Estimation of digestible tryptophan:lysine ratios for maximum performance, egg quality and welfare of white-egg-laying hens by fitting the different non-linear models

Abstract

A total of 360 Hy-Line W-36 hens at 30 wk of age were assigned to 6 dietary treatments that consisted of 6 different (11, 15, 19, 23, 27 and 31) digestible Trp:Lys ratios. Hens were fed the experimental diets from 30 to 36 wk of age. Productive traits were recorded every wk and egg quality was measured at 36 wk of age. Total IgM, IgG, anti-sheep red blood cell antibody titres, plasma corticosterone, serotonine and glucose concentrations and heterophil to lymphocyte ratio (H:L) were determined at wk 6 of the experiment. Results showed a significant improvement (P < .0001) in egg production, egg mass, feed intake, feed conversion ratio and body weight by increasing the standardized ileal digestible (SID) Trp:Lys ratio from 11 to 19. Relative weights of shell (P < .05) and shell strength (P < .06) were affected by dietary treatments. Hens fed graded levels of SID Trp responded by decreasing the H:L ratio in a linear or curvilinear manner (P < .05). The study reported here indicated that the ideal SID Trp:Lys ratio for laying hens ranged from17.5 to 29 based on the response criteria and regression models.

Amino acid requirements for laying hens: a comprehensive review

“…It is considered that conventional layer diets contain sufficient tryptophan to meet requirements ( Mousavi et al., 2018 ); however, supplementation of feed-grade tryptophan may become necessary in diets with reduced crude protein and increased levels of feed-grade amino acids. Moreover, Dong et al.…”

“…Dietary tryptophan has positive impacts on feed intake, but results are too inconsistent to provide any estimations. However, it has been reported that layer hens offered diets with 1.56 g/kg or lower levels of tryptophan showed depressed feed intake ( Mousavi et al., 2018 ; Wen et al., 2019a ). However, Table 11 shows that dietary tryptophan was positively correlated with feed intake in layer hens (r = 0.554, P = 0.0012).…”

“…There were 8 studies ( Peganova et al., 2003 ; Saki et al., 2012 ; Kakhki et al., 2016a , 2016b ; Mousavi et al., 2018 ; Wen et al., 2019a , 2019b ; Spangler et al., 2019 ) in which more than one assessment method was applied; therefore, it is possible to compare the impacts that different methods have on amino acid recommendations. Both linear and quadratic broken-line assessments were used in 5 studies ( Kakhki et al., 2016a , 2016b ; Mousavi et al., 2018 ; Wen et al., 2019a , 2019b ), and on average, quadratic broken-line models generated 15.2% higher recommendations than linear broken-line models. Alternatively, polynomial regressions generated 23.1% higher recommendations than linear broken-line models in 4 studies ( Mousavi et al., 2018 ; Spangler et al., 2019 ; Wen et al., 2019a , 2019b ).…”

“…Both linear and quadratic broken-line assessments were used in 5 studies ( Kakhki et al., 2016a , 2016b ; Mousavi et al., 2018 ; Wen et al., 2019a , 2019b ), and on average, quadratic broken-line models generated 15.2% higher recommendations than linear broken-line models. Alternatively, polynomial regressions generated 23.1% higher recommendations than linear broken-line models in 4 studies ( Mousavi et al., 2018 ; Spangler et al., 2019 ; Wen et al., 2019a , 2019b ).…”

Tryptophan requirement of first-cycle commercial laying hens in peak egg production

“…(2008) reported a Trp requirement of 120 mg/d of Trp relative to 482 mg/d of Lys based on broken line estimates using Hy-Line W-36 hens from 28 to 34 wk of age. A more recent publication estimated a higher requirement of 151 mg Trp/d relative to 675 mg/d of Lys based on 95 g/d intake of Hy-Line W-36 hens from 30 to 36 wk of age ( Mousavi et al., 2017 ). However, none of the previous experiments have investigated the requirement of Trp as the pullets are transitioning into egg production.…”