A study was performed to compare the effects of dietary supplementation of DL-Methionine (DL-Met) or Hydroxy-Methionine (OH-Met) at the requirement in sulfur amino acids on laying hen’s performance under tropical summer season. Four-hundred and forty-eight Babcock layers were randomly allocated based on their body weight in two treatments of 14 replicates each (16 hens per replicate). Hens were offered either DL-Met or OH-Met at the requirement from week 18 to 31 weeks of age. Body weight increased with age and was not significantly different between treatments. Feed intakes were lower than breed standards, as influenced by heat stress but were similar between the two sources of methionine. There were no significant differences between egg mass, egg weight and feed conversion ratio of hens fed OH-Met or DL-Met. Similarly, egg density, eggshell strength and Haugh units were not significantly different between methionine sources. This study demonstrated that DL-Met and OH-Met are similar in laying hens under tropical conditions.
Introduction and objectives
Methionine (Met) is the first limiting amino acid in poultry species. It is available as LMethionine, DL-methionine (DL-Met) and hydroxy-methionine (OH-Met). The addition of Met in the poultry feed industry is still facing the relative efficacy dilemma between DL-Met and OH-Met (BUNCHASAK et al., 2012; NIE et al., 2007). In laying hens, only few studies have been performed to compare these two sources in tropical conditions. Therefore, the aim of the present study is to compare the effects of dietary supplementation of DL-Met or OH-Met at the requirement in sulfur amino acids on laying hen’s performance under tropical conditions.
Materials and methods
Four-hundred and forty-eight Babcock layers were reared from 18 to 31 weeks in collective cages in an open-sided facility at Sri Ramadhootha Poultry Research Farm Pvt Ltd, India. Birds were randomly allocated to two treatments with 14 replicates of 16 hens each. The egg mass and feed intake usually observed in the facility were used as factors to calculate the amino acids recommendations, based on the Rhodimet nutrition guide recommendations (Adisseo). Corn and soybean meal-based diets were supplemented on equimolar doses with either DL-Met or OH-Met, respectively at 0.14% and 0.16% (Table 1). Birds were habituated to the experimental diets from 18 to 20 weeks and data was collected from 21 to 31 weeks. Laying hens had free access to feed and water during the whole trial.
Temperature (Min. 18.3°C; Max. 39.3°C) and relative humidity (Min. 20%; Max. 90%) varied widely along the day and throughout the experimental period (Figure). Body weight was measured at the end of week 17, 23 and 28. Feed intake, egg production, egg weight, egg mass and feed conversion rate were measured on a weekly basis. Data was analyzed with a one-way ANOVA, respectively for the periods: weeks 21-25, and 26-31. Data of the overall experimental period (Week 21-31) was submitted to a repeated-measures ANOVA with the treatment and age as variables. Egg quality parameters were measured at week 22, 26 and 30, taking one egg per replicate per treatment (n=14), and were submitted to an ANCOVA model using the age and the treatment as variables (XLSTAT, Version 2015.3.01.19199).
Figure. Evolution of temperature and relative humidity throughout the trial
Results and Discussion
Body weight of laying hens increased linearly with age (P < 0.001) and was not significantly (P = 0.52) different between DL-Met (1258 ± 119 g/b) and OH-Met (1269 ± 122 g/b). This is in accordance with the results observed by (AGOSTINI et al., 2016) and (ZHAO et al., 2018), indicating that DL-Met and OH-Met similarly sustain bird’s growth. Table 2 shows the evolution of laying performance with age for the two groups. All parameters were improved with age (P < 0.001). However, feed intake, egg production, egg weight and egg mass were below the references of Babcock as the result of the high temperature and variable relative humidity (RENAUDEAU et al., 2012; CHENG et al., 1990). As demonstrated by (DANIEL AND BALNAVE, 1981), when temperatures gradually rise and remain high for an extended period, birds can acclimatize and maintain egg production and body weight at satisfactory levels. However, heat changes on a short period jeopardize birds’ ability to acclimatize. Additionally, a high relative humidity hampers adaptation to extreme of temperatures (DANIEL AND BALNAVE, 1981; CHENG et al., 1990). In addition, all the laying performance criteria were similar between DL-Met and OH-Met throughout the experimental period. These results are in accordance with (BUNCHASAK et al., 2012; CUEVAS et al., 2001) who showed that the two sources can be equally used to ensure laying hens performance.
Egg quality parameters are presented Table 3. Egg density, Haugh unit, shell weight and shell thickness were affected by the age but they were similar between DL-Met and OH-Met. Egg strength was neither affected by the age, nor by the dietary treatment. Therefore, the supplementation of DL-Met and OH-Met did not impact egg quality under tropical conditions.
There is no significant difference of layers’ body weights between treatments indicating that DL-Met and OH-Met similarly sustain hen’s growth performance. There is no significant difference between DL-Met and OH-Met in all criteria of performance and on egg quality parameters. Overall, this study shows that OH-Met is as efficient as DL-Met as source of supplemental Met in laying hens diets under tropical climate.
This extended abstract has been presented at the 22nd European Symposium on Poultry Nutrition, 10-13 June 2019 Gdansk, Poland and is available in the proceedings of the conference.