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During a broiler breeder trial with 3200 Cobb 500 hens, the effects of lighting treatment after 20 weeks’ feed allocation and of feed form on the length of time taken to consume the daily allocation of feed were measured. Pullets were reared on 8-hour photoperiods to 20 weeks, then transferred to one of four lighting treatments: permanently to 11 h or 16 hours, transferred temporarily to 11 hours, then given 2-hours increments at 40, 44 and 48 weeks to reach 17 hours or a commercially recommended step-up lighting programme (11 hours at 20 weeks, incrementing by 30 min per week to reach 16 h by 30 weeks). Feed was made available in mash or pelleted form, and hens received 160 g or 180 g by 30 weeks. This allocation was increased linearly from 100 g at 20 weeks. After 40 weeks, the daily feed allocation was reduced by 5 g/bird for each 5% reduction in rate of lay to a minimum of 150 or 160 g/bird. On five occasions, when the hens were 39, 40, 41, 45 and 54 weeks old, the time taken by the hens to consume all their feed was measured and scaled to min/100 g consumed. Hens learned to consume the feed more rapidly as the laying period progressed. The mean clean-up time over all treatments was 67.7, 62.1, 63.4, 47.1 and 40.2 min/100 g at the five ages. Over all treatments and ages, the time taken to consume all their feed was 40.0 min/100 g for birds fed 160 g, versus 72.2 min for those given 180 g of food daily, but this difference was greater at 39 weeks (43.5 versus 91.8) than at 54 weeks (34.0 versus 46.4 min/100 g, respectively). This effect was also evident with feed form, the difference in time taken to consume mash and pellets being greater at 39 weeks (69.2 versus 66.1) than at 54 weeks (54.7 versus 25.7 min/100 g, respectively). The lighting programmes also had an effect on the feed clean-up time. The main effects were 53.5, 56.3, 52.1 and 62.5 min/100 g for the 11-hour constant, 11 to 16 hours, 16-hour constant and step-up programmes, respectively. Significant interactions occurred between treatments. The main reason was the much longer time taken initially by birds receiving the step-up lighting programme and 180 g of pelleted feed to consume all their feed. The effects of these treatments on bird welfare are discussed. Keywords: Breeders, laying period, lipid reserves, welfare

This paper reports the allometric relationships between some of the physical parts and body protein weight of three commercial broiler strains reared, sexes separate, on four dietary protein levels to six weeks of age. Birds were sampled at day old and then weekly from each of the treatments to determine the weights of the physical parts and the chemical composition of each of 582 birds. Allometric regressions were compared between strains, sexes and dietary protein levels using linear regression with groups. Whereas these regressions were similar over strains and sexes, some interactions were evident between factors, and differences occurred when broilers were fed differing dietary protein levels. These differences may be explained on the basis that lipid is deposited to different extents in each of the parts in response to dietary protein, although this was not tested. The allometric regressions presented are an attempt to provide information that would enable the prediction of the weights of breast meat, thigh, drum and wing at different stages of growth of broilers whose genotype and feed composition are adequately described.Keywords: Breast meat, thigh, drum, wing, carcass yield, simulation modelling

This paper describes the responses of two genotypes of male broilers to constant 8- and 16-h photoperiods, and to an abrupt transfer from 8 to 16 h at 10, 15 or 20 d. Body weight, feed intake, and feed conversion efficiency were not significantly different at any stage during the 35 d study. Mortality and the incidence of Sudden Death Syndrome were similar for all lighting groups at 35 d. When these data were pooled with previously reported data for female broilers, growth and feed conversion efficiency post 21 d and through to depletion for constant 8-h and birds transferred from 8 to 16 h at 20 d were significantly superior to constant 16-h birds. Constant 8-h birds ate about half their feed during the dark period, whilst 16-h birds consumed no more than 10%. Birds which had been started on 8 h and transferred to 16 h at 10, 15 or 20 d reduced their rate of nocturnal feeding when changed to the longer photoperiod, however, they still consumed more feed in the 8-h dark period than birds that had always been given 16 h illumination. Cobb and Ross genotypes responded similarly to all lighting treatments. Keywords : Photoperiod, broiler growth, nocturnal feeding South African Journal of Animal Science Vol. 38 (3) 2008: pp. 159-165