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the process of obtaining milk from farm animals (cows, goats, sheep, mares).
In a lactating cow, milk forms in the udder between milkings and is retained in it because of the capillarity of the mammary gland, the special arrangement of ducts, and the presence of sphincters in the teats. Milking is possible because of a complex series of natural reflexes. Under the stimulation of nerve endings in the mammary gland during milking, the sphincters of the teats relax, the smooth muscles of the udder contract, and the milk is released from the milk cisterns and the large efferent ducts. Several seconds later, under the effect of the hormone oxytocin, the stellate cells around the alveoli contract, the alveoli themselves contract, and the milk moves into the ducts and cisterns. However, even after careful milking, a certain amount (10-15 percent) of the milk, with a fat content of 9-12 percent, remains in the udder.
In time, lactating cows develop conditioned responses to the surroundings for letting down the milk. The noise of the milking machine motor, the appearance of the milkmaid, and other conditioned stimuli cause the contraction of the alveoli and the secretion of the pituitary hormone, just as in the ordinary milking process. Unusual stimuli (for example, an abrupt noise or a change in the usual surroundings) can inhibit the let-down reflex. Therefore, it is important in milking to be quiet and not to disturb the usual order.
Cows may be milked by machine or by hand. The most favorable physiological conditions are created for removing the milk from the udder in mechanical milking. The machine milks all four lobes of the udder simultaneously, whereas in hand milking only two lobes are squeezed at a time (however, stimulation of even two teats causes the let-down reflex in all quarters of the udder).
Cows must be prepared for milking. The udders are washed with warm water, the first jets are milked by hand into a separate vessel, and not more than 1-1.5 min later the cups of the milking machine are placed on the teats. So-called stripping is carried out before the end of milking. The milking cups are drawn downward and somewhat forward several times by hand. The duration of milking depends on the amount of milk and the let-down reflex; a well-prepared cow can be milked in four or five minutes.
The most correct and hygienic manual method is milking by fist. It is best to start milking from the rear quarters of the udder, where there is more milk. One should not milk one-half of the udder first and then the other; rather, the milking of the hind and front pairs of teats should be alternated, without waiting until the milk has been extracted completely. The order should be consistent. The milkmaid always sits on the right side of the animal.
Milking times should be arranged so that in the intervals between milkings the udder can fill with milk and thus the milk formation is not impeded. Cows are usually milked two or three times a day, although high-yielding and newly calved cows are milked three or four times daily. The number of milkings is gradually reduced before steaming up.
G. I. AZIMOV
The milking of sheep is most widespread in astrakhan lamb raising. Sheep of other coarse-fleeced breeds are also sometimes milked. Ewes whose lambs have been slaughtered for astrakhan fur or weaned are milked twice a day. Nursing ewes are first milked 2-2.5 months after lambing; they are milked once a day until weaning. Milking is discontinued no later than 1-1.5 months before pairing. Milk goats are milked twice a day. Because of the small capacity of the udder, the mares must be milked every 2 hours during the first two months of lactation, and subsequently, every three or four hours. Sheep, goats, and mares are milked by hand.
REFERENCESKorolev, V. ¥. Mashinnoe doenie korov. Moscow, 1953.
Mashinnoe doenie korov, 2nd ed. Moscow, 1964.
Azimov, G. I. Kak obrazuetsia moloko. Moscow, 1965.