The determination of milk yield in the Merino ewe

Yield was measured by hand milking following injection of posterior pituitary extract (PPE) to obtain milk ejection. Lambs put with ewes hand milked after 2 doses of 5 i.u. of PPE could obtain little or no milk. Yield depended on the interval between milkings, the rate of secretion being apparently faster in the first 2 hr. The effect was less marked as lactation declined. Yields were independent of time of day and speed of milking. When successive yields were used to rank ewes in order of performance, the rankings were always significantly concordant. Earlier applications of the method had no detectable effect on later lactation. It is concluded that the method provides a simple means of obtaining useful estimates of milk production.