Biopotency of Methionine Sources for Young Turkeys1

Biopotency of Methionine Sources for Young Turkeys1 SALLY L. NOLL, PAUL E. WAIBEL,2 R. DENNIS COOK, and JEFFREY A. WITMER3 Departments of Animal Science and Applied Statistics, University of Minnesota, St. Paul, Minnesota 55108 (Received for publication January 30, 1984)

1984 Poultry Science 63:2458-2470 INTRODUCTION Methionine is c o m m o n l y added t o t u r k e y diets of t h e corn-soybean meal t y p e because of its limiting n a t u r e in starter and grower diets. Several studies have indicated beneficial g r o w t h and feed efficiency responses from addition of m e t h i o n i n e to starter-type diets (27 to 30% crude p r o t e i n ) for y o u n g t u r k e y s ( K u h l and Sullivan, 1 9 7 3 ; P e p p e r and Slinger, 1 9 5 5 ; P o t t e r and Shelton, 1 9 7 6 a , b , 1 9 7 9 ; P o t t e r et al, 1 9 7 7 ; W a i b e l , 1 9 5 9 ) . T w o s u p p l e m e n t s used are D L - m e t h i o n i n e and m e t h i o n i n e h y d r o x y analogue, t h e latter now p r o d u c e d as t h e free acid (MHA-FA). T h e MHA-FA has been s h o w n t o vary in m e t h i o n i n e activity for broilers. Little is k n o w n of its b i o p o t e n c y for t u r k e y s . T h e M H A - F A was equivalent t o L-methionine for broiler g r o w t h in semipurified diets (Creger et al, 1 9 6 8 ; R o m o s e r et al, 1976) and in a corn-soybean meal diet (Waldroup et al, 1981). In o t h e r practical diet studies, Elkin and

'Paper No. 13769 of the Scientific Journal Series of the Minnesota Agricultural Experiment Station. - reriitoctc

'Department of Statistics, University of Florida, Gainesville, FL 32611.

Hester ( 1 9 8 3 ) found t h e activity of t h e free acid t o be superior t o L-methionine b u t equivalent t o DL-methionine. van Weerden et al. ( 1 9 8 3 ) r e p o r t e d an efficacy estimate of 72% for M H A - F A in comparison to D L - m e t h i o n i n e , although t h e 9 5 % confidence limits were from 4 3 t o 130%. Estimates of b i o p o t e n c y have been lower w h e n M H A - F A was tested in crystalline amino acid-type diets for chicks. Boebel and Baker ( 1 9 8 2 ) and van Weerden et al. ( 1 9 8 2 ) r e p o r t e d m e t h i o n i n e potencies of 78% and 76%, respectively, relative t o D L - m e t h i o n i n e . A similar situation exists for t h e calcium salt of t h e analogue, i.e., t h e lower b i o p o t e n c y in crystalline amino acid diets. Several discussions (Boebel and Baker, 1 9 8 2 ; Smith, 1 9 6 6 ; van Weerden et al, 1982) have suggested t h a t t h e degree of m e t h i o n i n e deficiency and levels of m e t h i o n i n e and cystine in t h e diet m a y influence t h e utilization of t h e h y d r o x y analogue. T h e differences in b i o p o t e n c y t h a t appear diet related raise t h e question of utilizing estimates o b t a i n e d with o n e t y p e of diet and applying t h e information t o a n o t h e r diet t y p e (Elkin and Hester, 1 9 8 3 ) . B i o p o t e n c y is often d e t e r m i n e d b y t h e slope ratio m e t h o d ( F i n n e y , 1 9 7 8 ) , which uses t h e linear p o r t i o n of t h e g r o w t h curve. A nonlinear m o d e l has t h e capacity to q u a n t i t a t e t h e

