Utilization of Different Soy Products as Affected by Age in Chicks

Transcription

1 Utilization of Different Soy Products as Affected by Age in Chicks A. B. Batal 1 and C. M. Parsons 2 Department of Animal Sciences, University of Illinois, Urbana, Illinois ABSTRACT Two experiments were conducted to evaluate increased (P < 0.05) with age for all four diets, with the the utilization of several different soy products at different ages in New Hampshire Columbian male chicks. Six pens of eight chicks were fed dextrose-protein source diets (23% CP) containing 1 of 10 different protein sources from 0 to 21 d of age. Excreta were collected at 0 to 2, 3 to 4, 7, 14, and 21 d of age, and AME n and amino acid (AA) digestibility were determined using acid-insoluble ash as a marker. Protein sources evaluated were as follows: Experiment 1 casein, soybean meal (SBM), soy protein concentrate (SPC), and soy protein isolate (SPI); Experiment 2 raw soyflakes, SBM, Williams 82 soybeans, heated Williams 82 soybeans, Kunitz-free soybeans (reduced trypsin inhibitor), lectin-free soybeans, and Kunitz/lectin-free soybeans. In Experiment 1, when comparing the ME n and AA digestibility values among diets at the same age, the ranking (from highest to lowest) for the four diets was casein, SPI, SPC, SBM. The ME n values increase being much smaller for the casein diet (3%) than the soy diets (mean increase of 13%). In Experiment 2, the SBM diet yielded the highest (P < 0.05) growth performance, ME n, and AA digestibility values. The ME n and AA digestibility values of the Williams 82 soybeans, Kunitz-free soybeans, and lectin-free soybeans diets were much lower than those for the SBM diet. In general, the Kunitz/lectin-free soybeans yielded higher growth performance and ME n values than the Williams 82 soybeans, Kunitz-free soybeans, and lectin-free soybeans. The ME n values increased with age for most diets, and AA digestibility increased with age for the soyflake and Kunitz/ lectin-free soybean diets. Our results suggest there may be some potential benefits of feeding SPC or SPI during the first 1 to 3 wk posthatching and that underprocessed (under heated) soybeans should not be included in the diets of very young chicks. (Key words: age, soybean meal, soybean, amino acid digestibility, metabolizable energy) 2003 Poultry Science 82: INTRODUCTION Soybean meal (SBM) and other soy products are important sources of dietary protein for poultry in the United States and much of the world. It has been recognized for many years that heating (processing) soybeans is needed to increase the protein nutritive value (Balloun, 1980), mainly by destroying the antinutritional factors. Soybeans contain a number of natural toxins for poultry, the most problematic being trypsin (protease) inhibitors. Trypsin inhibitors disrupt protein digestion, which results in decreased release of free amino acids (AA). Their presence is characterized by compensatory hypertrophy of the pancreas due to stimulation of pancreatic secretions. Fortunately, the heat treatment employed during processing is usually adequate to destroy trypsin inhibitors and other toxins such as lectins. Lectins are glycoproteins that have the ability to bind to cellular surfaces via 2003 Poultry Science Association, Inc. Received for publication June 10, Accepted for publication October 13, Present address: Department of Poultry Science, University of Georgia, Athens, GA To whom correspondence should be addressed: poultry@uiuc.edu. specific oligosaccharides or glycopeptides (Oliveria et al., 1989) and have a relatively high binding affinity to small intestinal epithelium (Pustzai, 1991). The growth-depressant effect of lectins is believed to be due primarily to their damaging impact on intestinal enterocytes (Pustzai et al., 1979) and to appetite depression (Liener, 1986). In addition to trypsin inhibitors and lectins, Coon et al. (1990) reported that oligosaccharides, raffinose and stachyose, in SBM might be antinutritional factors. New soybean variants have been developed at the University of Illinois that are isogenic to the commercially grown Williams 82 cultivar, except that they lack the Kunitz trypsin-inhibitor allele (Bernard and Hymowitz, 1986), the lectin component (Bernard and Nelson, 1996), or both. Studies have shown that the Williams 82 isogenic variant lacking the Kunitz trypsin inhibitor (Cook et al., 1988) and other soybean variants low in Kunitz trypsin inhibitor (Yen et al., 1973; Han and Parsons, 1991) are nutritionally superior to conventional raw soybeans but not as good as commercial SBM. Previous research at the University of Illinois on lectin-free soybeans found that Abbreviation Key: AA = amino acid; SBM = soybean meal; SPC = soy protein concentrate; SPI = soy protein isolate. 454

