Digestible tryptophan:lysine ratio for laying hens

Abstract

-The objective of this study was to evaluate the requirement of digestible tryptophan for white laying hens in the production stage fed diets of different digestible tryptophan:digestible lysine ratios, as well as animal performance and histological alterations in their reproductive and digestive systems. A total of 280 white laying hens at 29 weeks of age were distributed in a completely randomized design with five treatments and seven replications with eight birds in each. The treatments consisted of a base feed, formulated with corn, soybean meal and corn gluten meal, and supplemented with the synthetic amino acids L-lysine, DL-methionine, L-threonine, L-isoleucine, L-arginine, and L-valine, so as to meet the nutritional requirements for laying hens, except for digestible tryptophan. The basal diet was supplemented with 0.00; 0.017; 0.035; 0.052; and 0.069 g/kg of L-tryptophan in substitution for corn starch with the objective of reaching the levels of 0.151; 0.167; 0.183; 0.199; and 0.215 g/kg of digestible tryptophan in the feed. For the ratio between digestible amino acids and lysine, the recommendation of Brazilian Tables for Poultry and Swine was followed, except for the digestible tryptophan: digestible lysine ratios, which were 19, 21, 23, 25 and 27 for each treatment. The variation in the digestible tryptophan: digestible lysine ratio promoted changes in performance and in the histological characteristics, improving the results. The digestible tryptophan:digestible lysine ratio of 24.5% in the feed of white laying hens in production stage promotes better animal performance and histological results.

Digestible tryptophan:digestible lysine ratio in diets for laying hens from 24 to 40 weeks of age

“…The ideal digestible tryptophan:digestible lysine ratio of 0.252, estimated in this study based on the efficiency of utilization of digestible lysine for production of eggs mass was similar to the ratio of 0.253 estimated by Lima et al (2011), based on the feed conversion per dozen eggs of hens from 29 to 45 weeks of age.…”

“…The feed conversion per dozen eggs was not affected (P>0.05) by dietary digestible tryptophan levels in diets. The digestible tryptophan: digestible lysine ratio of 0.252 estimated in this study was higher than the value found by Lima et al (2011) for feed conversion per eggs mass (0.246%); however, it was similar to the value obtained by the same authors for feed conversion per dozen eggs (0.253%) of hens from 29 to 45 weeks of age.…”

Digestible tryptophan-to-digestible lysine ratio in diets for laying hens of 42 to 58 weeks of age

“…However, Russell & Harms (1999) observed that only levels of tryptophan lower than or equal to 0.130% promoted reduction in the egg mass produced by laying hens of 55 to 59 weeks of age. The ideal ratio of 24.3% estimated for feed conversion per egg mass, found in the present study, was similar to the 24.6% obtained by Lima et al (2012) As occurred in this present study, in experiments aimed to establish ideal ratios between essential amino acids and lysine, it is ideal that the feed intake of the birds for different treatments not present significant variation. A variation in feed intake results in variation in the amount of digestible lysine consumed, which could influence the performance parameters and mask the estimated ideal ratio.…”

“…Taking the feed conversion per egg mass into account, the estimated ideal digestible tryptophan-to-digestible lysine ratio was 24.3%. This value was similar to the 24.6% estimated by Lima et al (2012) based on the feed conversion per egg mass of hens of 29 to 45 weeks of age. This ratio was higher than the values obtained by Deponti et al (2007), who concluded that depending on the trait (production or egg mass) and on the regression model applied on data analyses (quadratic, exponential or segmented), the ideal tryptophan-tolysine ratios for laying hens of 53 to 58 weeks of age are in the range of 17.4 to 20.3%.…”

“…The ideal digestible tryptophan-todigestible lysine ratio of 23.6% estimated in this study for egg production was close to the 24.0% estimated for the same parameter by Lima et al (2012), who studied the tryptophan-to-digestible ratios of 19, 21, 23, 25 and 27% in diets. The overall average egg production in the present study was 80.3%, which is below the expected according to the strain manual.…”