Apparent metabolizable energy value of expeller-extracted canola meal subjected to different processing conditions for growing broiler chickens

Apparent metabolizable energy value of expeller-extracted canola meal subjected to different processing conditions for growing broiler chickens M. Toghyani, N. Rodgers, M. R. Barekatain, P. A. Iji, and R. A. Swick1 Department of Animal Science, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia zation compared with low torque (P < 0.001). There was also an interaction (P < 0.001) between conditioning temperature and screw torque. For ECM subjected to low or medium conditioning temperature at low screw torque, IDE, AME, and AMEn values ranging from 2,137 to 2,705, 2,089 to 2,655, and 1,977 to 2,482 kcal/kg of DM, respectively, were obtained. The mean AMEn values were 2,260 kcal/kg of DM, indicating a 7% reduction compared with AME values. The AMEn values were negatively correlated with neutral detergent fiber (NDF; r = −0.93; P = 0.001) and NDIN (r = −0.87; P = 0.001). Stepwise regression to predict AMEn value resulted in the following equation: AMEn (kcal/kg of DM) = 3,397.8 + (−100.1 × NDF %) + (279.5 × ash %) + (−33.8 × ADF %) (R2 = 0.91; SE = 61.9; P = 0.001). These results indicate that AMEn values vary markedly among ECM samples, and chemical constituents, especially the fiber components, may have a considerable effect on AMEn value.

Key words: expeller-extracted canola meal, processing conditions, apparent metabolizable energy, broiler chicken 2014 Poultry Science 93:2227–2236 http://dx.doi.org/10.3382/ps.2013-03790

INTRODUCTION Rapeseed production, including canola varieties, ranks second among oilseed crops worldwide (USDA, 2014). Canola seed production in Australia has grown from 1.9 to 3.6 million metric tons over the past 5 yr (Sebbery et al., 2013; USDA, 2014). Canola meal (CM), a by-product of the canola seed-crushing industry to extract oil, is widely used as an alternative protein source to soybean meal (SBM) in poultry diets because it has a good balance of essential amino acids (Canola Council of Canada, 2009). However, CM has

©2014 Poultry Science Association Inc. Received November 26, 2013. Accepted June 4, 2014. 1 Corresponding author: [email protected]

lower available energy content than SBM for poultry and the presence of some antinutritional factors may restrict its use to less than full replacement of SBM in poultry diets (Khajali and Slominski, 2012). The fiber components of CM have been shown to be inversely related to energy digestibility of the meal (Downey and Bell, 1990). The average ME content of solvent-extracted CM is 2,000 kcal/kg for poultry, which is lower by approximately 230 kcal/kg, than that of nondehulled SBM (NRC, 1994). The methods commonly used to obtain canola oil are prepress with further solvent extraction, resulting in a meal with less than 5% residual oil. Expeller extraction methods are also applied to obtain canola oil but are less efficient at oil removal, resulting in a meal with higher (8.0 to 15%) residual oil content (Spragg and Mailer, 2007). Expeller-extracted canola meal (ECM) is subjected to higher moisture (15 to 18%) and moderate

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ABSTRACT The objective of this study was to investigate the effect of processing conditions and chemical composition on ileal digestible energy (IDE), AME, and AMEn of 6 expeller-extracted canola meal (ECM) samples subjected to conditioning temperature at 90, 95, or 100°C and high or low screw torque over the second presses in a 3 × 2 factorial arrangement. The ECM samples were incorporated into a corn-soybean meal reference diet at 30% by replacing energy-yielding ingredients. A total of 210 one-day-old male broiler chicks (Ross 308) were fed common starter and grower diets until d 18, and then assigned to 7 experimental diets replicated 6 times, with 5 chicks per cage. After a 5-d diet acclimation period from d 18 to 22, excreta was collected for 72 h. The difference method was used to determine AME, which was corrected to zero N balance to obtain AMEn. Medium seed conditioning temperature resulted in the highest IDE, AME, and AMEn compared with low or high temperature, and high screw torque resulted in higher energy utili-

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MATERIALS AND METHODS

for all samples. The variables tested were conditioning temperature of the seeds before first press and torque applied to the second presses. Seeds were conditioned for 5 min at 90, 95, and 100°C and allowed to rest for an additional 2 min in a surge bin before first press. Two second presses were used and maintained under the same conditions for each test. Final samples were a composite of material from both second presses maintained at either high or low screw torque. The combination of 3 conditioning temperatures and 2 secondary press torque settings resulted in 6 ECM samples in a 3 × 2 factorial arrangement. The screw torque and ampere draw of the motors driving the second presses were reported as means of 12 records taken every 30 min for 6 h (Table 1). Once a change was made to conditioning temperature or press settings, the expeller ran for a minimum of 3 h before collecting any samples. A total of 50 kg of sample was collected every 30 min, and the 12 subsamples were mixed to form a 600-kg composite (processed under the same conditions) of each of the 6 ECM collected over a 6-h period. The 600-kg samples were placed into 1,000-kg bulk bags and delivered to our laboratory. Upon receipt of the ECM samples, 12 subsamples were obtained from spatially separated sections of each of the bulk bags using a sampling probe, and a triple-rifled representative composite sample for each ECM was used for the chemical analyses (conducted in triplicate). Meal subsamples were analyzed for DM, CP, total lysine, reactive lysine, crude fat, crude fiber, acid detergent fiber (ADF), neutral detergent fiber (NDF), NDIN, glucosinolates, and ash (Table 2) before formulating the experimental diets.

