Diet nutrient digestibility and growth performance of weaned pigs fed Brassica napus canola meal varying in nutritive quality

Animal Feed Science and Technology 223 (2017) 90–98

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Diet nutrient digestibility and growth performance of weaned pigs fed Brassica napus canola meal varying in nutritive quality L.F. Wang a , E. Beltranena a,b , R.T. Zijlstra a,∗ a b

Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada Alberta Agriculture and Forestry, Edmonton, Alberta T6H 5T6, Canada

a r t i c l e

i n f o

Article history: Received 28 August 2016 Received in revised form 14 November 2016 Accepted 19 November 2016 Keywords: Canola meal Digestibility Growth Performance Pig Variability

a b s t r a c t Canola meal (CM) is the second most fed protein source in swine production worldwide. However, nutritive quality of CM varies and may affect growth performance of pigs. To explore, 240 pigs (initial body weight: 9.6 ± 0.7 kg) were weaned at 19 ± 1 days of age and fed diets containing 200 g/kg soybean meal (SBM) or 4 Brassica napus CM samples (CM1, CM2, CM3 and CM4 selected from 4 solvent extraction plants in 3 western Canadian provinces) starting 2 weeks post-weaning for 4 weeks (day 1–28). In the 4 CM samples, crude protein (CP) ranged from 362 to 419 g/kg, acid detergent fibre from 158 to 195 g/kg and total glucosinolates from 1.13 to 7.38 ␮mol/g. Diets were formulated to provide 9.6 MJ net energy (NE)/kg and 1.2 g standardised ileal digestible (SID) lysine (Lys)/MJ NE and were steam-pelleted. Comparing CM with SBM, dietary inclusion of CM decreased (P < 0.001) diet CATTD of dry matter (DM) by 0.037, of gross energy (GE) by 0.036 and of CP by 0.040, whereas digestible energy (DE) value of CM diets was maintained and predicted NE value of CM diets was increased (P = 0.027) by 0.078 MJ/kg. Among the 4 CM diets, the CATTD of DM, GE and CP did not differ, but DE and predicted NE value differed (P < 0.01). Average daily feed intake (ADFI) and average daily gain (ADG) of pigs did not differ between CM diets and the SBM diet for each week and for the entire trial (day 1–28), but gain:feed was greater (P < 0.05) for the CM diets than the SBM diet for day 1–7 and for the entire trial. Among the 4 CM diets, ADFI and ADG differed (P < 0.05) for the entire trial. In conclusion, inclusion of 200 g CM/kg to replace SBM did not affect ADFI and ADG in weaned pigs. However, growth performance differed among CM sources indicating that quality differences among CM samples affect growth performance of pigs. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Globally, canola meal (CM) including rapeseed meal is the most widely used alternative protein source to soybean meal (SBM) in swine production (Woyengo et al., 2014). Canola or double-zero rapeseed is grown in temperate climates, with

Abbreviations: AA, amino acids; ADF, acid detergent fibre; ADFI, average daily feed intake; ADG, average daily gain; BW, body weight; CATTD, apparent total tract digestibility coefficient; CM, canola meal; CP, crude protein; CV, coefficient of variation; DE, digestible energy; DM, dry matter; GF, gain feed; GE, gross energy; Lys, lysine; NDF, neutral detergent fibre; NE, net energy; SBM, soybean meal; SID, standardised ileal digestible. ∗ Corresponding author. E-mail address: [email protected] (R.T. Zijlstra). http://dx.doi.org/10.1016/j.anifeedsci.2016.11.011 0377-8401/© 2016 Elsevier B.V. All rights reserved.

