HERD-TESTING.

New Zealand Journal of Agriculture, Volume XXVI, Issue 6, 20 June 1923, Page 351

HERD-TESTING.

WHY AGGREGATE ASSOCIATION RECORDS ARE HIGHER THAN FACTORY RETURNS.

W. G. BATT,

Farm Dairy Instructor, Taumarunui.

Herd-testing association members often ask why association records, as a rule, show a greater aggregate amount of butterfat than the actual factory returns, and in this article an endeavour is made to outline some of the chief causes of the difference. In the first place it may be pointed out that the comparison in question is totally unfair, and rather tends to show a lack of understanding of the working of the system on the part of the farmer concerned. When one considers that the association records are the result of an average taken from two days' production in every thirty, and that conditions are all in favour of this being on the high side, it is no surprise that the figures recorded are often greater than the actual return. ■ It must be understood, however, that this can make no difference to the value of such figures in culling, as they must be taken on a comparative basis, which, providing each cow receives the same treatment, is of value even if the records are considerably higher than the amount of butterfat actually produced. This has been amply demonstrated, and I , have no hesitation in asserting that the association figures provide a safe and reliable basis for culling. . 'causes of discrepancy. Some of the causes of the discrepancy referred to are as follows : — Milk fed to calves and used by household : In the early part of the season this is fairly considerable, and takes a material amount, of fat away from the factory returns while being credited to the association records. There is in this way a difference set up-between the two returns more or less throughout the season.

Loss of fat in separation : In some cases this loss is considerable, and in all cases there is some. I would suggest to all farmers the advisability of having separated milk tested at intervals during the year. Loss of fat in transit of cream : In some cases this also is considerable, especially where the cream supplied is of a thin consistency and churns in transit to the factory. Cream used for buttermaking on the farm : Where this is the practice a considerable difference is made between the two returns — to the credit of the association and debit of the factory return. Carelessness in sampling : Care in this direction is very important if the work is to be well done, and the milk must be thoroughly stirred before sampling. Discrepancies also occur in connection with damage received by samples in transit to the factory. Occasionally farmers check or think they are checking this class of testing by placing the milk from one cow in. two . or more bottles, again showing how little farmers in general know of the damage samples may receive in transit, the necessity for careful sampling, and the consistency of milk and its relation to testing. The butterfat in milk is suspended in the serum in the shape of small globules, and this suspension is often broken by the shaking samples receive in transit, especially in hot weather, when milk expands. Once this happens the fat floats on the top of the serum as an. oil, and usually it is difficult to make a correct test. Other variations in the test of two samples of the same milk may occur in the leakage of fat in transit, the absorption of fat in corks, the churning of samples on their way to the factory, and irregular and careless sampling on the farm.

Variations in general conditions : Factory returns embody all variations in. weather conditions, feeding-conditions, and weights of milk and tests, while the association records as a rule are not so handicapped. This is usually the main cause of the difference between the two returns. The factory has to take all these variations as they come, while, generally speaking, the association records are. affected by only a comparatively small proportion, owing to the latter samples being taken on only two days in the month, as compared with thirty in the case of the factory. It is well known that cows (especially those of a nervous temperament) will rise and fall in their tests from day to day to a very great extent. This also applies to the milk-flow—in some cases a change of milker or feed or weather conditions being sufficient to cause a large variation in production. This being the case, it is not surprising that in some periods the figures may be very much in favour of the association. This is the more likely seeing that most farmers appear to wait for good weather and feeding conditions before taking their two days’ samples for the association.

Sampling not representative : A fully representative sample can only be obtained when the weights of milk are the same for each sampling, unless the size of the sample is varied according to the variation in the weight of milk. This, again, is usually in favour of the association. The milking-hours on most farms are so arranged that cows produce more milk at the morning than at the evening milking, and most cows show a greater percentage of butterfat at the evening milking than in the morning. This means that where

the same amount of milk is sampled from each milking, and the weight of milk differs, the test received will usually be higher than it should, be, owing to a proportionately greater amount being taken from the higher-testing evening milk.

Variations from normal in the milk : Allowance must, of course, be made for these variations, especially when the tests are rising. They are usually in favour of the association returns. Retrospective records : Providing the cow has been in milk less than one hundred days of the end of the period in which she was first tested, the association record is made retrospective to calving-date. This means that a cow calving.in the late winter and being tested for the first time in the spring, when there was a good flush of milk, would get more fat to her credit for that period than she had actually produced. This can be overcome by commencing the test of each cow as soon as possible after she calves, and it is important that this should be done. THE SOUND BASIS FOR CULLING. When judging the merits, of individual cows for factory dairying, it is necessary to do so on their butterfat production for the season, not on the quantity of milk produced, and not on the test. The latter is only the percentage of fat in a given quantity of milk, and is likely to fluctuate considerably. Farmers very often make the mistake of judging cows on their tests, and as this is usually misleading good cows have sometimes been culled while poor ones were retained in the herd. A sound basis and an accurate conclusion on which to cull can only be obtained by taking the amount of butterfat produced by the cow for the season, in conjunction with her age and the number of days she has been in milk. When this is done, and the causes of discrepancy just enumerated are appreciated, farmers will realize that if they do their part of the work conscientiously the association will do its part towards providing a safe and reliable basis for culling.

THE FIELDS DIVISION.

The Fields Division of the Department has been reconstituted as from ist May, with Mr. A. H. Cockayne as Director. The Division incorporates the following branches : The Biological Laboratory (including the seed-testing station) ; the Agricultural Instruction Service; experimental and demonstrational areas (not including at present the Ruakura, Weraroa, and Moumahaki Farms) ; ' the Hempgrading Service ; and the Grain-grading Service. Under the Director, Mr. R. Waters has been appointed Officer in Change of the Biological Laboratory.

Importation of Game- Birds. — An application by the Auckland Acclimatization Society for permission to import Virginian quail was further considered by the Board of Agriculture last month. The Board decided that it could not support the request in view of the many complaints which had reached it as to the damage now being done by quail in the Auckland District. .A. further application by the same society to import from England a small number of Mongolian pheasants and black-necked pheasants was recommended for favourable consideration, as was also the request of the Southland Acclimatization Society for permission to capture quail in the Lakes Acclimatization District for liberation in the Southland District.