Studies on the relative bioavailability (RBV) of DL-Methionine (DL-Met) to L-Methionine (L-Met) have produced variable results. An experiment was conducted to determine the RBV of DL to L-Met. A total of 2268 1-day old male chicken were housed in 54 floor pens (42 bird/pen). There were 9 treatments (6 repetitions) including the basal diet (BD). The BD was deficient in Met content with 0.27, 0.26 and 0.25 in the starter, grower and finisher periods respectively. Four levels of experimental diets for each DL-Met and L-Met were created by supplementing 0.05%, 0.10%, 0.15% and 0.20% of DL- or L-Met to the BD. The feeding program consisted of starter (0-14 d, 21% CP and 2900 kcal ME/kg), grower (15 - 28 d, 20% CP and 3000 kcal ME/kg) and finisher period (29 - 37 d, 18.5% CP and 3050 kcal ME/kg). Chickens and feed were weighed at the end of each age period. Regression coefficients of a common plateau asymptotic regression were used to calculate RBV. Birds responded to gradual increase in Met levels, BW, FCR and ADG were significantly (P < 0.05) higher in treatment groups as compared to control. Through the study period (37 d), the RBVs of DL-Met for BW and FCR were 89 and 77 respectively.
Better growth, economy and environment friendly commercial broiler production is limited to the right amount of available amino acids for efficient utilization in animal body. All of the crystalline amino acids supplemented in commercial poultry production are in their natural (L-isomer) form except methionine (Met), which may be utilized in its synthetic (D- and L-isomers) form in poultry. However, birds have to transform the D-isomer form into L-isomer in order to make it available for protein synthesis and other essential metabolic functions. It is not clear whether this conversion process in 100% efficient and all of the supplemented D-isomer form is being converted into L-isomer for its further utilization in animal body.
Inefficient intestinal absorption of supplemented Met is one of the factors which may limit its availability to body metabolism. For instance, Esteve-Garcia and Austic [
A number of studies have been carried out about the bio-efficiency of D, L and DL-Met. However, their results remained indecisive. Some reports showed that D- and L-Methionine were equivalent [
The goal of the present study was to determine the RBV of two sources of Met (DL vs. L-Met), supplemented at graded levels to practical broiler diets, using growth parameters as response criteria.
All animal housing and husbandry conformed to the European Union Guidelines [
The basal diet was formulated according to nutrient recommendations of Ross 308 [
The feeding program was divided into three age periods; starter (0 - 14 d), grower (15 - 28 d) and finisher (29 - 37 d). Eight experimental diets were created by supplementing crystalline DL or L-Met to the BD in four graded levels, plus the un-supplemented diet. The calculated values for the experimental diets of DL-Met1-4 or L-Met1-4 were BD + 0.05, 0.10, 0.15 and 0.20% respectively, based on expected responses to methionine (Esteve-Garcia and Austic [
Dietary ingredients and experimental diets were analysed according to AOAC [
Body weight and feed consumption were measured at 14, 28 and 37 d on a pen basis. Dead animals were not taken into account, and their weight was subtracted from the initial weight of the pen, according to the mean weight, or in case the animal was smaller than the initial weight due to disease, its weight at the time of death was subtracted from the initial weight of the pen. Corrected
