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MOST the research reported on photoperiodism as related to avian reproduction has been concerned either with testis changes in wild birds or with egg production in domestic fowl. The male domestic fowl has received relatively little attention. The effects of varying the length of daily light periods on spermatogenesis and changes in testis size have been reviewed by numerous investigators including Lamoreux (1943a), Amoroso and Marshall (1960) and Romanoff (1960). Lamoreux also reported results of experiments showing the effect of the amount of daily light on semen production in White Leghorn and concluded that 12 hours or more of daily light were required to effectively stimulate semen production. He did not determine the effect of daily light periods on the fertilizing capacity of semen produced. Bonadonna and Pozzi (1955) observed that cocks “steadily kept in the dark,” as well as males kept under continuous illumination, produced smaller semen volumes than…

TO DETERMINE if maintaining chicken breeding males in wire cages had any influence on their semen production and the fertilizing capacity of the semen an experiment was commenced at the Oregon Agricultural Experiment Station in December, 1957. A group of 17 Delaware cockerels hatched in March, 1957, which had been reared in confinement in a 16′X16′ pen of a multiple-pen brooder house, were available for the experiment. On December 5 and 12 semen was collected from the first 16 of these males by the technique described by Burrows and Quinn (1939). The cockerels, numbered 1511 to 1527, were divided into two groups on December 14, the eight even numbered males being put into two 28×36 inch cages in a steel fattening battery. Four males were put in each cage. The battery was located in another pen of the brooder house similar to the one in which the cockerels were raised… .

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…