The purpose of this study was to evaluate the Val/
Lys ratio in broiler diets that contained ingredients
normally used in the diets produced by feed mills and
used by poultry companies. To fine-tune the digestible
Val/Lys ratio, the CP in the diet was reduced and
industrial amino acids were added. In both experiments
(8 to 21 and 30 to 42 d of age), the formulated diets
contained corn, soybean meal, and sorghum, and the
amino acid contents of all the diets were analyzed to
confirm the calculated values. To provide better data
on the Val/Lys ratio, the total amino acids were converted
to digestible amino acids using Rostagno’s digestibility
coefficient. This method is consistent with
the method of Emmert and Baker (1997), who suggested
that digestible amino acid values should be used
to avoid any differences in absorption efficiency arising
from the ingredient sources. Given that the ideal protein
level involves the optimal ratios of all the essential
amino acids to lysine, the regression analysis used Val/
Lys ratio, not digestible valine. Most studies that have
evaluated the Val/Lys ratio have first estimated the
optimal valine level and then used this level to find the
optimal Val/Lys ratio.