Use and Interpretation of Milk Flow Curves in Measuring Variations in the Response of Cows to Machine Milking1,2

Abstract

Summary A method is described for adapting the use of a continuous-feed kymograph to obtain graphic measurements of the rate of milk flow during the machine milking process. Various numerical measures taken from the milk flow curves were highly repeatable, not only from day to day, but from week to week over a 6-wk. period, and from lactation to lactation where similar stages of lactation were compared. Cows differ in their response to standardized methods of machine milking in a characteristic individual fashion, as shown by milk flow curves. Numerical measurements of average rate of flow, maximum rate of flow, when maximum flow starts, how long maximum flow is sustained, per cent of the milk yield obtained during the first 2 min. of milking and time required to machine strip, selected from the milk flow curves for the purposes of statistically interpreting differences in the milking responses of cows, were found to be significantly correlated with machine time. Time required to milk any cow depends primarily on these three variables—(a) maximum rate of flow, (b) when maximum flow starts and (c) how long maximum flow is sustained. The interrelationship of these three factors to the total machine time was shown by the highly significant multiple correlation coefficient of 0.936. As a simple objective measurement of the time required to milk a cow, the per cent of the milk yield obtained during the first 2 min. of milking is highly reliable, having a simple correlation of 0.922 with machine time and a multiple correlation of 0.956 with the three maximum rate variables.