BUTTER FAT

Wanganui Chronicle, Volume LXXXIII, Issue 19840, 14 May 1927, Page 21 (Supplement)

BUTTER FAT

AN INGREDIENT OF MILK FACTORS IN PRODUCTION Milk producers appear to have accepted too literally the statement that the percentage of butter-fat in milk is something which is inherited, to the extent of precluding the possibility of fluctuations in milk fat from other causes. Speaking generally, the fat of milk is an inherited character, and can be permanently increased or lowered only Iby arbitrary selection in breeding. There are, however, many factors which cause fluctuations from the mean or average characteristic of the individual and breed, and such may conceivably alter from time to time the test of the mixed milk of the herd. Moreover there arc various misconceptions of the manner in which the different factors affect the fat content, hence a resume ,of the findings to date may be of interest to many milk producers.

Feed, either in kind or amount, cannot alter the fat content of milk for a long period, provided always the cow is receiving sufficient nutriment to maintain the body weight. Kind and quantity of food, however, do play a limited part. Cows, for example, receiving rations greatly under the requirements for maintenance and production, may for a time produce milk under norms# in fat, but with a return to normal nutrition the fat average is restored. Cows calving in fat condition may for several weeks yield milk much higher in fat than the yearly average. This fact is taken advantage of by owners who make a practice of running cows .on short-time tests, although obviously the results of such tests may not afford a very reliable indication of a cow’s ability to produce for a year.

Not only do cows of different breeds differ in their normal yields of butterfat, but there are marked differences between individuals of the same breed. Some of the recognised dairy herds, Jerseys and Guernseys yield the richer milk; Shorthorns, Red Polls, and grades thereof next; then Ayrshires and Hol- , steins. Variations in individuals of the same breed may occur to the extent of il per cent, and over, hence the object in selecting bulls of high fat-producing ancestry. When the intervals between milkings are equal there is no regular difference in test, hut with unequal intervals the milk following the longer period invariably tests lower.

Tn so far as the first drawn milk is very low in fat and tue last drawm very high, it follows that Failure to milk out clean may have a very marked effect on the test of a composite sample. Lowering temperatures are most frequently followed by an increase in fat, hence, on the average, cows produce richer milk in winter, although this may be counter-balanced at any time by the stage of lactation. Exposure to cold rains or inclement weather tends to depress the fat. The effect of the period of hot or oestrum is various, in some instances appearing to depress the fat, and again to increase it. Effects of oestrum, however, are most noticeable with extremely nervous cows. A fevered condition is nearly always accompanied by an increase in fat. Tn conclusion, it may be said that much remains to be discovered of the physiology of milk production.