Journal of Nutrition OpenSOurce Diets- www.ResearchDiets.com

Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Emmert, J. L.
Right arrow Articles by Baker, D. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Emmert, J. L.
Right arrow Articles by Baker, D. H.

The Journal of Nutrition Vol. 127 No. 5 May 1997, pp. 745-752
Copyright ©1997 by the American Society for Nutritional Sciences

A Chick Bioassay Approach for Determining the Bioavailable Choline Concentration in Normal and Overheated Soybean Meal, Canola Meal and Peanut Meal1,2

Jason L. Emmert and David H. Baker3

Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois, Urbana, IL 61801

ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
FOOTNOTES
LITERATURE CITED

ABSTRACT

Our objectives were to use a soy protein isolate (SPI) diet containing 2-amino-2-methyl-1-propanol, an inhibitor of choline biosynthesis, to determine the bioavailable choline content of normal and overheated soybean meal (SBM), canola meal (CM) and peanut meal (PM). In the first four experiments, it was determined that weight gain of chicks fed the basal diet would respond linearly (P < 0.05) to graded levels of crystalline choline and would not respond to betaine, and that when fortified with adequate choline, no weight gain or feed intake response would occur upon addition of 100 g/kg SBM, CM or PM to the basal diet. Furthermore, addition of crystalline amino acids simulating the amino acid composition of 100 g/kg SBM did not alter the utilization of crystalline choline. In Experiment 5, feeding graded doses of choline, SBM, CM or PM resulted in linear (P < 0.05) increases in weight gain. Multiple linear regression analysis indicated bioavailable choline concentrations of 1708, 1545 and 1203 mg/kg for SBM, CM and PM, respectively. In Experiment 6, no differences (P > 0.05) in bioavailable choline concentrations occurred between normal and overheated SBM, CM or PM, and the bioavailable choline concentration of normal SBM, CM and PM was 2002, 1464 and 1320 mg/kg, respectively. Average bioavailable choline levels were 83, 24 and 76% of analytically determined choline levels in SBM, CM and PM, respectively. Canola meal, although three times as rich in total choline as SBM, has less bioavailable choline than SBM. A substantial portion of choline in SBM, CM and PM is unavailable, and overheating does not appear to decrease the bioavailability of choline in these products.

KEY WORDS: oilseed meals · choline · bioavailability · chicks

INTRODUCTION

Choline is essential for the prevention of fatty liver and perosis in poultry, and it has long been known that chicks fed corn-soybean meal diets containing (total) choline in excess of the NRC (1994) requirement still need supplemental choline to achieve maximum growth (Berry et al. 1943, Marvel et al. 1943). The obvious implication is that choline bioavailability is <100% in these diets. Previous estimates of choline bioavailability in soybean meal (SBM)4 have ranged from 60 to 75% (Molitoris and Baker 1976a), and choline in canola meal (CM), although present at high concentrations, has also been found to be less than fully available (March and MacMillan 1980). However, attempts to quantify choline bioavailability have met with criticism (Pesti et al. 1980 and 1981), primarily because of the use of weight gain as the response criterion for chicks fed choline-deficient diets. In addition, weight gain of chicks fed purified crystalline amino acid diets, such as have been used previously, may respond to components other than choline in ingredients such as SBM (Molitoris and Baker 1976a). Therefore, it is imperative that an appropriate basal diet be used that will allow reliable estimates of choline bioavailability from various feed ingredients.

We have previously developed an experimental diet containing soy protein isolate (SPI) and 2-amino-2-methyl-1-propanol (AMeP) that is singularly deficient in choline and will elicit a weight gain response only upon addition of choline (Emmert et al. 1996). Our objective in this study was to estimate the bioavailable concentration and percentage bioavailability of choline in SBM, CM and peanut meal (PM). In addition, the effects of overheating on choline bioavailability were assessed.