2 UTILIZATION OF SOY PRODUCTS 455 approximately 15% of the total growth depression from raw soybeans in chicks was associated with lectins (Douglas et al., 1999). These authors also reported that the nutritional value of raw lectin-free soybeans was greater than raw conventional soybeans but was lower than raw Kunitz-free soybeans and SBM, suggesting that trypsin inhibitors are a greater antinutritional factor than lectins. The new soybean variant devoid in both Kunitz trypsin inhibitor and lectin (Kunitz/lectin-free) has not been evaluated. Recent research from our laboratory (Batal and Parsons, 2002a,b) showed that both ME n and AA digestibility for a corn-sbm diet for chicks increase substantially with age (0 to 21 d), and it is hypothesized that at least part of this response could be due to changes in the digestibility of the SBM as the chicks become older. Thus, the objective of the present study was to evaluate the effect of age on the utilization of several different soy products varying in level of oligosaccharides, trypsin inhibitors, lectins, and heat processing when fed to young chicks. We hope this work will identify types of soybeans and soy products that are more highly digested by very young chicks and types that are a potential problem in diets of very young chicks. MATERIALS AND METHODS General Procedures All procedures were approved by the University of Illinois Committee on Laboratory Animal Care. New Hampshire Columbian male chicks were housed in thermostatically controlled starter batteries 3 with raised wire floors in an environmentally controlled building. At hatch, chicks were weighed, wing-banded, and randomly allotted to pens so that each pen of chicks had a similar initial weight and weight distribution. Chicks were allowed ad libitum access to each experimental diet from 0 to 21 d posthatching. Body weight of individual chicks within each replicate group and group feed intakes were measured at weekly intervals. Weight gain and feed efficiency (gain:feed) were then calculated for each pen replicate. For determination of apparent ME n and apparent AA digestibilities, excreta from each pen were collected for 24-h periods on d 1 and 2 (0 2), d 3 and 4 (3 4), d 7, d 14, and d 21 posthatching and then were freeze-dried. Feed and excreta samples were then ground to pass through a 60-mesh screen and analyzed for gross energy 3 Petersime Incubator Co., Gettysburg, OH. 4 Parr Instruments Co., Moline, IL. 5 Celite Corporation, Lompoc, CA. 6 ARCON F (65-301), Archer Daniels Midland Company, Decatur, IL. 7 ARDEX AF (66-960), Archer Daniels Midland Company, Decatur, IL. 8 Soyflakes were obtained from Owensboro Grain Company, Owensboro, KY. 9 The Williams 82 soybeans and the Kunitz-free soybeans were obtained from the Illinois Foundation Seeds, Inc., Champaign, IL; the lectin-free and Kunitz-lectin-free soybeans were obtained from the Department of Crop Sciences, University of Illinois, Urbana, IL. using an adiabatic bomb calorimeter. 4 Analysis for crude protein was performed using the Kjeldahl procedure of the Association of Official Analytical Chemists (1980) (7.015). Amino acid concentrations in the feed and excreta were determined using ion exchange chromatography following hydrolysis in 6 N HCl for 24 h at 110 C (Spackman et al., 1958). Analysis of methionine and cystine were conducted following performic acid oxidation by the method of Moore (1963), except that samples were diluted with water and then lyophilized to remove excess performic acid. Celite 5 was added to all experimental diets (2%) as a source of acid-insoluble ash (indigestible marker), and the concentration of acid-insoluble ash in the feed and excreta was as described by Vogtmann et al. (1975). The ME n of the diets was calculated using the equation described by Hill and Anderson (1958), except that acid-insoluble ash was used rather than chromic oxide. Experiment 1 The objective of this experiment was to determine the utilization of three soy protein sources compared to casein at different ages. Six pens of eight chicks were fed one of four dextrose-protein source diets (Table 1) from 0 to 21 d. Protein sources evaluated were casein, SBM, soy protein concentrate (SPC), 6 and soy protein isolate (SPI). 