Although low-protein diets seem to adversely affect growth rate, there is little indication that excessively high levels of protein have any benefit on growth and development.
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Low-protein diets have a transitory effect on muscle fiber size rather than any long-term effect on numbers of such fibers (Timson et al., 1983). Rate of both white-egg- (Douglas and Harms, 1982 Kwakkel et al., 1991) and brown-egg-laying pullets (Maurice et al., 1982), and early growth depression often depresses mature body weight and thereby adversely affects adult performance (Milby and Sherwood, 1953 Leeson and Summers, 1979, 1987a). TABLE 2-2 Body Weight and Feed Consumption of Immature Leghorn-Type ChickensĪ Average genetic potential when feed is consumed on an ad libitum basis.ĭifferent commercial strains may show different growth rates and different final mature body weights. Suggested requirements for crude protein are typical of those derived with corn-soybean meal diets, and levels can be reduced somewhat when synthetic amino acids are used.ĭ The calcium requirement may be increased when diets contain high levels of phytate phosphorus (Nelson, 1984). There, however, should be sufficient crude protein to ensure an adequate nitrogen supply for synthesis of nonessential amino acids. NOTE: Where experimental data are lacking, values typeset in bold italics represent an estimate based on values obtained for other ages or related species.ī These are typical dietary energy concentrations for diets based mainly on corn and soybean meal, expressed in kcal ME n/kg diet.Ĭ Chickens do not have a requirement for crude protein per se. TABLE 2-1 Nutrient Requirements of Immature Leghorn-Type Chickens as Percentages or Units per Kilogram of Diet Managers should routinely consider restricted feeding only for brown-egg-laying strains, and even then only in temperate climates and with high-energy diets. Ad libitum feed consumption is important for Leghorn birds, especially when reared in hot climates, because of their inherently low appetites. The nutrient requirement values shown in Table 2-1 and the performance characteristics shown in Table 2-2 are based on the assumption that the birds will be allowed to consume feed in an ad libitum manner. In large part, however, these requirement values have been extrapolated from studies conducted with Leghorns with consideration for the larger body weight and/or appetite and increased maintenance requirement of brown-egg layers. Because brown-egg-laying birds predominate in many parts of the world, the committee has attempted to define their nutrient requirements as well. The dearth of research information for immature pullets is even more acute for brown-egg-laying strains. It is well documented that mature body weight can greatly influence the subsequent reproductive performance (Leeson and Summers, 1987a), and, as such, this criterion becomes critical in the assessment of nutritional status. Although requirements are assessed ultimately in terms of subsequent reproductive performance, the criteria used by the committee were adequate growth rate (in terms of final body weight at different ages) and normal metabolism. Nutrient requirements of immature Leghorn-type chickens (pullets) are listed in Table 2-1. The available information is reviewed in Appendix Table A-1. Most current research activity deals with nutrients of major economic significance. Thus, although growth and maturity characteristics of egg-strain pullets have changed considerably over the last 10 years, particularly for brown-egg-laying birds, the only data available on requirements for many nutrients are dated. In large part, this situation is due to the use of meat-strain birds in requirement studies involving avian species.
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Relatively little research has been conducted in the last 10 years to obtain definitive nutrient requirements for immature Leghorn-type birds.