Birds and Housing

CM Sample Processing and Chemical Composition The expeller CM samples were processed and provided by the MSM Milling oilseed crushing plant located at Manildra in central west New South Wales, Australia. Six batches of expeller canola meal (ECM) were processed under various conditions. All CM samples were sourced from the same batch of seed to ensure that cultivar and agronomic conditions were constant

All experimental procedures were reviewed and approved by the University of New England Animal Ethics Committee. Two hundred ten 1-d-old Ross 308 male broiler chicks were obtained from a commercial hatchery. Chicks were reared and housed in battery brooders in a room with continuous fluorescent lighting. Room temperature was gradually decreased from 33°C at first week to 24°C during the third week. From d 1 to 10 and d 10 to 18, chicks had ad libitum access to conventional corn-SBM starter and grower diets (Table 3), respec-

Table 1. Processing conditions of expeller extracted canola meal (ECM) samples First press Item ECM ECM ECM ECM ECM ECM

1 2 3 4 5 6

Second A press

Second B press

Conditioning temperature (°C)

Torque1 (%)

Amp2

Torque (%)

Amp

Torque (%)

Amp

90 95 100 90 95 100

83.6 83.4 83.3 82.9 83.4 82.5

578.5 577.0 576.8 577.2 578.3 576.3

82.1 82.6 80.9 73.3 72.5 73.5

337.6 338.2 338.3 305.3 305.1 304.7

82.8 83.2 82.7 73.3 73.4 73.1

329.8 331.3 329.5 297.6 295.5 298.5

1Torque = the force applied to rotate an object expressed in Newton-meters. The values here are given as a percentage of the maximum achievable in pressing barrel. 2Amp = ampere, the electric current going into the motor driving the pressing barrel.

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temperatures of 95 to 115°C during the oil extraction process, whereas solvent-extracted meal is subjected to lower moisture (less than 12%) but higher temperatures up to 160°C (Canola Council of Canada, 2009). In both processes, seeds are typically dry heat conditioned for several minutes to aid in removal of oil during the first press. Higher processing temperature has been reported to affect the nutritive value of feedstuffs (AndersonHafermann et al., 1993). The major processing issues of relevance for the oilseed crushing industry are the effects of temperature applied via steam and pressure within both the expeller and desolventizing operations (Spragg and Mailer, 2007). Woyengo et al. (2010) reported higher AME and AMEn values for ECM compared with solvent-extracted CM for broiler chickens. However, to our knowledge, the possible variation of AME within different ECM samples and the effect of chemical composition and processing conditions on AME values of ECM in broiler chickens have not been investigated. The hypothesis tested in the current research was that the ileal digestible energy (IDE), AME, and AMEn of ECM vary among samples differing in chemical composition and subjected to various processing conditions during oil extraction. Thus this study was designed to determine and compare the effect of processing conditions such as temperature and screw torque during oil extraction on chemical composition and AME content of ECM for broiler chickens. The relationship between quality parameters [fiber composition, neutral detergent insoluble nitrogen (NDIN), reactive lysine, glucosinolate] and AMEn content of ECM was also investigated.

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METABOLIZABLE ENERGY OF EXPELLER CANOLA MEAL Table 2. Analyzed chemical composition (on a DM basis) of expeller-extracted canola meal samples Seed conditioning temperature (°C) 90 Composition1

100

90

High screw torque 97.1 2.08 1.90 39.38 8.84 6.34 10.13 16.30 22.10 5.8 0.78 7.64 5,084

97.2 2.03 1.88 39.65 8.16 6.3 10.69 16.74 21.86 5.12 0.86 7.36 5,106

95

100

Low screw torque 97.7 2.08 1.91 40.78 8.10 6.15 10.46 17.29 24.10 6.81 1.15 6.32 5,081

97.8 1.79 1.62 35.53 8.10 6.79 11.93 19.77 26.48 6.71 1.21 6.88 5,069

97.7 2.06 1.88 39.63 8.32 6.47 10.51 17.66 21.81 4.15 0.91 8.1 5,062

98.1 2.05 1.86 39.27 8.27 6.35 10.92 17.44 24.67 7.23 1.14 7.63 5,085

1ADF

= acid detergent fiber; NDF = neutral detergent fiber; NDIN = neutral detergent insoluble nitrogen; GE = gross energy. assay: fluoro dinitrobenzene reaction with epsilon amino group of lysine. 3Hemicellulose was calculated as the difference between NDF and ADF. 2Carpenter

tively, to meet the nutrient specification of the strain as recommended by Ross 308 manual (Aviagen, 2012).

