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ANIMAL NUTRITION |
Department of Animal Science, University of Manitoba, Winnipeg, Canada R3T 2N2
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONIMPLICATIONSLITERATURE CITED |
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0.05) true digestibility for isoleucine, leucine, cysteine, proline, serine, and tyrosine compared with DESBM-1. The results indicate that, relative to regular, solvent-extracted soybean meal, AA digestibilities of different batches of dry extruded-expelled soybean meal varied in pigs and poultry.
Key Words: amino acid • digestibility • pig • poultry • soybean meal
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONIMPLICATIONSLITERATURE CITED |
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). Because of the presence of antinutritional factors in soybean, it has been subjected to various types of heat treatments such as jet-sploding, micronization, and roasting, to inactivate the antinutritional factors (Marty et al., 1994; Subuh et al., 2002). Dry extrusion-expelling is an alternative processing technology that combines extrusion with expelling. Dry extrusion-expelling of soybeans produces a SBM product, dry extruded-expelled SBM (DESBM), with greater oil content compared with regular, solvent-extracted SBM (Nelson et al., 1987; Woodworth et al., 2001).
Although extensive work has been done on the feeding value of different types of SBM for pigs and poultry (Marty et al., 1994; Subuh et al., 2002; Palacios et al., 2004), only limited information is available on the feeding value of DESBM. The nutritional value of DESBM has been assessed through performance and apparent nutrient digestibility studies in pigs (Woodworth et al., 2001; Webster et al., 2003). However, for accurate dietary AA supply, true as opposed to apparent ileal digestibilities (AID) should be used because true ileal digestibilities (TID) are more additive in a mixture of feed ingredients (Imbeah et al., 1988; Furuya and Kaji, 1991; Nyachoti et al., 1997). The true ileal CP and AA digestibilities in DESBM fed to pigs and poultry have not been reported.
The objective of the current study, therefore, was to determine the AID and TID of CP and AA in DESBM fed to pigs and poultry.
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONIMPLICATIONSLITERATURE CITED |
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).
Pig Assay
Four Cotswold barrows, obtained from the University of Manitoba Glenlea Research Farm, with an average initial BW of 80.4 (SD = 7.1) kg, were used in this study. At an average BW of 20 kg, each pig was surgically fitted with a simple T-cannula at the distal ileum, as described by Nyachoti et al. (2002). Pigs were used previously in an experiment to determine energy and nutrient digestibilities of selected corn hybrids, and they had 46 d of rest between that study and the current experiment. All pigs were housed in pens (1.47 x 1.14 m) with smooth sides and plastic-covered, expended metal, sheet flooring in a temperature-controlled room (20 to 21°C). Each pen was equipped with a feeder and also with a nipple drinker that allowed the pigs to have unlimited access to water at all times.
Four semipurified diets (Table 1) were fed to the 4 pigs in a 4 x 4 Latin square design. Diet 1 was a low-protein diet containing 5% casein as the sole source of protein and was used to quantify the minimum endogenous protein and AA losses. Diets 2, 3, and 4 were formulated to contain 35% regular, solvent-extracted SBM, batch 1 of DESBM (DESBM-1), and batch 2 of DESBM (DESBM-2), respectively. Soybean meal was included at 35% to provide the CP requirement (NRC, 1998) for pigs within the weight range used. Vitamins and minerals were supplemented to meet or exceed NRC (1998) standards. Diets were provided to the animals as a mash. Pigs were fed at 2.6 times the maintenance energy requirement (ARC, 1981) based on their BW at the beginning of each Latin square period. The daily dietary allowance was divided into 2 equal portions and fed at 0800 and 1600. Chromic oxide (0.3%) was used as an indigestible marker for determining nutrient digestibilities. Feed refusal and spillage were recorded and used to determine actual DMI.
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. Digesta samples were pooled within each pig per period by homogenizing the samples in a heavy-duty blender (Waring Commercial, Torrington, CT), and approximately 200 g of digesta was subsampled and lyophilized for later analysis.
