Effect of intermittent light regimens on the performance of intact male turkeys

An 8-h photoperiod, compared with 12-, 16- or 23-h photoperiods, has been s hown to reduce the incidence of injurious pecking and leg problems in intac t male turkeys but to result in lower body weights, slower sexual developme nt and less efficient food conversion. The effect of 8 h of illumination gi ven as a solid photoperiod, as eight 1-h periods equally spread through the 24 h or concentrated into a 12-h part of the day on the performance of BUT 8 intact male turkeys was investigated. Fragmentation of the daily illumination increased body weight, improved foo d conversion efficiency but did not significantly affect food intake. Incre ased sexual displaying and significantly better food conversion between 16 and 20 weeks by the two intermittently illuminated groups strongly Suggeste d that both regimens were interpreted as stimulatory daylengths. Generally, losses due to mortality and culling were higher in both fragmented groups, while injurious pecking was higher in 8(1L :2D) birds before 5 weeks and i n birds given a 12-h 'subjective day' after 5 weeks than in 8-h controls. G ulling due to leg problems Tons significantly higher in birds on the 8(1L:2 D) regimen but the incidence of leg imperfections was minimal (< 0.037) in all groups. Both intermittent groups but the 8(1L:2D) in particular, showed a reduced response to hand movement across the eyes compared with 8-h cont rols. The controls ate proportionately more food during their 16-h dark per iod than did the intermittent group during their 12-h 'subjective night', t hough both groups increased their 'nocturnal' feeding with age.