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annually 17 million tonnes canola seed produced in Canada (Statistics Canada, 2016) and 20 million tonnes double-zero rapeseed produced in the EU (European Commission, Agriculture and Rural Development, 2016). In Canada, processing canola seed generates 4 million tonnes of CM annually (Canola Council of Canada, 2016). With advances in plant breeding, CM contains much less glucosinolates nowadays than rapeseed meal decades ago permitting greater dietary inclusion of CM in swine diets (Bell, 1993; Woyengo et al., 2016a). Previously, 200 g CM/kg replacing SBM in diets for weaned pigs did not affect growth performance (Landero et al., 2011). With increasing dietary inclusion of CM in swine diets, variation of nutritive quality of CM, e.g., glucosinolates content and protein quality can become a concern (Maison and Stein, 2014). Many factors can affect nutritive quality of CM (Bell, 1993). As such, digestibility of amino acids (AA) in CM varies considerably in growing and growing-finishing pigs (Fan et al., 1996; Trindade Neto et al., 2012). Differences in processing conditions among processing facilities may also cause variation in chemical and nutritive characteristics of CM (Adewole et al., 2016). Whether variation of CM quality translates into variation of digestibility of nutrients and growth performance of young pigs remains unknown. The hypothesis of present study was that pigs offered diets containing 200 g CM/kg from different canola crushing plants and formulated to equal net energy (NE) and standardised ileal digestible (SID) AA content would not reach different dietary nutrient digestibility and growth performance among CM sources and reach different dietary nutrient digestibility but not growth performance from pigs fed a SBM diet. The objective was to evaluate variability of apparent total tract digestibility coefficients (CATTD) of protein and energy and growth performance of weaned pigs fed CM from different sources to replace SBM. 2. Materials and methods 2.1. Experimental design and diets Animal use and procedures were reviewed by the University of Alberta Animal Care and Use Committee for Livestock and followed principles established by the Canadian Council on Animal Care (CCAC, 2009). The study was conducted at the Swine Research and Technology Centre, University of Alberta (Edmonton, AB, Canada). In total, 240 pigs were selected from 353 pigs (Duroc × Large White/Landrace F1 ; Hypor, Regina, SK, Canada) that were weaned in four groups at 19 ± 1 days of age, based on post-weaning average daily gain (ADG) and body weight (BW) on day 12 after weaning. Pigs were divided within gender into heavy or light BW into 4 subgroups. Pigs within each subgroup were then randomly placed into pens, with four pigs per pen. Pigs received creep-feeding prior to weaning. Immediately after weaning, pigs were fed sequentially commercial pre-starter [228 g crude protein (CP)/kg, 10.3 MJ NE/kg, 13.7 g SID Lys/kg] and starter (203 g CP/kg, 11.0 MJ NE/kg, 12.4 SID Lys/kg) diets (Hi-Pro Feeds, Sherwood Park, AB, Canada) for 2 and 12 days, respectively. Wheat, SBM, oat groats, lactose and highly digestible protein sources were included in these diets. A wheat-based control diet and four diets containing 200 g CM/kg were formulated by replacing SBM with 4 solventextracted CM samples individually sourced from 1 of 4 commercial canola crushers in Alberta, Saskatchewan and Manitoba, Canada (Table 1). These 4 CM samples were processed from regular dark-seeded Brassica napus canola seed. Diets were formulated without antimicrobials or growth promoters to provide 9.6 MJ NE/kg and 1.2 g SID Lys/MJ NE (Table 2). Other indispensable AA were formulated as an ideal ratio to Lys (NRC, 2012). Table NE values (Sauvant et al., 2004) and SID AA data (NRC, 2012) were used for all main ingredients. Acid-insoluble ash (Celite 281; World Minerals, Santa Barbara, CA, USA) was included at 8 g/kg in diets as an indigestible marker and index. Diets were mixed and steam-pelleted at 70 ◦ C (70 hp; California Pellet Mill, Crawfordsville, IN, USA). Pigs (initial BW: 9.58 ± 0.66 kg) were fed the experimental diets starting from 2 weeks after weaning for 4 weeks (day 1–28). The study was conducted as a randomised complete block design with in total 60 pens in three groups of 20 pens with an interval of two weeks between two consecutive groups. Pens (1.1 × 1.5 m) were equipped with a self-feeder with 4 feeding spaces, a nipple drinker, PVC partition and plastic slatted flooring. The rooms were ventilated using negative pressure, with room temperature maintained at 22 ± 1 ◦ C, and a 12-h light (0600–1800 h) and 12-h dark cycle. Pens were blocked by area within each nursery room and were randomly assigned to one of the five experimental diets. Per diet, 12 pen-replicates were achieved. Pigs had free access to feed and water. Individual pigs, feed added and remaining feed were weighed weekly to calculate average daily feed intake (ADFI), average daily gain (ADG) and feed efficiency as gain:feed (G:F) for each pen. Freshly-voided faeces were collected from 0800 to 1600 h by hand grab-sampling from pen floors and pooled by pen (>500 g/pen) on day 26–27. Faeces were frozen at −20 ◦ C. Upon completion of the growth trial, faeces were thawed, homogenised, sub-sampled and freeze-dried. 2.2. Chemical analyses and calculations The CM samples, diets and lyophilised faeces were ground through a 1-mm screen in a centrifugal mill (Retsch GmbH, Haan, Germany). The CM samples and diets were analysed for dry matter (DM; method 930.15), CP (N × 6.25; method 988.03), acid detergent fibre (ADF) inclusive of residual ash (method 973.18), ash (method 942.05) and crude fat (method 920.39A) as described by AOAC (2006), starch (assay kit STA-20; Sigma, St. Louis, MO, USA) and neutral detergent fibre (NDF) assayed without a heat stable amylase and expressed inclusive of residual ash (Holst, 1973). The CM samples were analysed for total dietary fibre (method 985.29), calcium (method 968.08), phosphorus (method 946.06), AA (method 982.30E) and

