Carlos A Montoya and Pascal Leterme 1

Transcription

1 Determination of the digestible energy and prediction of the net energy content of toasted and non-toasted canola meals from Brassica juncea and Brassica napus in growing pigs by the total faecal collection and the indigestible marker methods Carlos A Montoya and Pascal Leterme 1 Prairie Swine Centre, th Street East, Saskatoon, Saskatchewan, Canada S7H 5N9. Received 30 March 2009, accepted 23 June Montoya, C. A. and Leterme, P Determination of the digestible energy and prediction of the net energy content of toasted and non-toasted canola meals from Brassica juncea and Brassica napus in growing pigs by the total faecal collection and the indigestible marker methods. Can. J. Anim. Sci. 89: The study aimed to compare the digestible and net energy (DE and NE) contents of three canola meals (CM) toasted (958C) or not after desolventization from yellow Brassica juncea (YBJ) and yellow and black Brassica napus (YBN and BBN) in growing pigs. A basal diet and six CMbased diets (2/3 basal diet and 1/3 CM) supplemented with acid-insoluble ash (indigestible marker) were prepared. The growing pigs (28 kg; six per treatment) were kept in metabolic cages for 18 d and their faeces were collected for the last 10 d. The digestibilities and DE content of the CM were determined based on the total faecal excretion and the indigestible marker methods. NE was estimated with a prediction equation. The DE and NE contents of the YBN meal (3.98 and 2.73 Mcal kg 1 DM) were higher (P0.007) than that of the YBJ (3.76 and 2.59 Mcal kg 1 DM) and BBN (3.64 and 2.43 Mcal kg 1 DM) meals. Toasting had no effect (P0.05) on the DE and NE contents. Inconsistent values were obtained with the indigestible marker, as compared with the total faecal collection method. In conclusion, YBN canola presents the highest energy content, and toasting of CM does not affect its energy values in growing pigs. Key words: Canola meal, growing pigs, toasting, digestible energy, net energy Montoya, C. A. et Leterme, P Détermination de l e nergie digestible et pre diction de l e nergie nette detourteaux de canola toaste s et non toaste sdebrassica juncea et Brassica napus chez le porc en croissance par les me thodes de collecte fe cale totale et demarqueur indigestible. Can. J. Anim. Sci. 89: L e tude visait a` comparer la teneur en e nergie digestible (ED) et e nergie nette (EN) chez le porc en croissance de 3 sortes de tourteau de canola (TC) toaste s (958C) ounon apre` s elimination dusolvant: Brassica juncea jaune (BJJ) et Brassica napus jaune ou noir (BNJ and BNN). Un aliment de base et 6 aliments a` base de TC (2/3 aliment de base, 1/3 TC) ont été pre pare s. Les porcs en croissance (28 kg; 6/traitement) ont été maintenus dans des cages a` me tabolisme pendant 18 jours et leurs matie` res fécales récoltées pendant 10 jours. Les valeurs de digestibilite et les teneurs en ED du TC seul ont ensuite été calcule es sur base de l excrétion fe cale totale et de la technique du marqueur. L EN a été calcule e à l aide d une équation de pre diction. L ED et l EN dutourteaude BNJ (3.98 et 2.73 Mcal kg 1 MS) ont e te plus éleve es (P0.007) que celles du BJJ (3.76 et 2.59 Mcal kg 1 MS) et dubnn (3.64 et 2.43 Mcal kg 1 MS). Le toastage n a eu aucun effet (P0.05) sur les valeurs de DE et NE. Les valeurs obtenues avec le marqueur indigestible e taient moins pre cises que celles obtenues avec l excrétion totale. En conclusion, le BNJ pre sente des valeurs plus élevées que les BNN et BJN et le toastage n ame liore pas la valeur e nerge tique des TC. Mots clés: Tourteau de canola, porcs en croissance, toastage, e nergie digestible, e nergie nette Canola meal (CM) is a valuable source of essential amino acids for pigs (Bell 1993). However, the digestibility and availability of its nutrients are limited by both its composition (high dietary fibre level) and processing (toasting) (Grala et al. 1994; Pastuszewska et al. 2003). Its low energy content is likely the most limiting factor for its use in swine diets, due to the absence of digestible 1 To whom correspondence should be addressed ( pascal.leterme@usask.ca). 481 carbohydrates and oil, as well as its high dietary fibre level (Bell 1993). A breeding program has been initiated to develop canola seeds with lower fibre content. It is based on cultivars of Brassica napus and Brassica juncea that carry the yellow-seeded colour genes (Simbaya et al. Abbreviations: ADF, acid detergent fibre; AIA, acid insoluble ash; BBN, black B. napus; CM, canola meal(s); DE, digestible energy; DM, dry matter; NDF, neutral detergent fibre; NE, net energy; YBJ, yellow B. juncea; YBN, yellow B. napus

