Observations on the utilisation of dietary energy by medium‐ and fast‐growing strains of cockerels and on their arginine and methionine requirements

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Abstract
Diets containing levels of crude protein that were critical for normal growth were fed alone or with supplements of arginine, methionine or lysine or combinations of these amino acids to Rhode Island Red × Light Sussex and hybrid (Chunky Chicks) cockerels. By calculation and comparison with the (U.S.A.) National Research Council (1960) recommendations, the basal diets were inadequate in arginine and sulphur‐amino acids. Live‐weight, energy and protein gains were measured. Growth and efficiency of conversion of dietary protein and meta‐bolisable energy to tissue protein and energy were not greatly improved by any of the supplements. It is suggested that the U.S.A. requirement values for arginine and the sulphur‐amino acids might be generous by as much as 20 per cent. The lower figures suggested by the (U.K.) Agricultural Research Council (1963) are preferred. The hybrids grew faster, generally contained more fat, and were more efficient than Rhode Island Red × Light Sussex birds in converting feed to live‐weight and dietary protein and energy to tissue protein and energy. The energy lost as heat per unit of mean live‐weight per experimental week was the same for both breeds. Implications of these findings are discussed.
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