MATERIALS AND METHODS

All procedures were approved by the University of Illinois Committee on Laboratory Animal Care. Experiments were conducted using male chicks from the cross of New Hampshire males and Columbian females (University of Illinois Poultry Farm). Chicks were housed in thermostatically controlled batteries equipped with raised wire floors, and 24-h constant lighting was maintained. Water and experimental diets were freely available and diets were formulated to meet or exceed NRC (1994) requirements for all nutrients with the exception of choline.

In all experiments, chicks were fed a 24% crude protein corn-SBM starter diet (Lowry and Baker 1987) during the first 7 d posthatching. From d 8 to 10 posthatching, chicks were placed on a choline-free crystalline amino acid diet (Emmert et al. 1996) to deplete choline stores. On the morning of d 10 posthatching, chicks were weighed and randomly allotted to dietary treatments. Experimental diets (Table 1) were fed until d 22 posthatching, at which time chicks and feed were weighed for determination of weight gain, feed intake and feed efficiency.

Table 1. Composition of the choline-deficient experimental diet

[View Table]

The SPI used in the basal diet (Table 1) was a functional alcohol-extracted product (Ardex AF, ADM, Decatur, IL). Analysis of this product yielded the following: 824 g/kg crude protein, 49 g/kg lipid (chloroform-methanol extraction), 89 g/kg H2O, 22.3 MJ/kg gross energy, 21.8 g/kg methionine plus cysteine, 31.7 g/kg threonine and 51.7 g/kg lysine (Emmert and Baker 1995).

In Experiments 3, 4, 5 and 6, addition of amino acids, SBM, CM or PM to experimental diets was made at the expense of a combination of cornstarch and arenaceous flour such that all experimental diets were kept isocaloric. Metabolizable energy values for SBM, CM and PM were assumed to be 10.2, 8.4 and 9.2 MJ/kg, respectively (NRC 1994). To accomplish overheating of SBM, CM and PM, samples were placed in a thin layer (1.25 cm in depth) on metal trays covered tightly with aluminum foil, and were autoclaved at 121°C and 105 kPa for 60 min, which has previously been shown to decrease weight gain and the protein efficiency ratio of chicks fed SBM, CM and PM (Anderson-Hafermann et al. 1993, Parsons et al. 1992, Zhang and Parsons 1996). Those studies confirmed a relationship between protein solubility in KOH and protein quality of these oilseed meals, such that protein solubility can be used to assess the effects of severe heating on protein quality. To verify the negative effects of autoclaving on nutritional quality, protein solubility in 0.036 mol/L KOH (for SBM and PM) or 0.089 mol/L KOH (for CM) was determined as described by Parsons et al. (1991) and Anderson-Hafermann et al. (1993). In addition, a bioassay was conducted using methodology as previously described for determining protein efficiency ratio of a feedstuff (Emmert and Baker 1995). For SBM, CM and PM, protein efficiency ratio was substantially decreased (P < 0.05) by overheating (data not shown).

Total choline content of SBM, CM and PM was measured in duplicate by J. F. Menten (University of Georgia), using methodology previously reported (Menten and Pesti 1996). The method is based on chemical extraction of choline and phospholipid-bound choline, followed by cleavage of choline from phosphatidylcholine and subsequent phosphorylation to phosphorylcholine, producing adenosine diphosphate. Quantification of choline in this system is proportional to production of nicotinamide adenine dinucleotide via an enzymatic system. For normal SBM, CM and PM, total choline was determined to be 2218, 6198 and 1685 mg/kg, respectively. For overheated SBM, CM and PM, total choline was determined to be 2115, 6138 and 1771 mg/kg, respectively.

