Abstract
Four Nutritional Programs (NP) used in the Brazilian poultry industry were tested in two broiler strains (Cobb 500 and Ross 308). NP varied in the concentrations of their main essential amino acids (AA) and were classified as Low, Regular, High and Mixed (high AA concentrations up to 21 days and regular concentrations after that). Minimum digestible Met+Cys/Lys, Thr/Lys, Arg/Lys, Ile/Lys, and Val/Lys ratios were 0.74, 0.64, 1.05, 0.65 and 0.75, respectively, in all NP, and no minimum amount of CP was fixed. There were no interactions between strain and NP for any of the evaluated responses. From 1 to 47 days of age, birds fed the Low NP presented lower average body weight and body weight gain (BWG). The high NP allowed for better feed conversion ratio (FCR), followed by the Regular and the Mixed NP. Ross 308 broilers were heavier, presenting worse FCR due to higher FI. Birds fed the High NP had lower carcass yield than those fed the Low NP. The Low and Regular NP had lower costs per WG when compared with the High NP. Low and Regular NP presented higher gross margin returns compared with the High NP. The Regular and Mixed NP are the most recommended, presenting intermediate performance and higher economic returns.
Highlights
The accuracy in meeting broiler nutritional protein requirement, as well as the search for an ideal profile of amino acids (AA) to obtain the maximum protein utilization of protein has guided the research in this area
Broiler chickens offered free choice between two diets with different CP and AA levels presented similar performance as the control group (22% CP), by choosing diets with less protein, but rich in essential AA (Kolling et al, 2005). These results indicate that the birds regulated their feed intake according to their protein requirements
The results found in the economic analysis of this study are attributed especially to the high price of ingredients and synthetic AA used in 2012
Summary
The accuracy in meeting broiler nutritional protein requirement, as well as the search for an ideal profile of amino acids (AA) to obtain the maximum protein utilization of protein has guided the research in this area. New formulation approaches started to be applied when measuring AA in feeds became feasible, allowing the transition from using crude protein values to the use of total AA. Feed formulations for poultry and pigs recommended of digestible (dig) AA values, based on the ideal protein concept; this was aided by the development and availability of synthetic AA. The genetic progress of broilers, including gender and strain, can influence the ideal AA ratio needed; any alteration in the proportion of body protein, feathers and maintenance requirements may result in changes in the ideal AA ratios (Hackenhaar & Lemme, 2005). A portion of 100 g of cooked chicken meat contains 239 calories and 27 g of protein, which
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