7 The diets were formulated to be isonitrogenous at 23% CP and to meet or exceed the NRC (1994) nutrient requirements. Levels of all indispensable AA met or exceeded NRC (1994) requirements, but they were not kept constant across diets. The casein, SBM, SPC, and SPI contained 87, 48, 64, and 86% protein by analysis, respectively. Soy protein concentrate is manufactured by selectively removing the soluble carbohydrates, mainly oligosaccharides, from soy protein flour by aqueous alcohol or isoelectric leaching (Beery, 1989). Further processing to SPI involves an alkaline extraction and centrifugation to remove cotyledons, followed by an acid precipitation, after which soy whey is removed (Johnson and Kikuchi, 1989). Casein was chosen for evaluation because a dextrosecasein diet has been very well utilized by young chicks in earlier studies in our lab (Batal and Parsons, 2002a,b). Experiment 2 This experiment was conducted to evaluate how age affects the utilization of different soybeans and SBM varying in levels of antinutritional factors and heat processing. Six pens of eight chicks per pen were fed soybean or SBMdextrose diets (Table 2) containing one of seven different soybean or SBM sources immediately after hatching. Diets were formulated to be isonitrogenous at 23% CP and to meet or exceed the NRC (1994) nutrient requirements. Soybeans or SBM evaluated were raw solvent-extracted soyflakes 8 (postexpander but prior to desolventizer toaster) (51.3% CP), commercial SBM (47.6% CP), Williams 82 soybeans 9 (38.2% CP), Williams 82 heated soybeans (38.2% CP), Kunitz trypsin inhibitor-free soybeans 9

3 456 BATAL AND PARSONS TABLE 1. Composition (as-fed basis) of the diets for experiment 1 1 Ingredient Casein SBM 2 SPC 3 SPI 4 Protein source Dextrose Soybean oil Mineral mix Vitamin mix Celite DL-Methionine Amino acid mixture Sodium bicarbonate 1.0 Choline chloride Bacitracin MD DL-α-Tocopherol acetate (20 mg/kg) Ethoxyquin (125 mg/kg) Calculated analysis ME n, kcal/kg 3,291 2,872 3,347 3,360 Crude protein, % Calcium, % Nonphytate P, % Lysine, % Total sulfur amino acids, % Diets were formulated to be isonitrogenous at 23% CP. The casein, SBM, SPC, and SPI contained 87, 48, 64, and 86% CP, respectively. 2 SBM = soybean meal. 3 SPC = soy protein concentrate. 4 SPI = soy protein isolate. 5 Provided (per kg of diet): Ca 3 (PO 4 ) 2, 28.0 g; K 2 HPO 4, 9.0 g; NaCl, 8.89 g; MgSO 4 H 2 O, 3.5 g; ZnCO 3, 0.10 g; CaCO 3, 3.0 g; MnSO 4 H 2 O, 0.65 g; FeSO 4 7H 2 O, 0.42 g; KI, 40 mg; CuSO 4 5H 2 O, 20 mg; Na 2 MoO 4 2H 2 O, 9 mg; H 3 BO 3, 9 mg; CoSO 4 7H 2 O, 1 mg; Na 2 SeO 3, 0.22 mg. 6 Provided (per kg of diet): thiamin HCl, 20 mg; niacin, 50 g; riboflavin, 10 g; D-Ca-pantothenate, 30 g; vitamin B 12, 0.04 mg; pyridoxine HCl, 6 mg; D-biotin, 0.6 mg; folic acid, 4 mg; menadione dimethylpyridinol bisulfite, 2 mg; cholecalciferol, 15 µg; retinyl acetate, 1,789 µg; ascorbic acid, 250 mg. 7 Celite Corporation, Lompoc, CA. 8 Amino acid mixture provided 1.00% arginine, 0.60% threonine, 0.69% phenylalanine, and 2.0% glycine. 9 Contributed 27.5 mg/kg bacitracin methylene disalicylate. (35.8% CP) (Bernard and Hymowitz, 1986), lectin-free soybeans 9 (36.6% CP) (Bernard and Nelson, 1996), and Kunitz trypsin inhibitor/lectin-free soybeans 9 (34.9% CP). To obtain heated Williams 82 soybeans, the material was spread (2.5 cm thick) in aluminum pans, covered with aluminum foil, and autoclaved at 121 C and 15 psi for approximately 8 min. SOY-CHECK 10 was used to estimate the degree of heating of the Williams 82 soybeans. SOY-CHEK is a liquid containing a ph-sensitive color indicator that provides a rapid estimation of digestive inhibitors and enzymes that remain from inadequate heat treatment. The objective was to destroy the majority but not all of the antinutritional factors in the soybeans to determine how well very young chicks tolerate moderate levels of antinutritional factors at different ages. The heat treatment and different genetic lines of soybeans were selected in an attempt to provide a wide range in levels of antinutritional factors such as trypsin inhibitors and lectins. Statistical Analysis Data from all experiments were subjected to analysis of variance procedures for completely randomized designs 10 SOY-CHEK, LSB Products, Manhattan, KS. (Steel and Torrie, 1980) by using the general linear models procedure of SAS software (SAS Institute, 1990). Data for growth performance, ME n, and AA digestibility were analyzed to determine dietary treatment effects at different ages, and data for ME n and AA digestibility were also analyzed to determine age effects for the different dietary treatments. Statistical significance of differences among diets and age were assessed using the least significant difference test (Steel and Torrie, 1980). Experiment 1 RESULTS Weight gain at wk 1 was substantially (P < 0.05) lower for chicks fed SPC and SPI compared to chicks fed casein or SBM (Table 3). At the end of 3 wk, chicks fed SBM had higher weight gains (P < 0.05) than chicks fed the other protein sources. The weight gain obtained from the dextrose-sbm diet was optimum for the New Hampshire Columbian chicks used in this study. Feed efficiency was higher (P < 0.05) at wk 1 for chicks fed casein compared to chicks fed SBM, SPC, or SPI. However, at the end of wk 3, there was no difference (P < 0.05) among feed efficiencies for chicks fed casein, SBM, and SPI. Feed efficiency of chicks fed the SPC was lower through 3 wk than that of the chicks fed the other protein sources.

