Effect of local stimulation of one quarter on milk production and milk components.

The existence of local udder regulatory mechanisms involved in the regulation of milk production was demonstrated. Because the four quarters of the udder are independent, yet share a common environment, the experiment was designed to give one quarter extra stimulation by hand-milking while the other quarters were machine-milked. A difference in milk production was found, proving the existence of local mechanisms. The largest differences were during evening milking with an increased production in the hand-milked quarter. The machine-milked quarters did not increase their production. The increased production was probably due to enhanced activity in the secretory cells, induced by some factor produced or activated locally in the udder.