The possibility of preventing cannibalism through dietary manipulation was investigated in the 1940s and 1950s. For example, Bearse, Miller and McClary (1940) and Scott, Holm and Reynolds (1954) found that inclusion of oat hulls in diets decreased the incidence of feather pecking and birds showed superior feather condition. No other studies had been made on the role of nutrition in feather pecking and cannibalism until recently, when several dietary deficiencies were found to be related to feather pecking and/or cannibalism (Cain, Weber, Lockamy and Creger 1984; Cooke 1992; Ambrosen and Petersen 1997). Low levels of dietary protein (Cain et al., 1984; Ambrosen and Petersen 1997), of tryptophan (Shea, Mench and Thomas 1990; Savory, Mann and MacLeod 1999), and of lysine, methionine, and threonine (Ambrosen and Petersen 1997) have been reported to cause aggressive pecking and cannibalism in birds. Diets deficient in phosphorus and sodium have also been linked with the outbreak of cannibalism in chickens (Cooke 1992; Cumming, Chubb, Nolan and Ball 1995). Of particular significance are the findings of Esmail (1997) that addition of oat hulls to a layer diet reduced the incidence of feather pecking and cannibalism in a dose-response manner. Recent research by Hartini, Choct, Hinch, Kocher and Nolan (2002) also found that insoluble dietary fibre was very effective in reducing cannibalism mortality.