Validation of the Lysine Requirement as Reference Amino Acid for Ideal In-Feed Amino Acid Ratios in Modern Fast Growing Meat-Type Chickens

Abstract

Nitrogen (N) balance studies were conducted with male growing broiler chickens to reevaluate the lysine (Lys) requirement of a modern broiler strain (Ross 308), making use of eight diets with graded crude protein (CP) supply (6%-34% CP as-fed). Wheat, soy protein concentrate, wheat gluten, fishmeal and crystalline amino acids (AAs) were the protein sources in the experimental diets with Lys as limiting AA. Following an adaptation period of five days, two consecutive excreta collection periods (2 × 5 d) were conducted: 10-20 d of age (starter period) and 25-35 d of age (grower period). Statistical evaluation of N balance data utilized an exponential modelling approach. Based on different dietary Lys efficiency, Lys requirement data were derived by modelling depending on average body weight (BW) during starter and grower period and targeted body protein deposition (PD), respectively. In addition, the influence of graded feed intake was taken into account. For the starter period at 600 g BW and assumed 10 g daily body PD, Lys requirement data between 741 mg and 823 mg per day were observed. The corresponding Lys in-feed concentration was 1.06% and 1.18%, dependent on supposed Lys efficiency at 70 g daily feed intake. For the grower period (average BW 1800 g), 1272 mg to 1473 mg Lys per day was needed to yield 16.5 g daily PD. The corresponding required Lys in-feed concentration was between 0.85% and 0.94% Lys for 150 g daily feed intake.

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

“…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.…”

“…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).…”

“…From this point of view, both feed factors and animal factors are involved when comparisons are made at the level of observed AA efficiency data. As pointed out by Wecke et al (2016), the reliability of measured AA efficiency data for the reference AA Lys is a fundamental precondition for such applications. The summarized results of a meta-analysis are given in Table 5.…”

“…Nörenberg, 1987;Farke, 2011;Wecke and Liebert, 2009;Khan et al, 2015) and observed individual AA efficiency data in mixed diets with and ingredient composition near practical feeding conditions (e.g. Liebert, 2008;Samadi and Liebert, 2008;Wecke and Liebert, 2009Wecke et al, 2016;Pastor et al, 2013;Samadi et al, 2017), which may reflect the real variation in this model parameter in common feedstuffs.…”

“…Baker, 2003;Wecke and Liebert, 2013;Wecke et al, 2016). The individual indispensable AAs have to be related to a reference AA, mostly lysine (Lys), which is almost exclusively utilized for body protein deposition in growing animals.…”