Influence of light on the physiology of turkeys: II sexual maturity

Light duration is a crucial importance to sexual maturation of turkeys. It enhances the development. gonadal activity and is responsible for circadian and circannual periodicity, For seasonal maturation turkeys need certain m inimum levels of light intensity. For males the threshold intensity is abou t 5.41x. A rising light intensity accelerates sexual maturation. Hens need about 201x for gonadal development. Short day conditions (6L) are not suffi cient for gonadal development. Sexual maturation of male turkeys needs betw een 10.5-14L in order to be initiated. Long light duration (23L), intermitt end and increasing duration of the light period accelerates spermatogenesis . In females light duration exceeding 20L has no further effects. Female fe rtility is positively influenced by a previous phase of light reduction, ma le fertility remains unaltered. Light should be reduced however, for at lea st three weeks (preferentially 8-12 weeks) and should not be extended befor e the turkey hen has reached 30 weeks of age. A starting signal for egg lay is an abrupt change of the day length from 6L to 10.5-13L depending on sea son. In contrast to light duration and light intensity neither natural light nor various other light sources are crucial to sexual development of turkeys. White light, a mixture of all visible wavelengths, affects sexual maturatio n of turkeys most favourably, while blue light delays a sexual maturation.