weight of the individual cows was determined by use of a chest-girth live-weight tape sold by the New York Farm Bureau Federation, Ithaca, New York.The determination was made uniformly for each cow at the first visit of the tester after the cow calved, that is, within the first 30 days following parturition.The tape used is marked at one centimeter intervals and each mark is labeled with a corresponding live weight in pounds.The following figures, taken from the tape, cover the range of size encountered in the present trial : Chest girth, cm.