2458

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ABSTRACT L-Methionine (100%) and methionine hydroxy analogue-free aeid (88%) were evaluated for biopotency compared to DL-methionine (99%) in a starter diet for Large White turkeys during 7 to 28 days of age. The basal corn-soybean meal diet contained 28% protein, .87% total sulfur amino acids, and 2974 kcal metabolizable energy/kg by calculation and .865% sulfur amino acids by analysis. In Experiments 1 (males) and 2 (females), levels of methionine supplementation were 0, .04, .10, .16, .28, .44, and 1.00%. In Experiment 3 (male and female poults), supplemental methionine levels were 0, .12, .22, .32, and .44%. Level of methionine significantly affected growth and feed efficiency in all experiments. A nonlinear regression model (exponential) was used to describe the body weight response to supplemental methionine (0 to .44%) for each source and to obtain biopotency estimates relative to DL-methionine (at 100). Based on the three studies the biopotency (± SE) of L-methionine was significantly superior to DL-methionine (131 ± 10%); the biopotency of the analogue was not significantly different from DL-methionine (96 ± 7%). Feed efficiency was similar for all sources in Experiments 1 and 3. In Experiment 2, differences in feed/gain were detected among the three sources, where the mean values were in the order: analogue>DL-methionine>L-methionine. (Key words: turkeys, methionine, methionine hydroxy analogue, growth assay)

METHIONINE SOURCES FOR TURKEYS complete growth curve in response to nutrient supplementation (Parks, 1982; Robbins et al., 1979) and may be used to determine biopotency. In diets where a basal level of nutrient is present and response to further supplementation is likely to be curvilinear, this technique would be more appropriate. The objective of this study was to determine the biopotency for turkey poults of MHA-FA and L-methionine as compared to DL-methionine. Biopotency was estimated by nonlinear regression so that the nature of the growth response over a wide range of supplemental levels could be examined using a practicaltype diet.

2459

each source supplied the following molar equivalent levels of supplemental methionine: 0, .04, .10, .16, .28, .44, and 1.00% in the diet. In Experiment 3 the supplemental methionine levels were 0, .12, .22, .32, and .44% of the diet. Experimental diets were analyzed chemically for basal and supplemental methionine levels. The MHA-FA was analyzed by the method of Day et al. (1983) and DL-methionine was quantified by ion exchange chromatography after mild aqueous extraction of the sample. Analytical values averaged 99.3% of prescribed levels.

MATERIALS AND METHODS General Care and Stock. Sexed commercial Large White turkey poults (Nicholas) were used in all experiments. Poults were housed in a heated and ventilated negative pressure building and brooded with infrared heat lamps in floor pens (1.83 m X 2.44 m) with rice hulls used for bedding. Feed and water were offered ad libitum throughout the study. From 1 day to 1 week of age all poults were fed a pre-experimental diet containing .052% methionine from each of the three methionine sources. The basal diet used in both the preexperimental and experimental periods is given in Table 1 and meets the nutritional requirements of the starting poult (National Research Council, 1977) when supplemented with methionine. Each experiment began at 7 days of age and continued for 21 days. Prior to the start of the experiment, the poults were sorted into weight groups, and birds from each group were randomly assigned to pens such that bird distribution and pen weights were similar for all pens. In Experiment 1, there were 15 male poults per pen and in Experiment 2, there were 12 female poults per pen. In Experiment 3, the male and female poults were housed in separate pens with 15 poults per pen.

Methionine

Sources. Three methionine

sources were used in each experiment: Lmethionine of Ajinomoto, DL-methionine of Degussa, and methionine hydroxy analogue-free acid as supplied by Monsanto Co. The same lot of each material was used in all experiments. These sources were assumed to contain 100, 99, and 88% methionine on a molar equivalent basis, respectively. In Experiments 1 and 2,

Ingredient Corn, ground yellow Soybean meal, dehulled Fat, feed grade, stabilized Fish solubles product 1 Fermentation residue product 2 Defluorinated phosphate Calcium carbonate Salt (plain) Trace mineral mixture MN-743 Vitamin mixture MTS-744 Calculated nutrient composition Protein, % Metabolizable energy, kcal/kg Calcium, % Phosphorus, inorganic, % Methionine, % Methionine plus cystine, % s Lysine, %