Poultry Assay
Adult cecectomized Single Comb White Leghorn roosters (n = 32) were used for the determination of true AA digestibility (TAAD) in the 3 SBM samples. The birds, housed in an environmentally controlled room, were kept in individual cages with raised wire floors and subjected to a daily photoperiod of 16 h. A wheat-based maintenance diet was fed between assays. Cecectomy was performed according to the procedures of Payne et al. (1971) when birds were 17 wk of age (average BW of 1.4 kg).
The assay procedure was as described by Sibbald (1979), with some modifications (Zhang et al., 1994). The birds were fasted for 28 h. After 5 h of fasting, 30 mL of glucose solution (80% glucose) was given by gavage. After the fast period, 25 g of test diet was administered to each bird by crop intubation. A nonnitrogenous diet (sucrose:canola oil; 9:1, wt/wt; NND) was used to obtain the endogenous AA losses. The TAAD values were determined from a pooled excreta sample collected from the 32 individual roosters. The 25-g test diet consisted of the NND with the equivalent of 5 g of protein from SBM, DESBM-1, or DESBM-2. The excreta, collected for 48 h after crop intubation, was transferred to preweighed collection bags, immediately frozen, and subsequently freeze-dried. Ten to 12 birds were assigned to each test diet. Because of limited excreta, to make 4 replicates per diet, the excreta samples from 2 to 3 birds fed the test diets were pooled and analyzed for AA.
Sample Preparation and Chemical Analyses
All diets, digesta (pig assay), and excreta (poultry assay) were finely ground in a coffee grinder (CBG5 Smart Grind; Applica Consumer Products, Inc., Shelton, CT) and thoroughly mixed before analysis. Dry matter was determined according to the method of AOAC (1990), and CP (N x 6.25) was determined using an N analyzer (model CNS-2000; Leco Corp., St. Joseph, MI). Chromium was determined according to the procedure described by Williams et al. (1962). Amino acid contents were determined using an LKB 4151 Alpha plus AA analyzer (LKB Biochrom, Cambridge, UK) according to AOAC procedures (1990), and as modified by Mills et al. (1989). Briefly, about 100 mg of each sample was hydrolyzed with 6 N HCl, sealed, evacuated, and digested at 110°C for 24 h. Before hydrolysis, cysteine and methionine were oxidized with formic acid. Tryptophan was not determined. The SBM, DESBM-1, and DESBM-2 samples were analyzed for urease activity and KOH protein solubility according to the procedures of AOCS (1980) and Araba and Dale (1990), respectively. All analyses were performed in duplicate.
Digestibility Calculations and Statistical Analysis
In the pig assay, AID of DM, CP, and AA were calculated as described by Nyachoti et al. (1997). True ileal digestibilities of CP and AA were determined by correcting the AID for endogenous CP and AA losses. Endogenous losses (EL) of CP and AA were estimated from the casein-based diet using the following equation:
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in which Crdiet = Cr concentration (mg/kg DM) in the casein diet; Crdigesta = Cr concentration (mg/kg of DM) in digesta of pigs fed the casein diet; and Ndigesta = CP or AA concentration (mg/kg of DM) in digesta of pigs fed the casein diet.
True ileal digestibilities of CP and AA were calculated using the following formula:
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in which AID = apparent ileal digestibility (decimal percent) of CP or AA; Ndiet = CP or AA concentration (mg of DM/kg) in the diet; and NEL = average endogenous CP or AA loss (mg of DMI/kg).
In the poultry assay, TAAD was calculated by correcting the AA in the excreta of the birds fed the test diet for the endogenous losses of AA as follows:
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in which AAI = AA intake (mg); AAE = AA excreted (mg); AANND = average AA excreted (mg) by birds fed NND.
In the pig assay, the data were analyzed as a Latin square design using GLM procedures of SAS (SAS Inst., Inc., Cary, NC). The effects of pig (n = 4), period (n = 4), and diet (n = 4) were included in the model as sources of variation. Individual pig served as the experimental unit. The poultry assay data were analyzed as a completely randomized design using GLM procedures of SAS. Single degree of freedom comparisons were used to test the difference in nutrient digestibility between SBM and DESBM-1, or DESBM-2, and between DESBM-1 and DESBM-2, in both the pig and rooster assays. The alpha level was 0.05.
