663. The relationship between milk secretion and the rate of milking by machine

Abstract

Lactation has two phases: the continuous process of secretion and the mechanism of ejection which occurs only during milking. Because ejection is a transitory phase it is to be expected that within certain limits milk yield will be inversely related to the duration of milking, which, was, in fact, demonstrated many years ago with hand-milked cows(i). With machine milking the situation is different because the forces which the machine applies to the udders of all cows within a herd are the same, and thus the differences in milking rate that occur are due to differences between the cows. Under these conditions, if milking rate can be shown to affect milk yield it is a demonstration of how the physiological factors controlling milking rate can modify the expression of the inheritance of milk secretion.The machine milking-rate and milk-yield records of eighty-six first lactation heifers presented by Dodd & Foot (2) indicated that a significant relationship existed between milking rate and lactation yield, persistency and lactation length. Since these results were published milking-rate and milk-yield records have been obtained from a further 266 firstlactation heifers and an analysis of these data is given in this paper.

A note on the relationship between the rate of machine-milking and milk production of Ayrshire heifers

“…The results in Table 2 show that the direct relationship between lactation yield and peak flow rate was not close and this result agrees with the findings of Clough and Dodd (1957). There was no simple correlation between lactation yield and milking time.…”

“…The time and rate values used were averages for the three consecutive milkings at which the rate measurements were made. The coefficients of variation in Table 1 show trends similar to those reported by Clough and Dodd (1957) with the highest variability associated with the measures of flow rate and the lowest with milk composition. The mean, minimum and maximum values with the coefficients of variation for each variable are given in Table 1.…”

“…The rate of milking, as one of the major factors determining the total time of machine-milking (Donald, 1960), has received considerable attention in the herd of the National Institute for Research in Dairying (Dodd and Foot, 1953;Dodd, 1953;Clough and Dodd, 1957). The rate of milking, as one of the major factors determining the total time of machine-milking (Donald, 1960), has received considerable attention in the herd of the National Institute for Research in Dairying (Dodd and Foot, 1953;Dodd, 1953;Clough and Dodd, 1957).…”

The effect of selection for milk yield on milk flow and udder measurements

“…A controversy exists as to the relationship between rate of milking and the total lactation yield. Brumby (1961) demonstrated no genetic correlation between lactation yield and peak flow rate, while other researchers have found rate of milking to be related to lactation yield (Castle and Henderson, 1971;Clough and Dodd, 1957;Dodd and Neave, 1951;Donald, 1960;Johansson and Malven, 1961;Kawanishi et al, 1982;Miller et al, 1976;Rajamannan et al, 1966;Tomaszewski and Legates, 1972). Donald (1960) found that 11% of the variation in yield was removed by holding peak rate constant and concluded that high producing cows tended to be rapid milkers.…”