2 482 CANADIAN JOURNAL OF ANIMAL SCIENCE 1995; Slominski 1997; Relf-Eckstein et al. 2007). However, little information is available on the digestible and net energy content of their defatted meals in swine. On the other hand, plant breeders have been successful in reducing the level of antinutritional factors in canola, namely the glucosinolates. Therefore, swine nutritionists are questioning whether flake toasting at 958C after oil extraction and removal of hexane is still required. This treatment destroys the antinutritional factors, but it may also lead to the occurrence of the Maillard reaction between sugars and the epsilon-nh 2 radical of lysine, making lysine unavailable for protein synthesis (Moughan and Rutherfurd 1996; Newkirk and Classen 2002). Therefore, the present study was aimed at comparing the DE and NE content of CM with different fibre content (yellow- and black-seeded B. napus, and yellowseeded B. juncea) in growing pigs, as well as the effect of toasting. In a previous study, the use of an indigestible marker led to a poor estimation of the energy value of CM in pigs (Leterme et al. 2008). For that reason, the present study also compared the use of an indigestible marker (acid-insoluble ash) with the total faecal collection technique. MATERIALS AND METHODS Canola Meal Samples Three different types of CM were studied: yellow-seeded B. juncea (YBJ) and yellow- and black-seeded B. napus (YBN and BBN). The samples of CM were processed at the POS Pilot Plant Corp (Saskatoon, Canada). After removal of the solvent, two batches were prepared. The first was toasted at 958C and the second was not treated. The temperature of the latter did not exceed 608C (non-toasted). Animals Animal care and use for these experiments was approved by the University of Saskatchewan Committee on Animal Care and Supply protocol # Animals were cared for under the guidelines of the Canadian Council on Animal Care (1993). The 42 male growing pigs (Camborough Plus females C337 sires, PIC Canada Ltd., Winnipeg MB) had an initial bodyweight of kg. They were kept in individual metabolic cages for the duration of the experiment. Dietary Treatments A basal diet was formulated to contain 695 g barley kg 1 DM, 250 g soybean meal, 47 g mineral-vitamin premix (319 g dicalcium phosphate kg 1, 234 g limestone, 149 g salt, 149 g mineral premix and 149 g vitamin premix). The basal diet was supplemented with Celite 545 (8 g kg 1 diet, Celite Corporation, Lompoc CA), used as a source of acid insoluble ash (AIA), an indigestible marker. Additionally, six diets containing 667 g kg 1 DM of the basal diet and 333 g kg 1 of one of six CM samples were prepared. Experimental Procedure The experiment was a factorial treatment arrangement with three CM types and two treatments (toasted or non-toasted) as the main factors. A total of 42 male pigs were randomly allocated to one of the experimental diets (n 6 per diet). Due to the limited number of cages available, the experiment was conducted during three consecutive periods, with 14 pigs per period and two pigs per treatment. The pigs were fed according to scale, based on their body weight and corresponding to 90 g DM kg 1 BW After an adaptation period of 8 d to the diet, the faeces were totally collected for 10 d. An aliquot corresponding to 10% of the collection per day was prepared and kept at 188C. At the end of the experiment, they were freeze-dried and ground with a centrifugal mill (Retsch Mill ZM1, Newtown, PA) and passed through a 1 mm-mesh screen. Chemical Analysis CM types and diets were analyzed for dry matter [DM, AOAC ; Association of Official Analytical Chemists (AOAC 2007)], ash (AOAC ; AOAC 2007), nitrogen (AOAC using an elemental analyzer LECO FP528, St Joseph MI; AOAC 2007), ether extract (AOAC using Soxhlet apparatus and petroleum ether; AOAC 2007), gross energy (PARR 1281 calorimeter, Moline IL), neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin (van Soest et al. 1991). Acid-insoluble ash was obtained after treatment of the diets (2 g) and faeces (1 g) with 3 M HCl, followed by filtration on cellulose paper, combustion (5508C for 4 h) and weighing of the residue (AOAC ; AOAC 2007). Faeces were analyzed for DM, nitrogen, ash and gross energy using the described methods. Calculations and Statistical Analysis The apparent digestibility of DM, nitrogen and the gross energy of diets were calculated directly or with the indigestible marker. The digestibility measured directly was calculated as follows: AD (N ingested N excreted ) = N ingested ] 100% where AD is the apparent digestibility, N ingested the amount of DM or any nutrient ingested and N excreted, the amount of DM or any nutrient excreted. The digestibility calculated by means of the marker was calculated as follows: AD f1 [(IA D =IA F ) = (N F =N D )]g 100% where AD is the apparent digestibility, IA D and IA F the insoluble ash in the diet and in the faeces, respectively. N F and N D the nutrient content in the faeces and in the diet, respectively. For the calculations, the analytical values of AIA from diets and faeces were used.