Percent 41.60 47.30 4.00 2.60 .260 2.75 .700 .400 .125 .265 28.05 2974.0 1.30 .640 .447 .872 1.689

1 Fish solubles product is fish solubles dried on soybean meal at 100% equivalence (52% protein). 2 Fermentation residue product, Fermacto-500® (Borden). 3 Trace mineral mixture MN-74 supplied (per kg of diet) 25 mg iron (from ferrous sulfate); 2.5 mg copper (from copper sulfate); 75 mg manganese (from manganese sulfate); 75 mg zinc (from zinc oxide); 1.5 mg iodine (from ethylene diamine dihydroiodide). In Experiment 3, additional copper (1.25 mg) and .2 mg selenium (from sodium selenite) were provided. 4 Vitamin mixture MTS-74 supplied (per kg of diet) 11,684 IU vitamin A acetate; 4,381 ICU vitamin D 3 ; 14.6 IU vitamin E acetate; 2.9 mg menadione dimethylpyrimidinol bisulfite; 7 mg riboflavin; 10.5 mg d-calcium pantothenate; 70 mg niacin; 526 mg choline chloride; 10 jig vitamin B, 2 ; .58 mg folic acid; 1.5 mg pyridoxine HC1; and 58 ng biotin. 5 Methionine and cystine contents by performic acid oxidation method (Moore et al., 1963) were .435 and .430%, respectively.

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TABLE 1. Composition of basal diet

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NOLL ET AL.

Yi = Bi + B 2 (1 -

e (B3ixii

B32X12 + B33Xj3)\

+

+

g.

where: Yj = average body weight for pen i, Xj = level of supplemental methionine (0 to .44%), (Xji, X[2, X'tf) = Xj ( Z j , Z 2 , Z 3 ), ( Z 1 , Z 2 , Z 3 ) = indicator variables with the values (1, 0, 0), (0, 1, 0), and (0, 0, 1) for sources L-methionine, DL-methionine, and MHA-FA, respectively, Bj = intercept, Bi + B 2 = asymptote, B 3 j = steepness coefficient for source j , Ej = error for pen i, ~N (0, a 2 ) ,

The nonlinear model was fit by a computer program utilizing a version of the LevenbergMarquardt maximization technique with numerical derivatives. For a detailed discussion of nonlinear regression see Draper and Smith (1981) and Gallant (1975). The first model (Model 1) was extended to allow for a different asymptote for each source. A test for lack of fit was performed for all experiments and indicated that the model fit the growth data well. A likelihood-ratio (chisquare) test was performed to check the assumption of a common asymptote. The assumption of a common asymptote was accepted in all of the experiments. A chi-square test was also utilized to determine if the B 3 j coefficients differed. To calculate estimates of biopotency, Model 1 was reparameterized as follows (Model 2): Y; = Bi + B 2 (1 - e BsX; 3 ) ) + E .