AME Assay Experimental Diets and Procedures Seven experimental diets were fed in this study. Dietary treatments consisted of a common corn-SBM reference diet, formulated to meet or exceed the nutrient requirements of broiler chicks as described in the Ross 308 manual (Aviagen, 2012), and 6 test diets, each containing 30% of each expeller CM sample at the expense of corn, SBM, and oil (70% reference diet + 30% CM; Table 3). The ECM samples for feed formulation were obtained by compositing 6 grab samples taken from different locations in half-full respective bulk bags and repeating 5 times after tumbling the bags with a fork lift. Titanium dioxide was added as an indigestible marker at 0.3% of diet. At 18 d of age, chicks were weighed and randomly allocated to battery cages (80 × 45 × 50 cm) with 5 birds per cage and 6 replicate cages per dietary treatments. Birds were fed each of 7 experimental diets (reference diet + 6 CM test diets) for 5 d as an adaptation period followed by a 72-h energy balance assay from 22 to 25 d of age. All the diets were cold-pelleted at 65 ± 2°C and pelleting conditions were monitored and maintained at a constant ampere draw of the load meter for the mill motor to ensure consistency of pelleting conditions for each diet. Fresh water and feed were available to all chicks for ad libitum intake over the adaptation and collection period. During the 72-h collection period, feed consumption and excreta weights were recorded daily and used to calculate energy and nitrogen intake and excretion. Multiple subsamples were collected and homogenized from the total amount of excreta at the end of the collection period, and then a 250-g representative sample was placed in a plastic container for further analysis.

At 25 d of age, all birds within cages were euthanized by CO2 asphyxiation. The contents of the ileum (portion of the small intestine from Meckel’s diverticulum to approximately 1 cm proximal to the ileo-cecal junction) were gently removed and pooled per replicate cages, then frozen and stored at −20°C until processed. Representative samples of excreta and digesta were freeze-dried and finely ground with an electric grinder equipped with a 4-mm screen to ensure a homogeneous mixture.

Chemical Analyses The diets, excreta, digesta, and ECM samples were analyzed for DM by placing duplicate samples in a drying oven at 105°C for 24 h (method 930.15; AOAC, 1990). Gross energy content of feed, excreta, digesta and ECM samples were determined on a 0.5-g sample using an adiabatic bomb calorimeter (IKA Werke, C7000, GMBH and Co., Staufen, Germany) with benzoic acid as standard. Nitrogen content of feed, excreta, digesta, and ECM samples were determined on a 0.25-g sample with a combustion analyzer (Leco model FP2000 N analyzer, Leco Corp., St. Joseph, MI) using EDTA as a calibration standard, with CP being calculated by multiplying percentage N by a correction factor (6.25). Titanium dioxide concentrations were determined in triplicate and duplicate for diets and digesta samples, respectively, by colorimetric method (Short et al., 1996). Proximate analyses were conducted using AOAC methods (methods 920.39 for crude fat, 982.30 E for total lysine, 975.44 for reactive lysine, 978.10 for crude fiber, 973.18 for NDF and ADF, and 942.05 for ash; AOAC International, 2006). The NDIN was determined by measuring N content of the insoluble fraction obtained from the NDF assay. Assays on ECM samples were conducted in triplicate at the University

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DM Total lysine Reactive lysine2 CP Crude fat Ash Crude fiber ADF NDF Hemicellulose3 NDIN Glucosinolate (µmol/g) GE (kcal/kg of DM)

95

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Table 3. Ingredient and nutrient composition of the starter, grower, and experimental diets for the AME assay (as-is basis) Item

ECM1 diet 1

ECM diet 2

ECM diet 3

ECM diet 4

ECM diet 5

ECM diet 6

Starter diet (1–10 d)

Grower diet (10–18 d)

60 31.47 — 4.05 1.54 1.50 0.20 0.14 0.30 0.075 0.05 0.057 0.250 0.226 0.146 100   88.78 19.57 3,120 1.00 0.40 0.84 0.60 1.10 0.73 1.15 0.21

41.14 21.61 30.00 2.77 1.54 1.50 0.20 0.14 0.30 0.075 0.05 0.057 0.250 0.226 0.146 100   91.23 25.76 — 1.10 0.41 1.11 0.72 1.23 0.91 1.32 0.24   26.00 8.74 6.40 4.20 1.20 0.85 0.13

41.14 21.61 30.00 2.77 1.54 1.50 0.20 0.14 0.30 0.075 0.05 0.057 0.250 0.226 0.146 100   91.23 26.00 — 1.10 0.41 1.11 0.72 1.23 0.91 1.32 0.24   26.28 8.65 6.40 4.00 1.21 0.82 0.12

41.14 21.61 30.00 2.77 1.54 1.50 0.20 0.14 0.30 0.075 0.05 0.057 0.250 0.226 0.146 100   91.34 26.18 — 1.10 0.41 1.11 0.72 1.23 0.91 1.32 0.24   26.22 8.63 6.30 3.91 1.22 0.84 0.13

