Restricted feeding of egg-strain chickens during growth and throughout an extended laying period

Abstract

White Leghorn x Australorp crossbred pullets were either fed ad libitum or given restricted access to food from 8 to 20 weeks of age. Birds from each of these rearing treatments were thereafter distributed among five feeding regimes: ad libitum and four allowances representing reductions of 3, 6, 12 and 24 per cent of the food intake of the birds fed ad libitum throughout life. Biological and economic performance data were examined for the rearing period and for three periods of lay terminating at 66, 78 and 90 weeks of age. From 8 to 20 weeks of age the restrictively reared pullets ate 30.5 per cent less food, suffered 1.7 per cent higher mortality, cost 19 cents per bird less to rear and were 20.5 per cent lighter in weight at 20 weeks than the pullets fed ad libitum. Compared with ad libitum feeding, restricted feeding in the rearing period gave higher values for hen-housed egg production and hen-housed gross margin when food intake in lay was restricted by 0, 3 and 6 per cent, and lower values for these criteria when food intake in lay was restricted by 12 and 24 per cent. Birds whose food intake was restricted by 6 per cent in the laying period laid about 25 more eggs to 90 weeks of age than birds fed ad libitum in lay. Optimum slaughter time (age at which average gross margin per week was maximized) was at about week 90 for the ad libitum/12 per cent restriction and ad libitum/24 per cent restriction treatments, and between weeks 66 and 78 for all other treatments. The highest weekly average gross margin was achieved with the birds that were restrictively reared and restricted by 6 per cent throughout a laying period terminating at 78 weeks of age; at this stage their gross margin was $2.30 per bird higher than that of the birds fed ad libitum throughout life