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Table 1 Ingredient composition (g/kg diet as fed) of experimental diets. Variable

Soybean meal

Canola meala

Ingredient Wheat (ground) Soybean meal (460 g CP/kg) Canola meal (370 g CP/kg) Menhaden fish meal (620 g CP/kg) Soy protein concentrate (560 g CP/kg)b Canola oil Limestone Celitec Salt Mono/di-calcium phosphate Vitamin premixd Mineral premixe l-Lysine HCl (780 g/kg) l-Threonine (990 g/kg) l-Tryptophan (990 g/kg) dl-Methionine (990 g/kg) Choline chloride (600 g/kg)

683.2 200 – 50 25 – 8.0 8.0 7.5 5.5 5 5 1.50 0.8 – 0.3 0.25

658.9 – 200 50 25 21.2 6.3 8.0 7.5 6.0 5 5 4.58 1.5 0.7 0.1 0.25

a

The 4 canola meal samples were sourced from 4 commercial canola crushers in Alberta, Saskatchewan and Manitoba, Canada. HP300 (Hamlet Protein Inc., Findlay, OH, USA). c Celite 281 (World Minerals Inc., Santa Barbara, CA, USA) used as acid insoluble ash. d Supplied per kilogram of diet: 7500 IU of vitamin A, 750 IU of vitamin D, 50 IU of vitamin E, 37.5 mg of niacin, 15 mg of pantothenic acid, 2.5 mg of folacin, 5 mg of riboflavin, 1.5 mg of pyridoxine, 2.5 mg of thiamine, 2000 mg of choline, 4 mg of vitamin K, 0.25 mg of biotin and 0.02 mg of vitamin B12 . e Supplied per kilogram of diet: 125 mg of Zn as ZnSO4 , 50 mg of Cu as CuSO4 , 75 mg of Fe as FeSO4 , 25 mg of Mn as MnSO4 , 0.5 mg of I as Ca(IO3 )2 and 0.3 mg of Se as Na2 SeO3 . b

Table 2 Analysed nutrient content (g/kg diet as fed) of experimental diets containing soybean meal or 1 of 4 canola meal (CM) samplesa . Item

Soybean meal

CM1

CM2

CM3

CM4

Moisture Starch Crude protein Crude fat Ash Neutral detergent fibre Acid detergent fibre Gross energy (MJ/kg)

114 370 250 27 64 99 37 16.24

110 345 224 47 59 124 60 16.92

108 350 219 45 58 128 62 16.91

108 338 231 43 59 133 63 16.98

110 360 231 56 59 121 56 16.86

a The 4 canola meal samples were sourced from 4 canola crushers in Alberta, Saskatchewan and Manitoba, Canada. Diets were formulated to provide (as fed): 9.6 MJ net energy (NE)/kg and 1.2 g SID lysine/MJ NE, 3.8 g standardised ileal digestible (SID) methionine/kg, 7.3 g SID threonine/kg and 2.7 g SID tryptophan/kg.