41.14 21.61 30.00 2.77 1.54 1.50 0.20 0.14 0.30 0.075 0.05 0.057 0.250 0.226 0.146 100   91.35 24.68 — 1.10 0.41 1.11 0.72 1.23 0.91 1.32 0.24   25.02 8.82 6.56 4.39 1.22 0.84 0.14

41.14 21.61 30.00 2.77 1.54 1.50 0.20 0.14 0.30 0.075 0.05 0.057 0.250 0.226 0.146 100   91.34 25.82 — 1.10 0.41 1.11 0.72 1.23 0.91 1.32 0.24   26.06 8.68 6.58 4.19 1.21 0.84 0.14

41.14 21.61 30.00 2.77 1.54 1.50 0.20 0.14 0.30 0.075 0.05 0.057 0.250 0.226 0.146 100   91.43 25.68 — 1.10 0.41 1.11 0.72 1.23 0.91 1.32 0.24   26.21 8.58 6.37 4.17 1.23 0.83 0.12

54.96 37.21 — 3.25 1.29 1.87 0.19 0.18 — 0.075 0.05 0.078 0.292 0.381 0.177 100   89.12 22.00 3,025 1.00 0.48 0.94 0.48 1.27 0.83 1.39 0.22   — — — — — — —

57.81 34.23 — 4.41 1.07 1.36 0.22 0.19 — 0.075 0.05 0.065 0.133 0.295 0.099 100   88.54 20.8 3,140 0.90 0.39 0.84 0.44 1.10 0.73 1.14 0.21   — — — — — — —

20.28 11.13 5.21 2.04 1.07 0.72 0.14

1ECM

= expeller-extracted canola meal. phosphate contained: phosphorus, 18%; calcium, 21%. 3Trace mineral concentrate supplied per kilogram of diet: Cu (sulfate), 16 mg; Fe (sulfate), 40 mg; I (iodide), 1.25 mg; Se (selenate), 0.3 mg; Mn (sulfate and oxide), 120 mg; Zn (sulfate and oxide), 100 mg; cereal-based carrier, 128 mg; mineral oil, 3.75 mg. 4Vitamin concentrate supplied per kilogram of diet: retinol, 12,000 IU; cholecalciferol, 5,000 IU; tocopheryl acetate, 75 mg, menadione, 3 mg; thiamine, 3 mg; riboflavin, 8 mg; niacin, 55 mg; pantothenate, 13 mg; pyridoxine, 5 mg; folate, 2 mg; cyanocobalamin, 16 μg; biotin, 200 μg; cereal-based carrier, 149 mg; mineral oil, 2.5 mg. 5Dig = digestible. 2Dicalcium

of Missouri Experiment Station Chemical Laboratories. Hemicellulose was calculated as the difference between NDF and ADF. The glucosinolate content of the meal was determined by colorimetric analyses, using a spectrophotometer according to the method described by Thies (1982) with the use of tetrachloropalladate as the highly specific reagent for glucosinolates.

Calculations The AME and AMEn of the reference and test diets were determined using the following equations:

AME (kcal/kg) = (GEI – GEE)/FI, and

[1]

AMEn (kcal/kg) = AME – [8.22 × (NI – NE)/FI]. [2]

Accordingly, the AMEn of the ECM samples was calculated as ECM AMEn (kcal/kg of DM) = basal AMEn – [(basal AMEn – test diet AMEn)/percentage

of inclusion rate],

[3]

where GEI is the gross energy intake and GEE is the gross energy output of excreta (kcal/kg of DM); 8.22 is nitrogen correction factor reported from previous research (Hill and Anderson, 1958); NI is nitrogen intake from the diet and NE is the nitrogen output from the excreta (kg); FI is the feed intake (kg). Ileal digestible energy of the reference and test diets was calculated using the following equations:

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Ingredient (%)   Corn (8.1% CP)   Soybean meal (45.2% CP)   Canola meal   Canola oil  Limestone   Dicalcium phosphate2   Sodium chloride   Na bicarbonate  TiO2   Mineral premix3   Vitamin premix4   Choline Cl 70%   l-Lysine HCl 78.4   dl-Methionine   l-Threonine  Total Calculated composition   DM (%)   CP (%)  AMEn (kcal/kg)   Ca (%)   Available phosphorus (%)  Dig5 methionine + cysteine (%)   Dig methionine (%)   Dig lysine (%)   Dig threonine (%)   Dig arginine (%)   Dig tryptophan (%) Determined composition (%)  CP  Moisture   Crude fat   Crude fiber  Calcium  Phosphorus  Sodium

Reference diet

METABOLIZABLE ENERGY OF EXPELLER CANOLA MEAL

IE = GE in digesta × TiO2 in diet/TiO2

in digesta, and

[4]

IDEC = [(diet gross energy – IE) × 100]/

diet gross energy,

[5]

where IE is ileal digesta gross energy content (kcal/kg of DM) and IDEC is ileal digestibility of energy coefficient. Equation [3] was used to calculate IDE of the ECM samples.