Experiment 1. The first study was conducted to confirm that weight gain of chicks fed the SPI basal diet (Emmert et al. 1996; Table 1) would respond in a linear fashion to crystalline choline. This diet contains 2 g/kg AMeP, which inhibits choline synthesis and utilization (Wells 1956, Wells and Remy 1961), consequently causing a substantial increase in the choline requirement of chicks fed this compound (Molitoris and Baker 1976a, Wells 1956). Four replicates of four chicks were fed graded levels of choline from choline chloride (74.6% choline; Emmert et al. 1996) from 0 to 825 mg/kg (in increments of 165 mg/kg), and linearity of the weight gain response was evaluated.

Experiment 2. Because weight gain of chicks fed diets deficient in choline will respond to betaine provided enough choline per se is present to meet the needs for phospholipid and acetylcholine synthesis (Lowry et al. 1987), the level of dietary choline at which betaine would elicit a weight gain response in chicks fed the SPI basal diet containing AMeP (Table 1) was evaluated. Eight replicates of four chicks were fed graded doses of choline from 0 to 495 mg/kg (in increments of 165 mg/kg) in the presence or absence of 500 mg/kg betaine, and growth performance was evaluated.

Experiment 3. When evaluating nutrient bioavailability from complex feedstuffs, it is imperative that the criterion by which bioavailability is assessed responds only to the nutrient in question upon addition of the test feedstuff to the basal diet. We have previously shown that the growth performance of chicks fed our SPI basal diet supplemented with 10% SBM and an adequate level of crystalline choline is equivalent to that of chicks fed adequate choline alone (Emmert et al. 1996), indicating that secondary components in SBM are neither beneficial nor harmful. To repeat this observation and to confirm a similar lack of response to secondary ingredients in CM and PM, four replicates of four chicks were fed the basal diet alone or with the addition of 1500 mg/kg choline (adequate for chicks fed this basal diet, J. L. Emmert and D. H. Baker, unpublished data). In addition, 10% SBM, CM or PM was added in the presence of 1500 mg/kg choline and growth performance was evaluated.

Experiment 4. Because an increase in dietary protein has been shown to cause an increase in the requirement for choline (Ketola and Nesheim 1974, Molitoris and Baker 1976b), Experiment 4 was conducted to determine if excess amino acids would alter the utilization of choline added to the basal diet. An amino acid mixture simulating 10% dietary SBM (Fernandez and Parsons 1996) was added to the basal diet, and four replicates of four chicks were fed diets supplemented with 0, 165 or 330 mg/kg choline in the presence or absence of the amino acid mixture. Growth performance was then evaluated.

Experiment 5. In Experiment 5, choline bioavailability was determined for SBM, CM and PM. Eight replicates of four chicks were fed graded levels of choline from choline chloride (0, 165 or 330 mg/kg) to establish a standard curve. In addition, four replicates of four chicks were fed the basal diet supplemented with 5 or 10% SBM, CM or PM, and weight gain was used to determine choline bioavailability.

Experiment 6. In Experiment 6, the effects of overheating on choline bioavailability of SBM, CM and PM were assessed. Eight replicates of four chicks were fed graded levels of choline from choline chloride (0, 165 or 330 mg/kg) to establish a standard curve. In addition, four replicates of four chicks were fed the basal diet supplemented with 10% normal or overheated SBM, CM or PM, and weight gain was used to determine choline bioavailability.

Statistical analysis. Each experiment was analyzed as a completely randomized design, and ANOVA was conducted on all data using the General Linear Models (GLM) procedure of SAS (SAS 1985). In Experiments 2 and 3, orthogonal comparisons (SAS 1985) and the least significant difference multiple comparison procedure (Carmer and Walker 1985) were used to establish differences among treatment means. In Experiment 1, in which graded levels of choline were fed to confirm a linear response to choline, weight gain data were fitted to a two-slope broken line model (Robbins 1986, Robbins et al. 1979), such that both linear portions had positive slope values.