Ingredient | Starter | Grower | Finisher |
---|---|---|---|
Maize | 550.2 | 480.4 | 503.4 |
Wheat | 60 | 100 | 100 |
Soybean meal, 48% CP | 280 | 224.7 | 200 |
Full fat extruded soybeans | - | 45 | 38.1 |
Peas | - | 40 | 52.5 |
Soy oil | 29.7 | - | - |
Animal fat | - | 42.8 | 55 |
Dicalcium phosphate | 19.3 | 15 | 13.5 |
Calcium carbonate | 7.7 | 7.9 | 7.9 |
Sodium chloride | 4 | 3.5 | 3.5 |
L-Glu | 30 | 30 | 15 |
L-Lys HCl | 4.8 | 2.7 | 2.7 |
L-Arg HCl | 2.3 | 0.5 | 0.8 |
L-Val | 2.6 | 1.4 | 1.4 |
L-Thr | 1.8 | 0.9 | 1 |
L-Ile | 2.3 | 1.4 | 1.6 |
L-Trp | 0.6 | 0.1 | 0.4 |
Choline chloride | 1 | - | - |
Mineral and vitamin premix1 | 3 | 3 | 3 |
Maxiban G 1602 | 0.5 | - | |
Elancoban3 | - | 0.5 | - |
Ethoxyquin, 66% | 0.2 | 0.2 | 0.2 |
1Provides per kg feed: vitamin A (E-672) 13500 IU; vitamin D3 (E-671) 4800 IU; vitamin E (alfa-tocopherol) 45 mg; vitamin B1 3 mg; vitamin B2 9 mg; vitamin B6 4.5 mg; vitamin B12 16.5 µg; vitamin K3 3 mg; calcium panthotenate 16.5 mg; nicotinic acid 51 mg; folic acid 1.8 mg; biotin 30 µg; Fe (E-1) (from FeSO4・7H2O) 54 mg; I (E-2) (from Ca(I2O3)2) 1.2 mg; Co (E-3) (from 2CoCO3・3Co(OH)2・H2O) 0.6 mg; Cu (E-4) (from CuSO4・5H2O) 12 mg; Mn (E-5) (from MnO) 90 mg; Zn (E-6) (from ZnO) 66 mg; Se (E‑8) (from Na2SeO3) 0.18 mg; Mo (E-7) ((NH4)6Mo7O24) 1.2 mg. 2Maxiban G 160: 80 g Narasin and 80 g Nicarbazin per kg of product. 3Elancoban: 200 g Sodium Monensin per kg of product
Nutrient | Starter | Grower | Finisher |
---|---|---|---|
0 - 14 d | 15 - 28 | 29 - 37 d | |
ME MJ/kg1 | 12.13 | 12.55 | 12.55 |
CP g/kg | 209.7 | 203.5 | 184.4 |
Ether extract g/kg | 51.9 | 68.8 | 79.9 |
Crude ash g/kg | 50.2 | 47.5 | 44.9 |
Amino acids g/kg | |||
Lys | 13.2 | 11.4 | 10.6 |
Met2 | 2.70 (2.70) | 2.50 (2.60) | 2.30 (2.50) |
Cys | 3.2 | 3.3 | 2.8 |
Thr | 8.1 | 7.6 | 7 |
Trp | 2.6 | 2.4 | 2.1 |
Arg | 12.9 | 11.8 | 11.5 |
Ile | 9.7 | 9.1 | 8.5 |
Leu | 15.6 | 14.6 | 13.8 |
Val | 9.9 | 9.9 | 9 |
Glu | 59.1 | 62.8 | 45.7 |
Phe | 9.1 | 8.9 | 8.3 |
His | 5 | 4.7 | 4.3 |
Asp | 17.4 | 18.2 | 16.8 |
Gly | 7.8 | 7.6 | 7.3 |
Ala | 9 | 8.6 | 8.2 |
Pro | 11.4 | 11.1 | 9.9 |
1ME contents were calculated based on WPSA [
Trt. | Met source supplements (%) | |||
---|---|---|---|---|
Expected suppl. level | Starter 0 - 14 d | Grower 15 - 28 d | Finisher 29 - 37 d | |
Basal | - | - | - | - |
L-Met11 | 0.05 | 0.04 | 0.05 | 0.04 |
L-Met2 | 0.10 | 0.08 | 0.09 | 0.09 |
L-Met3 | 0.15 | 0.13 | 0.14 | 0.15 |
L-Met4 | 0.20 | 0.15 | 0.19 | 0.20 |
DL-Met12 | 0.05 | 0.05 | 0.05 | 0.05 |
DL-Met2 | 0.10 | 0.09 | 0.09 | 0.10 |
DL-Met3 | 0.15 | 0.14 | 0.14 | 0.15 |
DL-Met4 | 0.20 | 0.19 | 0.19 | 0.20 |
1L-Met: Procured from CJ Europe GmbH, Germany; 2DL-Met: Procured from Sumitomo Chemical Company, Japan.
feed conversion ratio (FCR) was calculated dividing the total feed consumed within the period to the weight gained by the live animals within the period plus the weight gain of the dead animals during the period. Average feed consumption was calculated as the product of weight gain (WG) and feed conversion ratio (FCR).
Results were analysed as a randomized complete block design by two way ANOVA with 6 blocks corresponding to location within the house and 9 treatments corresponding to the basal diet and each of the four levels of DL and L-Met. Treatment means were compared for significance (P < 0.05) using Tukey’s test.