Statistical Analyses

RESULTS AND DISCUSSION The chemical composition of ECM samples is shown in Table 2. The samples were low in moisture content (1.85 to 2.9%) compared with an average of 6 to 8% reported for CM (Spragg and Mailer, 2007). The crude fat content of samples was consistent among the 6 samples, with an average of 8.3% (CV = 3.4%), implying that variation in processing temperature and screw torque did not have a substantial effect on oil extraction efficiency. The glucosinolate concentrations of the samples were low, with an average of 7.3 µmol/g of meal; this is substantially lower than the levels previously reported (23.2 µmol/g) for ECM (Seneviratne et al., 2010). The gross energy content ranged from 5,062 to 5,106 kcal/kg (DM basis) and the variation was considered small (CV% = 0.29). The fiber composition varied considerably among samples with CV% of 7.4, 17.9, and 6.3 for NDF, hemicellulose, and ADF, respectively. The ECM1 (low temperature, high screw torque) appeared to be of highest quality based on chemical analysis, with the highest reactive lysine (1.92%) and lowest NDIN (0.78%). The ECM4 (low temperature, low screw torque) had the highest NDIN and NDF, and lowest CP, total lysine, and reactive lysine (1.21, 26.48, 35.5, 1.79, and 1.62%, respectively). The overall

chemical composition of the samples ranged within the standard values reported for Australian CM (Sebbery et al., 2013) and was within the same range previously reported for ECM (Woyengo et al., 2010). No mortality occurred during the feeding period from 18 to 25 d of age. The BWG, daily feed intake, and FCR of the birds were not affected by differences in CM samples, and no interactions (P > 0.05) of temperature and screw torque were detected (Table 4). Birds fed CM diets consumed less feed (P < 0.001) and exhibited a lower FCR (P < 0.05) compared with birds fed the reference diet. Feeding a diet high in glucosinolate to broiler chicks has been reported to result in reduced feed intake and growth rate, and increased mortality (McNeill et al., 2004). However, glucosinolate levels of the ECM test diets in the current study should not have exceeded 4 μmol/g of diet, which has been reported as within the tolerance level for broiler chicks (Mawson et al., 1994). Possibly, the high inclusion of ECM may have reduced diet palatability and consequently resulted in depressed feed intake. The different energy, nutrient contents, or both, of canola diets versus the reference diet may also to some extent account for lower feed intake of birds that were fed the canola diets. The reduced feed intake did not compromise growth rate of birds on test diets, probably because the feeding period was not long enough (8 d) to detect a difference. A lower ME content is referred to as one of the factors restricting high inclusion rate of CM in broiler diets. Theoretically, higher energy values are considered for expeller-extracted CM compared with solventextracted CM because the former is known to have a higher residual oil content; however, the impact of other chemical composition on energy value of ECM and CM is usually overlooked. The values of IDE, AME, and AMEn, and gross energy retention of ECM samples fed to broiler chicks are presented in Table 5. A conditioning temperature by screw torque interaction was detected for all the energy utilization values of ECM samples obtained at d 25 of age (P < 0.001). Meal samples subjected to medium conditioning temperature (95°C) and low screw torque during oil extraction had the highest energy utilization values. The values of IDE among all ECM samples ranged from 2,137 for ECM4 (low temperature, low screw torque) to 2,705 kcal/ kg of DM for ECM5 (medium temperature, low screw torque). Consequently, ECM4 and 5 had the lowest and highest AME and AMEn values (2,098 to 2,655 and 1,977 to 2,482 kcal/kg of DM, respectively). In fact, IDE represents energy available to birds from a feed ingredient before microbial fermentation of energy substrates in the ceca and the relatively short colon (Adeola and Zhai, 2012). The IDE accounts for the energy digested and absorbed in the gastrointestinal tract only up to the ileum and the energy-containing compounds of endogenous origin and urinary duct secreted postileum are not taken into consideration; thus, the IDE value of an ingredient is usually estimated to be greater than its AME value. The IDE values obtained for ECM

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Performance data (derived from pen means), IDE, AME, and AMEn values were analyzed as a 3 × 2 factorial arrangement using the PROC GLM procedure of SAS 9.3 package (SAS Institute Inc., 2010) to assess the main effects (conditioning temperature and screw torque) and 2-way interactions. Tukey’s mean separation test was used to make pairwise comparisons between treatment means (P < 0.05). Stepwise regression was used to determine the effect of the nutrient composition of the ECM samples on AMEn. The R2, SE of the regression estimate, and the Mallows (1973) statistic C(p) were used to define the best-fit equation. Pearson correlation coefficients and associated significance were generated using PROC GLM of SAS to determine the relationship between conditioning temperature and the analyzed chemical composition (AME, AMEn, and IDE) of the meals, and also to assist in interpreting the stepwise regression results.

