An Assessment of Field Measures of Milking Rate

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Abstract
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 mea- sure of milking rate. Milking rates were estimated by peak flow which has been taken as the standard measure for milk- ing rate, average flow, percent of milk produced in the first 2 rain of machine milking, and the amount of milk pro- dueed through the 1st min, first 1.5 rain, and first 2 rain of milking. Variables con- structed from pess~ble differences among these last three variables were also as- sessed. A measurement solely used to indicate rate should be obtainable before the 3rd rain of milking. If rate were measured after that time, an increas- ingly larger number of cows would have completed their milking, and their rec- ords would not be considered in deter- mining 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 repeat- able 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.
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