The RBV of DL and L-Met was calculated using the model of Littell et al. [
Y = B1 + B2 × ( 1 − e ( B31 × X1 + B32 × X2 ) ) (1)
where Y = response variable (Feed intake, BW, ADG and FCR,)
B1 = intercept (response of basal diet)
B1 + B2 = asymptote
B31 = Steepness coefficient for L-Met
B32 = Steepness coefficient for DL-Met
X1 = level of L-Met
X2 = level of DL-Met
The bioavailability for DL-Met relative to L-Met was calculated by the ratios of regression coefficients B31 and B32 according to Elwert et al. [
The statistical means for BW, FI, ADG and FCR attributed by two way ANOVA did not reveal any significant (P > 0.05) difference depending on the source of Met, however, the growth parameters for the basal diet were significantly (P < 0.05) lower as compared to the experimental diets supplemented with Met (
The growth response corresponding to L-Met supplementation in relation to DL-Met was numerically higher, but Tukey’s test does not reveal significant (P > 0.05) difference due to the different Met sources.
A curvilinear response was observed from 0-37d for BW and FCR with graded Met supplementation (
Trt. | Met% | 0 - 14 d | Met% | 15 - 28 d | ||||||
---|---|---|---|---|---|---|---|---|---|---|
FI | BW | ADG | FCR | FI | BW | ADG | FCR | |||
g | g | g | g/g | g | g | g | g/g | |||
BD | 0 | 22.10a | 252a | 14.90a | 1.48a | 0 | 75.76a | 742a | 32.60a | 2.32a |
L-Met1 | 0.04 | 31.40b | 392b | 24.90b | 1.26b | 0.05 | 109.30b | 1383b | 66.00b | 1.65b |
L-Met2 | 0.08 | 35.30c | 447c | 28.80c | 1.22bc | 0.09 | 119.20c | 1674c | 81.80c | 1.45c |
L-Met3 | 0.13 | 35.70c | 457c | 29.50c | 1.21c | 0.14 | 123.30c | 1749d | 86.10d | 1.43c |
L-Met4 | 0.15 | 35.90c | 464c | 30.00c | 1.19c | 0.19 | 126.00c | 1798d | 88.90d | 1.41c |
DL-Met1 | 0.05 | 31.50b | 400b | 25.50b | 1.24bc | 0.05 | 112.50b | 1375b | 64.90b | 1.73b |
DL-Met2 | 0.09 | 34.60c | 445c | 28.70c | 1.21c | 0.09 | 122.40c | 1675c | 82.00c | 1.49c |
DL-Met3 | 0.14 | 35.60c | 458c | 29.60c | 1.20c | 0.14 | 122.70c | 1747d | 85.90d | 1.42c |
DL-Met4 | 0.19 | 36.10c | 454c | 29.30c | 1.24c | 0.19 | 123.40c | 1767d | 87.50d | 1.41c |
Trt. | 29 - 37 d | 0 - 37 d | |||||||
---|---|---|---|---|---|---|---|---|---|
FI | BW | ADG | FCR | FI | BW | ADG | FCR | ||
g | g | g | g/g | g | g | g | g/g | ||
BD | 0 | 113.00a | 1137a | 49.40a | 2.28a | 63.50a | 1137a | 29.50a | 2.15a |
L-Met1 | 0.04 | 177.90b | 2168b | 98.10b | 1.81b | 94.60b | 2168b | 57.40b | 1.64b |
L-Met2 | 0.09 | 196.60c | 2552c | 109.60c | 1.79bc | 104.10c | 2552c | 67.80c | 1.53c |
L-Met3 | 0.15 | 200.50c | 2683d | 116.70d | 1.72bc | 106.80c | 2683d | 71.30d | 1.49c |
L-Met4 | 0.2 | 201.80c | 2747d | 118.40d | 1.70c | 108.20c | 2746d | 73.00d | 1.48c |
DL-Met1 | 0.05 | 180.00b | 2162b | 98.40b | 1.83b | 96.40b | 2162b | 57.20b | 1.68b |
DL-Met2 | 0.1 | 199.10c | 2562c | 110.80c | 1.79bc | 105.80c | 2562c | 68.00c | 1.55c |
DL-Met3 | 0.15 | 200.50c | 2672d | 115.50d | 1.74bc | 106.40c | 2672d | 71.00d | 1.49c |
DL-Met4 | 0.2 | 199.00c | 2698d | 116.20d | 1.71c | 107.10c | 2698d | 71.70d | 1.49c |
The RBV of DL to L-Met was calculated by the ratio of B32/B31 as described in Equation 1. The results of RBV of DL-Met through the study period are summarized in
Based on ANOVA, the statistical non-significant differences (P > 0.05) on performance parameters depending on Met sources may be attributed to the difference in calculated and analysed contents of the dietary treatments of L-Met, which were found lower than expected (