Bs

< B 4 x ii

+ X

i2

+

where: Yj, Xji, X j 2 , X; 3 , B i , B 2 , and E; are defined as in Model 1 B3

= curvature steepness coefficient for DLmethionine,

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Experimental Design and Analyses, A randomized block design was used in assigning dietary treatments to pens in the first two experiments. In Experiments 1 and 2 there were 10 replicate pens for the basal group and five replicate pens for the remaining treatments. In Experiment 3, treatments were completely randomized throughout the building, as the design did not yield to blocking. An optimal design of allocating replicate pens to treatments was used to increase precision of the regression parameters. As a result, the number of replicate pens at the supplemental methionine levels Of 0, .12, .22, .32, and .44% were 10, 5, 2, 2, and 5 pens, respectively. Data from previous studies were used to construct a D-optimal design for the nonlinear model with observations at levels of 0, .10 or .12, and .44%. These levels represent areas on the growth curve at which methionine is severely deficient, marginally deficient, and in excess of the requirement. Additional levels were added to check the appropriateness of the model. Analyses of variance were conducted to determine effects of methionine source and level on body weight, gain, feed intake, and feed efficiency for the 7 to 28-day experimental period. The SAS analysis of variance procedure (Goodnight, 1979) was used for analysis of Experiments 1 and 2. The general linear model procedure was used to analyze the unbalanced design for Experiment 3. Differences between treatment means were tested by the least significant difference method. A nonlinear model (exponential) was used to estimate the efficacy of L-methionine and MHA-FA relative to DL-methionine. A similar model has been used previously by Robbins et al. (1979) for calculation of nutrient requirements. A discussion of the model is given in Section 9.8 of Parks (1982). In using the nonlinear model to measure the growth response it is assumed that each product may be acting as a source of methionine or cystine and that the relative biopotency is the same at all levels of supplementation. As each product is being studied under the same conditions, a direct measurement of growth as related to methionine supplementation is being obtained regardless of how the methionine is utilized by the poult. To obtain biopotency estimates the data are first fit to the following model (Model 1):

METHIONINE SOURCES FOR TURKEYS

B4 B5

= ratio of steepness coefficient, L-methionine to DL-methionine, = ratio of steepness coefficient, MHA-FA to DL-methionine.

RESULTS

Experiment 1. Level of methionine significantly affected performance of male poults from 1 to 4 weeks of age (Table 2). Growth and feed efficiency improved and feed intake increased as supplemental methionine increased with a plateau in response occurring between .28% and .44%. No differences in body weight, gain, or feed efficiency were detected between the methionine sources by analyses of variance. A significant source by level interaction occurred for body weight (gain) and feed intake and appeared because of the results at 1% supplemental methionine. Poults fed the L or DLmethionine diets at the 1% methionine level exhibited some signs of methionine toxicity with depressed growth and feed intake. Growth and feed intake of poults fed 1% methionine as MHA-FA were unaffected in comparison to the response at .44%. Body weight data obtained at 0 to .44% methionine were used in fitting the exponential growth curve (Figure 1). The B 3 j coefficients were significantly different (P<.05). The biopotency (± SE) of L-methionine was significantly (P<.05) greater (127 ± 13%) than DL-methionine. The MHA-FA was numerically

more potent than DL-methionine at 107 ± 1 1 % on a molecular weight basis. Experiment 2. The performance results for the female poults are presented in Table 3. Although body weight and gain were not affected by methionine source, feed efficiency was significantly different for all products. Averaged over all levels of supplementation, poults fed L-methionine were more efficient than poults fed DL-methionine, which in turn were more efficient than poults fed MHA-FA diets. Feed efficiency was poorest for poults fed the MHA-FA at low levels. At levels of .28 and .44%, feed efficiencies were similar for poults fed DL-methionine and MHA-FA diets. As level of methionine supplementation increased, body weight gains and feed efficiency improved. As in Experiment 1, significantly greater body weights (gains) were seen at .28% than at .16% supplemental methionine. Feed efficiency and feed intake responses tended to plateau at .28 to .44% supplemental methionine for all sources. At 1.00% supplementation, body weights were depressed more with the L- and DL-methionine groups than MHA-FA; however, no significant interaction between source and level was detected. Exponential growth curves were fitted to body weight data from 0 to .44% methionine (Figure 2). Statistical differences in the B 3 j coefficients existed. As in the first experiment, L-methionine was numerically more potent (112 ± 18%) than DL-methionine. For the female poults, however, the methionine hydroxy analogue (free acid) was numerically less potent, 80 ± 12%. The lower biopotency is reflected in the body weight data where poults fed the free acid form were dominated in body weight at all levels by treatment groups fed the L- and DL-methionine diets. Experiment 3. A third experiment was conducted using both male and female poults in the same study. Results are presented in Table 4. Level of methionine, source, and sex significantly affected all criteria except feed efficiency, which was unaffected by source. No significant interactions were detected between level, source, or sex. Differences between methionine sources appeared to be due to the superior growth performance of the L-methionine treatment groups. Although growth at .44% methionine was similar for all groups, the growth response plateaued much earlier for the poults