4 UTILIZATION OF SOY PRODUCTS 457 TABLE 2. Composition (as-fed basis) of the diets for experiment 2 1,2 Ingredient Treatments 1 2 Treatments 3 7 Soyflakes/soybean meal to Soybeans to Dextrose to to Soybean oil 3.00 Limestone Dicalcium phosphate Salt Vitamin mix Mineral mix DL-Methionine Choline chloride Celite Bacitracin MD Soybean, soybean meal and dextrose levels varied to keep the diets isonitrogenous at 23% crude protein. The CP contents of the soybean meals and soybeans were as follows: soyflakes, 51.3; soybean meal, 47.6; Williams 82 soybeans, 38.2; Kunitz-free soybeans, 35.8; lectin-free soybeans, 36.6; and Kunitz/lectin-free soybeans, The diets contained 23% CP, 2,950 kcal/kg ME n, 0.90% total sulfur amino acids, lysine levels varying from 1.36 to 1.47%, 1.0% Ca, and 0.45% nonphytate P. 3 The level of inclusion of the soy products in the diets were soyflakes, 44.75; soybean meal, 47.55; Williams 82 soybeans, 60.25; Kunitz-free soybeans, 63.50; Lectin-free soybeans, 61.85; Kunitz/lectin-free soybeans, Provided (per kg of diet): retinyl acetate, 4,400 IU; cholecalciferol, 1,000 IU; DL-α-tocopheryl acetate, 11 IU; niacin, 22 mg; D-Ca-pantothenate, 10 mg; riboflavin, 4.4 mg; vitamin B 12, 0.01 mg; menadione sodium bisulfite, 2.33 mg. 5 Provided (mg per kg diet): Mn, 75 from MnO; Fe, 75 from FeSO 4 H 2 O; Zn, 75 from ZnO; Cu, 5 from CuSO 4 H 2 O; I, 0.75 from ethylene diamine dihydroiodide; Se, 0.1 from Na 2 SeO 3. 6 Celite Corporation, Lompoc, CA. 7 Contributed 27.5 mg/kg bacitracin methylene disalicylate. When comparing the ME n values among diets at the same age, the casein diet was consistently higher (P < 0.05) than all other diets at all ages (Table 4). The ME n of the SBM diet was consistently lower (P < 0.05) than those of the SPC and SPI diets, and the ME n of the SPI diet was also higher (P < 0.05) than the SPC diet. When evaluating the effect of age, ME n values increased (P < 0.05) with age for all four diets; however, the increase was much larger for the soy diets than the casein diet. For example, the ME n of the casein diet increased only 3% from 3 4 to 21 d, whereas the ME n of the SBM, SPC and SPI diets increased 13, 16, and 11%, respectively, during the same time period. When comparing AA digestibility among dietary treatments, values for the casein diet were generally high and significantly (P < 0.05) higher than the soy diets (Table 5). When comparing AA digestibility among soy products, there were no large consistent differences during the 0- to-7-d period. The AA digestibility of the SPC and SPI diets were generally higher (P < 0.05) than the SBM diet at 14 and 21 d of age. Digestibility of AA increased with age for all three soy products. In contrast, the digestibility of AA in the casein diet was high initially (94 to 98%) and increased only slightly with age. Experiment 2 The heat treatment and different genetic lines of soybeans produced a wide range in growth rates and feed efficiencies (Table 6). Chicks fed the SBM-dextrose diet had the highest (P < 0.05) weight gain and gain to feed ratio through 3 wk of age. The lowest (P < 0.05) performance was observed for chicks fed the raw unheated Williams 82 soybeans. When the Williams 82 soybeans were heated, an improvement (P < 0.05) was observed in both chick growth and feed efficiency compared to chicks fed the unheated Williams 82 soybeans, soyflakes, Kunitzfree, lectin-free, or Kunitz/lectin-free soybeans. Chicks fed the Kunitz-free soybeans or the lectin-free soybeans had increased growth rates compared to those fed unheated Williams 82 soybeans for the 0-to-3-wk period, but differences were much less for the 0-to-7-d period. Chicks fed the Kunitz/lectin-free soybeans had better performance (P < 0.05) than chicks fed Kunitz-free soybeans or lectin-free soybeans. When comparing ME n values among diets at the same age, the ME n of the SBM-dextrose diet was higher (P < 0.05) than all other diets at all ages (Table 7). The ME n value of the soyflake diet was higher (P < 0.05) than most of the soybean diets at all ages, except the heated Williams 82 soybeans. Heating the Williams 82 soybeans produced an increase (P < 0.05) in ME n compared to the raw Williams 82 soybeans, Kunitz-free soybeans, and lectin-free soybeans. In addition, the ME n of the heated Williams 82 soybeans was higher (P < 0.05) than the Kunitz/lectinfree soybeans at 0 to 2, 7, and 14 d of age. The ME n of the Kunitz/lectin-free soybeans was higher than the raw Williams 82 soybeans at 3 to 4, 14, and 21 d of age and was higher than the Kunitz-free soybeans and the lectinfree soybeans at 14 and 21 d. When evaluating the effect TABLE 3. Effect of protein sources on weight gain and feed efficiency of chicks, experiment 1 1 Weight gain (g) Gain:feed (g/kg) Protein source Week 1 Week 0 3 Week 1 Week 0 3 Casein 74 a 364 b 863 a 642 a Soybean meal 75 a 405 a 738 b 625 a Soy protein concentrate 65 b 356 b 669 c 583 b Soy protein isolate 63 b 366 b 777 b 650 a Pooled SEM a c Means within a column with no common superscript differ significantly (P < 0.05).

