Ruakura Experiment in Milking Management

New Zealand Journal of Agriculture, Volume 101, Issue 3, 15 September 1960, Page 221

Ruakura Experiment in Milking Management

Gives 32% Production Gain from 30 Sec Pre-milking Hand Stimulus

A SUBSTANTIAL increase in dairy cows' milk production (32 per cent in a Ruakura experiment) and reduction in milking time can be expected from the practice of a 30 second wash and hand stimulus of the lower udder and teats before milking, as against a system where the machine is relied on to produce the let-down stimulus. This finding and results of attempts to measure other factors in cows' milking behaviour were announced to the Ruakura Farmers' Conference in June by D. S. M. Phillips, Senior Principal Scientific Officer, Department of Agriculture's Ruakura Animal Research Station, in a paper to the conference and at a demonstration at the Station's No. I Dairy during the conference field day. An adaptation of the paper follows.

WITH hand milking there was no need for a pre-milking stimulus, as the act of milking itself constitutes a very vigorous and : prolonged stimulus. The pre-milking wash served no other purpose than to cleanse the teats and lower udder of dirt. The advent of machine milking has changed the picture to some extent. Because of the use of the high vacuum for milking, the machine is undoubtedly much less comfortable and stimulating than hand milking and does the job in a much shorter time. In New Zealand it has been the practice to wash the cow briefly before machine milking because of the frequently muddy surroundings and the need for preventing dirt entering the machine. - This wash has, generally, been somewhat perfunctory and little attention has been paid to its possible importance as a stimulus to let-down. The development of the let-down theory in recent years and the introduction of the conditioned reflex theory of let-down have made it apparent that the use of a vigorous wash as a direct stimulus to let-down may be very desirable. In practice many farmers have relied on “starting”, or a short period of hand milking before machine milking, to facilitate the milking of some of the more difficult cows, and the efficacy of this practice has suggested that a good “hand-induced” let-down before machine milking will often prevent slow or incomplete milking.

For some years now a vigorous wash has been advocated, but to date there has been no conclusive evidence that it would affect production. In 1956 W. G. Whittlestone carried out a full lactation experiment at Ruakura using, identical twins to measure the effect of pre-milking stimulus on total production. This experiment, using five sets of identical twins, compared the production of cows which were stimulated for 30 seconds immediately before machine milking with that of their twin mates who were not stimulated in any way before the teat cups were put on. The average within-set difference was 18 per cent in favour of the stimulated cows, but because of the large variability in response between twin sets the results were not conclusive. The responses to the treatment varied from —2 per cent to 36 per cent. In view of the inconclusive nature of this experiment it was decided to repeat it on a larger scale and at the same time to attempt to measure any other possibly relevant factors associated with the cow’s milking behaviour which might provide some reason for the very large variation in the response of individual twin sets to the treatment. Description of the Present Experiment For the purposes of the experiment 13 sets of identical twin cows were used. One set was subsequently not included in the result because of a very short lactation. One member of each set was stimulated and the other

was not. The treatments were as follows: Stimulated cows: The cows were washed for 30 seconds immediately before the cups were put on. The wash consisted of hosing with cold running water and rubbing with the

hand, followed by massage of the teats and lower udder and squirting of each teat. Non-stimulated cows: The nonstimulated cows were not given any stimulus to the udder before the cups were put on, the only stimulus to letdown being that produced by the machine. The cows were bailed up in the normal way and when the next cow was finished the cups were put straight on without any wash, or other preparation. . All cows were milked normally in a herd of approximately 65 cows and Were taken into the bail in any order. A four-cow single Ruakura machine was used, with the vacuum set at 15 in. of mercury. The pulsation was set at 40 per minute with a reduced squeeze giving approximately 30 per cent full air pressure. A weight of 3J lb was used on the claw at the end of milking for machine stripping; it was applied when the sight glass started to clear and continued until the cow was finished. Results of Experiment The milk from each cow was weighed at each milking and samples for fat test were taken weekly. The average production figures for the 12 sets of twins given in Table 1 show large differences between the two treatments. ■ TABLE I—EFFECT ON PRODUCTION OF 30 SEC PRE-MILKING STIMULUS (AVERAGE 12 SETS OF TWINS) Fat percenGroup Milk Fat Days tage , gallons lb 30 second stimulus .. 5,850.5 294.9 250 5.04 Non-stimulated 4,405.5 223.3 203 5.07 Difference .. 1,445.0 71.6 47 Difference per cent of nonstimulated .. 32.8 32.0 23.2 Difference per cent of stimulated 24.7 24.2 18.8 —. The average differences in the fat and milk are given as a percentage of both the stimulated (30 second wash) group and of the non-stimulated group, because though the 30 second wash and stimulus is standard practice at Ruakura, it may well be that the “non-stimulation” treatment is closer to the practice of many farmers. The percentage difference is the increase due to the use of the wash stimulus. It is apparent from the present experiment that the use of a 30 second wash stimulus for milk-.. ing increased the production by an . average of 71 lb of butterfat or 32 per cent. The average butterfat test was . the same for both groups. The average lactation curves for the two groups in Fig. 1 show very little difference for the first 50 days of lactation. Thereafter the non-stimulated group fell rapidly. The apparent improvement