3 MONTOYA AND LETERME * ENERGY CONTENT OF CANOLA MEALS IN PIGS 483 The digestible energy (DE) was calculated using the following equation: DE D GE Gross energy where D GE is the digestibility of gross energy. The apparent digestibility of the CM alone was calculated as follows: RESULTS Composition Major differences in composition (Table 1) were observed between CM samples for crude protein (456 to 519 g kg 1 DM) and fibre content (156 to 228 g NDF kg 1 DM and 93 to 170 g ADF kg 1 DM). The BBN meal had the lowest protein content and highest fibre (NDF) content. No effect of toasting was observed on the chemical composition of the meals. AD CM [AD CM-based diet (AD Basal Diet 0:667)]=0:333 where AD CM is the apparent digestibility of CM, AD CM-based diet the digestibility of the diet (containing 667 and 333 g kg 1 of basal diet and CM, respectively) and AD Basal Diet the apparent digestibility of the basal diet alone. The net energy (NE) was calculated using Noblet s equation (Noblet et al. 1994): NE (kcal kg 1 ) 0:70 DE 1:61 EE 0:48 Starch 0:91 CP 0:87ADF where DE is digestible energy (kcal kg 1 ), EE the ether extract (g kg 1 ), CP the crude protein (g kg 1 ) and ADF the acid detergent fibre content (g kg 1 ) of CM. All statistical analyses were performed using the mixed procedure of SAS (SAS/STAT Version 9.1, SAS Institute Inc., Cary, NC). The digestibility values and energy content of the diets and the methods of digestibility determination were compared as a fixed effect. The fixed effects of CM, toasting and their interaction were tested, using a factorial treatment arrangement (32) (Steel and Torrie 1980). The statistical models included the effect of period (n 3) as a random effect. When the F-value of the ANOVA was significant (P B0.05), the means were compared using the adjusted Tukey test. Differences in digestibility were observed between diets (Table 2) and CM types (Table 3). In both cases, the YBN meals had higher DM and gross energy digestibility than the BBN meals (PB0.01). For the meals, the highest DE and NE content was observed for YBN (P0.007). No effect was observed for the CM type toasting interaction, nor for toasting effect, for any of the evaluated variables (P 0.05). Differences were observed for the digestibility values obtained using the indigestible marker (P B0.001). The diet containing non-toasted BBN had the highest DM, crude protein and gross energy digestibility. By contrast, the toasted YBJ had the lowest values (Table 2). A strong CM type toasting interaction (P B0.001) was observed for the digestibility and energy values (Table 3). The non-toasted YBN had the highest DM and gross energy digestibility values and DE and NE content, whereas the toasted YBJ meal had the lowest values. Comparison Between the Methods of Determination The DM and gross energy digestibility values and DE and NE content of the control and CM-based diets were lower with the indigestible marker method, as compared with the total faecal collection (P B0.05, Table 2). The digestibility values and energy content of the ingredients were different between methods for toasted YBJ and BBN and non-toasted YBN (P B0.01; Table 3) but not for toasted YBN and non-toasted YBJ and BBN (P0.05). Table 1. Chemical composition (g kg 1 DM) of the toasted or non-toasted canola meals Toasting Toasted Non-toasted Species (Brassica) juncea napus napus juncea napus napus Colour yellow black yellow yellow black yellow Dry matter (g kg 1 ) Crude protein Ash Ether extract Neutral detergent fibre Acid detergent fibre Lignin Gross energy (Mcal kg 1 DM)

4 484 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 2. values of CM-based diets and comparison between the methods of digestibility determination in growing pigs Diets Toasted Non-toasted Species (Brassica) juncea napus napus juncea napus napus Colour Control yellow black yellow yellow black yellow RSD z P Acid insoluble ash (g kg 1 DM) Total faecal collection (%) Dry matter 82.2ab 81.7abc 79.8c 82.2a 80.7abc 80.0bc 82.6a Crude protein Gross energy 81.9ab 81.4ab 79.9b 82.1ab 80.6ab 79.9b 82.6a Digestible energy (Mcal kg 1 DM) 3.47b 3.53b 3.53b 3.63a 3.54b 3.51b 3.65a Net energy (Mcal kg 1 DM) 2.43b 2.45b 2.45b 2.52a 2.46b 2.44b 2.53a Indigestible marker (%) Dry matter 77.8d 75.2e 80.7b 79.5bc 78.2cd 77.9d 81.9a Crude protein 79.8c 79.5c 84.0ab 82.7b 82.4b 82.2b 84.9a Gross energy 77.4d 74.9e 80.8b 79.4c 78.1cd 77.8d 