5 458 BATAL AND PARSONS TABLE 4. Effect of age on apparent ME n values for chicks fed various protein sources, experiment 1 1 Pooled Protein source SEM (kcal/kg DM) Casein 3,796 bw 3,751 cw 3,755 bcw 3,857 aw 3,878 aw 12 Soybean meal 2,783 cz 2,725 cz 3,034 bz 3,128 az 3,089 abz 30 Soy protein concentrate 3,077 by 2,852 cy 3,080 by 3,278 ay 3,320 ay 20 Soy protein isolate 3,444 bx 3,280 cx 3,324 cx 3,609 ax 3,627 ax 20 Pooled SEM a c Means within a row with no common superscript differ significantly (P < 0.05). w z Means within a column with no common superscript differ significantly (P < 0.05). TABLE 5. Effect of age on apparent digestibility of selected amino acids (AA) for chicks fed various protein sources, experiment 1 1 AA and Pooled protein source SEM Arginine Casein 97 cw 97 cw 98 bw 99 aw 99 aw 0.3 Soybean meal 82 by 84 bxy 91 ay 90 az 89 ay 1.4 Soy protein concentrate 85 bxy 80 cy 94 ax 95 ay 96 ax 1.5 Soy protein isolate 89 bx 89 bx 94 ax 97 ax 97 ax 1.1 Pooled SEM Cystine Casein 75 b 70 cw 68 cy 83 aw 77 bx 1.5 Soybean meal 62 b 57 bxy 78 aw 78 ax 72 ay 2.8 Soy protein concentrate 64 c 52 dy 74 bx 83 aw 81 abw 2.6 Soy protein isolate 71 cd 64 dwx 76 bcwx 83 abw 86 aw 2.5 Pooled SEM Isoleucine Casein 94 cw 94 cw 96 bw 97 aw 97 aw 0.3 Soybean meal 76 bx 77 by 87 ay 85 az 83 ay 1.8 Soy protein concentrate 76 bx 69 cz 88 ay 92 ay 92 ax 1.8 Soy protein isolate 87 cw 85 cx 91 bx 94 abx 95 aw 1.2 Pooled SEM Lysine Casein 97 bw 97 bw 97 bw 98 aw 98 aw 0.3 Soybean meal 77 by 79 by 89 ay 87 ay 84 az 1.7 Soy protein concentrate 83 bxy 76 cy 91 ax 94 ax 94 ay 1.4 Soy protein isolate 87 cx 86 cx 92 bx 95 ax 96 ax 1.1 Pooled SEM Methionine Casein 98 bw 98 bw 98 bw 99 aw 99 aw 0.2 Soybean meal 77 dx 84 cx 93 ax 90 aby 86 bcy 1.9 Soy protein concentrate 80 bx 75 by 91 ax 94 ax 89 ay 1.9 Soy protein isolate 85 bcx 82 cx 89 by 94 ax 94 ax 1.3 Pooled SEM Threonine Casein 95 bw 95 bcw 94 bw 97 aw 97 aw 0.2 Soybean meal 70 bx 70 bxy 83 ax 82 ay 82 ay 1.8 Soy protein concentrate 72 cx 63 dy 81 bx 87 ax 89 ax 1.8 Soy protein isolate 76 bcx 71 cx 81 bx 88 ax 90 ax 2.0 Pooled SEM Valine Casein 95 bw 95 bw 96 bw 97 aw 97 aw 0.4 Soybean meal 72 bx 74 bx 85 ax 83 ay 81 ay 2.1 Soy protein concentrate 72 bx 65 cy 86 ax 90 ax 89 ax 2.1 Soy protein isolate 78 cx 76 cx 85 bx 91 ax 91 ax 1.9 Pooled SEM a c Means within a row and amino acid with no common superscript differ significantly (P < 0.05). w z Means within a column and amino acid with no common superscript differ significantly (P < 0.05).

6 UTILIZATION OF SOY PRODUCTS 459 TABLE 6. Effect of soybean or soybean meal protein sources on weight gain and feed efficiency of chicks, experiment 2 1 Weight gain (g) Gain:feed (/kg) Soybean or soybean meal 2 Week 1 Week 0 3 Week 1 Week 0 3 Soyflakes 44 c 288 d 563 c 471 cd Soybean meal 72 a 467 a 738 a 630 a Williams 82 soybeans 28 e 232 f 358 f 380 f Kunitz-free soybeans 30 e 268 de 396 e 451 d Lectin-free soybeans 35 d 259 e 408 e 414 e Kunitz/lectin-free soybeans 43 c 327 c 485 d 497 c Heated Williams 82 soybeans 53 b 398 b 644 b 574 b Pooled SEM a f Means within a column with no common superscript differ significantly (P < 0.05). 2 Diets containing different soybeans or soybean meals as the only source of protein in 23% CP diets. The heated Williams 82 soybeans were soybeans that had been autoclaved for approximately 8 min at 121 C and 15 psi to remove some of the antinutritional factors. of age, there was an increase in the ME n of the soyflake and soybean diets with increasing age; however, this effect was due primarily to higher values at 14 and 21 d, with values from 0 to 14 d being low and variable. When comparing AA digestibility among dietary treatments, values for the SBM diet were higher (P < 0.05) than the other diets within the same age (Table 8). Digestibilities of AA in the soyflake diet were generally higher (P < 0.05) than those in all the soybean diets except the heated Williams 82 soybeans. The AA digestibility values for the heated Williams 82 soybeans were generally higher (P < 0.05) than all the other soybean diets at most ages. There were no large or consistent differences in AA digestibility among the other soybean diets except for the generally higher values for the Kunitz/lectin-free soybeans at 14 and 21 d and the higher Cys digestibility values for Kunitz/lectin-free soybeans at all ages except 0 to 2 d. The effect of age on AA digestibility varied among treatment. Amino acid digestibility increased with age for the Kunitz/lectin-free soybean diet and to a lesser extent for the soyflake diet. The effect of age was generally variable and inconsistent for the other dietary treatments. The digestibility of cystine was lower than that for the other AA and was particularly low for most of the unheated soybean diets at 7 d of age. DISCUSSION Our results indicate that digestibility varies among soybean products or ingredients in young chicks and is also affected by age for many products. Results of the first experiment showed that ME n and AA digestibility of soy could be improved by further processing from SBM to SPC and SPI. The increase in the nutrient utilization for SPC and SPI compared with SBM may be largely due to the removal of oligosaccharides. Oligosaccahrides, raffinose and stachyose, in SBM have been reported to be poorly digestible and may be antinutritional factors because of their effects in reducing the TME n and fiber digestion of SBM (Coon et al., 1990; Leske et al., 1993; Parsons et al., 2000). There was also further improvement in the digestibility of SPI compared with SPC. The latter could be due to further concentrating the protein, which is highly digestible, and the further removal of poorly TABLE 7. Effect of age on ME n values for chicks fed different soybeans or soybean meal diets, experiment 2 1 Soybean or soybean meal Pooled SEM (kcal/kg DM) Soyflakes 2,450 dv 2,546 cv 2,372 dv 2,682 bvw 2,820 av 32 Soybean meal 2,941 cu 2,956 bcu 2,840 du 3,015 abu 3,048 au 23 Williams 82 soybeans 2,154 bw 1,946 cz 1,846 cwx 2,301 bz 2,474 axy 57 Kunitz-free soybeans 2,107 bw 2,066 byz 1,821 cwx 2,531 axy 2,357 ay 82 Lectin-free soybeans 2,107 bw 2,200 bxy 1,705 cx 2,412 ayz 2,480 ax 47 Kunitz/lectin-free soybeans 2,078 cw 2,304 bwx 2,007 cw 2,649 awx 2,656 aw 65 Heated Williams 82 soybeans 2,392 bv 2,427 bvw 2,535 bv 2,794 av 2,742 avw 56 Pooled SEM a d Means within a row with no common superscript differ significantly (P < 0.05). u z Means within a column with no common superscript differ significantly (P < 0.05). 2 Diets containing different soybeans or soybean meals as the only source of protein in 23% CP diets. The heated Williams 82 soybeans were soybeans that had been autoclaved for approximately 8 min at 121 C and 15 psi to remove some of the antinutritional factors.