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values within a row with no common letters are significantly different (Tukey test; P < 0.05). are means of 6 replicate cages with 5 broilers per cage. 2ECM = expeller-extracted canola meal. 3Temp = conditioning temperature of canola seed before oil extraction; screw = screw torque over the second run of press during oil extraction; R-diet = reference diet; T-diet = canola meal test diet. 4FI = feed intake. 5FCR = feed conversion ratio. 1Data

a,bMean

0.999 0.984 0.958 <0.001 0.049 — 0.614 0.806 0.968 0.649 — 0.928 0.984 0.699 0.424 — 0.921 0.861 0.780 0.948 678 1,321 92.3 128.9a 1.39a 677 1,310 90.3 115.6b 1.28b 676 1,308 90.1 115.6b 1.30b 677 1,312 90.6 118.2b 1.30b 676 1,308 90.4 118.2b 1.31b 677 1,317 91.3 118.5b 1.31b 678 1,317 91.5 119.4b 1.33b Initial BW (g) Final BW (g) BW gain (g/bird per d) FI4 (g/bird per d) FCR5 (g/g)

100°C 95°C 90°C Item

High screw torque

5.7 18.37 1.9 3.6 0.022

Screw Temp R-diet 100°C 95°C 90°C

Low screw torque ECM2 diet

Table 4. Effect of dietary treatments on performance of broilers from 18 to 25 d of age1

samples were all higher than AME values, with the highest difference being 5% for ECM1 and the lowest difference 1.8% for ECM5. The low hemicellulose content of ECM5 could to some extent account for the minimal discrepancy between IDE and corresponding AME value (50 kcal/kg) because hemicellulose could partially be digested by the hydrochloric acid secreted in the proventriculus and accordingly contribute to the energy availability for the birds (Leeson and Summers, 2001). However, despite the high hemicellulose content of ECM4 (6.71%) compared with the other samples, particularly ECM5 (3.75%), its IDE value was only 2.2% higher than the corresponding AME value. This most likely is due to the higher fiber concentration in this sample, which should have accelerated digesta transit time and limited the capacity of the gut microbiota to use complex carbohydrates, which could translate to higher excreta energy output. Adeola and Ileleji (2009) also estimated 589 kcal/kg higher AME in corn distillers grains with solubles, which had 50 and 45% lower concentrations of NDF and ADF, respectively, than corn distillers grains without solubles. When nitrogen is retained in the body, it yields energy-containing compounds with metabolites that are voided in the urine; therefore, nitrogen correction partially adjusts for the effect of differences in protein retention across birds in any assay to reduce the variability in estimates of AME (Leeson et al., 1977; Lopez and Leeson, 2007). When AME was corrected for nitrogen retention, the values decreased approximately 7% from the corresponding AME values (Table 5). It seems that because the test diets were in excess of nitrogen (approximately 25% CP) and the bird’s need for protein was met, catabolism of body protein was reduced, resulting in a positive nitrogen balance. Reductions in the range of 4 to 10% have been reported in several studies with broilers and ducks (Hong et al., 2002; Adeola et al., 2007; Adeola and Ileleji, 2009). The average AMEn content of ECM samples (2,260 kcal/kg of DM) evaluated in this study is higher than the average value of 2,000 kcal/kg reported for solvent-extracted canola meal in broiler chickens (Mandal et al., 2005). It has been documented that ECM not only is higher in oil content compared with solvent-extracted CM, but also residual oil in meal from expeller plants is more variable than meal from solvent plants (Spragg and Mailer, 2007). We are not aware of published data on the AME variations of differently processed ECM for broilers. In agreement to current findings, Woyengo et al. (2010) reported an AME value of 3,039 kcal/kg for ECM in broiler chicks, the value being reduced to 2,694 kcal/ kg when corrected for nitrogen retention; however, the ECM sample used in their study had 23.8% NDF and 12% crude fat. Pearson correlations between energy utilization, conditioning temperature, and chemical components of ECM are presented in Table 6. Conditioning temperature had negative correlation with ash content of the samples (r = −0.65, P = 0.001), but CP was positively correlated

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SEM

P-value3

Temp × screw

R-diet vs. T-diet

Toghyani et al.

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METABOLIZABLE ENERGY OF EXPELLER CANOLA MEAL Table 5. Ileal digestible energy (IDE), AME, and AMEn of expeller canola meal samples fed to broiler chicks1 Item2

Screw High High High Low Low Low         High Low

IDE (kcal/kg)

AME (kcal/kg)

AMEn (kcal/kg)

GE retention (%)

2,700a 2,684a 2,329b 2,137c 2,705a 2,410b 48 2,418 2,694 2,369   2,571 2,417

2,571a 2,614a 2,250b 2,089c 2,655a 2,330b 46 2,330 2,634 2,290   2,478 2,358   <0.001 <0.001 <0.001

2,397a 2,413a 2,111b 1,976c 2,481a 2,172b 43 2,187 2,447 2,141   2,307 2,210   <0.001 <0.001 <0.001

50.6a 51.2a 44.3b 41.4c 52.4a 45.8b 0.94 46.1 51.8 45.1   48.8 46.5   <0.001 <0.001 <0.001

