Studies of Prolactin in the Fowl Pituitary. II. Effects of Genetic Constitution With Respect to Broodiness on Prolactin Content

Abstract

Broodiness was induced in laying fowls of broody races by the injection of prolactin, by Riddle, Bates, and Lahr. 1 After prolactin injections laying fowl of non-broody races and males of a broody race became only partially broody, usually clucking without nesting. Burrows and Byerly 2 showed that pituitaries from broody fowl have a much greater prolactin content than those from laying fowl and from males, as judged by local pigeon crop-gland response to pituitary implantation.

The present work was undertaken to determine the relative potency of fowl pituitaries with respect to genetic constitution of the fowls. White King pigeons of 8-10 weeks conception age were used as recipients for the fowl pituitaries. The local implantation technique of Lyons as described by McQueen-Williams 3 was used. The crop-gland responses were recorded as “plus” when any visible stimulation was obtained, “2 plus” when the stimulation was roughly twice the minimal visible response, and so on.

Crossbred females were used in their second laying year. Occurrence or absence of broodiness during their first laying year was assumed to reflect their genetic constitution with respect to broodiness. Crossbred males used were assumed to be genetically broody since females from the crosses showed a high incidence of broodiness. The crossbreds were chiefly from matings of Single Comb Rhode Island Reds x Barred Plymouth Rocks, and White Wyandottes x Single Comb White Leghorns. The Single Comb White Leghorn females and males and the Single Comb Rhode Island Red males used were assumed to be of non-broody genetic constitution, since incidence of broodiness is low in birds of these breeds in the flocks at the National Agricultural Research Center. Obviously, broody constitution of the females so designated is proven while the genetic constitution of the other groups is presumptive. Fortunately, presence of broody birds among the presumptively nonbroody ones could only reduce, not increase, the apparent difference found between pituitaries from birds of broody and non-broody genetic constitution.