7 460 BATAL AND PARSONS digestible carbohydrates. Further processing to SPC and SPI had little or no influence on the age response, where the increases in ME n and AA digestibility with age were similar in magnitude for both diets. These results indicate that even the more highly digestible SPC and SPI contain substantial carbohydrates and protein that are not digested well by very young chicks. The lower growth rates of chicks fed the SPC and SPI diets could have been due to AA imbalances because of the low-sulfur AA and Thr concentrations of the processed soy products (Emmert and Baker, 1995). The high ME n and AA digestibility of the dextrosecasein diet, even at 0 to 4 d posthatching, agrees with previous reports from our laboratory (Batal and Parsons, 2002a,b). The very high ME n of the dextrose-casein diet indicates that glucose is highly utilized by the very young TABLE 8. Effect of age on apparent digestibility of selected amino acids (AA) for chicks fed different soybeans or soybean meal diets, experiment 2 1 AA and soybean or soybean meal Pooled SEM Arginine Soyflakes 68 bcv 70 bv 66 cw 77 av 80 av 1.2 Soybean meal 88 cu 91 bu 90 bu 93 au 93 au 0.6 Williams 82 soybeans 54 bcx 56 bwx 51 cx 57 by 64 awx 1.8 Kunitz-free soybeans 57 abwx 54 bx 41 cy 66 ax 59 abx 3.3 Lectin-free soybeans 55 bx 60 abw 45 cxy 64 ax 64 awx 1.8 Kunitz/lectin-free soybeans 54 bx 54 bx 49 bx 71 aw 68 aw 2.5 Heated Williams 82 soybeans 61 dvw 73 cv 83 av 78 bv 77 bcv 1.6 Pooled SEM Cystine Soyflakes 46 avw 38 bvw 36 bw 39 bwx 46 aw 2.0 Soybean meal 80 au 71 cu 70 cu 76 bu 76 bu 1.1 Williams 82 soybeans 39 avwx 17 cy 18 cxy 15 cz 26 bx 2.4 Kunitz-free soybeans 41 avw 25 bcxy 12 cy 33 abx 32 abx 5.0 Lectin-free soybeans 29 ax 31 awx 10 by 23 ay 29 ay 2.7 Kunitz/lectin-free soybeans 36 awx 42 av 24 bx 45 aw 41 aw 3.7 Heated Williams 82 soybeans 50 abv 47 bv 53 abv 55 av 53 abv 2.7 Pooled SEM Isoleucine Soyflakes 61 cv 64 cbv 61 cw 65 abw 69 av 1.5 Soybean meal 89 u 89 u 87 u 90 u 90 u 0.7 Williams 82 soybeans 42 abw 42 abx 35 cx 40 bcz 48 ax 1.9 Kunitz-free soybeans 45 abw 41 bx 25 cy 53 ay 48 abx 3.3 Lectin-free soybeans 45 bw 51 aw 32 cxy 50 ay 52 awx 1.8 Kunitz/lectin-free soybeans 41 bw 43 bx 30 cxy 59 ax 56 aw 3.0 Heated Williams 82 soybeans 54 cv 65 bv 75 av 73 av 72 av 1.7 Pooled SEM Lysine Soyflakes 67 cv 68 cv 70 cw 74 bv 78 av 1.1 Soybean meal 88 u 88 u 89 u 90 u 89 u 0.6 Williams 82 soybeans 52 bw 52 bx 51 bxy 53 by 59 awx 1.8 Kunitz-free soybeans 57 abw 49 bcx 45 cy 63 ax 57 abx 2.8 Lectin-free soybeans 61 avw 59 aw 47 bxy 61 ax 61 awx 3.0 Kunitz/lectin-free soybeans 52 bw 52 bx 52 bx 67 aw 63 aw 2.3 Heated Williams 82 soybeans 59 cvw 70 bv 80 av 75 bv 73 bv 2.7 Pooled SEM Methionine Soyflakes 76 bcvw 75 cvw 81 av 79 abv 79 abv 1.2 Soybean meal 94 au 92 bu 95 au 92 bu 92 bu 0.6 Williams 82 soybeans 70 abwx 70 abxy 73 aw 67 bx 72 aw 1.2 Kunitz-free soybeans 68 ax 65 aby 60 bx 69 ax 68 ax 2.6 Lectin-free soybeans 69 ax 71 awx 63 bx 69 ax 71 awx 1.5 Kunitz/lectin-free soybeans 66 bx 72 awx 65 bx 74 aw 73 aw 2.1 Heated Williams 82 soybeans 76 cvw 79 bcv 85 av 81 abv 80 bcv 1.4 Pooled SEM Threonine Soyflakes 59 bcv 61 bcv 58 cw 63 bw 68 av 1.5 Soybean meal 84 abu 84 abu 83 bu 86 au 86 au 0.6 Williams 82 soybeans 42 bw 43 bx 39 bx 43 by 55 aw 2.8 Kunitz-free soybeans 51 av 41 bx 28 cy 52 ax 46 abx 3.1 Lectin-free soybeans 52 av 50 aw 36 bxy 51 ax 52 awx 1.9 Kunitz/lectin-free soybeans 50 bvw 49 bw 38 cx 61 aw 56 abw 2.6 Heated Williams 82 soybeans 53 bv 63 av 67 av 71 av 68 av 2.8 Pooled SEM continued

8 UTILIZATION OF SOY PRODUCTS 461 TABLE 8 (continued) AA and soybean or soybean meal Pooled SEM Valine Soyflakes 60 bcv 62 bcv 59 cw 64 abw 67 av 1.5 Soybean meal 88 au 87 au 85 bu 89 au 88 au 0.7 Williams 82 soybeans 41 abw 41 abx 35 bx 43 aby 46 ax 2.1 Kunitz-free soybeans 43 abw 40 bx 26 cy 52 ax 47 abx 3.3 Lectin-free soybeans 45 bw 50 abw 33 cx 50 abx 52 ax 1.9 Kunitz/lectin-free soybeans 44 bw 45 bwx 36 cx 61 aw 57 aw 2.7 Heated Williams 82 soybeans 53 cv 64 bv 74 av 72 av 70 av 1.7 Pooled SEM a c Means within a row and amino acid with no common superscript differ significantly (P < 0.05). u z Means within a column and amino acid with no common superscript differ significantly (P < 0.05). 