at the end of lactation is due to the fact that only the higher producers were left in each group. Milking Times The effect of the washing on milking, rates and times was. quite, marked (Table 2). The . rate ,of milking in pounds of milk per minute was much higher for the stimulated cows. TABLE 2—EFFECT OF WASHING ON MILKING RATES AND TIMES NonStimulated stimulated Milking rate, pounds per . . min 1 .. .. 3.0 2.3 Average milking time, min .. . . 4.05 4.35 Milking time for normal production, min .. 3.9 . ' 5.1 Milking times averaged 20 seconds shorter for the stimulated cows, but these cows produced 32 per cent more than their non-stimulated . mates. If the milking times are calculated on the basis of the milk produced by the stimulated cows, they would be as shown, that is, 3.9 minutes for the stimulated cows and 5.1 minutes for

the non-stimulated cows. This represents a reduction of nearly 1| minutes’ milking time per cow due to the use of the wash stimulus. Influence of Let-down on Response to Wash Stimulus The individual production figures for the cows (Table 3) show that the different twin sets responded in different' ways. Some showed a large difference in production and others a very small difference. This same effect was noticed in the earlier experiment. ,

TABLE 3—EFFECT ON BUTTERFAT PRODUCTION OF PRE-MILKING STIMULUS Total fat (lb) Twin Nonnumbers Stimulus stimulus 701-2 .. .. 335.3 113.1 601-2 216.3 38.1 661-2 246.4 84.6 667-8 199.7 63.0 657-8 .. . . . . 388.4 290.5 603-4 273.4 184.1 663-4 373.6 320.9 673-4 328.4 330.9 669-70 256.7 268.0 817-8145.3 161.4 743-4 460.0 477.2 627-8 314.7 332.5

In an attempt to account for this variab lity in response. measurements were made of the duration of let-down activity in the cows involved in the experiment. . This technique of measurement, developed at Ruakura some years ago, had not previously been applied on a large scale. DuraEon of Letdown The measurement, is best explained by Fig. 2. It represents the time during which the let-down hormone released at milking time is active in the udder. Our measurements showed that this time varied from as little as two minutes for some cows to as much as 30 minutes for others. The method of measurement requires the use of the milk flow recording units built at Ruakura for the No. 1 Dairy and precise timing of the period between let-down and milking, under controlled conditions. Results of LeKdown Tesis A relation between the duration of let-down action and response to the stimulus is seen in Table 4. The large differences in production between twins occurred most often in the cows with very short let-down.

TABLE 4—DIFFERENCE IN TOTAL FAT AS PERCENTAGE OF NORMALLY STIMULATED TWIN AND LET-DOWN DURATION

Twin Letdown numbers Difference duration per cent minutes 701-2 .. .. 66.0 3-4 601-2 .. .. 82.3 . 2 661-2 . . . . 65.6 2 667-8 .. .. 68.5 5-6 657-8 .. .. . 25.2 14-15 S. 12- N.S. 603-4 .. .. 32.6 6-7 S. . 8-9 N.S. 663-4 .. .. 14.1 10-11 S. 13- N.S. 673-4 .. .. —O.B 6-7 S. 6- N.S. 669-70 .. .. —4.4 8 9 S. . 8-9 N.S. 817 8 . . . . —ll.l 5-6 S. 7- N.S. 743-4 .. .. —3.8 29-30 S. 22-25 N.S. 627-8 .. .. —5.6 6-7 S. 7-8 N.S.

These figures suggest very strongly that the cows with a highly active let-down response are little affected by lack of stimulus, while those with a relatively poor let-down response are markedly reduced in production by lack of stimulus. The cows with the most active letdown proved to be also the highest producers, particularly in the nonstimulated group.

Conclusions

'T'HE experiments with the 30 second wash and hand stimulation of the lower udder and teats before milking made the following points evident : 1. The use of a pre-milking hand stimulus of 30 seconds can result in a substantial increase in production as against a system where the machine is relied on to produce* the let-down stimulus. The increase in production in the present experiment amounted to 32 per cent for the well stimulated group. 2. It is clear that some cows are much reduced in production by lack of stimulus while others are comparatively little affected. 3. Those cows with a poor letdown response appear to be the most affected in their production by a lack of stimulus. Unfortunately, it is not possible yet to distinguish readily between these two types of cows in the field, though it is hoped that tests may be devised for field use. 4. The reduction in milking time for the well stimulated cows will more than make up for the extra time spent on the wash stimulus. There can be little doubt that the increased production resulting from the use of an adequate pre-milking stimulus, with . the reduction ■ in milking time, will make its introduction, very worth while.