In Experiments 4, 5 and 6, the amounts of choline, SBM, CM and PM chosen were those expected to result in weight gain in the linear portion of the growth curve, based on previous work (Emmert et al. 1996) and the results of Experiment 1. Linear regression equations were calculated (SAS 1985), with weight gain per chick (g) as the dependent variable and consumption (mg) of crystalline choline, SBM, CM or PM as independent variables. After establishing that Y intercepts were not different (P > 0.05), the slope-ratio technique (Sasse and Baker 1973) was used to calculate the bioavailable choline concentration (mg/kg) in SBM, CM and PM. A multiple linear regression equation was caculated (SAS 1985) that was composed of several straight lines with regression coefficients representing grams gain per milligram choline, SBM, CM or PM intake. To calculate bioavailable choline concentration (mg/kg), a ratio of two regression coefficients was made, such that the division of grams gain per milligram test ingredient consumed by grams gain per milligram choline consumed resulted in milligrams bioavailable choline per kilogram test ingredient. Differences in bioavailable choline concentration among treatments were determined by a comparison of regression coefficients using a t test (SAS 1985).

RESULTS

Experiment 1. Weight gain of chicks fed the SPI basal diet containing AMeP was plotted against supplemental choline and was best represented by a two-slope broken line model (Fig. 1). Weight gain increased linearly (P < 0.05) with a slope of 0.229 until a choline concentration of 330 mg/kg was reached, after which weight gain continued to increase linearly (P < 0.05) with a lesser slope of 0.082. The results confirmed that weight gain of chicks fed the SPI basal diet would increase maximally and in a linear fashion up to a dietary choline concentration of 330 mg/kg.
Fig. 1. Fitted two-slope broken line of weight gain of chicks as a function of supplemental choline concentration (Experiment 1). Four groups of four chicks with an average initial weight of 130 g were fed a soy protein isolate diet containing 2-amino-2-methyl-1-propanol (Table 1) and containing 0, 165, 330, 495, 660 or 825 mg/kg choline for a 12-d period. Data points represent means ± SEM. Slope before the inflection point was 0.229 ± 0.05, and slope after the inflection point was 0.082 ± 0.02.
[View Larger Version of this Image (14K GIF file)]

Experiment 2. Addition of choline resulted in a linear (P < 0.01) increase in weight gain, feed intake and feed efficiency, both in the presence and absence of 500 mg/kg betaine (Table 2). Betaine was without effect (P > 0.05) on growth performance of chicks fed 0, 165 or 330 mg choline/kg, but weight gain of chicks fed 495 mg/kg was increased (P < 0.05) by addition of betaine. Therefore, in subsequent experiments, concentrations of choline at or below 330 mg/kg were used to generate standard curves.

Table 2. Effect of betaine in chicks fed graded levels of choline (Experiment 2)1

[View Table]

Experiment 3. Weight gain of chicks fed the SPI basal diet was dramatically increased (P < 0.05) by the addition of 1500 mg/kg choline (Table 3). Addition of 100 g/kg SBM, CM or PM together with 1500 mg/kg choline did not affect (P > 0.05) weight gain or feed intake relative to chicks fed choline alone, although feed efficiency was improved by the addition of PM. These data confirm that no weight gain response to SBM, CM or PM occurs when chicks are fed a cholineadequate basal diet, indicating that any response to these feed ingredients observed in chicks fed choline-deficient diets should be due to choline per se, and not to secondary ingredients present in the feedstuffs.

Table 3. Response of chicks to various oilseed meals in diets adequate in choline (Experiment 3)1

[View Table]

