# Bioavailability of Tryptophan Biomass for Laying Hens

## TL;DR

This study shows that 60% L-tryptophan biomass is as effective as the standard 98% L-tryptophan for laying hens.

## Contribution

The study establishes the bioequivalence of 60% L-tryptophan biomass to 98% L-tryptophan in laying hens.

## Key findings

- No significant difference was found between the two tryptophan sources in performance or egg quality.
- The relative bioavailability value of 60% L-tryptophan biomass was determined to be 100%.
- Only body lipids showed a significant effect among body composition variables.

## Abstract

There has been extensive research on amino acid nutrition for layers over the past five decades, but the studies have used a single source of supplemental tryptophan, L-tryptophan 98%. Bioavailability is a crucial aspect of nutrient utilization, encompassing the processes of the digestion, absorption, metabolism, and utilization of the nutrient. This research was conducted to evaluate bioequivalence and determine the relative bioavailability value (RBV) of 60% L-tryptophan biomass for commercial Hy-Line Brown laying hens. Two assays were performed using a completely randomized experimental design. The first assay used a direct comparison method. A total of 66 layers were distributed in two treatments and 11 replicates, with 3 birds per replicate, totaling 21 experimental units. The second assay used the slope ratio method. A total of 150 layers were distributed in such a way that there were five treatments and ten replicates of three hens, totaling 50 experimental units. Performance, egg quality, and body composition were evaluated. The results obtained with the direct comparison method showed no significant difference (p > 0.05) between the L-tryptophan biomass 60% and L-tryptophan 98%. Among the body composition variables, only body lipids showed a significant effect (p < 0.05). According to the results obtained, the RBV of L-tryptophan biomass 60% was determined at 100% relative to L-tryptophan 98%. Thus, L-tryptophan biomass 60% is bioequivalent to and equally bioavailable as L-tryptophan 98%.

Two concurrent assays were conducted with the objective of evaluating the bioequivalence and determining the relative bioavailability value (RBV) of L-tryptophan biomass 60% for laying hens. In both assays, L-tryptophan 98% was used as the reference source. A total of 216 hens were used in the two assays. The first assay was performed using the direct comparison method to assess bioequivalence between the sources. In the second assay, the slope ratio method was used to determine the RBV. The variables analyzed were feed intake, tryptophan intake, egg production, egg weight, daily egg mass, feed conversion ratio, feed efficiency, yolk weight, shell weight, albumen weight, albumen height, eggshell thickness, Haugh unit, body protein weight, body lipid weight, body water weight, and body ash weight. The data from both assays were submitted to analysis of variance, and we only applied linear regression to variables from the data obtained using the slope ratio method that were significant at 0.05. The results obtained via the direct comparison method showed no significant difference (p > 0.05) between the L-tryptophan sources when using ANOVA. In the slope ratio method, the treatments only affected the egg production and daily tryptophan intake responses of the hens and linear equations were adjusted. No differences (p > 0.05) were found for egg quality. When we applied the slope ratio in adjusted equations, we found that the RBV = 100%. The results showed that the utilization of L-tryptophan biomass 60% in the diet of laying hens was bioequivalent.