An Assessment of Field Measures of Milking Rate

Several measures of milking rate were taken twice per lactatiort during 1457 Holstein lactations in five herds. These were taken to determine which variable would be most practical as a field measure of milking rate. Milking rates were estimated by peak flow which has been taken as the standard measure for milking rate, average flow, percent of milk produced in the first 2 rain of machine milking, and the amount of milk produeed through the 1st min, first 1.5 rain, and first 2 rain of milking. Variables constructed from pess~ble differences among these last three variables were also assessed. A measurement solely used to indicate rate should be obtainable before the 3rd rain of milking. If rate were measured after that time, an increasingly larger number of cows would have completed their milking, and their records would not be considered in determining rate of flow. The percent of milk yielded in the first 2 min of machine milking had high phenotypie (.90) and genetic (1.0) correlations with peak flow. Percent 2 min milk was as repeatable within lactations and as heritable as peak flow. These four properties pins the ease with which percent 2 min milk was obtained indicated that percent 2 min milk was an adequate field measure of milking rate.