<0.001 <0.001 <0.001

a–cMean

values within a column with different superscripts are different (Tukey test; P < 0.05). are means of 6 replicate cages with 5 broilers per cage. 2Temperature = seed conditioning temperature; screw = screw torque applied over the second run of press to squeeze the oil out. 1Data

with temperature (r = 0.63, P = 0.001). No strong correlation between conditioning temperature and crude fiber content (r = −0.24, P = 0.152) and composition was detected. Contrary to current results, an increase of NDF and NDIN by increasing the heat in the desolventizer-toaster has been reported for CM (Mustafa et al., 2000). Seneviratne et al. (2011) also showed that processing conditions can affect chemical composition of cold-pressed canola cake. These authors reported that screw speed and heat interacted for ether extract content of pressed cake; so that increasing screw speed in nonheated cake increased the ether extract content. Furthermore, their findings indicated that crude fiber of cold-pressed canola cake was greater in nonheated than heated meal at slow screw speed. Processing temperature can modify cell-wall matrix, which may have different effects on dietary fiber. Increased temperature would result in a breakage of weak bonds between polysaccharide chains. Consequently, decreased association between fiber molecules, their depolymerization, or both, can lead to formation of alcohol-soluble fragments, resulting in a decreased content of dietary fiber (Björck et al., 1984). On the other hand, overheating during processing also causes the formation of Maillard reaction products, thus adding to the lignin content, which could be manifested in NDF and ADF fractions (Molero-Vilchez and Wedzicha, 1997). Apparently, the temperature applied to the current ECM samples was not high enough to linearly affect fiber composition. It is noteworthy that Australian canola seed is low in glucosinolates, and the application of heat to reduce these levels is not required during oil extraction and meal processing (Spragg and Mailer, 2007). Because the samples varied in chemical composition, there was no direct and significant correlation between conditioning temperature and energy utilization from ECM by

growing broiler chickens. However, several relationships were detected between the chemical constituents and energy utilization of the samples. Reactive lysine had a strong inverse correlation with crude fiber and ADF (r = −0.98, P = 0.001; r = −0.96, P = 0.001, respectively). Crude protein was also negatively correlated with crude fiber (r = −0.88, P = 0.001). Neutral detergent fiber exhibited the strongest negative correlation with AMEn (r = −0.93, P = 0.001), followed by NDIN and then hemicellulose (r = −0.87 and −0.79, respectively, P = 0.001). Residual glucosinolate was not affected by conditioning temperature but had a negative correlation with AMEn and hemicellulose (r = −0.70, P = 0.001; r = −0.62, P = 0.001, respectively). Similarly, Classen et al. (1991) found a 16% improvement in AME of CM with a very low level of glucosinolate compared with the commercial CM fed to broilers. Nevertheless, because fiber is poorly digested by poultry, its effect on AMEn is more considerable (Bell et al., 1991). The main reason for the lower AMEn of ECM samples high in NDF may be that dietary fiber accelerates digesta passage, which in turn may result in reduced time for digestion and thus reduced nutrient utilization (Khajali and Slominski, 2012). Glycoproteins, which represent the structural protein of the cell walls and Maillard reaction products, often referred to as NDIN, are also poorly digested by poultry. In the current study, NDIN was significantly correlated with NDF (r = 0.90, P = 0.001); in addition, IDE had the strongest negative correlation with NDIN (r = −0.92, P = 0.001). The lower AMEn value obtained for ECM4 (higher excreta energy output per bird) could be attributed to its high content of NDF and NDIN and also lower CP content, because AMEn value was correlated with CP as well (r = 0.57, P = 0.001). Interestingly, Baker et al. (2011) also reported a higher AMEn for a high CP SBM (54.9% CP

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Treatment   Temperature (°C)   90   95   100   90   95   100  SEM   90   95   100       Source of variation (P-value)  Temperature   Screw torque   Temperature × screw

Item

    1.00 — 0.99 0.001 0.92 0.001 −0.579 0.002 −0.93 0.001 −0.67 0.001 −0.78 0.001 −0.88 0.001 0.66 0.001 0.48 0.022 0.52 0.029 −0.35 0.033 −0.70 0.001

        1.00 — 0.91 0.001 −0.69 0.001 −0.93 0.001 −0.65 0.001 −0.79 0.001 −0.87 0.001 0.65 0.001 0.49 0.022 0.52 0.022 −0.33 0.042 −0.70 0.001

AMEn             1.00 — −0.75 0.001 −0.94 0.001 −0.75 0.001 −0.73 0.001 −0.92 0.001 0.73 0.001 0.56 0.074 0.57 0.013 −0.41 0.015 −0.68 0.001

IDE                 1.00 — 0.81 0.001 0.91 0.001 0.37 0.021 0.70 0.001 −0.98 0.001 −0.58 0.002 −0.88 0.001 0.81 0.001 −0.28 0.090

Crude fiber                     1.00 — 0.76 0.001 0.80 0.001 0.90 0.001 −0.76 0.001 −0.47 0.003 −0.66 0.001 0.49 0.001 −0.58 0.002

NDF                         1.00 — 0.21 0.199 0.72 0.001 −0.96 0.001 −0.56 0.001 −0.83 0.001 −0.84 0.119 −0.37 0.280

ADF                             1.00 — 0.70 0.001 −0.27 0.101 0.20 0.23 −0.23 0.174 −0.03 0.852 −0.62 0.001

Hemicellulose                                 1.00 — −0.67 0.001 −0.70 0.001 −0.40 0.014 0.29 0.077 −0.60 0.001

NDIN                                     1.00 — 0.60 0.001 0.89 0.001 −0.84 0.001 0.28 0.288

Reactive Lys CP

                                            1.00 — −0.94 0.001 0.08 0.631

Crude fat                                         1.00 — 0.18 0.291 −0.14 0.402 0.52 0.011

= temperature; IDE = ileal digestible energy; NDF = neutral detergent fiber; ADF = acid detergent fiber; NDIN = neutral detergent insoluble nitrogen.