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The parameters B 4 and B 5 represent biopotencies relative to DL-methionine. These are the factors that, when multiplied by the corresponding levels of methionine supplementation, make the DL-methionine growth curve coincide with that of the other source. Standard errors of B 3 , B4, and B5 were obtained through the inverse Hessian matrix, which approximates the covariance matrix. Model 2 was used to combine the data across experiments for each sex as response curves in each experiment were found to be similar. It was not, however, used to combine data across the sexes, as this would have required the additional assumption that for each source, the male and female growth responses to methionine supplementation are identical. To combine the male and female responses, the biopotencies were averaged using as weights the inverse of the variance estimates.

2461

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NOLL ET AL.

TABLE 2. Growth performance of male poults fed varying levels and sources of methionine from 1 to 4 weeks of age (Experiment 1) Methionine source

Supplemental methionine

Feed intake

Feed/ gain

23.5

40.9

1.743

672 709 729 778 797 746

25.8 27.5 28.3 30.8 31.7 29.3

43.4 44.6 45.7 48.1 48.6 45.2

1.682 1.621 1.612 1.563 1.533 1.544

Average

738

28.9

45.9

1.592

.04 .10 .16 .28 .44 1.00

680 721 750 790 799 750

26.2 28.0 29.5 31.4 31.7 29.5

44.2 45.9 46.9 48.8 48.8 45.2

1.687 1.637 1.589 1.554 1.543 1.532

Body weight

Gain

0

(g) 623

.04 .10 .16 .28 .44 1.00

(%) DL-Methionine

L-Methionine

Average

748

29.4

46.6

1.590

.04 .10 .16 .28 .44 1.00

668 715 732 794 785 787

25.6 27.8 28.6 31.6 31.2 31.3

43.0 45.5 45.7 49.4 48.7 49.4

1.678 1.637 1.601 1.564 1.563 1.582

Average

747

29.3

47.0

1.604

Analysis of variance1 Significance of F-test (P-value) Methionine source Level Source by level Error mean square (68 df) SEM Least significant difference (P
.086 .001 .051 343.3 8.3 23.4

.070 .001 .034

.070 .001 .001

.732 .383 1.08

1.525 .552 1.56

.138 .001 .425 8.222 X 10~4 .013 .0362

Basal group omitted from analysis of variance. Between any two treatment means.

fed L-methionine, especially for the males (Figure 3). Feed intake was also greater for L-methionine-fed poults. The superior growth response from Lmethionine is evident when the exponential growth curve is fit and biopotency ratios are obtained. Significant differences between the B 3 ; coefficients for the products were observed for male but not female poults (Figure 4). For the males, L-methionine (160 ± 28%) was significantly more efficacious than DL-methionine. MHA-FA was slightly less potent for the males at 92 ± 14% but not statistically different from DL-methionine at 100%. For the females,

the biopotencies of L-methionine and MHA-FA were 141 ± 33% and 104 + 22%, respectively. Compilation of Biopotency Estimates. To obtain biopotency estimates for male and female poults based on the three experiments, data of Experiments 1 and 3 for the males and Experiments 2 and 3 for the females were combined and analyzed together. The combined estimates are given in Table 5. The biopotency of L-methionine for both males and females was greater than Dl.-methionine. but significantly so only for males. A weighted average of the estimates for the sexes resulted in an estimated biopotency of 131 ± 10% for

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Methionine hydroxy analogue - free acid

(g/day)

METHIONINE SOURCES FOR TURKEYS

2463

850 i-

759

-

700

-

658

-7

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ID

>

O O PQ

I I I I I I I I I l—L-1 I I I I I 1

600 0.

