Testis development and daily sperm output in guinea-fowl raised under constant daily photoperiods

The testicular growth of guinea-fowls in relation to age was compared under 3 constant photoperiods (7L: 17D; 14L: 10D; 20L: 4D) from 3 weeks of age. Although long daylength (14L or 20L) caused precocious development of the gonads, it also limited total adult gonadal weight to around 1 800 +/- 200 mg. Short daylengths (7L) delayed the development of the gonads but their adult weight was enhanced to 2 800 +/- 200 mg. A comparison of the changes in daily sperm output (DSO) under 7L: 17D and 14L: 10D was consistent with the observations on testis weights. Under neither photoschedule was a correlation found between individual age at first ejaculate and the individual DSO observed at sexual maturity. However, the mean individual DSO's estimated from the first 10 ejaculates were correlated to those observed at sexual maturity, and the latter were also correlated to the DSO's observed at 53-55 or 59-61 weeks of age.