chemically-available Lys (method 975.44) as described by AOAC (2006). Glucosinolates content in CM was determined by gas liquid chromatography (Daun and McGregor, 1981). Faeces were analysed for DM (method 930.15; AOAC, 2006) and CP (N × 6.25; method 988.03; AOAC, 2006). Diets and faeces were analysed for acid-insoluble ash (Vogtmann et al., 1975 modified by Newkirk et al., 2003) and gross energy (GE) using an adiabatic bomb calorimeter (model 5003; Ika-Werke, Staufen, Germany). Based on results of chemical analyses, the CATTD of DM, CP and GE and digestible energy (DE) values of diets were calculated using the acid-insoluble ash concentration of faeces relative to feed using the index method (Adeola, 2001). Diet NE values were calculated using Eq. (5) in Noblet et al. (1994) with the determined diet DE value and analysed content of ADF, starch, CP and crude fat, as adopted by NRC (2012). Gain:feed was calculated based on ADG and ADFI for each period and the entire trial. 2.3. Statistical analyses Diet nutrient digestibility and growth performance data were analysed using the MIXED procedure of SAS (Version 9.2; SAS Inst. Inc., Cary, NC, USA) with pen as the experimental unit. Diet was the fixed effect and block was the random factor in the statistical model. Growth performance data were analysed as repeated measures using weekly pen data with the first-order ante-dependence variance-covariance structure based on the Bayesian information criterion (BIC) fit statistics and initial BW as a covariate if significant. Pearson correlations among or between concentrations of total or each component of glucosinolates in CM samples and weekly performance data of each pen were analysed using the CORR procedure of SAS. Single-degree of freedom contrasts were used to compare digestibility and performance of 4 CM diets combined with that of SBM diet for each week and the entire trial (Littell et al., 2006). To control Type I error, alpha at 0.05 was divided by number

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Table 3 Analysed nutrient content (g/kg, as fed) and glucosinolate content (␮mol/g, as fed) of 4 canola meal (CM) samples and soybean meal (SBM) included in experimental dietsa . Item

SBM

CM1

CM2

CM3

CM4

Moisture Crude protein Crude fat Starch Ash Calcium Phosphorus Neutral detergent fibre Acid detergent fibre Total dietary fibre Insoluble fibre Soluble fibre

95 460 34 19 64 5 7 71 36 68 64 4

88 373 35 2 67 7 11 247 193 200 181 19

88 362 38 7 69 7 11 276 195 229 201 28

82 383 36 2 73 7 12 237 187 194 175 19

94 419 31 2 69 7 12 225 158 188 168 19

Indispensable amino acids Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Total amino acidsb Chemically-available lysine

33 12 21 36 30 6 24 18 6 23 455 29

22 10 15 26 22 8 15 16 4 19 339 21

21 10 14 25 21 7 15 15 4 18 332 20

23 10 15 27 23 8 15 16 5 20 358 22

25 11 16 30 23 9 17 17 5 21 386 21

Glucosinolates, ␮mol/g 3-butenyl 4-pentenyl 2-OH-3-butenyl 2-OH-4-pentenyl CH3 -thiobutenyl Phenylethyl CH3 -thiopentenyl 3-CH3 -indolyl 4-OH-3-CH3 -indolyl Total

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

1.04 0.09 2.43 – – 0.08 – 0.14 0.89 4.67

0.52 0.05 1.20 – – – – 0.07 0.26 2.10

1.50 0.16 3.49 0.09 0.05 0.10 0.05 0.25 1.69 7.38

0.31 0.05 0.68 – – – – – 0.09 1.13

a

The 4 canola meal samples were sourced from 4 canola crushers in Alberta, Saskatchewan and Manitoba, Canada. Dispensable amino acid content (g/kg, as fed) in SBM, CM1, CM2, CM3 and CM4 was 20, 16, 16, 17, 18 for alanine, 52, 25, 25, 27, 29 for aspartic acid, 7, 9, 8, 9, 10 for cysteine, 85, 65, 64, 69, 76 for glutamic acid, 19, 17, 18, 19, 21 for glycine, 24, 22, 22, 23, 26 for proline, 21, 14, 14, 15, 16 for serine, 17, 10, 9, 10, 11 for tyrosine, respectively. b

