the amount of fat in milk, one of the main criteria of milk quality.
Butterfat content is expressed in percentage. The average fat content of milk from various animal species is as follows (in percent): cows, 3.9; goats, 4.3; sheep, 7.2; swine, 5.9; water buffaloes, 7.7; zebus, 7.0; yaks, 6.8; camels, 5.0; horses, 1.8; asses, 1.4; and reindeer, 18.7. The butterfat content is a breed character, the highest being in Jersey cows (5–6 percent) and the lowest in Holstein-Friesian cows (3.35–3.75 percent). The butterfat content varies in the same breed from zone to zone and with the individual characteristics of the animal and changes little with age. It is higher in fall and winter than in spring and summer. The fat content of milk during the day differs only with the length of time between milkings; the last portion of milk contains more fat than the first.
The quality of milk, like the quantity, depends on the feed given the animals and conditions under which they are maintained. Feed containing adequate protein, fat, minerals, and vitamins promotes the formation of fat in milk. Feed with readily assimilable carbohydrates—sugar and starch—are the main source of milk fat formation. Butterfat content is a comparatively stable hereditary character. One of the principal ways of increasing it is to select and breed animals for this characteristic. Significant breed differences in butterfat content suggest that the fat content of milk can be increased by crossing watery-milk cows with bulls of breeds high in butterfat.
A. A. SOLOV’EV