Measuring the Influence of Hormone and Mechanical Stimulation by Means of a Non-Fecund Lactation

Abstract

Summary The review of literature and limited data obtained from an unusual case of non-fecund lactation in a Holstein-Friesian cow, indicate that the internal stimulus produced by pregnancy and released at parturition, was the largest factor controlling maximum daily milk yield. The more rapid decline in milk flow in normal lactations than in the non-fecund lactation, is attributed to a gradually diminishing internal or hormone influence arising from reproduction. Maximum daily milk yield was attained later in lactation when influenced mainly by external mechanical stimulation from the act of milking. This internal stimulus originating from reproduction, was not necessarily a factor in determining persistency of milk flow, as indicated by duration of the lactation period. At the peak of production, total daily milk yield following normal reproduction, was from 3 1 2 to 5 times as great as when milk flow was induced by mechanical stimulation alone. A small part of the difference is attributable to the fact that the cow was milked thrice daily in the normal lactations.