Experiment 4. Weight gain of chicks fed the SPI basal diet with or without an amino acid mixture simulating 100 g/kg dietary SBM was plotted against supplemental choline intake (Fig. 2). Weight gain increased linearly (P < 0.05) in the presence and absence of excess amino acids, and no difference (P > 0.05) in gain per milligram choline intake was detected between chicks fed choline alone or choline in the presence of excess amino acids. The multiple linear regression equation (R2 = 0.88) for choline in the absence (X1) or presence (X2) of excess amino acids was Y = 130.1 + 0.761 ± 0.067X1 + 0.782 ± 0.075X2.
Fig. 2. Linear regression plot of weight gain of chicks as a function of supplemental choline intake (Experiment 4). Four groups of four chicks with an average initial weight of 142 g were fed a soy protein isolate diet containing 2-amino-2-methyl-1-propanol (Table 1) and containing 0, 165 or 330 mg/kg choline in the presence or absence of an amino acid mixture simulating the amino acid composition of 100 g/kg soybean meal for a 12-d period. Data points represent means ± SEM. Multiple linear regression of choline without (X1) or with (X2) excess amino acids was Y = 130.1 + 0.761 ± 0.067X1 + 0.782 ± 0.075X2; R2 = 0.88.
[View Larger Version of this Image (14K GIF file)]

Experiment 5. Weight gain and feed intake values of chicks fed graded doses of choline, SBM, CM and PM are shown in Table 4. Supplementation of the choline-deficient basal diet with SBM, CM or PM resulted in linear (P < 0.01) increases in weight gain and feed intake. Weight gain data of chicks fed choline from choline chloride were used in generating the multiple linear regression equation (R2 = 0.89) for choline (X1), SBM (X2), CM (X3) and PM (X4), which was Y = 127.4 + 0.756 ± 0.041X1 + 0.00129 ± 0.00020X2 + 0.00117 ± 0.00020X3 + 0.00091 ± 0.00023X4. The slope-ratio technique revealed bioavailable choline concentrations of 1708, 1545 and 1203 mg/kg for SBM, CM and PM, respectively.

Table 4. Determination of bioavailable choline content of soybean meal (SBM), canola meal (CM) and peanut meal (PM) (Experiment 5)

[View Table]

For purposes of comparison, bioavailable choline concentration (mg/kg) of SBM, CM and PM was also determined (data not shown) using standard curve methodology (Sasse and Baker 1973), in which weight gain and choline intake of chicks fed crystalline choline were used to establish a standard curve. Weight gain data from chicks fed 10% SBM, CM or PM were substituted into the standard curve to allow for calculation of bioavailable choline intake. Division of bioavailable choline intake by total intake of each ingredient resulted in bioavailable choline concentration values that were very similar to those determined using multiple linear regression methodology. Therefore, multiple linear regression analysis was deemed appropriate for use in Experiment 6. 

Experiment 6. Protein solubilities (Table 5) in 0.036 mol/L KOH (SBM and PM) or 0.089 mol/L KOH (CM) and protein efficiency ration (PER) values for SBM, PM and CM (data not shown) confirmed that the protein quality of each of the test ingredients was decreased by autoclaving. However, weight gain and feed efficiency values (Table 5) of chicks fed SBM, CM or PM as a source of choline were not signifantly affected (P > 0.05) by overheating. Weight gain data of chicks fed choline from choline chloride were used in generating the multiple linear regression equation (R2 = 0.89) for choline (X1), normal SBM (X2), overheated SBM (X3), normal CM (X4), overheated CM (X5), normal PM (X6) and overheated PM (X7), which was Y = 116.5 + 0.869 ± 0.050X1 + 0.00174 ± 0.00025X2 + 0.00174 ± 0.00025X3 + 0.00127 ± 0.00027X4 +0.00173 ± 0.00026X5 + 0.00115 ± 0.00027X6 + 0.00127 ± 0.0028X7. The slope-ratio technique revealed bioavailable choline concentrations of 2002, 2006, 1464, 1994, 1320 and 1460 mg/kg for normal SBM, overheated SBM, normal CM, overheated CM, normal PM and overheated PM, respectively. Comparison of regression coefficients revealed no significant effect (P > 0.05) of overheating on the bioavailable choline concentration of oilseed meals.