2 Diets containing different soybeans or soybean meals as the only source of protein in 23% CP diets. The heated Williams 82 soybeans were soybeans that had been autoclaved for approximately 8 min at 121 C and 15 psi to remove some of the antinutritional factors. chick. Amino acid digestibility of the dextrose-casein diet was also very high and not affected by age, indicating that the very young chick has a high ability to absorb the AA and digest the protein in casein. Our results also indicate that the milk protein in casein is more highly digested than soy protein during the first wk posthatch. Results of the second experiment indicate that severely underprocessed soybeans should definitely not be included in the diet of the very young chick. Growth, ME n, and AA digestibility were quite low for the soyflake and raw (unheated) soybean diets and ME n and AA digestibility were particularly low at the younger ages. The poor growth performance was probably caused mainly by antinutritional factors, such as trypsin inhibitors and lectin, which have been shown to be detrimental to chick performance (Friedman et al., 1991). Heating the Williams 82 soybeans in an autoclave improved weight gain, ME n, and AA digestibility, and the beneficial effect of heating the soybeans was probably due largely to reduction of antinutritional factors (Friedman et al., 1991). The reduced growth, ME, and AA digestibility obtained from the heated soybeans compared to commercial SBM was expected because the former were intentionally autoclaved to remove a large proportion, but not all, of the antinutritional factors. The improved growth performance obtained with Kunitz-free soybeans and lectin-free soybeans compared to the Williams 82 soybeans is in agreement with previous reports from our lab (Han and Parsons, 1991; Zhang et al., 1991; Douglas et al., 1999). The improvements in growth were much greater for the 0-to-3-wk period than for the first week, suggesting that the Kunitz-free and lectin-free soybeans still contain sufficiently high levels of antinutritional factors to greatly depress growth at very young ages. Our results indicated that there generally was no substantial increase in the ME n and AA digestibility of the Kunitz-free soybeans and lectin-free soybeans compared to the Williams 82 soybeans. However, when chicks were fed soybeans that had both the Kunitz trypsin inhibitor and lectins genetically removed, there was a substantial improvement in growth and ME n, and to a lesser extent, AA digestibility. Moreover, the increase in growth was greater than the sum of individual responses for the Kunitz-free soybeans and the lectin-free soybeans, suggesting some synergistic effect of removing both antinutritional factors together. The marked growth response for the Kunitz/lectin-free soybeans might have been largely due to its substantially higher Cys digestibility (sulfur AA are first limiting in SBM). Our study is the first to evaluate soybeans that have had both the Kunitz trypsin inhibitor and lectins genetically removed. Although there was little to no consistent effect of age on ME n and AA digestibility for most of the soybean products in Experiment 2, we did observe some increase with age for the Kunitz/lectin-free soybeans, heated Williams 82 soybeans and the soyflakes. Based on growth data, these diets contained lower levels of antinutritional factors than the other soybean diets. Thus, chicks may be able to compensate somewhat as they age if the levels of antinutritional factors are not too high. In summary, our results indicate that the ME n and AA digestibility of soy for very young chicks can be improved by further processing to SPC and SPI and by genetically reducing antinutritional factors such as trypsin inhibitors and lectins. In addition, the negative effects of undercooked soy products on nutrient digestibility are profound in young chicks, and these products should definitely not be included in their diets. REFERENCES Association of Official Analytical Chemists Official Methods of Analysis. 13th ed. Association of Official Analytical Chemists, Washington, DC. Balloun, S. L Effect of processing on the nutritional value of soybean meal for poultry. Pages in Soybean Meal In Poultry Nutrition. K.C. Lepley, ed. Ovid Bell Press, Fulton, MO. Batal, A. B., and C. M. Parsons. 2002a. Effects of age on nutrient digestibility in chicks fed different diets. Poult. Sci. 81:

