Assessing the age-dependent optimal dietary branched-chain amino acid ratio in growing chicken by application of a nonlinear modeling procedure

Abstract

Based on a nonlinear N utilization model, 2 N balance experiments with growing broiler chickens were conducted, investigating the ideal amino acid (AA) ratio (IAAR) of the branched-chain AA (BCAA) Leu, Ile, and Val related to Lys. In both of the experiments, the starter (I: 10-20 d of age) and grower periods (II: 25-35 d of age) utilized 36 male Ross 308 chickens each (n = 144). Nitrogen balance periods were divided into an adaptation period (5 d) and 2 consecutive collection periods (2 × 5 d). Diets of experiment 1 were based on a consistent mixture of wheat, soy protein concentrate, wheat gluten, fish meal, and crystalline AA, subsequently diluted by wheat starch to provide 8 graded CP levels (6-34% CP). Results of nonlinear regression between N intake and N deposition yielded the theoretical maximum for N deposition (NDmaxT; I: 4,593 mg of N/BWkg(0.67)/d; II: 4,302 mg of N/BWkg(0.67)/d). Furthermore, the daily N maintenance requirement (NMR) was derived (I: 113 mg of N/BWkg(0.67); II: 215 mg of N/BWkg(0.67)/d). Both the age-dependent data for NMR and NDmaxT were applied to calculate the model parameter b (protein quality, independent of N intake) and bc(-1) (efficiency of limiting AA), respectively. Five diets based on the same ingredients as in experiment 1 were formulated for experiment 2: an AA balanced basal diet and 4 diets of the same composition but lacking in supply of Lys, Leu, Ile, or Val. All experimental diets were isocaloric and isonitrogenous. For calculation of the IAAR, observed bc(-1) data of each AA diluted diet were utilized. The concluded IAAR of Lys:Leu:Ile:Val for the starter and grower period were 100:94:55:65 and 100:106:56:72, respectively. These results indicated a higher demand for Leu and Val during the grower phase and, generally, a lower IAAR for the BCAA than previously reported in comparable experiments.

Assessing Lysine Requirement of Growing Chicken by Direct Comparison between Supplementation Technique and “Goettingen Approach”

“…The derived model parameter b as measure of the feed protein quality was significantly increased by gradually elevated Lys concentration up to the requirement level. In line with results of Pastor et al [21] and Khan et al [25], the parameter …”

An Elevated Dietary Cysteine to Methionine Ratio Does Not Impact on Dietary Methionine Efficiency and the Derived Optimal Methionine to Lysine Ratio in Diets for Meat Type Chicken

“…In addition, the model parameters of observed dietary AA efficiency are validated to be used for assessing optimal dietary AA ratios [7]- [9] [31] by application of equation (4). Unfortunately, literature data provide no validated information about the extent to which Cys should contribute to the total SAA supply in growing chicken depending on age.…”

“…N balance studies were divided into an adaptation period (5 d) and 2 consecutive collecting periods (each 5 d) according to the procedure of Pastor et al [7]. At start of the adaptation period, the feed supply was ad libitum to estimate the proper level of individual feed intake under housing conditions in metabolic cages.…”

“…The order of observed bc −1 data from individual AA is indirectly correlated to the physiological requirement per unit protein deposition. According to [9], the reciprocal relationship between Lys efficiency (as reference AA) and the observed efficiency of the individual LAA under study is utilized to derive optimal dietary AA ratios (IAAR) as currently reported [7] [8]:…”

“…Currently, there are indications that optimal ratios of individual AAs related to lysine might change depending on age period, feed protein source and dietary AA efficiency [7]- [11].…”