of multiple comparisons (Hoffman, 2015). For multiple comparisons among least squares means of 4 CM diets, alpha was set at 0.008; CM means were separated if P < 0.10. For contrast between 4 CM diets and control diet, P < 0.05 was considered significant whereas 0.05 ≤ P < 0.10 was considered a trend. 3. Results Pigs maintained good health and diarrhoea was not observed during the study. Dietary inclusion of 200 g CM/kg to replace SBM increased ADF content of diets by up to 26 g/kg (Table 2). The CM samples contained up to 161 g more total dietary fibre, 205 g more NDF, 159 g more ADF and 98 g less CP/kg than SBM (Table 3). Among the 4 CM samples, the coefficient of variation (CV) for moisture, CP, crude fat, ADF, NDF, total dietary fibre, calcium and phosphorous was 5.6, 6.4, 8.6, 9.4, 8.8, 9.0, 3.3 and 5.6%, respectively. The CV for indispensable AA ranged from 3.3 to 8.6% and was 4.1% for chemically-available Lys. Total glucosinolates content in the 4 CM samples ranged from 1.13 to 7.38 ␮mol/g (CV, 73%), with 2-OH-3-butenyl as the major glucosinolate followed by 3-butenyl or 4-OH-3-CH3 -indolyl. Comparing CM with SBM diet, dietary inclusion of CM decreased (P < 0.001; Table 4) diet CATTD of DM, GE and CP by 0.033, 0.034 and 0.038, respectively, whereas calculated NE value was increased (P = 0.027) by 0.08 MJ/kg. Among CM diets, the CATTD of DM, GE and CP did not differ, but CM3 had greater (P < 0.008) DE value than CM2 and CM4 had greater (P < 0.008) predicted NE value than CM2. For growth performance, ADFI did not differ between pigs fed CM diets and pigs fed the SBM diet for each week and for the entire trial (day 1–28). Pigs fed CM diets tended to have greater (P = 0.074; Table 5) ADG for day 1–7 and had greater (P < 0.05) G:F for day 1–7 and for the entire trial than pigs fed the SBM diet. Among the CM diets, CM2 diet had greater (P < 0.008) ADFI than CM1 diet for day 1–14 and for the entire trial and greater (P < 0.008) ADFI than CM3 for day 8–14. The

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Table 4 Apparent total tract digestibility coefficients (CATTD) of nutrients, digestible energy (DE) and net energy (NE) values of diets containing canola meal (CM) in substitution for soybean meal (SBM) fed to weaned pigsa . Variable

SEMb

Diet

CATTD Dry matter Gross energy Crude protein DE (MJ/kg as fed) NE (MJ/kg as fed)c

SBM

CM1

CM2

CM3

CM4

0.858 0.862 0.859 14.01 9.65

0.820 0.825 0.817 13.96xy 9.71xy

0.818 0.822 0.814 13.90y 9.68y

0.823 0.829 0.821 14.08x 9.72xy

0.825 0.829 0.821 13.97xy 9.80x

0.003 0.004 0.005 0.061 0.043

P-value SBM vs CM

CM

<0.001 <0.001 <0.001 0.528 0.027

0.129 0.175 0.418 0.040 0.053

x,y

Within a row, means of CM without a common superscript differ (P < 0.008). Least-squares means based on 12 pen observations of 4 pigs per diet. b SEM = standard error of the mean. c Diet NE values were calculated using Eq. (5) in Noblet et al. (1994). a

Table 5 Average daily feed intake (ADFI), average daily gain (ADG) and feed efficiency (gain:feed) of weaned pigs fed diets containing canola meal (CM) in substitution for soybean meal (SBM)a , b . Variable

