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

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 < 0.05) in response on body weight gain (BWG) and observed dietary protein quality with unexpected consequences for the derived Lys requirement data. According to the independent variable (Lys in % of diet versus daily Lys intake) and aimed level of daily ND, the needed in-feed content of Lys varied between 1.24% and 1.46%. Application of the exponential modelling by "Goettingen approach" overcame these misleading conclusions by modelling the relationship between required Lys intake and observed response data (BWG, ND) taking also into account the expected real feed intake to formulate the needed in-feed concentration.

Invited review: Further progress is needed in procedures for the biological evaluation of dietary protein quality in pig and poultry feeds

“…Today, the procedure is called the "Göttingen approach" due to further developments over 2 decades at the University of Göttingen Dorigam et al, 2017;Samadi et al, 2017). However, it will not be possible to outline in detail how the different issues of the current procedure differ from other approaches recently in use.…”

“…Wecke et al, 2016;Samadi et al, 2017). However, also from the viewpoint of animal breeding, the observed ND max T data are of interest because they provide additional information about breeding success.…”

“…These factors are also important when traditional dose-response experiments are applied in AA requirement studies, but they are insufficiently taken into account as currently demonstrated by Samadi et al (2017). Dose-response experiments are widely applied when the efficacy of supplemented AAs is under study.…”

“…Model-specific parameters as utilized in current applications were justified in earlier and recent publications (e.g. Liebert et al, 2000;Thong and Liebert, 2004a-c;Samadi and Liebert, 2006a, b, 2007a, b, 2008Liebert and Benkendorff, 2007a, b;Liebert, 2008Liebert, , 2009Liebert and Wecke, 2008;Samadi et al, 2017;Wecke and Liebert, 2009Wecke et al, 2016;Dorigam et al, 2017) and can be condensed as follows: , b is the slope of the NR curve indicating the dietary protein quality (the slope of the curve for a given protein quality is independent on NI), and e is the basic number of the natural logarithm (ln).…”

“…Equation (4) is widely applied for assessing quantitative AA requirement data in both earlier Liebert and Gebhardt, 1988;Thong and Liebert, 2004a-c;Liebert, 2006a, b, 2007a, b;Liebert, 2009;Liebert, 2009, 2010) and recent studies (Pastor et al, 2013;Wecke and Liebert, 2013;Khan et al, 2015;Dorigam et al, 2017;Samadi et al, 2017). An important precondition for validated conclusions is that experimental data are available which describe the NR or ND response to a defined LAAI at a specific level of dietary efficiency of the LAA, as reflected by the model parameter (bc −1 ).…”