1

.3 SUPPLEMENTAL METHIONINE

(%)

FIG. 1. Nonlinear regression function (Model 1) of poult body weight (Y) and supplemental methionine (X) as affected by source (L-methionine O — O , DL-methionine X X, MHA-FA A A) where Y = 626.0 + 179.8 ( 1 - e (-7.816X;i - 6 . 1 5 7 X i 2 -6.608X; 3 )) for Experiment 1.

2464

NOLL ET AL.

TABLE 3. Growth performance of female poults fed varying levels and sources of methionine from 1 to 4 weeks of age (Experiment 2)

Methionine source

DL-Methionine

Methionine h y d r o x y analogue - free acid

Body weight

(%)

(g)

0

555

.04 .10 .16 .28 .44 1.00

573 623 651 675 679 635

Average

Feed intake

Feed/ gain

21.3

38.0

1.789

22.1 24.3 25.8 27.0 27.2 24.9

38.6 40.6 41.4 42.8 44.2 40.0

1.745 1.669 1.607 1.581 1.643 1.603

639

25.2

41.3ab

1.641b

.04 .10 .16 .28 .44 1.00

587 634 647 676 671 633

22.7 24.9 25.8 27.0 26.8 25.1

38.2 40.9 41.7 42.0 41.7 40.3

1.680 1.644 1.618 1.553 1.556 1.606

Average

641

25.4

40.8a

1.610*

.04 .10 .16 .28 .44 1.00

569 613 641 664 667 654

21.9 24.1 25.4 26.6 26.4 26.0

40.4 40.5 41.9 42.7 42.8 42.4

1.851 1.682 1.661 1.608 1.622 1.635

Average

635

25.1

41.8b

1.677c

Analysis of variance 1 Significance of F-test (P-'value) Methionine source Level Source by level Error m e a n square ( 6 8 df) SEM Least significant difference ( P < . 0 5 ) 2

Gain /

/1

\

(g/day)

.361 .001 .377 332.4 8.2 23.0

.310 .001 .405

.038 .001 .125

.696 .373 1.05

2.197 .663 1.87

.001 .001 .090 2 . 8 8 9 X lOT3 .024 .0678

a.b.Cc.

' Source means with different superscripts are significantly different (P<.05).

1

Basal group omitted from analysis of variance.

1

Between any two treatment means.

L-methionine. For MHA-FA the compiled estimate for the females (87 ± 11%) was numerically lower than for the males at 102 ± 9%. The weighted biopotency average for both sexes was 96 ± 7%, which was not significantly different from DL-methionine at 100%. DISCUSSION

Under the stated experimental conditions, the turkey poults showed an excellent growth response to methionine supplementation. Body weights at .44% supplemental methionine

averaged 24% greater than body weights of poults fed the unsupplemented (basal) diet. Due to the limiting nature of methionine in high protein diets of the corn-soybean meal type and the high dietary sulfur amino acid requirement of the turkey poult, the methionine-deficient, corn-soy diet is ideal to assay the response to different methionine sources. The nonlinear technique to determine biopotency allowed a full range of supplemental methionine levels to be used from a very deficient to an excessive but not toxic level. The exponential curve fit the data well in all

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L-Methionine

Supplemental methionine

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METHIONINE SOURCES FOR TURKEYS

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SUPPLEMENTAL

METHIONINE

(%)

FIG. 2. Nonlinear regression function (Model 1) of poult body weight (Y) and supplemental methionine (X) as affected by source (L-methionine O——O, DL-methionine X X, MHA—FA A A) where Y = 547.9 + 132.7 ( 1 - e (-9.444X1! - 8 . 4 4 9 X i 2 -6.717X i 3 )) f o r Experiment 2.