SEMc

Diet SBM

CM1

CM2

CM3

CM4

ADFI, g/d Day 1–7 Day 8–14 Day 15–21 Day 22–28 Day 1–28

600 919 1234 1334 1022

580y 874y 1172 1268 973y

644x 958x 1223 1362 1047x

595xy 871y 1177 1339 996xy

601xy 922xy 1204 1349 1019xy

ADG, g/d Day 1–7 Day 8–14 Day 15–21 Day 22–28 Day 1–28

464 622 781 771 660

460y 627 760 754 650y

541x 642 777 783 686x

487xy 625 752 753 654xy

Feed efficiency Day 1–7 Day 8–14 Day 15–21 Day 22–28 Day 1–28

0.77 0.68 0.63 0.58 0.65

0.79 0.72 0.65 0.59 0.67

0.84 0.67 0.64 0.58 0.66

0.82 0.72 0.64 0.57 0.66

P-value SBM vs CM

CM

18 24 33 50 22

0.737 0.521 0.137 0.904 0.457

0.014 0.004 0.402 0.299 0.022

464xy 622 781 771 660xy

20 34 28 31 12

0.074 0.712 0.447 0.822 0.653

0.006 0.962 0.861 0.752 0.030

0.81 0.69 0.64 0.58 0.66

0.022 0.030 0.017 0.021 0.008

0.025 0.363 0.539 0.994 0.047

0.204 0.369 0.925 0.569 0.329

x,y

Within a row, means of CM without a common superscript differ (P < 0.008). Least-squares means based on 12 pen observations of 4 pigs per diet. b For ADFI, ADG and feed efficiency, a week effect was observed (P < 0.001), but an interaction between diet and week was not observed (P > 0.05). c SEM = standard error of the mean. a

CM2 diet had greater (P < 0.008) ADG than CM1 diet for day 1–7 and the entire trial. However, G:F did not differ among CM diets for each week and the entire trial. Final BW was 27.9, 27.8, 28.9, 28.0 and 28.3 kg for SBM, CM1, CM2, CM3 and CM4 diets, respectively, and did not differ between SBM and CM, and among CM diets. Among chemical characteristics, glucosinolates best predicted ADFI. Specifically, content of total glucosinolates (r = −0.38; P = 0.008), 4-OH-3-CH3 -indolyl (r = −0.37; P = 0.009), 3-CH3 -indolyl (r = −0.44; P = 0.007), 2-OH-3-butenyl (r = −0.38; P = 0.008), 4-pentenyl (r = −0.36; P = 0.011) and 3-butenyl (r = −0.38; P = 0.007) in CM samples was negatively correlated with ADFI for day 8–14, but did not correlate with ADG or G:F for any week. The ADFI in all weeks was not correlated to ADF (r = −0.02; P = 0.40), NDF (r = 0.05; P = 0.51), crude fat (r = 0.02; P = 0.80) and CP (r = 0.00; P = 0.98) in CM samples. For CM diets, ADFI was positively related to ADG for day 1–7 (r = 0.83, P < 0.001), day 8–14 (r = 0.62, P < 0.001), day 15–21 (r = 0.66, P < 0.001), day 22–28 (r = 0.61, P < 0.001) and negatively related to G:F for day 22–28 (r = −0.46, P = 0.001). 4. Discussion 4.1. Factors affecting nutritive value of CM Two decades ago, the recommended maximum inclusion rates of CM for starter, grower and finisher pig diets were 80, 120 and 150 g/kg, respectively (Edwards and Gill, 1991). Recently, solvent-extracted CM was included at up to 200 g/kg diet for weaner pigs without reducing growth performance (Landero et al., 2011). The present study confirmed that CM from