Table 5. Determination of choline bioavailability of normal and overheated soybean meal (SBM), canola meal (CM), and peanut meal (PM) (Experiment 6)

[View Table]

A summary of bioavailable choline concentration values determined in Experiments 4 and 5 is shown in Table 6. Values were similar between Experiments 5 and 6, although Experiment 6 tended to give slightly higher choline bioavailability values for SBM and PM. Values for total choline concentration were determined as described by Menten and Pesti (1996) and were lower than those listed by NRC (1994). Percentage bioavailability values were calculated by dividing bioavailable choline content by total choline content and clearly showed that the choline in CM is poorly available, whereas 70-95% of the choline in SBM and PM appears to be bioavailable under our experimental conditions.

Table 6. Summary of bioavailable choline concentration of soybean meal (SBM), canola meal (CM) and peanut meal (PM)

[View Table]

DISCUSSION

It is well established that choline is an essential nutrient, necessary for the prevention of fatty liver and persosis in young chickens because of the diminished ability of avians to perform the first methylation of phosphatidylethanolamine (Baker and Sugahara 1970, Jukes et al. 1945). Practical corn-SBM diets are typically supplemented with choline to ensure maximal growth of young broiler chicks, despite containing a total concentration of choline exceeding NRC (1994) requirements, implying that the choline contained in these diets is <100% bioavailable.

Previous attempts to evaluate choline bioavailability in ingredients such as SBM have been hampered by the lack of an appropriate experimental diet. Molitoris and Baker (1976a) attempted to estimate the bioavailable choline content of SBM using a crystalline amino acid purified diet. However, this diet, when fully fortified with choline, still elicited a weight gain and feed efficiency response when SBM was added, indicating that constituents other than choline were having an effect. In addition, Pesti et al. (1981) suggested that assessment of choline bioavailability using growth as a criterion is confounded because of the effects of constituents such as methionine in products like SBM.

Although dietary methionine can provide methyl groups for de novo synthesis of choline from phosphatidylethanolamine, this pathway is very ineffecient in young chicks (Baker and Sugahara 1970, Jukes et al. 1945), because S-adenosylmethionine is inefficient as a methyl donor in choline biosynthesis. Similarly, choline oxidation to betaine is irreversible, preventing betaine from serving as a choline precursor. Methionine and betaine are able to replace one function of choline, namely, provision of a methyl group to the single-carbon pool. However, choline is also needed for acetylcholine and phospholipid synthesis; those needs take priority over methyl donation, as indicated by previous research showing that no response to betaine occurs in a choline-free purified diet until ~two thirds of the choline requirement has been furnished by choline per se (Lowry et al. 1987). For these reasons, a diet severely deficient in choline should not elicit a growth response upon addition of methionine or betaine, whereas a diet marginally deficient in choline will probably respond to either of these compounds.

We previously formulated a diet based on SPI that contains supplemental methionine and AMeP, which inhibit choline synthesis and to utilization (Wells 1956, Wells and Remy 1961), for use in studies evaluating bioavailable choline content of various feedstuffs (Emmert et al. 1996). As expected, the severity of the choline deficiency in this basal diet prevented a growth response upon addition of methionine or betaine. In Experiment 3, addition of 100 g/kg SBM, CM or PM did not elicit a growth response when added to the basal diet containing an adequate level of choline (Table 3), suggesting that any response to these feedstuffs upon addition to the basal diet is due to choline per se, not to secondary constituents.

In Experiment 1, it was determined that weight gain of chicks fed the basal diet would respond markedly and in a linear fashion up to a choline concentration of 330 mg/kg (Fig. 1). However, because the SPI basal diet was intended for use in evaluating products such as SBM, which contain methionine in addition to choline, it was conceivable that addition of the test product could bring the total choline concentration of the diet into a range within which methionine or betaine would elicit a growth response. However, it was unclear at which point within the linear range a response to betaine (or methionine) might occur. In Experiment 2 (Table 2), no increase in weight gain or feed efficiency occurred upon addition of betaine until a choline concentration of 495 mg/kg was reached, indicating that choline levels of 330 mg/kg or less would prevent a response to betaine. This also supports previous research (Emmert et al. 1996, Lowry et al. 1987) that indicated that no response to betaine will occur in a diet severely deficient in choline until a substantial proportion of the choline requirement has been furnished by choline per se.