82.4a Digestible energy (Mcal kg 1 DM) 3.28e 3.24e 3.57b 3.50c 3.43d 3.42d 3.64a Net energy (Mcal kg 1 DM) 2.30e 2.25e 2.48b 2.43c 2.38d 2.37d 2.53a RSD y Dry matter Crude protein Gross energy Digestible energy Net energy P values y Dry matter Crude protein Gross energy Digestible energy Net energy z RSD, residual standard deviation. y RSD and statistical significance for the comparison between the methods of digestibility determination. ae Values with different letters in the same row differ significantly. DISCUSSION Plant breeders hypothesize that the use of yellow-seeded canola, with lower dietary fibre content, namely lignin, will improve the energy value of the meal product. This hypothesis is supported by the fact that the CM studied here had higher (30%) content in DE and NE (3.79 and 2.6 Mcal kg 1 ) than values previously reported for rapeseed meal or canola meal by Noblet et al. (1993) (3.12 and 1.64 Mcal kg 1 ), National Research Council (1998) (2.89 and 1.61 Mcal kg 1 ) and INRA (2004) (2.76 and 1.51 Mcal kg 1 ), with lower content in detergent fiber (3050% NDF), especially in lignin: 1653 g kg 1 here vs g (Noblet et al. 1993; INRA 2004). Bell et al. (1998) also obtained higher DE content for yellow-seeded B. juncea (3.32 Mcal kg 1 ) than for B. napus (3.11 Mcal kg 1 ), also with a difference in NDF content (195 vs. 246 g kg 1 ). In another experiment with growing pigs, the lower fibre content of dehulled CM increased the DE content from 2.92 to 3.18 Mcal kg 1 DM (de Lange et al. 1998). In the present study, YBN presented higher DM and GE digestibility values and DE and NE content than BBN. This is ascribable to the lower NDF (25%) and lignin (67%) content of YBN. However, despite the lower NDF content of YBJ, as compared with the black-seeded B. napus, the digestibility values and energy contents of both meals did not differ statistically (P0.05). Also, the YBJ meal presented lower DE and NE contents than the YBN. In broilers, the true metabolizable energy content of yellow-seeded B. napus or B. juncea was also higher than that of black-seeded B. napus (Newkirk et al. 1997; Slominski et al. 1999). The NE content was predicted by means of prediction equations based on the DE content of CM and a correction for its chemical composition. These equations were developed for whole diets (Noblet et al. 1994) and not for individual feed ingredients. However, the equations based on the DE content of the feeds with just a correction for the chemical composition, can also be used for individual feed ingredients (Noblet and

5 MONTOYA AND LETERME * ENERGY CONTENT OF CANOLA MEALS IN PIGS 485 Table 3. values and energy content of different canola meals and comparison between the methods of digestibility determination in growing pigs Toasting Toasted Non-toasted P z Species (Brassica) juncea napus napus juncea napus napus RSD y CM x Toasting CMT Colour yellow black yellow yellow black yellow Total faecal collection (%) Dry matter Crude protein Gross energy Digestible energy (Mcal kg 1 DM) Net energy (Mcal kg 1 DM) Indigestible marker (%) Dry matter 70.1d 86.3b 82.6bc 79.0c 78.1c 91.2a Crude protein 78.8d 92.3ab 88.4bc 87.4c 86.7c 94.5a Gross energy 70.0e 87.5b 83.1c 79.5cd 78.5d 92.0a Digestible energy (Mcal kg 1 DM) 3.33d 4.14b 3.97b 3.77c 3.76c 4.36a Net energy (Mcal kg 1 DM) 2.28d 2.85b 2.73b 2.59c 2.58c 3.0a RSD w Dry matter Crude protein Gross energy Digestible energy Net energy P values w Dry matter Crude protein Gross energy Digestible energy Net energy z CM, canola meal; CMT: CMtoasting interaction. y RSD, residual standard deviation. x CM type effect for total faecal collection. (%): DM, 79.3ab, 75.5b and 83.0a; Protein, 86.1, 83.1 and 87.4; Energy, 79.4ab, 76.2b and 83.4a; DE (Mcal kg 1 ), 3.76b, 3.63b and 3.97a; NE (Mcal kg 1 ), 2.58b, 2.49b and 2.73a for BJ, BBN and YBN, respectively. w RSD and statistical significance for the comparison between the methods of digestibility determination. ae Values with different letters in the same row differ significantly. van Milgen 2004; J. Noblet, personal communication). The NE:DE ratio (69%) is higher than that reported by others (54%; INRA 2004), but the composition of the CM studied here is also different. It is higher in CP ( vs. 380 g kg 1 DM) and lower in NDF ( vs. 319 g kg 1 DM) content. Toasting is justified by the necessity of eliminating remnants of hexane and also the antinutritional factors still