RESEARCH INTO PROBLEMS OF MACHINE MILKING

New Zealand Journal of Agriculture, Volume 73, Issue 6, 16 December 1946, Page 565

RESEARCH INTO PROBLEMS OF MACHINE MILKING

By

W. G. WHITTLESTON,

Animal Research Station, Ruakura.

PROBLEMS obscuring a solution to the many difficulties which still beset the dairy farmer at milking time may. be classified/ into two groups, mechanical and physiological. The milking machine is unusual among machines in that it depends for its operation on the way in which a living, animal responds to its action. That means that the best mechanical solution to a problem may not be the best way to obtain over-all milking efficiency. Further, any mechanical device or method must be considered with respect to its possible effect on the health of the udder and on the hygiene of the milk. In other words,, the ideal mechanical milker < must fulfil the physiological requirements of the cow’s organism, must have no injurious effect on the delicate mechanism of the udder, must be easily cleaned, so that the milk drawn through it will be free from contamination, and. must be simple and reliable so that the farmer can operate it without likelihood of its breaking down. ,

IF dairy farms are. to be made more efficient, and if the unpleasantness of tugging at a recalcitrant cow’s teats on cold wet mornings while the rest of the world is snugly in bed is to be removed,’ an improvement in the mechanical milking procedure must contribute. That the milking machine is an important part of normal farm life may be gathered from the following figures, for 1940: The number of machines in use in. New Zealand was 29,564, and these milked 1,445,756 cows, representing 84 per. cent. :of all cows in milk. . Small herds are not usually machine ; milked, which accounts for the fact that, only 41 per. cent, of the Dominion’s herds were machine milked, 46 per cent, of the herds being of fewer . than , 10 cows. - Milking machines milked an average of 3.41 cows simultaneously and the average machine-milked herd consisted of 48.9 cows in 1940.

Stripping Question Not Yet Answered Until the past few years, when labour shortage presented a very serious problem, most herds were hand stripped; that is, after the teat-cups of the machine were taken from the cow. the remaining milk was removed- by hand.: This stripping process is an unpleasant one requiring extra time and labour in the shed. With the coming of the war great interest was taken in the non-stripping idea, which had : been pioneered by a few farmers for quite a long time, but the question “Is stripping necessary?” has not been answered finally yet. Nevertheless an increasing number of successful dairy herds is being milked without hand stripping.

This problem of stripping is at the ■ using an automatic .apparatus which bottom of'much” of ' the research intoplots volume of milk delivered against '.

the' milking process being carried on at the Ruakura Animal Research Station and in other parts of the world at present. Before the question can be answered definitely the nature of the mechanism by . which the cow lets ' down its milk must be understood. Mechanical Problems The milking machine owes its origin to the inventiveness of two Scotsmen, William Murchland of Kilmarnoch and -Dr.' Shiels of Glasgow, who in 1890 -and 1895 respectively developed vacuum milkers which showed re,al promise. The final basic contribution, the invention of the double-chambered teat-cup which . makes possible the application of a positive squeeze to the teats of the cow, was made almost simultaneously by Hulbert and Park, New York, and Gillies, in ■ Australia, in 1902 and 1903 respectively. Since then no basic invention really necessary to the principles of mechanical milking has been made. In the past 40 years there has been an immense amount of inventive activity, some of . which has resulted in the improvement . of . the. means .of applying the basic principles so that the modern machine is convenient, reliable, . and hygienic. Much inventive energy, however, has been spent in producing devices the value of which in the light of modern knowledge of the cow’s mechanism is highly dubious. '

Where a field of human endeavour is not guided by a sound theoretical knowledge it is almost certain to abound with ingenious devices many of which have no real use. This is particularly true in the field of mechanical milking.

Because of .this a large amount- of time at Ruakura is occupied in testing machine-milking methods and devices,

time on. a graph. This supplies an exact record of how the cow is milking. During the past two seasons an exact record has been made of the response of a variety of cows to a.wide range of adjustments, such as the level of vacuum used, the rate at which the squeezing action or pulsation' is applied to the teats, and the nature of the squeezing —sluggish or snappy, short or long. When the work is completed the essentials for an efficient mechanical milker will be able to be stated fairly definitely.

• The making of such a recording apparatus is typical of the problems confronting all research workers. Knowledge is limited by the means available for obtaining it.' In this case an instrument had to be : made which would record the . way, in which the cow milked without altering the action of the machine,. without changing in any way the procedure in the milking shed, and. without requiring the presence of any extra people about the shed during milking. To study what was going on at the cow’s ? teats a recording vacuum gauge had to be devised; to / standardise' milking procedure automatic timers and accurate milk-flow . indicators were needed. Hence the research programme involves considerable work on the design. and construction of measuring apparatus.