It is difficult to ascertain the level of one source over the other when two different sources of the test product are supplemented at closer levels [
Criterion of response | RBV | 95% Confidence interval |
---|---|---|
Feed intake | 99 | 71 - 128 |
Body weight | 89 | 78 - 100 |
Average daily gain | 89 | 78 - 100 |
Feed to gain | 77 | 51 - 103 |
Criteria of response | Parameter | Estimate | Standard error | 95% confidence interval | R2 | |
---|---|---|---|---|---|---|
Lower | Upper | |||||
Feed intake (g) | B1 | 63.442 | 1.864 | 59.697 | 67.187 | 0.90 |
B2 | 44.504 | 2.077 | 40.332 | 48.677 | ||
B31 | −27.477 | 3.503 | −34.513 | −20.441 | ||
B32 | −27.4 | 3.68 | −34.792 | −20.009 | ||
Body weight (g) | B1 | 1133.57 | 34.051 | 1065.18 | 1201.96 | 0.97 |
B2 | 1624.19 | 38.776 | 1546.31 | 1702.07 | ||
B31 | −23.067 | 1.493 | −26.066 | −20.069 | ||
B32 | −20.56 | 1.297 | −23.165 | −17.955 | ||
Average daily gain (g) | B1 | 29.467 | 0.92 | 27.618 | 31.315 | 0.93 |
B2 | 43.897 | 1.048 | 41.792 | 46.002 | ||
B31 | −23.067 | 1.493 | −26.066 | −20.069 | ||
B32 | −20.56 | 1.297 | −23.165 | −17.955 | ||
Feed to gain | B1 | 2.149 | 0.033 | 2.083 | 2.215 | 0.87 |
B2 | −0.665 | 0.037 | −0.739 | −0.591 | ||
B31 | −31.018 | 4.97 | −41.001 | −21.034 | ||
B32 | −23.926 | 3.513 | −30.982 | −16.869 |
B1 = intercept (response of basal diet); B1 + B2 = asymptote; B31 = Steepness coefficient for L-Met; B32 = Steepness coefficient for DL-Met.
study remained indecisive to quantify one sources over the other without affecting the performance parameters.
Studies conducted by Zelenka et al. [
In a metabolic experiment for 20 days in post weaned growing pigs, Shen et al. [
Whereas, Kong et al. [
ANOVA appears to be insufficient for the above mentioned as well as the present study to estimate the difference between the closely matching treatments. Moreover, two-way ANOVA also suffers from some limitations related to the present study, for instance it considers the levels of Met as categorical, while in fact they are continuous.
Therefore, the non-linear model of Littell et al. [
The RBV estimated in the present study is in agreement with the dose response studies of Noll et al. [
They observed that the level of Met effected the growth of the birds significantly (P < 0.05). Based on the three studies the biopotency (± SE) of L-Met was significantly superior to DL-Met (131% ± 10%); the biopotency of the analogue was not significantly different from DL-Met (96% ± 7%). In the present study, as a whole (37d), the RBV of DL- and L-Met was considerably diverse as compared to the observation of Noll et al. [
The difference in exponential graphic curves (
The RBV for body weight, DL-Met = 89, is in contrast with the observations of Dilger et al. [
Statistically, when comparing if one source (DL-Met) “equivalent” to the reference (L-Met) ignoring the type II error could have important practical consequences. D-Met must be converted to L-Met in the body. The process requires different steps, and it is not clear that process is 100% efficient; this may be projected through performance parameters. In the present experiment the RBV of DL to L-Met was 89:100 for BW and 77:100 for FCR.
Esteve-Garcia, E. and Khan, D.R. (2018) Relative Bioavailability of DL and L-Methionine in Broilers. Open Journal of Animal Sciences, 8, 151-162. https://doi.org/10.4236/ojas.2018.82011