Photoperiodism and Age as Factors Affecting the Protein Requirements of Laying Pullets

THE manipulation of dietary protein levels to provide minimal intakes of essential amino acids by laying pullets during various phases of the laying period is a complex problem involving, among other factors, the genetic constitution of the pullets (Deaton and Quisenberry, 1965), the level of egg output (Bray et al., 1965), body weight of the pullets (Sharpe et al., 1965), environmental temperature (Bray and Gesell, 1961), the caloric density of the diet (Frank and Waibel, 1960) and changes in the balance of essential amino acids that occur coincident with the manipulation of dietary protein level (Bray, 1960). Several reports, including those of Owings (1964) and Quisenberry (1965), indicate that the level of dietary protein may be reduced as the level of egg output declines during the laying period. Contrary to these reports, Bray and Morrissey (1962) found that 12 and 18 percent protein corn-soya diets supported equal egg outputs only . . .