THE EFFECT OF LENGTH OF DAILY LIGHT PERIODS ON SEXUAL DEVELOPMENT AND SUBSEQUENT FERTILIZING CAPACITY OF MALE CHICKENS

REVIEWS of the literature concerning testicular response of birds to photostimulation have been written by Lamoreux (1943a), Romanoff (1960) and Amoroso and Marshall (1960). Lamoreux also reported results showing that semen production and testis size in Leghorn cockerels were related to the length of the daily light period. Recently, Parker and McCluskey (1964) showed that sexually mature male fowls produce satisfactory volumes of potent semen under as little as 1 hour of daily light exposure. The purpose of the investigations reported herein was to determine the effect of rearing cockerels under daily light exposures ranging from 1 to 13 hours on ages at which semen was first produced, and on their subsequent fertilizing capacity in natural matings. EXPERIMENTAL PROCEDURE Four groups of Delaware chicks hatched in November, 1960, were reared from time of hatching under four regimes of 1, 3, 9 and 13 hours of daily light. There was no…