506. The importance of machine milking rate in dairy cow management and breeding

Abstract

With 2 Figures)The discoveries of the last decade have considerably improved our understanding of the neural and hormonal mechanisms controlling milk ejection. This, in turn, has stimulated research into the many practical problems concerned with hand and machine milking. The discovery that milk ejection is a transitory mechanism encouraged the study of the rate of machine milking of dairy cows since it was inferred that less milk is obtained when milking is slow. This research work has shown that there are very wide differences in the machine milking rate of cows in the same herd, even when they are under identical management (l, 2, 3). However, the milking rate of a particular cow is relatively stable over long periods (2, 3, 4) and cannot be altered even by severe changes in management (5, 6,7). The explanation of this appears to be that milking rate is mainly controlled by the structure of the teat orifice (8).The results given in this paper carry this study a stage further. They show the effect of inherent milking rate on milk yield, milk composition and the rate of decline of milk yield. In addition, some preliminary observations on the inheritance of milking rate are given. SOURCE OF DATAThe measurements of milking rate, milk yield and milk composition used in this analysis were all made in the herd of the National Institute for Research in Dairying. For details of the method of collection of the milking-rate data reference should be made to another publication (3). The lactation yields of the cows were all compiled from the daily weighing of the milk produced by each cow at each milking. Samples of milk for milk-composition analysis were collected on one day each month. Elsewhere, Bailey (9) has described in some detail the management, feeding and breeding of the herd. RESULTSFor convenience the following terms have been used in presenting the results:'Peak flow' (16/min)-maximum milking rate attained in any minute during milking. 'Standard lactation yield' (lb.)-amount of milk produced in 305 days or until dry, whichever is the shorter period. 'Lactation fat percentage'-mean weighted fat percentage in the total lactation period. 'Lactation solids-not-fat percentage'-mean solids-not-fat percentage in the total lactation period. 'Lactation length' (days)-days in milk from 4 days after calving until dry. 'Persistency' (days)-the number of days after calving before the weekly yield falls below one-half of the maximum weekly production.

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

“…The weighted mean regression coefficient calculated on the complete data is very highly significant. This direct relationship between inherent milking rate and yield in the first lactation confirms the earlier results (2).…”

“…In practice, involuntary culling on the basis of milking rate will occur even when its direct measurement is not made (2).…”

“…percentages given previously (2) apply to the new data, except that the standard lactation length at the Bull Progeny Testing Stations is 270 instead of 305 days.…”

521. Normal variations in the rate of machine milking

“…However, for all the determinations measured the overall changes between the first lactation group and the oldest lactation group are significant at either the 5 or 1 % level. Elsewhere (12) we have shown that in this herd the lactation age at culling is related to milking rate in such a way that slow milkers are culled at an earlier age than fast milkers. Thus the figures in Table 8 do not give a true measure of the effect of age on milking rate.…”

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

“…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).…”