2466

NOLL ET AL. TABLE 4. Growth performance of poults fed varying levels and sources of methionine froml to 4 weeks of age (Experiment 3)

Methionine source by sex

Male DL-Methionine

Supplemental methionine

Body weight

(%)

(g)

.12 .22 .32 .44

674 764 795 796 826

26.2 30.5 31.8 32.1 33.4

Average

795 a

32.0 a

48.2 a

1.509

.12 .22 .32 .44

782 834 836 830

31.4 33.8 33.9 33.7

48.2 50.3 50.5 50.2

1.539 1.489 1.492 1.492

Average

814 b

32.9 b

49.6 b

1.508

.12 .22 .32 .44

760 785 797 825

30.3 31.6 32.1 33.4

47.0 46.4 47.6 50.3

1.554 1.506 1.480 1.507

Average

792 a

31.8 a

48.2 a

1.520

.12 .22 .32 .44

607 681 729 742 730

23.3 26.6 28.6 29.6 28.9

41.0 42.6 44.6 45.4 44.5

1.760 1.601 1.561 1.530 1.541

Average

714

28.2

44.0 a

1.564

.12 .22 .32 .44

705 722 731 743

28.0 28.7 29.2 29.8

44.5 46.4 44.0 45.6

1.590 1.621 1.505 1.531

Average

725

28.9

45.lb

1.561

.12 .22 .32 .44

688 721 729 737

27.1 28.7 29.0 29.5

43.5 44.5 45.0 45.3

1.606 1.550 1.553 1.538

Average

716

28.5

44.5ab

1.566

.007 .001 .001 >.10

.002 .001 .001 >.10

>.10 .001 .001 >.10

1.028 .453 .717 .91

1.854 .609 .963 1.22

1.907 X 10"3 .020 .031 .039

0

L-Methionine

0

Female DL-Methionine

L-Methionine

Methionine hydroxy analogue - free acid

(g/da; * Y) 43.6 46.9 48.0 47.4 49.9

Feed/ gain

1.663 1.537 1.509 1.478 1.493

1

Analysis of variance Significance of F-test (P-value) Methionine source Level Sex Interactions (2 and 3 way) Error mean square (66 df) SEM (5 replicate pens) SEM (2 replicate pens) Least significant difference (P<.05) 2

.012 .001 .001 >.10 449.2 9.5 15.0 26.8

a,b,Source means within each sex with different superscripts are significantly different (P<.05). 1

Basal group omitted from analysis of variance.

"Between any two treatment means with 5 replicate pens.

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Methionine hydroxy analogue - free acid

Feed intake

Gain

METHIONINE SOURCES FOR TURKEYS

2467

850 r

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o o

~

750 -

>-

o o

700

I 1 1 I 1 I 1 I I 1 I 1 1 I I 1 lJ_i-LL I I 1

650 B

.1

.2

.3

SUPPLEMENTAL METHIONINE

.4

.5

(%)

FIG. 3. Nonlinear regression function (Model 1) of poult body weight (Y) and supplemental methionine (X) as affected by source (L-methionine O O, DL-methionine X X, MHA—FA A A) where Y = 674.7 + 159.2 ( 1 - e (-10.239X ; i - 6 . 3 9 0 X i 2 -5.891X i 3 )) for m a i e s i n Experiment 3.

NOLL ET AL.

2468

758

-

725

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700 -

675 r

650

625

1 I 1 I I IXLLJ-i-LLL M i l i-i-Li 0

.4

.2 SUPPLEMENTAL

METHIONINE (%)

FIG. 4. Nonlinear regression function (Model 1) of poult body weight (Y) and supplemental methionine (X) as affected by source (L-methionine O O, DL-methionine X X, MHA—FA A A) where Y = 606.1 + 134.9 d - e (-10.690Xn - 7 . 5 6 1 X i 2 -7.904X:,)) f o r f e r n a ! e s in Experiment 3.

METHIONINE SOURCES FOR TURKEYS TABLE 5. Biopotency (%) of L-methionine and methionine hydroxy analogue-free acid relative to DL-methionine (at 100) for turkey poults (1 to 4 weeks of age)

Experiment

Sex

1 2 3

Male Female Male Female 2 Compilation Male Female Average (weighted)

127(13)' 112(18) 160(28) 141 (33) 137(12) 121(16) 131 (10)

107(11) 80(12) 92 (14) 105 (22) 102 ( 9) 87(11) 96 ( 7)

Standard error.