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RESULTS AND DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONIMPLICATIONSLITERATURE CITED |
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. The DESBM-1 and DESBM-2 had greater fat, methionine, and cysteine content but lower CP and other AA compared with SBM. The DM contents of SBM, DESBM-1, and DESBM-2 were comparable with the values reported by Woodworth et al. (2001). The CP and AA contents of SBM were similar to published values (NRC, 1998).
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). Urease activity falls to zero as the SBM heating continues. Urease index has been proven to be a useful assay in determining whether SBM has been adequately heated to deactivate the antinutritional factors, but it is not a good indicator of excessive heating (Herkelman et al., 1991; Parsons et al., 1991). Although urease level between 0.05 and 0.20 is considered optimum, urease index below 0.05 does necessarily mean the SBM is overprocessed (Waldroup et al., 1985; Araba and Dale 1990; Parsons et al., 1991).
Potassium hydroxide protein solubility is a better indicator of overheated SBM (Herkelman et al., 1991). The KOH protein solubility values of SBM types analyzed in the current study ranged from 84.5 to 89.8% (Table 2). In poultry and swine trials, the KOH protein solubility values below 75% have been shown to be an indicator of overheated SBM (Parsons et al., 1991; Webster et al., 2003). The urease indices and KOH protein solubilities of the SBM types utilized in the current study show that they are adequately processed.
Analyzed diet composition is also shown in Table 2. Except for the casein-based diet, DM, CP, and AA components of the experimental diets were comparable.
Pig Assay
Table 3 shows the AID of DM, CP, and AA in SBM, DESBM-1, DESBM-2, and casein. Apparent ileal digestibility of DM was greater (P < 0.05) in SBM compared with DESBM-1 and DESBM-2. There was no difference (P > 0.05) in AID of AA in SBM and DESBM-1 except for methionine, where SBM had greater (P = 0.002) digestibility. The AID of methionine was greater (P = 0.04) in DESBM-2 compared with DESBM-1, but the digestibilities of other AA were not different. The apparent ileal AA digestibility of SBM was not different (P > 0.05) from that of DESBM-2 except for methionine and threonine (indispensable AA) and serine (dispensable AA), where SBM had greater (P < 0.05) digestibility. The AID of CP in SBM, DESBM-1 and DESBM-2 were not different (P > 0.05).
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; Stein et al., 1999; Otto et al., 2003). The AID of CP and AA in SBM were similar to the values reported by others (Furuya and Kaji, 1989; Marty et al., 1994; Grala et al., 1998). However, contrary to the results of the current study, Woodworth et al. (2001) reported greater AID values for CP, arginine, isoleucine, leucine, lysine, phenylalanine, valine, alanine, aspartic acid, glutamic acid, and serine in DESBM compared with SBM.
Increased CP and AA digestibility in DESBM has been attributed to its high fat content due to the processing technology. Greater dietary fat content is thought to increase nutrient digestibility by increasing the transit time and thus allowing more time for enzymatic digestion (Li and Sauer, 1994). However, the effect of dietary fat content on CP and AA digestibility has been contradictory. For instance, Imbeah and Sauer (1991), in a study with growing pigs (45 kg of BW), reported an increase in the AID of some but not all AA when dietary canola oil was increased from 2 to 10% but did not find any differences in digesta passage rate when the oil content was increased from 2 to 6%. Furthermore, Marty et al. (1994) observed lower AID of CP and AA in extruded full fat SBM compared with SBM when fed to growing pigs (36 kg of BW).
The contradictory results between the current experiment and others might be the result of the age difference of the animals used. Previous studies were done with younger growing pigs, unlike the current study in which finishing pigs were used. The amount of fat in DESBM is probably of little significance in increasing the transit time in finishing pigs that have shorter transit time compared with growing pigs (Le-Goff et al., 2002).
