Abstract
Validated procedures play an important role to obtain accurate information about individual amino acid requirement data. The aim of the present study was to assess lysine (Lys) requirement of growing chicken both by classical supplementation technique and principles of diet dilution technique as applied with “Goettingen approach”. During the starter period (1 - 21 d), a growth study with male meat type chicken (Ross 308) was conducted making use of five graded dietary Lys-levels (3 repetition boxes with 3 birds/box). L-Lys×HCl was gradually added to a diet based on wheat, soybean protein concentrate, wheat gluten and fishmeal to yield 80%, 87.5%, 95%, 102.5% and 110% of the expected requirement level (13 g Lys/kg as fed). Diets were iso-energetic (12.8 MJME/kg) and iso-nitrogenous (21.65% crude protein). Birds were fed on free choice level also to assess the feed intake (FI) effects as important factor on traditional response criteria. Analyzed body composition at start and end of the growth study yielded N deposition (ND) data for further data assessment using exponential approximations depending on dietary Lys content or observed Lys intake. The results indicated significant differences (p (BWG, ND) taking also into account the expected real feed intake to formulate the needed in-feed concentration.
Highlights
Inaccurate formulation of dietary amino acid supply will impair protein utilization and increase the total nitrogen output to the environment
The results indicated significant differences (p < 0.05) in response on body weight gain (BWG) and observed dietary protein quality with unexpected consequences for the derived Lys requirement data
Birds fed the diets with Lys supply below 95% (L1 and L2) of the expected requirement level (13 g Lys/kg diet as fed) responded with reduced FBW, BWG and feed intake (FI), respectively
Summary
Inaccurate formulation of dietary amino acid supply will impair protein utilization and increase the total nitrogen output to the environment. Mathematical models and statistical methods of data analysis have been created to improve the procedure for assessment of individual amino acid (AA) requirement data [1]-[10]. The AA requirement was derived at the dietary concentration of the limiting AA which yielded the maximum response or a definite percentage (mostly 95%) of the observed asymptote of the fitted non-linear function. The term “subjective estimate” was concluded from broken-line analysis. Deriving the first point at which the quadratic response curve intersected the plateau delivered from broken-line analysis was interpreted as “objective estimate”. Wang and Fuller [13] utilized individual AA deletion from a complete diet for estimation of AA requirement based on an observed slope of the response criteria between diets
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