2

Experiments 1 and 3 combined for males; Experiments 2 and 3 combined for females.

experiments and produced biopotency estimates with an acceptable level of variation in Experiments 1 and 2 where the number of replicates and levels were the greatest. In Experiment 3, variation around the estimates was greater possibly due to the lower number of replicate pens per treatment. In all three experiments the results indicated L-methionine to be more efficacious than DL-methionine in promoting growth with biopotency estimates ranging from 112 to 160%. Equivalence of the DL- and L-isomers of methionine for turkeys has been assumed although the area has not been studied sufficiently. In some chick studies, DL and Lmethionine have not differed statistically in activity (Baker and Boebel, 1980; Guttridge and Lewis, 1964; -Kuzmicky et al, 1977; Tipton et al, 1966). Parsons and Potter (1981) found no difference in L- and DL-methionine for growth in turkey poults fed supplemented diets composed mainly of corn, soy and gelatin. Other studies with chicks have indicated the L-isomer to be more efficacious than DLmethionine when methionine is deficient (Katz and Baker, 1975; Smith, 1966). The three experiments indicated a methionine activity of MHA-FA for male and female poults of 96%, not significantly different from DL-methionine. The biopotencies ranged from 80 to 107% for the three experiments. The lowest estimate of biopotency for MHA-FA (80%) was found in Experiment 2 for the hen

poults, where the biopotency of L-methionine was also the lowest. The lower estimates were not the result of feed mixing errors, as the supplemented methionine levels were confirmed by analysis. The lower estimates obtained in Experiment 2 with female poults as compared to estimates in Experiment 1 with male poults suggested the difference may be an effect of sex. However, in Experiment 3, where the estimates for L-methionine tended to be larger for the males as compared with the females, die reverse situation occurred with MHA-FA. Here the estimate for the female poults was larger. Differences in estimates based on sex could not be detected in the three experiments within the experimental error of the studies. The results obtained with MHA-FA agree with other studies using practical type diets for chicks showing that MHA-FA was equivalent to DL-methionine for growth promotion (Elkin and Hester, 1983; Waldroup et al, 1981). In our study, MHA-FA gave a biopotency slightly higher than that reported for the calcium salt of the analogue by Harms et al. (1977) for turkey poults. Although the nonlinear technique was not applied to the feed efficiency data, differences between sources were detected only in Experiment 2. Here, feed efficiency appeared to be associated with the growth rates, that is, the L-methionine-fed poults with the greatest body weights had the best feed efficiency, whereas the analogue-fed poults had smaller body weights and poorer feed efficiencies. Waldroup et al. (1981) found similar feed conversions for poults fed MHA-FA and L-methionine, but MHA-FA resulted in significantly poorer feed efficiency than DL-methionine in one experiment. Creger et al. (1968) and Elkin and Hester (1983) found no difference in feed efficiency between birds fed diets with Lmethionine or MHA-FA. Studies in which poor biopotencies were observed also indicated poor gain/feed ratios (Boebel and Baker, 1982; van Weerden et al, 1982). This would be expected as poor growth is usually associated with poor feed efficiency. Although biopotencies were calculated using data from poults fed 0 to .44% methionine, Experiments 1 and 2 included 1.00% supplemental methionine to examine possible differences in toxicity after the growth plateau had been reached. Although 1.00% supplemental methionine was not extremely toxic, growth

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Methionine hydroxy analoguefree acid

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and feed intake depressions were seen for L - a n d DL-methionine groups. No other symptoms were noted such as cervical paralysis (Hafez et al, 1 9 7 8 ) . A reduced t o x i c i t y o f M H A - F A h a s been r e p o r t e d previously (Boebel and Baker, 1982).

REFERENCES

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