From Farm to Market
Where Milk Comes From
For both the farmer and the cow, milking is a regularly scheduled routine that revolves around the needs of the cow. Where we might complain about living in a rut, cows prefer it. If a cow gets excited, is afraid, or in pain, the milk ejection reflex is inhibited and the cow won't give you any milk! So, for the cow, every day it is the same and the milking process is the same. First the udder is prepared by washing with a disinfectant, like iodine. Then the udder is dried because wet udders invite infection. This udder preparation usually stimulates the milk ejection reflex that causes a cow to "let down" her milk. Milk accumulates in alveoli—sort of like the individual cells of a honeycomb—and the cow must release that milk before it can be removed from the udder. Release begins when the cow receives some kind of stimuli that the brain interprets as milking time. The brain then sends a message to a gland that releases the hormone oxytocin into her bloodstream. The oxytocin gets transported to the udder where it stimulates contraction of tiny muscles surrounding the alveoli, which forces the milk through the ducts and into the teat cistern where it can be removed by a suckling calf, hand milking, or machine milking. Milk let-down doesn't last very long, so the milking machine is placed on the udder within a minute of preparation. It takes only a few minutes to remove all the milk from the udder. Then the milking machine is removed, the teats are dipped in a mild disinfectant, and the cow is released. While individual cows get a vacation from this process in between production cycles, for the farmer this process is repeated at least twice a day, every day, at regular intervals, at the same scheduled time (4AM and 4PM for example), 365 days a year, without interruption. That's an endless job!

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Copyright 1997 Kathleen A. O'Connell and Sean P. O'Connell