A MODEL FOR THE EFFECT OF CONSTANT PHOTOPERIODS ON THE RATE OF SEXUAL-MATURATION IN PULLETS

1. This paper reviews evidence from 15 experiments, reported over a sp an of 44 years, in which pullets were reared from hatching to sexual m aturity on 2 or more constant photoperiods. 2. The evidence strongly i ndicates that earliest age at first egg (AFE) was observed when pullet s were held on constant 10 h days (though earlier maturity is easily i nduced by increasing the photoperiod during rearing). The pair of equa tions which best describe the relationship between AFE (y, d) and phot operiod (x, h) are for x less than or equal to 10 h, y = 175.8 - 1.731 x; for x greater than or equal to 10 h; y = 155.5 + 0.301x. 3. This 2- straight-line model, hinged at 10 h, should be used in preference to c urvilinear models published earlier, which wrongly predict that pullet s reared on long days (14 h to 17 h) mature faster than birds reared o n constant 10 h.