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various sources can replace 200 g SBM/kg in diets for weaned pigs without reducing growth performance, but that relevant quality differences among CM samples exist. Glucosinolates can affect palatability of diets, depress feed intake, increase liver weight and cause thyroid hypertrophy (Lee et al., 1984; Schöne et al., 1996; Mullan et al., 2000). In the present study, the greatest total glucosinolates content among the 4 dark-seeded Brassica napus CM samples was 7.38 ␮mol/g, close to the reported 8.5 ␮mol/g for Brassica napus CM recently (Sanjayan et al., 2014) and greater than the 4–5 ␮mol/g in CM (King et al., 2001; Landero et al., 2011). The large CV for total glucosinolates indicated that the total glucosinolates content varied substantially among CM samples in the present study. The greatest calculated total glucosinolates content of CM diets was 1.5 ␮mol/g in the present study, still lower than 2.4 ␮mol glucosinolates/kg diet that growing pigs can tolerate without adverse effects (Schöne et al., 1997). Variation in nutritive quality of CM is another concern. Nutritive quality of canola seed can be affected by cultivar (Grami and LaCroix, 1977), seeding date and rate (Taylor and Smith, 1992; Kirkland and Johnson, 2000), growing location (Hamama et al., 2003) and harvest maturity (Elias and Copeland, 2001). Among nutrients of 4 CM samples in the present study, fibre measured as ADF and NDF varied most, followed by crude fat and CP. The CV for CP, ADF, NDF and EE of CM samples was greater in the present study than the maximum 3.9% CV for CM samples from seven canola-crushing plants in Western Canada surveyed previously (Bell and Keith, 1991). Moreover, variation of AA content of CM samples was greater in the present study than the maximum 3.6% CV reported previously (Bell and Keith, 1991). Processing steps during oil extraction and overheating during drying may affect quality of protein and digestibility of AA of CM (Almeida et al., 2014). In present study, chemically-available Lys content was close to total Lys content of CM samples, indicating that few Maillard reactions occurred during desolventising and drying of CM. 4.2. Nutrient digestibility, DE and NE Both SBM and CM contained negligible starch. Thus, the major energy-yielding macro-nutrients in SBM and CM are protein, fibre and fat. Among the 3 energy-yielding nutrients, fibre content differed most between CM and SBM. Noticeably, CM samples contained 3 to 4 times more ADF, NDF and total dietary fibre compared with SBM. The difference should account for most of the lower CATTD of DM and GE in diets containing CM instead of SBM (Montoya and Leterme, 2010). The hull fraction of canola seed is difficult to digest for pigs (Bell and Shires, 1982; de Lange et al., 1998) because half of ADF in CM is indigestible lignin (Slominski et al., 2012; Messerschmidt et al., 2014). The CATTD of GE of CM was 0.617–0.716 for growing pigs (de Lange et al., 1998; Zhou et al., 2015), much lower than 0.85 for SBM (Sauvant et al., 2004). The CATTD of GE is expected to be lower for weaned pigs because younger pigs have less ability to digest fibre than growing pigs (Noblet and Shi, 1994). The CATTD of energy was reduced by 0.046 for increased dietary inclusion of 50 g CM/kg in diets for weaned pigs (Sanjayan et al., 2014). The small variation in content of fibre, CP and fat among the 4 CM sources matched similar CATTD of DM and GE among the 4 CM diets. Canola meal contained less CP and had lower CATTD of CP than SBM, indicating that CM supplied less digestible AA for weaned pigs, requiring greater inclusion of synthetic AA in CM diets to meet AA requirements. Hulls in CM may contain 150 g CP/kg, but are difficult to digest, resulting in reduced protein digestibility (Bell and Shires, 1982). Fibre in CM, though less fermentable than SBM (Woyengo et al., 2016b), may contribute to the output of microbial protein and reduce ATTD of CP (Wang et al., 2006; Miner-Williams et al., 2009). Reduced CATTD of GE and similar DE value of CM diets comparing with SBM diet indicated that CM had lower DE value than SBM for weaned pigs. Compared with SBM, CM contained less protein, but more fibre that is only partly fermented in gastrointestinal tract of pigs and was strongly and negatively correlated with DE value (Noblet and Le Goff, 2001; Woyengo et al., 2016b). In the present study, CM diets were balanced for NE by increasing inclusion of canola oil thereby increased GE value of CM diets. Thus, DE value of CM diets could be maintained despite reduced CATTD of GE of CM diets. The CM diets had greater calculated NE value than SBM diet, despite greater ADF content that is associated with a penalty in NE prediction (Noblet et al., 1994). This outcome contrasts the reduced NE value of diets with increasing dietary inclusion of up to 225 g CM/kg to replace SBM for growing pigs (Montoya and Leterme, 2010). The CM samples in the present study contained more fat than the reported 23 g/kg for double-zero rapeseed meal (Sauvant et al., 2004) and 15–19 g/kg for CM (Montoya and Leterme, 2010; Heo et al., 2014). The greater NE value of CM diets than the SBM diet might be due to greater canola oil inclusion to formulate to equal NE. Moreover, the NE value for CM might be underestimated. Recently, the NE value for yellow Brassica napus CM containing 21 g ether extract/kg, 64 g ADF/kg and 253 g NDF/kg was 7.9 MJ/kg determined using indirect calorimetry in growing pigs with an initial BW of 15 kg (Heo et al., 2014), greater than 6.3 MJ/kg for rapeseed meal (Sauvant et al., 2004) that we used for diet formulation. Thus, the NE value of CM might be underestimated. Among the 4 CM samples, CM4 contained the least ADF and had the greater predicted NE value, indicating together that the NE value is greater for CM with low ADF. 4.3. Growth performance A concern of feeding CM to pigs is maintaining feed intake. Anti-nutritional factors in CM, e.g., 2-propenyl glucosinolates and tannins, taste bitter and make pigs prefer diets containing SBM over diets containing CM diets (Baidoo et al., 1986; Fenwick et al., 1981; Landero et al., 2012). Glucosinolates extracted from CM rather than sinapine or tannins were associated with low feed intake in growing pigs (Lee et al., 1984). The ADFI reduced by 4 g/day for each added dietary 10 g CM/kg