The ileal endogenous protein and AA losses determined using the low-protein diet are shown in Table 4. Endogenous protein concentration in the ileal digesta averaged 2,661 mg of DMI/kg, which is similar to the value of 2,943 mg of DMI/kg reported by Karr-Lilienthal et al. (2004). In agreement with Dilger et al. (2004), there was a large variability in ileal endogenous protein losses observed in the current study. Of all the analyzed AA, proline (5,383 mg of DMI/kg) and glycine (1,494 mg of DMI/kg) made the largest contribution to ileal endogenous AA losses, and methionine (129 mg of DMI/ kg) made the lowest contribution. The current data are in agreement with previous studies in which proline constituted the largest proportion of ileal endogenous AA losses in swine (Moughan and Schuttert, 1991; Dilger et al., 2004). Of the indispensable AA, arginine and threonine made the largest contribution to ileal endogenous AA losses, and this is in agreement with previous research (Furuya and Kaji, 1989; van Kempen et al., 2002). Mucin, which makes a large contribution to endogenous protein losses, contains large proportions of threonine, glycine, glutamic acid, aspartic acid, serine, and proline, hence the high losses of these AA (Taverner et al., 1981; Li and Sauer, 1994; Stein et al., 1999).
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. There was no difference in the TID of CP in SBM, DESBM-1, and DESBM-2. There were no differences (P > 0.05) in TID of AA in SBM and DESBM-1 except for methionine, in which SBM had greater (P = 0.004) digestibility. Similar to the trend observed for AID, the TID of methionine, threonine, and serine in SBM was greater (P < 0.05) compared with DESBM-2, but the digestibilities of other AA were not different. True digestibilities of most AA in SBM were similar or greater than values reported in previous research (Furuya and Kaji, 1989; Dilger et al., 2004; Karr-Lilienthal et al., 2004). True ileal digestibilities of protein and AA in the casein-based diet were approximately 100%, which agrees with the data reported by Chung and Baker (1992) and Dilger et al. (2004), but greater than the values (89 to 97%) reported by Furuya and Kaji (1989). However, as in a study by Dilger et al. (2004), estimates of ileal endogenous proline losses varied widely among pigs from 2,143 to 10,236 mg of DMI/ kg (Table 4). Thus, the TID of proline estimated using the low-protein, casein diet should be interpreted with caution.
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. Threonine (55 mg) and glutamic acid (100 mg), for indispensable and dispensable AA, respectively, made the largest contribution to endogenous AA losses. Endogenous secretion of methionine (10 mg) for indispensable and tyrosine (30 mg) and cysteine (32 mg) for dispensable AA were the smallest. The profile of endogenous AA composition in the current study is in agreement with previous research (Engster et al., 1985; Green and Kiener, 1989).
True AA digestibilities determined with the rooster assay are shown in Table 6. There were no differences (P > 0.05) in TAAD of SBM and DESBM-2 except for cysteine, which was greater (P = 0.05) in SBM. However, SBM had greater true digestibilities (P 0.05) for isoleucine, leucine, glycine, cysteine, proline, serine, and tyrosine compared with DESBM-1, thus confirming the existence of variability in the nutritive value of DESBM products as reported by Woodworth et al. (2001). True digestibilities of indispensable AA in SBM were between 2.5% (for lysine) and 9.6% (for cysteine) greater than values reported in NRC (1994) except for methionine, where it was 3.4% lower.
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The true AA digestibilities in the dietary treatments are different in poultry and pigs. In a study by Palacios et al. (2004), pigs and chicks utilized nutrients in SBM types differently with chicks having greater relative growth rate than pigs. Similarly, Green and Kiener (1989) reported greater true digestibility of AA in cecetomized roosters compared with pigs, although in the same study, true AA digestibilities in meat and rapeseed meals were similar in both species. Based on previous studies (Green and Kiener, 1989), true AA digestibilities can be predicted fairly accurately, using poultry assay for pig, in some feedstuffs but not in others. It is possible that different feed ingredients induce endogenous nutrient losses in pigs and poultry differently. Although the rooster assay is quicker and cheaper compared with ileal cannulation in pigs, the appropriateness of the rooster assay for pigs varies with feedstuffs and, from the results of the current study, it is inappropriate for SBM.
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IMPLICATIONS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONIMPLICATIONSLITERATURE CITED |
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Footnotes |
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2 Corresponding author: martin_nyachoti{at}umanitoba.ca
Received for publication March 1, 2005. Accepted for publication December 9, 2005.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONIMPLICATIONSLITERATURE CITED |
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