Mechanism of the Cow

Linked up with the work on the mechanics of the process is the work on the mechanism within the cow. Knowledge gained from observation of how. the cow responds to different sets of conditions. ; helps .in ' formulating theories about how the mechanism for letting the milk down works. Following is a brief account of this process as knowledge stands at present.

Milk is secreted slowly throughout the'day. It accumulates in the spongy structure of the secretory tissue of . the udder, where it is retained by capillarity and from which only .a. portion can be . obtained by ' passive' draining, the remainder having to be squeezed out as fro'm a sponge by mechanical force. This force is supplied by networks of tiny muscle fibres which when supplied with a special ’ chemical —a-hormone from the pituitary gland —will contract and force the milk down into the large ducts and the milk cistern of the udder. It is this forcingdown of the milk which causes the rise in pressure : within > the "udder at the . start of milking. There is reason to believe that this " hormone which causes the milk to be let down- is destroyed in the blood within a comparatively short time. This means that to get the most milk out of the udder the cow must be milked quickly.

The ~ milk let-down hormone is secreted into, the bloodstream as a result of - nervous ‘ stimulation of part of the small gland at the base of the brain— the - posterior lobe of the pituit- - ary gland. The natural stimulus which evokes - the secretion of the hormone is the suckling of the cow. by her calf - the application ;of tactile. stimuli - to the ’ sensitive . areas of : the teats Particularly --; with , • regular,* modern machine milking, such actions as .walk- ■ ing into the yards and being leg-roped and, washed/ soon; result •in these conditions associated with milking becoming as effective as the stimulation of - the teats in causing the milk to .be let down.

In other words, the “let-down” reflex becomes “conditioned,” a highly desirable situation which is strengthened by regular shed habits.;but weakened by irregularity, or by accidents which upset the shed routine.

Physiological Problems

The second, important phase of the work,/ the physiological aspect, con-cerns-finding out how the posterior pituitary gland secretes the hormone: Is it a continuous .secretion over a period, is it a sort of dose, or is there a possibility that it can be secreted in several / doses? - When the answer to those questions is known some progress will have been .made toward finding out why '. some cows do ■ not appear, to. respond to a -stripping shed technique. When it is . known why, toward the end of the season, some , cows become strippy, it may be possible to.. prolong the lactation ■ period. . . Work- at Ruakura suggests, as yet only. vaguely, that - the loss of the ability to let .down milk properly is part .; of . the : mechanism causing milk production to decline as lactation advances! .. ' ’

To , solve these '.problems / measuring .apparatus is necessary. At present the rabbit vis the best apparatus known and ways of estimating the ability. of extracts from the pituitary gland to force milk - down' when injected into the cow are being explored by injecting them into lactating rabbits - and measuring the time taken before the milk is ; let down— phenomenon which.is. easily observed in the rabbit. The-/ rabbit -is a very useful animal, not r only! because, the let-down action is easily seen, but because being small it requires only small doses of precious extracts , and is ; easily handled in the laboratory. The aim of this , work is to discover not only the manner in which ‘the hormone 'is secreted but what it is and where it goes. This information is essential for a’ complete understanding of the milking process, and with it will

come, answers to the awkward questions. which arise when a farmer tries non-stripping and a few cows dry. off prematurely, or when cows just do not give milk to the machine and have to be hand stripped. Efficiency of Machines A third aspect of the work is that relating ,to the efficiency of machine ■ milking..- How thorough, must the milkmg be?: How much strippings can be left., behind without reducing a . cow’s output?. To answer these questions, ways -of .- recording pressure changes within the udder throughout-the/- day and during the milking process are being studied. This problem ’is’ by no means simple. The aim is to measure pressure changes, without pushing tubes.up the teats— a procedure which -often causes a flare-up of infection. i

One of the strongest deterrents against non-stripping is the thought that the cow will not produce as much butterfat if . she is not stripped. Field observations suggest that stripping does not increase production. The factors involved in this have still to be explored, for until the conditions limiting secretion in the cow are understood there can be no certainty.

As an outcome of the work at Ruakura, - it is. hoped that the farmer will be able to do away with the messy procedures of starting and stripping cows, and .will have a simpler machine which is easier and quicker to clean. If that can be achieved, it will mean that knowledge' of the physiological: mechanism of the cow has been added' to and a real contribution made toward bringing the comforts and convenience of city life to the man on the land.