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containing 10.5 ␮mol glucosinolates/g CM fed to weaned pigs (Baidoo et al., 1987b). In the present study, feed intake of pigs fed 200 g CM/kg diet was maintained, possibly due to the low total glucosinolates content in modern CM samples (1.13–7.38 ␮mol glucosinolates/g). Previously, inclusion of 200 g CM/kg diet (3.84 ␮mol glucosinolates/g CM) to replace SBM did not affect feed intake in weaned pigs (Landero et al., 2011). Among CM diets, pigs fed CM2 had greater ADFI for day 8–14 than CM1 and CM3, partly associated with the low concentration of total glucosinolates, 3-CH3 -indolyl and 4-OH-3-CH3 -indolyl in CM2. Dietary indolyl glucosinolates may reduce feed intake in pigs. Increasing inclusion of extracted indolyl in diets linearly reduced feed intake of mice (Darroch et al., 1991). The weak negative effect of glucosinolates on feed intake for day 8–14 but not for day 15–28 in the present study indicated that young pigs may adapt to dietary glucosinolates. However, older growing pigs may reduce feed intake of CM with low glucosinolates content (1.66 ␮mol glucosinolates/g CM) at 209 g CM/kg of diet (Bell et al., 1991), indicating that other factors may affect feed intake. Pigs maintained growth performance, indicating that 200 g CM/kg can replace SBM in diets for weaned pigs. Achieved feed intake of pigs and formulating diets based on NE and SID AA are fundamental to maintain growth when introducing high fibre co-products into swine diets (Woyengo et al., 2014). Formulating diets based on DE and total AA, dietary inclusion of 196 g CM/kg to replace SBM in diets for growing pigs depressed ADG despite maintaining ADFI (Baidoo et al., 1987a). Depressed ADFI due to elevated content of bitter gluconapin with increased dietary inclusion of Brassica juncea CM reduced weight gain even though diets were formulated based on NE (Landero et al., 2013), indicating the importance of feed intake. Pigs fed CM2 with low glucosinolates had greatest ADG among 4 CM diets, which may be explained by greater ADFI and a positive correlation between ADFI and ADG for each week. Greater ADFI thus drives energy intake and thereby supports greater ADG (Jones and Patience, 2014). However, CM4 had lowest total glucosinolates content, but not the greatest ADFI or ADG. Thus, variation in glucosinolates content of CM and factors other than glucosinolates may affect ADFI and thereby ADG of pigs. Dietary inclusion of 200 g CM/kg to replace SBM in diets for weaned pigs increased G:F for day 1–7 and for the entire trial, indicating that weaned pigs can utilise CM to support growth. More growth per unit of feed intake of CM diets than SBM diet might be due to greater predicted NE value of CM diets, resulting in greater ADG per unit of ADFI. The increased G:F might also be due to increased gut fill caused by increased fibre intake combined with reduced nutrient digestibility that together increase the mass of undigested residue in the gut (Jørgensen et al., 1996; de Lange et al., 2003). Indeed, increasing dietary inclusion of CM to replace SBM tended to increase G:F previously (Landero et al., 2011). Even with depressed ADG due to increased dietary inclusion of CM with greater glucosinolates content, G:F may not be affected (Baidoo et al., 1987a). Among CM diets, G:F did not differ, indicating pigs utilised 4 CM samples with similar conversion efficiency. 5. Conclusion Dietary inclusion of 200 g CM/kg to replace SBM in diets for weaned pigs reduced diet protein and energy digestibility, but did not affect ADFI, ADG and G:F. Among CM sources, diet protein and energy digestibility did not differ. 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