present after processing (Newkirk and Classen 2002), but excessive toasting can cause browning of the CM, which is indicative of the Maillard reaction. Here, toasting CM did not negatively affect the digestibility values and the DE and NE contents of the meals in growing pigs as the toasted and non-toasted CM presented similar values. However, the availability of the amino acids, namely lysine, has not been measured. Overheated feed ingredients can present good lysine digestibility, but poor lysine availability (van Barneveld et al. 1994). In rats, Pastuszewska et al. (2003) found that toasting CM had no effect on protein digestibility, but decreased the lysine biological value. In chickens, Newkirk and Classen (2002) obtained better growth performances and feed efficiency with non-toasted CM compared with toasted CM, despite higher levels in glucosinolates. The absence of a negative effect of toasting on lysine availability thus needs to be confirmed. Comparison Between the Methods of Determination Total faecal collection is the most accurate method for faecal digestibility and DE determination (Adeola 2000). However, it is time-consuming and expensive in contrast to the use of indigestible markers. Good agreement between DM and crude protein digestibilities measured with total faecal collection and indigestible marker (chromic oxide) have been reported in several species (Gabert et al. 2000). Less variation in digestibility

6 486 CANADIAN JOURNAL OF ANIMAL SCIENCE coefficients was obtained when chromic oxide was compared with AIA (Van Leeuwen et al. 1996; Gabert et al. 2000). Therefore, the choice for the most appropriate methodology is not easy. The present results show lower digestibility values for the diets using AIA as a marker, as compared with the total faecal collection method. Moreover, the AIA method shows higher variability and inconsistency for the digestibility values and energy content of the ingredients. Here, the digestibility and energy values for the toasted YBJ meal were lower (e.g., NE 13%) with the AIA method than with the total faecal collection, while they were higher for toasted BBN and non-toasted YBN (e.g., NE 14 and 9%, respectively). It can be ascribed to problems in the estimation of the AIA content in the diets. The AIA content of all CM-based diets should have been similar, because the proportions of basal diet and CM were similar (2/3 and 1/3, respectively). However, after the AIA analysis of each diet, the toasted YBJ had the highest content and the toasted BBN and non-toasted YBN diets the lowest. It could have affected their digestibility values and energy content. Therefore, the results obtained for the ingredients with AIA generated different conclusions when the toasting and CM toasting interaction effects were tested. Based on these observations, the total faecal collection should be recommended for digestibility studies on CM. In conclusion, the results of the current study show that the meal from yellow-seeded B. napus has higher DE and NE content in growing pigs (3.97 and 2.73 Mcal kg 1 DM), compared with black-seeded B. napus and yellow-seeded B. juncea. Toasting did not modify the energy content of the CM. Further research is required to verify the availability of lysine. Finally, the energy values obtained with the AIA method did not agree with the values obtained from the total faecal collection method for CM. ACKNOWLEDGEMENTS The authors acknowledge with gratitude the financial support provided by the Canola Council of Canada and the technical assistance provided by Mrs Pam Kish in the laboratory. Strategic funding from Sask Pork, Alberta Pork, Manitoba Pork Council and the Saskatchewan Agriculture and Food Development Fund is gratefully acknowledged. Adeola, O Digestion and balance techniques in pigs. Pages in A. J. Lewis and L. L. Southern, eds. Swine nutrition. 2nd ed. CRC Press, Boca Raton, FL. Association of Official Analytical Chemists Official methods of analysis. 18th ed. AOAC, Arlington, VA. Bell, J. F Factors affecting the nutritional value of canola meal: a review. Can. J. Anim. Sci. 73: Bell, J. M., Tyler, R. T. and Rakow, G Nutritional composition and digestibility by 80-kg to 100-kg pigs of prepress solvent-extracted meals from low glucosinolate Brassica juncea, B. napus and B. rapa seed and of solvent-extract soybean meal. Can. J. Anim. 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