A previous concern in studies of choline bioavailability has been the effects of increasing dietary protein, which occurs upon addition of feedstuffs such as SBM, CM and PM. Because increasing dietary protein increases the choline requirement (Ketola and Nesheim 1974, Molitoris and Baker 1976b), it has been suggested that the lesser response to choline contained in products like SBM (relative to an equivalent amount of crystalline choline) may be due to an increase in the choline requirement upon addition of the test product (Pesti et al. 1980 and 1981). The results of Experiment 4 (Fig. 2), in which graded levels of choline were fed in the presence or absence of an amino acid mixture simulating 100 g/kg SBM, suggest that while the total requirement for choline may be increased, the utilization of choline (i.e., grams gain per milligram choline intake) below the requirement is not affected. In addition, the linearity of the response to 50 and 100 g/kg additions of oilseed meals in Experiment 5 supports the hypothesis that increasing dietary protein associated with such additions does not substantially affect the utilization of choline and therefore the estimates of bioavailability.

After completion of Experiment 4, the SPI basal diet containing AMeP was deemed appropriate for use in studying choline bioavailability in oilseed meals. For SBM, previous estimates of choline bioavailability have ranged from 60 to 75% (Molitoris and Baker 1976a). March and MacMillan (1980) examined choline bioavailability of CM in chickens, and found that intestinal contents of chicks fed equivalent amounts of choline from SBM or CM contained more choline and trimethylamine (a degradative product of choline) when CM was fed, suggesting a poor bioavailability of choline in CM. Furthermore, growth of chicks fed 20% CM was improved upon choline supplementation, even though the diet contained a total choline concentration exceeding NRC (1994) requirements. Summers and Leeson (1985) noted no growth response to choline in chicks fed basal diets containing SBM or CM as the sole source of protein. Therefore, SBM or CM was added at levels likely to supply adequate choline, even if bioavailability was <100%. To our knowledge, no estimation of choline bioavailability in PM has been reported.

A summary of bioavailable choline concentrations for SBM, CM and PM is shown in Table 6. Although CM and PM contain numerically lower amounts of bioavailable choline than SBM, no significant differences (P > 0.05) in bioavailable choline concentration (mg/kg) were noted among SBM, CM and PM in Experiments 4 or 5. This is interesting because despite containing vastly different amounts of total choline, bioavailable choline contents are similar, suggesting substantially different percentage bioavailabilities. Experiment 6 tended to give slightly higher estimates of bioavailable choline content than Experiment 5, particularly for SBM; these differences are likely due to variability associated with this type of assay. Severe overheating has previously been shown to decrease the protein quality of SBM, CM and PM (Anderson-Haffermann et al. 1993, Parsons et al. 1992, Zhang and Parsons 1996), but no effect (P > 0.05) of overheating on bioavailable choline content was detected in Experiment 6, although bioavailability values for overheated CM and PM were numerically higher (Table 6).

We have emphasized the determination of bioavailable choline concentration (i.e., milligrams bioavailable choline per kilogram test ingredient) because this method does not rely on determination of total choline in test ingredients. Rather, reliable intakes of crystalline choline and test ingredients are needed, which are easily determined and very accurate. In addition, bioavailable choline values, much like digestible amino acid values, are of greater use in diet formulation. However, to allow percentage bioavailbility estimates to be made, SBM, CM and PM samples were measured for total choline content (Table 6), using methodology previously reported (Menten and Pesti 1996). Total choline values measured by this procedure were lower than NRC (1994) estimated values, which are 2731, 6700 and 2396 mg/kg for SBM, CM and PM, respectively.