1.00 — −0.08 0.622 −0.09 0.575 −0.08 0.612 −0.24 0.152 0.02 0.901 −0.24 0.143 0.26 0.122 0.37 0.025 0.28 0.089 −0.45 0.115 0.63 0.001 −0.65 0.001 −0.20 0.238

Temp P-value AME P-value AMEn P-value IDE P-value Crude fiber P-value NDF P-value ADF P-value Hemicellulose P-value NDIN P-value Reactive Lys P-value Crude fat P-value CP P-value Ash P-value Glucosinolate P-value

AME

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1Temp

Temp

Item

                                                1.00 — 0.13 0.424

Ash

Table 6. Pearson correlation coefficients between conditioning temperature, chemical components, and energy utilization of expeller-extracted canola meal samples1

                                                    1.00 —

Glucosinolate

2234 Toghyani et al.

2235

METABOLIZABLE ENERGY OF EXPELLER CANOLA MEAL

Table 7. Stepwise regression equations for AMEn of expeller-extracted canola meal with an approximate 8.3% crude fat content in growing broiler chickens Regression coefficient parameter1

Statistical parameter2

AMEn equation

Intercept

NDF

Ash

ADF

SE

R2

C(p)

Equation 1  SE  Estimated P-value Equation 2  SE  Estimated P-value Equation 3  SE  Estimated P-value

4,606.4 151.2 <0.001 3,763.5 343.9 <0.001 3,397.8 446.9 <0.001

−100.1 6.43 <0.001 −109.2 6.82 <0.001 −100. 1 9.93 <0.001

      165.2 61.6 0.011 279.5 109.1 0.015

            −33.8 26.2 0.002

69.1 — — 63.4 — — 61.9 — —

0.87 — — 0.90 — — 0.91 — —

13.95 — — 7.74 — — 3.21 — —

1NDF

= neutral detergent fiber; ADF = acid detergent fiber. is the coefficient of determination; SE is the SE of the regression estimate, defined as the root of the mean square error; and C(p) is the Mallows statistic value. 2R2

samples based on the meal chemical composition. In addition, processing conditions of ECM may affect digestibility of energy, likely because of altering the chemical constituents of the meal; therefore, nutritionists should be cautious of the source of data for AME values of ECM when formulating diets to reduce feed costs and also improve performance. Considering the high correlation with energy digestibility, concentrations of NDF and NDIN may be used as simple laboratory tests to predict AMEn value of ECM.

ACKNOWLEDGMENTS Financial assistance for the current study was provided by the Rural Industries Research and Development Corporation (RIRDC, Australia). We are also thankful to MSM Milling Pty Ltd. (New South Wales, Australia) oilseed crushing plant for their kind cooperation in providing the meal samples (New South Wales, Australia).

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DM) compared with a control SBM. These authors suggested that increased AMEn of the high CP SBM may have occurred due to excess AA being metabolized for energy utilization. Generally, it is accepted that fiber content and composition and crude fat may have the greatest effect on AMEn content of CM. However, despite the high negative correlation between fiber and AMEn, crude fat was not significantly correlated with AMEn values (r = 0.49, P = 0.022) herein, probably because the fat content was rather consistent among the ECM samples. Indeed, more than one chemical component in a feed ingredient and the interactions between the components may influence AMEn values. Therefore, a stepwise regression analysis was conducted to predict the AMEn value of ECM based on its chemical composition (Table 7). As previously discussed, NDF had the strongest correlation with AMEn, so it was the first variable included in the multiple regression model, resulting in AMEn equation [1] with an R2 of 0.87. The equation was improved with the stepwise addition of ash and ADF; consequently, the best-fit equation was determined to be equation [3]: AMEn (kcal/kg of DM) = 3,397.8 + (−100.1 × NDF %) + (279.5 × ash %) + (−33.8 × ADF %) [R2 = 0.91, SE = 61.9, C(p) = 3.21, P = 0.001]. This predictive equation could be used to make a subtle AMEn estimation of ECM with an approximate crude fat of 8.3%. However, because fats and oil have a great energy value and are highly digestible for growing broiler chicks, any increase or decrease in the fat content should be taken into account when estimating the AMEn value of any prospective ECM. Furthermore, it is worth noting that the correlations conducted in this experiment would be strengthened with more samples incorporated in analyses. Therefore, inclusion of data from more samples from different seed sources and varying processing conditions will enhance the robustness of the correlations and the equations derived. In conclusion, the current results show that AME value of ECM can vary significantly between different

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