MILKING EXPERIMENTS.

Otago Witness, Issue 3278, 10 January 1917, Page 8

MILKING EXPERIMENTS.

Some extracts of the results of two dairy experiments conducted at Offerton Hall, extending from May., 1912, until April, 1915, arc here reproduced at; of mere than passing interest. They arc set out in fuller detail in the December number of the Victorian -Journal (if Agriculture. The experiments were conducted by Frank U. Walker, M.Sc, F.H.A.S., adviser in agriculture to the Armstrong College, New-castle-upon-Tyne, and were undertaken with a view of showing the effect on quantity and -quality of milk produced by cows when fed at equal and unequal periods. The exigencies of the new milk trade in many cases involve a great difference in the times between mornings and evening's milking 'periods. Apart from the general feeding and management of a milking herd this difference in the time of milking makes a considerable difference to the quality of the milk. Other experiments have shown that when the periods between the milkings more closely approximate than is the usua_i practice, the quality of the morning's and evening's milking is very similar. A previous experiment at Offerton Hall in 1905 confirmed this, but the experiment only lasted for a period of 18 days. It was demonstrated clearly enough in the experiments now under consideration that in every weekly average where the cows were milked at equal intervals, the quantity of milk given at the evening's milking was always greater than that given during the morning in the case of one lot of cows, while in another lot, when the hours of milking were uneven, the quantity of milk given at the morning's milking was always greater than at the evening. A result and agreement with general practice. It was held and demonstrated that equal periods of milking are strikingly conducive to normal percentages of fat in both morning's and evening's milk. As is well known, there is often a great difficulty hi getting the milk of cows up to the 3 per cent, of fat limit each morning. If bv every means possible care bo taken to equalise the intervals of milking there_ is no doubt that this would do away with a good deal of trouble and worry to those farmers who are anxiously desirous of producing milk of even quality. During a period of six weeks, in no case in the morning, in the case of the group of cows, constituting those cows milked at equal periods, was the mill; below the recognised standard. Twice during the evening it did fall below such a standard, but only just, below. On 12 occasions in the morning, however, the milk of the group comprising thoso cows milked at unequal periods fell below the 3 per cent, limit, and seriously so. Further, the average percentage of fat for the whole six weeks in equal periods of milking differs only by .25 per'cent, whereas this difference "in the ca~e of unequal periods of milking is equal to .93 per ccnt,_ The percentage of fat actually produced in the tot:: 1 , daily yield is in the two groups practically the same. In so far as these experiments went, it Avas not considered as proven that milk fell below the standard of 8.5 per cent, in non-fatty solids as result of even or uneven milking periods, but rather that the milk maintained it". normal quality. It should perhaps have been stated sooner that equal milkings took place at 6 a.m. and 6 p.m., and at unequal intervals at 6 a.m. and 4 p.m. There was no distinct evidence that drought affected the percentage of solids not fat in the milk, hut if was thought that the continued effect of drought might have some effect in influencing the quality of the mi!!;, and that where drought effects were much more marked some foundation for complaints about low nonfatty solids may have had some, justification.

The general conclusions come to then may be stated as follows:—It cannot be said that the total quantity of milk is influenced by the equal ct unequal periods of milking. ' So far as the percentage ol fat in milk is concerned it was distinctly shown that the length of time between morning and evening milkings does very materially alter it. The results distinctly emphasise the fact that one very important means of getting over the difficulty of poorer morning's milk is to endeavour to

make the periods of milking as even j.s possible. It is frequently asserted that the general public demand their milk at such times as to prevent the more general adoption of equal milking periods. If by these and similar experiments it can be shown to the public that equal milking periods produce moTe even quality of milk, they may in time he sufficiently sympathetic + o help the milk producer to get over what is at present a very serious trouble to him. The results again emphasise the necessity in cases of prosecution for selling milk below the standard to take into consideration the desirability of taking an evening as well as a morning sample of milk for analysis before such prosecution is pursued. It is possible that while the percentage of fat remains practically normal Under conditions of severe drought the "solids not

fat" may be lowered somewhat. The cows which were milked at even periods gave more milk in the evening that in the morning. The evening's milk was also slightly poorer in quality than the morning's. This is contrary to generally accepted experiences, as in ordinary farm practice unequal periods of milking are the rule. A note on the variations in the amount of fat in milk due to variations in the times of milking is supplied by S. H. Collins : —■ In 1911 I deduced a formula from over 600 tests of milk, which showed that if cows were milked at 6 a.m. and 6 p.m. the evening's milk would be .2 per cent, fat poorer than the morning's milk. If the cows were milked at 6 a.m. and 5 p.m. then the evening's milk would be the richer to the extent of .3 per cent. fat. If milked at; 6 a.m. and 4 p.m. the. evening's would show .8 per cent, more fat, and if milked at 6 a.m. and 3 p.m. [he evening milk would be 1.3 per cent, richer. The best test of any similar law, based on averages, is to find out if it agrees with facts discovered alter the rule has been established.

in the results explained by Mr Walker in 12 weeks’ trials the evening milk (6 p.m.) is poorer than the morning s (6 a.rn.) by .25 per cent, fat with equal intervals of milking (6 a.in.) by .80 per cent, fat with unequal intervals. These results are almost exactly what the rule predicts—namely, .25 against .20 and .80 against .80. As regards the weeks taken one at a time, tboro_ is only one week with equal intervals, during which the experiment differed from the rule by mere than .2 per cent., and there wore only three weeks with unequal intervals whore the experiment differed from the rule by more than .2 per cent. If one milking was 12 minutes too late and the next milking 12 minutes too early there would he a discrepancy of .2»per cent, fat, or the same discrepancy would result from a delay of 21 minutes from one milking, tho other milk being at correct time. Since accurate timing is quite impossible, the few cases where tho experiment appears to depart from tho rule hay bo no departure at all, but merely bo the result of the difficulty of accurate time-keeping. These results confirm many previous ones in various parts of tho country, and prove conclusively that tho percentage of fat in milk depends very largely on the times of milking and that tho relationship between times of milking and percentage of fat is a constant, one.

HOPES OP MILKING *Per Cent. Fat. G a.m.—6. p.m. — .2 6 a.m. —5.30 p.ru + .05 6 a.m. —5 p.m. + .3 6 a.m. —4.30 p.m + .55 6 a.m.—4 p.m. + .8 6 a.m.—3.30 p.m 4- 1.05 *Evening milk will be poorer (— (-(-) than morning milk. -) or richer