Percentage choline bioavailability (i.e., the percentage of total choline that is bioavailable) was calculated (Table 6) and indicates that for each oilseed meal tested, the bioavailability of choline is numerically less than 100%, relative to choline from choline chloride. For SBM, percentage bioavailability estimates (77-95%) were slightly higher than those reported previously by Molitoris and Baker (1976a), although those estimates were made using a total (estimated) choline concentration for SBM that was greater than the analytically determined value reported in Table 6. Had NRC values been used, percentage bioavailabilities would have been lower and in closer agreement with previous research. For CM, percentage bioavailability estimates (24-32%) clearly indicate a poor bioavailability of choline in this feedstuff, supporting previous work from March and MacMillan (1980). Although previous estimates of choline bioavailability from PM are not available, our estimates (71-82%) suggest a percentage bioavailability less than 100% and similar to SBM. It is unclear why the bioavailablility of choline from CM is so drastically reduced.

In conclusion, we have developed a SPI basal diet containing AMeP that is suitable for determination of bioavailable choline content and percentage bioavailability in various feedstuffs. Also, we have determined bioavailable choline concentration values for SBM, CM and PM, and it has been shown that the choline in these oilseed meals is <100% bioavailable, with CM being particularly poor. It is apparent that overheating, although clearly detrimental to protein quality, does not substantially affect choline bioavailability. Moreover, only the choline in unknown feedstuffs will elicit a response, and this is an advantage when evaluating feed ingredients that may contain betaine and methionine, in addition to choline.

FOOTNOTES

1   Appreciation is expressed to ADM Corporation, Decatur, IL 62525, and Chinook Group, Inc., North Branch, MN 55056, for financial and material support.
2   The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.
3   To whom correspondence should be addressed.
4   Abbreviations used: AMeP, 2-amino-2-methyl-1-propanol; CM, canola meal; PM, peanut meal; SBM, soybean meal; SPI, soy protein isolate.

Manuscript received 23 September 1996. Initial reviews completed 30 October 1996. Revision accepted 15 January 1997.

LITERATURE CITED

0022-3166/97 $3.00 ©1997 American Society for Nutritional Sciences



This article has been cited by other articles:


Home page
 J. Nutr.Home page
R. N. Dilger, T. A. Garrow, and D. H. Baker
Betaine Can Partially Spare Choline in Chicks but Only When Added to Diets Containing a Minimal Level of Choline
J. Nutr., October 1, 2007; 137(10): 2224 - 2228.
[Abstract] [Full Text] [PDF]

Home page
 J. Nutr.Home page
N. R. Augspurger, C. S. Scherer, T. A. Garrow, and D. H. Baker
Dietary S-Methylmethionine, a Component of Foods, Has Choline-Sparing Activity in Chickens
J. Nutr., July 1, 2005; 135(7): 1712 - 1717.
[Abstract] [Full Text] [PDF]

Home page
 J. Nutr.Home page
C. S. Scherer and D. H. Baker
Excess Dietary Methionine Markedly Increases the Vitamin B-6 Requirement of Young Chicks
J. Nutr., December 1, 2000; 130(12): 3055 - 3058.
[Abstract] [Full Text] [PDF]

Home page
 J. Nutr.Home page
D. H. Baker, H. M. Edwards III, C. S. Strunk, J. L. Emmert, C. M. Peter, I. Mavromichalis, and T. M. Parr
Single Versus Multiple Deficiencies of Methionine, Zinc, Riboflavin, Vitamin B-6 and Choline Elicit Surprising Growth Responses in Young Chicks
J. Nutr., December 1, 1999; 129(12): 2239 - 2245.
[Abstract] [Full Text]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Emmert, J. L.
Right arrow Articles by Baker, D. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Emmert, J. L.
Right arrow Articles by Baker, D. H.

Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]