The relation between the passage of time and the secretion of milk in the ewe

Abstract

The rate of milk secretion during 4, 8, 12, 16, 20, and 24 hr intervals between milkings was estimated in 24 ewes. The intervals were applied in a double 6 x 6 Latin square in which the second square was a mirror image of the first. Intervals were repeated four times per treatment in each square. There were no intervening periods either between the four repetitions of any given interval or between different treatment intervals. Residual milk was removed by intravenous administration of oxytocin after every milking. The milking was carried out by machine, and the stripping by hand. The experiment lasted 28 days. The secretion rates of milk, water, total solids, solids not fat, and fat increased up to 12 hr and then declined. Both ascending and descending phases were significant. There was a significant increase in milk yield when a given interval was repeated (taken over all treatments). The secretion rates of milk and of all the measured constituents increased following milking intervals of 4–12 hr, and decreased after intervals longer than 12 hr. No significant differences were found between the respective rates of milk secretion by day and by night. The variation in an estimate of the rate of milk secretion became significantly smaller as the interval became longer. The oxytocin removal of residual milk was shown to have a strong galactopoietic effect.