9 462 BATAL AND PARSONS Batal, A. B., and C. M. Parsons. 2002b. Effects of fasting versus feeding Oasis after hatching on nutrient utilization in chicks. Poult. Sci. 81: Beery, K. E Preparation of soy protein concentrate products and their application in food systems. Pages in Proceedings of the World Congress on Vegetable Protein Utilization in Human Foods and Animal Feedstuffs. American Oil Chemists Society, Champaign, IL. Bernard, R. L., and T. Hymowitz Registration of L81- L4871, and L soybean germplasm lines lacking the Kunitz trypsin inhibitor. Crop Sci. 26: Bernard, R. L., and R. L. Nelson additions to the isoline collection of the USDA soybean genetic collection. Soybean Genet. Newsletter 23: Cook, D. A., A. H. Jensen, J. R. Farley, and T. Hymowitz Utilization by growing and finishing pigs of raw soybeans of low Kunitz trypsin inhibitor content. J. Anim. Sci. 66: Coon, C. N., K. L. Leske, O. Akavanhican, and T. K. Cheng Effect of oligosaccharide-free soybean meal on true metabolizable energy and fiber digestion in adult rooster. Poult. Sci. 69: Douglas, M. W., C. M. Parsons, and T. Hymowitz Nutritional evaluation of lectin-free soybeans for poultry. Poult. Sci. 78: Emmert, J. L., and D. H. Baker Protein quality assessment of soy products. Nutr. Res. 15: Friedman, M., D. L. Brandon, A. H. Bates, and T. Hymowitz Comparison of a commercial soybean cultivar and an isoline lacking the Kunitz trypsin inhibitor; composition, nutritional value, and effect of heating. J. Agric. Food Chem. 39: Han, Y., and C. M. Parsons Nutritional evaluation of soybeans varying in trypsin inhibitor content. Poult. Sci. 70: Hill, F. W., and D. L. Anderson Comparison of the metabolizable energy and productive energy determination with growing chicks. J. Nutr. 64: Johnson D. W., and S. Kikuchi Processing for producing soy protein isolates. Pages in Proceedings of the World Congress on Vegetable Protein Utilization in Human Foods and Animal Feedstuffs. American Oil Chemists Society, Champaign, IL. Leske, K. L., C. J. Jevne, and C. N. Coon Effect of oligosaccharide additions on nitrogen-corrected true metabolizable energy of soy protein concentrate. Poult. Sci. 72: Liener, I. E Nutritional significance of lectins in the diet. Pages in The Lectins: Properties, Functions and Applications in Biology and Medicine. I. E. Liener, N. Sharon, and I. J. Goldstein, ed. Academic Pr, Orlando, FL. Moore, S On the determination of cystine as cysteic acid. J. Biol. Chem. 238: National Research Council Nutrient Requirements for Poultry. 9th rev. ed. National Academy Press, Washington, DC. Oliveira, A. C., B. C. Vidal, and V. C. Sgarbieri Lesions of intestinal epithelium by ingestion of bean lectins in rats. J. Nutr. Sci. Vitaminol. 35: Parsons, C. M., Y. Zhang, and M. Araba Nutritional evaluation of soybean meals varying in oligosaccharide content. Poult. Sci. 79: Pustzai, A Plant Lectins. Cambridge University Press, Cambridge, UK. Pustzai, A., E. M. W. Clarke, T. P. King, and J. C. Stewart Nutritional evaluation of kidney beans (Phaseolus vulgaris): Chemical composition, lectin content and nutritional value of selected cultivars. J. Sci. Food Agric. 30: SAS Institute Inc SAS STAT User s Guide Release SAS Institute Inc., Cary NC. Spackman, D. H., W. H. Stein, and S. Moore Automatic recording apparatus for use in the chromatography of amino acids. Anal. Chem. 30: Steel, R. G. D., and J. H. Torrie Principles and Procedures of Statistics. A Biometrical Approach. 2nd ed. McGraw-Hill, New York. Vogtmann, H., P. Frirter, and A. L. Prabuck A new method of determining metabolizability of energy and digestibility of fatty acids in broiler diets. Br. Poult. Sci. 16: Yen, J. T., A. H. Jensen, T. Hymowitz, and D. H. Baker Utilization of different varieties or raw soybeans by male and female chicks. Poult. Sci. 52: Zhang, Y., C. M. Parsons, and T. Hymowitz Research note: Effect of soybeans varying in trypsin inhibitor content on performance of laying hens. Poult. Sci. 70: