METABOLISM AND NUTRITION The effect of different dietary levels of canola meal on growth performance, nutrient digestibility, and gut morphology of broiler chickens E. Gopinger,1 E. G. Xavier, M. C. Elias, A. A. S. Catalan, M. L. S. Castro, A. P. Nunes, and V. F. B. Roll Federal University of Pelotas, Faculty of Agronomy Eliseu Maciel, Department of Animal Science, PO Box 354, 96010-900 Pelotas, RS, Brazil (P < 0.0001), CP (P < 0.0001), and nitrogen-free extract (P < 0.0001) decreased linearly with increased levels of canola meal. A quadratic effect was observed for villus height (P = 0.003), decreasing up to a 20% inclusion of canola meal in the diet and increasing beyond that level. In conclusion, canola meal can be added up to 16.7% in diets for broilers without affecting the key variables of growth performance. It can be added up to 20% with no negative effect on the CP digestibility, but there was a linear decrease in the digestibility of DM and nitrogen-free extract with increased inclusion of canola meal. Additionally, a quadratic response to canola was observed for villus height with a maximum at 23.6% canola meal.
Key words: alternative feedstuff, nutrient digestibility, nutrition, poultry 2014 Poultry Science 93:1130–1136 http://dx.doi.org/10.3382/ps.2013-03426
INTRODUCTION Canola varieties have been developed to produce oil and meal with lower levels of erucic acid and glucosinolatos, respectively (Bell, 1993). The oil in canola must contain less than 2% of erucic acid, and the meal should contain less than 30 µmol/g of aliphatic glucosinolates (Leeson and Summers, 2005; Khajali and Slominski, 2012). Canola meal is used as a protein source in poultry diets (Canola Council of Canada, 2009). Its composition and nutritional value vary substantially depending on the type of processing, and these characteristics also reflect differences among cultivars (Bell, 1993). In addition, these factors affect the content and composition of glucosinolates in canola meal (Jensen et al., 1995). Such variation can reduce the performance of the birds by reducing food intake (Tripathi and Mishra, 2007). For this reason, the determination of the coefficients of ©2014 Poultry Science Association Inc. Received June 17, 2013. Accepted January 20, 2014. 1 Corresponding author: [email protected]
nutrient digestibility of canola meal in the diet can aid in the optimization of the use of this protein source in diets for broilers. Canola meal can be included in the diet of broilers up to a level of 10% for chick starter and 20% for broiler grower without affecting the growth performance of broilers when diets are formulated based on the level of digestible amino acids (Canola Council of Canada, 2009). According to this source, canola meal may also be used as a protein source for turkeys, with a level of up to 30% considered suitable in the grower phase. Min et al. (2011) indicated that a 25% level of canola meal can be used in broiler diets without any negative effect on growth performance. Payvastagan et al. (2012) also found that feed intake of broilers was not affected by canola meal. However, weight gain and feed conversion ratio were negatively affected by the addition of 20% of canola meal. If alternative to SBM protein supplements are proposed for use in animal diets, it is important to consider the effects of these feed ingredients on the intestinal mucosa. Figueiredo et al. (2003) tested various inclusion levels of canola meal (0, 10, 20, 30, and 40%) in the diets of broilers at 21 d of age and found no dif-
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ABSTRACT This study evaluated the effects of different levels of canola meal in broiler diets on growth performance, nutrient digestibility, and duodenal morphometry. A total of 320 one-day-old Cobb broilers were used in a 35-d experiment. A completely randomized design with 5 levels of canola meal (0, 10, 20, 30, and 40%) as a substitute for soybean meal was used with 8 replicates of 8 birds each. The basal diets were formulated based on corn and soybean meal to meet nutrient requirements of broiler chickens. The levels of canola meal were evaluated with a polynomial regression at 5% of significance. Weight gain and average BW showed a quadratic response (P = 0.03 and P = 0.04, respectively), decreasing with the addition of 40% canola meal. The apparent nutrient digestibility of DM
GROWTH PERFORMANCE OF BROILERS FED CANOLA MEAL
MATERIALS AND METHODS Birds A total of 320 one-day-old male Cobb broilers were housed in metal batteries with a grid floor. During the first week, plate-type feeders, and child-cup waterers were used. The waterers were cleaned twice daily. After 21 d, the chickens were housed in pens with rice husk litter. Tubular feeders with a capacity of 20 kg and nipple waterers were used. This housing system was used until 35 d of age. Throughout the experimental period, the aviary lighting was furnished by 60 W incandescent bulbs and controlled by a clock timer. The lighting program used was consistent with the specifications in the Cobb Lineage Manual. During the initial weeks of the experiment, the temperature was controlled with gas hoods and air conditioning based on the recommended temperature in the lineage manual. The ventilation system used fans and adjustable windows. The maximum and minimum temperature and humidity in the aviary were monitored with digital thermohydrometers (HT208-ICEL, Manaus, AM, Brazil) placed between the metabolic cages.
Experimental Design and Diets The birds were assigned in a completely randomized design to 5 treatments each with 8 replicates with a total of 40 experimental units. Each pen constituted an experimental unit consisting of 8 birds. The experimental diets were formulated to meet the nutritional requirements of the birds at each stage of
development according to the recommendations of Rostagno et al. (2011). Starter diets were used at 8 to 21 d of age, and grower and finisher diets were used at 22 to 35 d of age. Five levels of canola meal (0, 10, 20, 30, and 40%) were used to replace SBM (see Table 1). The canola meal used in the present experiment was obtained from the feed industry. The calcium level of the experimental diets is higher than recommended due to the vitamin mix used, which contains a high level of this mineral. To balance all the other micro ingredients in the diets, the amount of Ca became high. However, it happened in all dietary treatments, and therefore, it did not interfere in the results herein obtained.
Growth Performance The following growth performance variables were evaluated: average bird weight, daily weight gain, feed intake, and feed conversion ratio. The birds were weighed on the first day of the experiment, then weighed weekly throughout the remaining experimental period (8 to 35 d of age). The feed was provided daily and the leftover feed were was weighed weekly to calculate the feed conversion data.
Nutrient Digestibility Nutrient digestibility was evaluated from 15 to 19 d of age (Sakomura and Rostagno, 2007). During this period, the birds were housed in metal batteries with a grid floor and a collector tray. The total collection of excreta was conducted with the aid of an indigestible marker (3% ferric oxide) in the feed to determine the beginning and end of the period of collection of excreta. Excreta were collected once daily, packaged, and frozen to prevent fermentation of the samples until subsequent processing. At the end of the collection period, samples were thawed, weighed, and homogenized. An aliquot of 500 g was removed and dried in an oven with forced ventilation at 60°C for 72 h for further analysis and calculation of nutrient digestibility of DM, CP, ether extract (EE), crude fiber (CF), crude ash (CA), and nitrogenfree extract (NFE). To determine the value for NFE, the formula NFE = 100 − (CF + EE + CP + CA + moisture) was used. For determination of DM, the samples were placed in a dry oven (105°C) for 16 h. The determination of CP was based on nitrogen determination by micro-Kjeldahl procedure, using the factor 6.25 to convert nitrogen into CP. The EE was obtained in a Soxhlet extraction apparatus with petroleum ether, as described by AOAC International (2000). During this period of the study (15 to 19 d of age), samples of the diets were also collected for the analysis of the apparent nutrient digestibility coefficient. The following formula was used for this purpose: ADC (%) = [(NC − NEx)/NC] × 100, where ADC = apparent nutrient digestibility coefficient (%), NC = amount of the nutrient consumed, and NEx = amount of the
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ferences (P < 0.05) among levels for villus height and the villus:crypt ratio; these authors concluded that the integrity of the villi was not impaired. Likewise, Chiang et al. (2010) found no significant differences in villus height or crypt depth in the duodenum of broilers at 21 and 42 d of age fed with a control diet (without canola meal) and 2 experimental diets, one with fermented canola meal (10%) and the other with unfermented canola meal (10%). However, Xu et al. (2012) tested the inclusion levels of 0, 5, 10, and 15% of fermented canola meal in the diets of broilers at up to 42 d of age and observed a higher villus height with 10% canola meal with no significant difference observed for crypt depth. Antinutritional factors contained in canola meal may affect the growth performance of broilers. Information on the effect of canola meal inclusion level on nutrient digestibility and the intestinal mucosa is lacking. Therefore, the aim of this study was to evaluate the effect of the substitution of soybean meal (SBM) for canola meal in broiler diets on production, nutrient digestibility, and morphometry of the intestinal mucosa.
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56.43 33.97 0.00 2.91 0.43 4.00 1.78 0.00 0.23 0.18 0.04 2,980 20.65 1.48 0.43 1.11 0.51 0.79 8.25 20.12 5.68 3.67
0 50.00 27.76 10.00 5.14 0.43 4.00 1.73 0.51 0.18 0.20 0.04 2,980 20.65 1.50 0.43 1.13 0.49 0.79 8.27 20.24 7.25 4.43
10 45.60 21.32 20.00 6.66 0.43 4.00 1.67 0.02 0.11 0.18 0.00 2,980 20.65 1.52 0.43 1.11 0.44 0.79 7.91 20.04 9.33 5.30
20 40.00 14.95 30.00 8.60 0.43 4.00 1.64 0.12 0.06 0.19 0.00 2,980 20.65 1.55 0.44 1.12 0.42 0.80 8.42 20.26 11.01 5.58
30
Inclusion level of canola meal (%)
Starter diet (8–21 d)
34.96 8.54 40.00 10.32 0.43 4.00 1.56 0.00 0.00 0.18 0.00 2,980 20.65 1.56 0.44 1.14 0.38 0.80 8.38 20.69 12.40 6.71
40 58.00 30.94 0.00 4.42 0.41 4.00 1.28 0.37 0.26 0.25 0.07 3,100 19.50 1.35 0.34 1.09 0.52 0.78 8.13 19.34 6.16 3.89
0
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20 47.92 18.08 20.00 7.90 0.40 4.00 1.20 0.05 0.14 0.25 0.06 3,100 19.50 1.40 0.34 1.09 0.45 0.79 8.09 19.67 9.83 5.55
10 53.00 24.52 10.00 6.16 0.40 4.00 1.26 0.15 0.20 0.25 0.06 3,100 19.50 1.38 0.34 1.09 0.49 0.79 8.37 19.18 7.96 4.61
42.40 11.73 30.00 9.80 0.40 4.00 1.14 0.14 0.08 0.25 0.06 3,100 19.50 1.42 0.34 1.09 0.42 0.79 8.44 19.12 11.75 5.72
30
Inclusion level of canola meal (%)
Grower and finisher diets (22–35 d)
37.00 5.46 40.00 11.66 0.40 4.00 1.08 0.13 0.02 0.25 0.00 3,100 19.50 1.44 0.34 1.09 0.38 0.79 8.26 19.08 13.12 6.87
40
1Composition per kilogram of product: zinc: 1,000 mg; manganese: 1,250 mg; zinc bacitracin: 637.50 mg; iron: 750 mg; iodine: 18.20 mg; vitamin E: 200 IU; vitamin B : 17 mg; vitamin B : 41 mg; 1 6 vitamin K3: 20.30 mg; vitamin B12: 230 µg; vitamin A: 150,000 IU; vitamin D3: 40,000 IU; vitamin B2: 88 mg; pantothenic acid: 180 mg; copper: 200 mg; selenium: 7.50 mg; methionine: 27.20 g; choline: 3.250 mg; biotin: 0.80 mg; folic acid: 14.60 mg; salinomycin: 1.650 mg; nicotinic acid: 524.60 mg; calcium: 230 g; phytase: 12,500 units of phytase activity; fluoride: 476.40 mg; phosphorus: 47.64 g.
Corn Soybean meal (45%) Canola meal (34%) Soybean oil Iodized salt Vitamin mineral mix1 Dicalcium phosphate Kaolin dl-Methionine l-Lysine HCl l-Threonine Calculated composition ME (kcal/kg) CP Calcium Available phosphorus Digestible lysine Digestible methionine Digestible methionine + cysteine Analyzed composition Ash CP Ether extract Crude fiber
Item
Table 1. Composition of experimental diets (%)
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GROWTH PERFORMANCE OF BROILERS FED CANOLA MEAL
nutrient excreted. The apparent nutrient digestibility coefficients of CP, DM, EE, and NFE were calculated. To determine the amount of nutrient consumed and excreted, the supply of feed was fully monitored. The amount of feed provided and the leftover amount were determined. The excreta were also measured. The total amount of excreta produced in the period was collected and weighted according to the methodology proposed by Sakomura and Rostagno (2007). To calculate the amount of nutrient consumed, the following formula was used: NC = TFC × NFA, where NC = amount of nutrient consumed, TFC = total feed consumption during the period, and NFA = amount of nutrient in the feed analyzed. Similarly, the amount excreted was obtained from the formula Nex = TPEx × NExA, where Nex = amount of nutrient excreted, TPEx = total production of excreta, and NExA = amount of nutrient in the excreta analyzed.
Four animals per treatment were randomly selected from the animals slaughtered. They were euthanized (electrically stunned and bled, following the Federal University of Pelotas Committee on Animal Research and Ethics, protocol n° 4154, in agreement with the Brazilian legislation, resolution n° 1000 of 05/2012) at the end of the experiment. A total of 20 duodenum samples were obtained for a morphometric analysis of villus height. Immediately after slaughter, samples of 2 cm of the duodenum were collected and fixed for 48 h in a 10% formalin solution. The samples were then dehydrated in an ethyl alcohol battery at increasing concentrations (70%, 80%, 90%, and absolute), followed by diaphanization with xylol and inclusion in paraffin. The paraffin blocks were cut with a rotary microtome
Statistical Analysis A polynomial regression analysis was used to predict the effect of the inclusion of various levels of canola meal in the diet on the parameters of growth performance, nutrient digestibility, and intestinal villus morphometry. Data were analyzed using the GLM procedure of the SAS program (SAS, 2002); the polynomial regression models were selected based on the significance of the regression coefficients (P < 0.05) and on the value of the coefficient of determination. The maximum of the curve corresponding to the quadratic effect was then calculated for the observed variables.
RESULTS AND DISCUSSION Growth Performance The average daily weight gain, average daily feed intake, feed conversion ratio, and average weight at the different ages of the birds relative to the levels of canola meal in the diet are shown in Table 2. In the period from 7 to 14 d of age, the regression analyses showed that the response of daily weight gain to the effect of replacement of SBM by canola meal was statistically significant (P < 0.05). The quadratic response increased to a maximum corresponding to the
Table 2. Growth performance of broilers fed diets containing different levels of canola meal1 Inclusion levels of canola meal (%) Age
Variable
7 to 14 d
DWG (g) ADC (g) FCR (g:g) AW (g) DWG (g) ADC (g) FCR (g:g) AW (g) DWG (g) ADC (g) FCR (g:g) AW (g) DWG (g) ADC (g) FCR (g:g) AW (g) DWG (g) ADC (g) FCR (g:g) AW (g)
14 to 21 d
21 to 28 d
28 to 35 d
7 to 35 d
P-value
0
10
20
30
40
SEM
Linear
Quadratic
Cubic
34.7 40.8 1.1 355.2 59.5 52.1 0.8 772.2 71.1 110.2 1.5 1,269.9 91.1 166.2 1.8 1,907.7 64.1 92.3 1.4 1,907.7
35.6 42.8 1.2 359.8 58.5 60.3 1.0 769.6 76.8 109.6 1.4 1,307.3 87.9 160.5 1.8 1,923.2 64.7 93.3 1.4 1,923.2
36.1 42.3 1.1 364.0 60.8 63.7 1.0 789.9 75.6 110.5 1.4 1,319.4 88.3 161.4 1.8 1,937.9 65.2 94.4 1.4 1,937.9
35.4 41.9 1.1 364.7 61.1 61.9 1.0 793.0 75.4 111.6 1.4 1,321.1 86.6 159.1 1.8 1,927.8 64.6 93.6 1.4 1,927.8
31.7 40.0 1.2 333.9 59.3 57.1 0.9 749.0 69.0 105.7 1.5 1,232.6 85.0 167.7 1.9 1,828.3 61.3 92.6 1.5 1,828.3
0.59 0.63 0.01 4.62 0.65 1.61 0.02 8.20 1.09 1.09 0.01 11.90 1.02 1.82 0.02 15.47 0.53 0.77 0.01 15.47
0.15 0.56 0.09 0.25 0.65 0.32 0.39 0.69 0.49 0.37 0.77 0.47 0.06 0.89 0.13 0.16 0.13 0.87 0.06 0.16
0.03 0.32 0.06 0.07 0.72 0.03 0.05 0.32 0.02 0.35 0.03 0.01 0.18 0.24 0.14 0.04 0.03 0.66 0.08 0.04
0.07 0.51 0.06 0.11 0.57 0.09 0.10 0.29 0.07 0.35 0.04 0.03 0.31 0.41 0.24 0.08 0.07 0.84 0.14 0.08
1P: significance level at 5% by the adjusted regression equation; DWG: daily weight gain (g); ADC: average daily feed consumption (g), FCR: feed conversion ratio; AW: average BW (g).
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Morphometric Analysis of Intestinal Mucosa
to a thickness of 5 µm in 10 transverse and semiseriated cuts. The blades were stained with hematoxylin and eosin and then mounted on microscope slides with Entellan resin (Merck, Darmstadt, Germany) between the blade and the coverslip. The morphometry of the intestinal villus was investigated using optical image capture and measurement with Image Pro-Plus 4.5 software (Media Cybernetics, Silver Spring, MD).
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Gopinger et al.
the average weight of the birds; these responses both decreased thereafter. It is, therefore, possible to predict that every 1% of inclusion of canola meal produces a corresponding increase of 5.55 g in the weight of the birds up to the inclusion level of 15.9%. No significant effect (P < 0.05) was found for feed consumption and feed conversion. The observed decrease in weight gain can be related to the imbalance of lysine:arginine in diets with high levels of canola meal (Taraz et al., 2006). The use of canola meal in large quantities is limited due to a low energy content and high fiber content relative to SBM. As a result, the CF content negatively affects the metabolizable energy of poultry, decreasing bird growth performance (Bell, 1993; Chibowska et al., 2000). The results of this experiment are consistent with the findings of Naseem et al. (2006), who showed that canola meal can be used at levels up to 25% without affecting the growth performance of broilers. The current results are also consistent with Payvastagan et al. (2012) because the inclusion of the meal did not affect feed consumption. However, the results of Min et al. (2011) are not consistent with the results of the current study. Min et al. (2011) found no significant effect of the level of canola meal on broiler growth performance with the inclusion of up to 25% of the ingredient. Mikulski et al. (2012) tested 60, 120, and 180 g/kg of canola meal in diets for growing turkeys and found that the inclusion of 60 and 120 g/kg of canola meal did not affect the average weight of birds. The decrease in weight gain and average weight of birds found in the current study at levels of canola meal inclusion greater than 16.7 and 15.9%, respectively, can be explained by the increase in CF content in the diets, causing a decrease in protein nutrient digestibility and thus resulting in lower BW gain (Khajali and Slominski, 2012). Because of this negative effect, the inclusion of canola meal in place of SBM is limited to a level of up to 20% in diets for broilers. Moreover, the decrease in growth performance at inclusion levels of canola meal of 20% and higher was most likely due to the presence of glucosinolates, tannins, and sinapine, antinutritional factors present in canola. Tannins might not only give a meal a dark unattractive color, but also form complexes with protein and proteolytic enzymes in the gastrointestinal tract, thereby negatively affecting protein digestion and growth performance (Khajali and Slominski, 2012).
Nutrient Digestibility The increase in the level of canola meal in the broiler diet significantly (P < 0.05) affected the apparent nutrient digestibility coefficient (Table 3) of DM, CP, and NFE. The nutrient digestibility of DM decreased linearly. The quadratic response of the nutrient digestibility of CP increased up to the 20% level and decreased
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inclusion of 16.4% of canola meal and decreased thereafter. The average daily consumption, feed conversion ratio, and average bird weight showed no statistically significant differences. In the period from 14 to 21 d, the level of inclusion of canola meal showed a statistically significant effect (P < 0.05) on daily feed consumption. The quadratic response increased to a maximum corresponding to the inclusion of 22.9% of canola meal and decreased thereafter. The response to daily weight gain, feed conversion, and average bird weight was not significant, as shown in Table 2. The presence of sinapine and others antinutritional factors, including glucosinolates in canola meal may have caused a reduction in feed consumption (Mushtaq et al., 2007; Min et al., 2011). In addition, an increase in the level of inclusion of canola meal results in an increase in the level of fiber in the diet. In turn, this increase decreases the protein digestibility and the consumption of feed by the birds, producing decreased weight gain, as noted in the present study at 7 to 14 d of age. From 14 to 21 d of age, a statistically significant decrease in feed consumption resulted from the inclusion of a 22.9% level of canola meal. Analysis of the experimental diets showed that the increase in CF content from 3.7 to 4.4, 5.3, 5.6, and 6.7% following the addition of 10, 20, 30, and 40% of canola meal, respectively, may have caused the observed decrease in feed consumption (Bell, 1993; Chibowska et al., 2000). A regression analysis of the data for 21 to 28 d of age showed that the effects of the substitution of canola meal for SBM on daily weight gain were statistically significant (P < 0.05). An increased quadratic response was observed up to the 30% level of inclusion. Feed conversion improved up to the 20% level of inclusion of canola meal and decreased thereafter. Average BW increased up to the 19.1% level of canola meal and decreased thereafter. For 28 to 35 d of age, the bird weight showed an increasing quadratic response (P < 0.05) up to a maximum level of 15.9% of inclusion of canola meal and decreased thereafter. The effect of the levels of replacement of canola meal for SBM on daily weight gain, feed consumption, and feed conversion was not significant (P < 0.05). The results of this study differ from those found by Nascimento et al. (1998), who observed a decrease in feed consumption in response to an increase in the inclusion of canola meal in the final phase. The results of the current study are not consistent with the findings of de Brum et al. (1998), who found the lowest BW at the 40% level of inclusion of canola meal. A regression analysis of the period from 7 to 35 d of age showed that the substitution levels of canola meal for SBM significantly affected (P < 0.05) the daily weight gain and average weight of the birds. An increasing quadratic response was observed up to the level of 16.7% of inclusion of canola meal for daily weight gain and up to the level of 15.9% of canola meal for
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GROWTH PERFORMANCE OF BROILERS FED CANOLA MEAL Table 3. Apparent digestibility coefficients (ADC) of DM, CP, ether extract (EE), crude fiber (CF), and nitrogen-free extract (NFE) of broilers fed diets containing different levels of canola meal Item Level of canola meal (%) 0 10 20 30 40 SEM P-value1 Linear Quadratic Cubic
DM (%)
CP (%)
EE (%)
CF (%)
NFE (%)
81.0 80.6 79.5 78.0 75.1 0.45
79.6 79.6 79.7 78.0 74.2 0.54
92.7 92.3 93.4 93.4 92.2 0.36
29.4 30.3 30.9 27.3 28.7 1.29
90.7 88.6 87.1 85.7 83.3 0.40
Key words: alternative feedstuff, nutrient digestibility, nutrition, poultry 2014 Poultry Science 93:1130–1136 http://dx.doi.org/10.3382/ps.2013-03426
INTRODUCTION Canola varieties have been developed to produce oil and meal with lower levels of erucic acid and glucosinolatos, respectively (Bell, 1993). The oil in canola must contain less than 2% of erucic acid, and the meal should contain less than 30 µmol/g of aliphatic glucosinolates (Leeson and Summers, 2005; Khajali and Slominski, 2012). Canola meal is used as a protein source in poultry diets (Canola Council of Canada, 2009). Its composition and nutritional value vary substantially depending on the type of processing, and these characteristics also reflect differences among cultivars (Bell, 1993). In addition, these factors affect the content and composition of glucosinolates in canola meal (Jensen et al., 1995). Such variation can reduce the performance of the birds by reducing food intake (Tripathi and Mishra, 2007). For this reason, the determination of the coefficients of ©2014 Poultry Science Association Inc. Received June 17, 2013. Accepted January 20, 2014. 1 Corresponding author: [email protected]
nutrient digestibility of canola meal in the diet can aid in the optimization of the use of this protein source in diets for broilers. Canola meal can be included in the diet of broilers up to a level of 10% for chick starter and 20% for broiler grower without affecting the growth performance of broilers when diets are formulated based on the level of digestible amino acids (Canola Council of Canada, 2009). According to this source, canola meal may also be used as a protein source for turkeys, with a level of up to 30% considered suitable in the grower phase. Min et al. (2011) indicated that a 25% level of canola meal can be used in broiler diets without any negative effect on growth performance. Payvastagan et al. (2012) also found that feed intake of broilers was not affected by canola meal. However, weight gain and feed conversion ratio were negatively affected by the addition of 20% of canola meal. If alternative to SBM protein supplements are proposed for use in animal diets, it is important to consider the effects of these feed ingredients on the intestinal mucosa. Figueiredo et al. (2003) tested various inclusion levels of canola meal (0, 10, 20, 30, and 40%) in the diets of broilers at 21 d of age and found no dif-
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ABSTRACT This study evaluated the effects of different levels of canola meal in broiler diets on growth performance, nutrient digestibility, and duodenal morphometry. A total of 320 one-day-old Cobb broilers were used in a 35-d experiment. A completely randomized design with 5 levels of canola meal (0, 10, 20, 30, and 40%) as a substitute for soybean meal was used with 8 replicates of 8 birds each. The basal diets were formulated based on corn and soybean meal to meet nutrient requirements of broiler chickens. The levels of canola meal were evaluated with a polynomial regression at 5% of significance. Weight gain and average BW showed a quadratic response (P = 0.03 and P = 0.04, respectively), decreasing with the addition of 40% canola meal. The apparent nutrient digestibility of DM
GROWTH PERFORMANCE OF BROILERS FED CANOLA MEAL
MATERIALS AND METHODS Birds A total of 320 one-day-old male Cobb broilers were housed in metal batteries with a grid floor. During the first week, plate-type feeders, and child-cup waterers were used. The waterers were cleaned twice daily. After 21 d, the chickens were housed in pens with rice husk litter. Tubular feeders with a capacity of 20 kg and nipple waterers were used. This housing system was used until 35 d of age. Throughout the experimental period, the aviary lighting was furnished by 60 W incandescent bulbs and controlled by a clock timer. The lighting program used was consistent with the specifications in the Cobb Lineage Manual. During the initial weeks of the experiment, the temperature was controlled with gas hoods and air conditioning based on the recommended temperature in the lineage manual. The ventilation system used fans and adjustable windows. The maximum and minimum temperature and humidity in the aviary were monitored with digital thermohydrometers (HT208-ICEL, Manaus, AM, Brazil) placed between the metabolic cages.
Experimental Design and Diets The birds were assigned in a completely randomized design to 5 treatments each with 8 replicates with a total of 40 experimental units. Each pen constituted an experimental unit consisting of 8 birds. The experimental diets were formulated to meet the nutritional requirements of the birds at each stage of
development according to the recommendations of Rostagno et al. (2011). Starter diets were used at 8 to 21 d of age, and grower and finisher diets were used at 22 to 35 d of age. Five levels of canola meal (0, 10, 20, 30, and 40%) were used to replace SBM (see Table 1). The canola meal used in the present experiment was obtained from the feed industry. The calcium level of the experimental diets is higher than recommended due to the vitamin mix used, which contains a high level of this mineral. To balance all the other micro ingredients in the diets, the amount of Ca became high. However, it happened in all dietary treatments, and therefore, it did not interfere in the results herein obtained.
Growth Performance The following growth performance variables were evaluated: average bird weight, daily weight gain, feed intake, and feed conversion ratio. The birds were weighed on the first day of the experiment, then weighed weekly throughout the remaining experimental period (8 to 35 d of age). The feed was provided daily and the leftover feed were was weighed weekly to calculate the feed conversion data.
Nutrient Digestibility Nutrient digestibility was evaluated from 15 to 19 d of age (Sakomura and Rostagno, 2007). During this period, the birds were housed in metal batteries with a grid floor and a collector tray. The total collection of excreta was conducted with the aid of an indigestible marker (3% ferric oxide) in the feed to determine the beginning and end of the period of collection of excreta. Excreta were collected once daily, packaged, and frozen to prevent fermentation of the samples until subsequent processing. At the end of the collection period, samples were thawed, weighed, and homogenized. An aliquot of 500 g was removed and dried in an oven with forced ventilation at 60°C for 72 h for further analysis and calculation of nutrient digestibility of DM, CP, ether extract (EE), crude fiber (CF), crude ash (CA), and nitrogenfree extract (NFE). To determine the value for NFE, the formula NFE = 100 − (CF + EE + CP + CA + moisture) was used. For determination of DM, the samples were placed in a dry oven (105°C) for 16 h. The determination of CP was based on nitrogen determination by micro-Kjeldahl procedure, using the factor 6.25 to convert nitrogen into CP. The EE was obtained in a Soxhlet extraction apparatus with petroleum ether, as described by AOAC International (2000). During this period of the study (15 to 19 d of age), samples of the diets were also collected for the analysis of the apparent nutrient digestibility coefficient. The following formula was used for this purpose: ADC (%) = [(NC − NEx)/NC] × 100, where ADC = apparent nutrient digestibility coefficient (%), NC = amount of the nutrient consumed, and NEx = amount of the
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ferences (P < 0.05) among levels for villus height and the villus:crypt ratio; these authors concluded that the integrity of the villi was not impaired. Likewise, Chiang et al. (2010) found no significant differences in villus height or crypt depth in the duodenum of broilers at 21 and 42 d of age fed with a control diet (without canola meal) and 2 experimental diets, one with fermented canola meal (10%) and the other with unfermented canola meal (10%). However, Xu et al. (2012) tested the inclusion levels of 0, 5, 10, and 15% of fermented canola meal in the diets of broilers at up to 42 d of age and observed a higher villus height with 10% canola meal with no significant difference observed for crypt depth. Antinutritional factors contained in canola meal may affect the growth performance of broilers. Information on the effect of canola meal inclusion level on nutrient digestibility and the intestinal mucosa is lacking. Therefore, the aim of this study was to evaluate the effect of the substitution of soybean meal (SBM) for canola meal in broiler diets on production, nutrient digestibility, and morphometry of the intestinal mucosa.
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56.43 33.97 0.00 2.91 0.43 4.00 1.78 0.00 0.23 0.18 0.04 2,980 20.65 1.48 0.43 1.11 0.51 0.79 8.25 20.12 5.68 3.67
0 50.00 27.76 10.00 5.14 0.43 4.00 1.73 0.51 0.18 0.20 0.04 2,980 20.65 1.50 0.43 1.13 0.49 0.79 8.27 20.24 7.25 4.43
10 45.60 21.32 20.00 6.66 0.43 4.00 1.67 0.02 0.11 0.18 0.00 2,980 20.65 1.52 0.43 1.11 0.44 0.79 7.91 20.04 9.33 5.30
20 40.00 14.95 30.00 8.60 0.43 4.00 1.64 0.12 0.06 0.19 0.00 2,980 20.65 1.55 0.44 1.12 0.42 0.80 8.42 20.26 11.01 5.58
30
Inclusion level of canola meal (%)
Starter diet (8–21 d)
34.96 8.54 40.00 10.32 0.43 4.00 1.56 0.00 0.00 0.18 0.00 2,980 20.65 1.56 0.44 1.14 0.38 0.80 8.38 20.69 12.40 6.71
40 58.00 30.94 0.00 4.42 0.41 4.00 1.28 0.37 0.26 0.25 0.07 3,100 19.50 1.35 0.34 1.09 0.52 0.78 8.13 19.34 6.16 3.89
0
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20 47.92 18.08 20.00 7.90 0.40 4.00 1.20 0.05 0.14 0.25 0.06 3,100 19.50 1.40 0.34 1.09 0.45 0.79 8.09 19.67 9.83 5.55
10 53.00 24.52 10.00 6.16 0.40 4.00 1.26 0.15 0.20 0.25 0.06 3,100 19.50 1.38 0.34 1.09 0.49 0.79 8.37 19.18 7.96 4.61
42.40 11.73 30.00 9.80 0.40 4.00 1.14 0.14 0.08 0.25 0.06 3,100 19.50 1.42 0.34 1.09 0.42 0.79 8.44 19.12 11.75 5.72
30
Inclusion level of canola meal (%)
Grower and finisher diets (22–35 d)
37.00 5.46 40.00 11.66 0.40 4.00 1.08 0.13 0.02 0.25 0.00 3,100 19.50 1.44 0.34 1.09 0.38 0.79 8.26 19.08 13.12 6.87
40
1Composition per kilogram of product: zinc: 1,000 mg; manganese: 1,250 mg; zinc bacitracin: 637.50 mg; iron: 750 mg; iodine: 18.20 mg; vitamin E: 200 IU; vitamin B : 17 mg; vitamin B : 41 mg; 1 6 vitamin K3: 20.30 mg; vitamin B12: 230 µg; vitamin A: 150,000 IU; vitamin D3: 40,000 IU; vitamin B2: 88 mg; pantothenic acid: 180 mg; copper: 200 mg; selenium: 7.50 mg; methionine: 27.20 g; choline: 3.250 mg; biotin: 0.80 mg; folic acid: 14.60 mg; salinomycin: 1.650 mg; nicotinic acid: 524.60 mg; calcium: 230 g; phytase: 12,500 units of phytase activity; fluoride: 476.40 mg; phosphorus: 47.64 g.
Corn Soybean meal (45%) Canola meal (34%) Soybean oil Iodized salt Vitamin mineral mix1 Dicalcium phosphate Kaolin dl-Methionine l-Lysine HCl l-Threonine Calculated composition ME (kcal/kg) CP Calcium Available phosphorus Digestible lysine Digestible methionine Digestible methionine + cysteine Analyzed composition Ash CP Ether extract Crude fiber
Item
Table 1. Composition of experimental diets (%)
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GROWTH PERFORMANCE OF BROILERS FED CANOLA MEAL
nutrient excreted. The apparent nutrient digestibility coefficients of CP, DM, EE, and NFE were calculated. To determine the amount of nutrient consumed and excreted, the supply of feed was fully monitored. The amount of feed provided and the leftover amount were determined. The excreta were also measured. The total amount of excreta produced in the period was collected and weighted according to the methodology proposed by Sakomura and Rostagno (2007). To calculate the amount of nutrient consumed, the following formula was used: NC = TFC × NFA, where NC = amount of nutrient consumed, TFC = total feed consumption during the period, and NFA = amount of nutrient in the feed analyzed. Similarly, the amount excreted was obtained from the formula Nex = TPEx × NExA, where Nex = amount of nutrient excreted, TPEx = total production of excreta, and NExA = amount of nutrient in the excreta analyzed.
Four animals per treatment were randomly selected from the animals slaughtered. They were euthanized (electrically stunned and bled, following the Federal University of Pelotas Committee on Animal Research and Ethics, protocol n° 4154, in agreement with the Brazilian legislation, resolution n° 1000 of 05/2012) at the end of the experiment. A total of 20 duodenum samples were obtained for a morphometric analysis of villus height. Immediately after slaughter, samples of 2 cm of the duodenum were collected and fixed for 48 h in a 10% formalin solution. The samples were then dehydrated in an ethyl alcohol battery at increasing concentrations (70%, 80%, 90%, and absolute), followed by diaphanization with xylol and inclusion in paraffin. The paraffin blocks were cut with a rotary microtome
Statistical Analysis A polynomial regression analysis was used to predict the effect of the inclusion of various levels of canola meal in the diet on the parameters of growth performance, nutrient digestibility, and intestinal villus morphometry. Data were analyzed using the GLM procedure of the SAS program (SAS, 2002); the polynomial regression models were selected based on the significance of the regression coefficients (P < 0.05) and on the value of the coefficient of determination. The maximum of the curve corresponding to the quadratic effect was then calculated for the observed variables.
RESULTS AND DISCUSSION Growth Performance The average daily weight gain, average daily feed intake, feed conversion ratio, and average weight at the different ages of the birds relative to the levels of canola meal in the diet are shown in Table 2. In the period from 7 to 14 d of age, the regression analyses showed that the response of daily weight gain to the effect of replacement of SBM by canola meal was statistically significant (P < 0.05). The quadratic response increased to a maximum corresponding to the
Table 2. Growth performance of broilers fed diets containing different levels of canola meal1 Inclusion levels of canola meal (%) Age
Variable
7 to 14 d
DWG (g) ADC (g) FCR (g:g) AW (g) DWG (g) ADC (g) FCR (g:g) AW (g) DWG (g) ADC (g) FCR (g:g) AW (g) DWG (g) ADC (g) FCR (g:g) AW (g) DWG (g) ADC (g) FCR (g:g) AW (g)
14 to 21 d
21 to 28 d
28 to 35 d
7 to 35 d
P-value
0
10
20
30
40
SEM
Linear
Quadratic
Cubic
34.7 40.8 1.1 355.2 59.5 52.1 0.8 772.2 71.1 110.2 1.5 1,269.9 91.1 166.2 1.8 1,907.7 64.1 92.3 1.4 1,907.7
35.6 42.8 1.2 359.8 58.5 60.3 1.0 769.6 76.8 109.6 1.4 1,307.3 87.9 160.5 1.8 1,923.2 64.7 93.3 1.4 1,923.2
36.1 42.3 1.1 364.0 60.8 63.7 1.0 789.9 75.6 110.5 1.4 1,319.4 88.3 161.4 1.8 1,937.9 65.2 94.4 1.4 1,937.9
35.4 41.9 1.1 364.7 61.1 61.9 1.0 793.0 75.4 111.6 1.4 1,321.1 86.6 159.1 1.8 1,927.8 64.6 93.6 1.4 1,927.8
31.7 40.0 1.2 333.9 59.3 57.1 0.9 749.0 69.0 105.7 1.5 1,232.6 85.0 167.7 1.9 1,828.3 61.3 92.6 1.5 1,828.3
0.59 0.63 0.01 4.62 0.65 1.61 0.02 8.20 1.09 1.09 0.01 11.90 1.02 1.82 0.02 15.47 0.53 0.77 0.01 15.47
0.15 0.56 0.09 0.25 0.65 0.32 0.39 0.69 0.49 0.37 0.77 0.47 0.06 0.89 0.13 0.16 0.13 0.87 0.06 0.16
0.03 0.32 0.06 0.07 0.72 0.03 0.05 0.32 0.02 0.35 0.03 0.01 0.18 0.24 0.14 0.04 0.03 0.66 0.08 0.04
0.07 0.51 0.06 0.11 0.57 0.09 0.10 0.29 0.07 0.35 0.04 0.03 0.31 0.41 0.24 0.08 0.07 0.84 0.14 0.08
1P: significance level at 5% by the adjusted regression equation; DWG: daily weight gain (g); ADC: average daily feed consumption (g), FCR: feed conversion ratio; AW: average BW (g).
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Morphometric Analysis of Intestinal Mucosa
to a thickness of 5 µm in 10 transverse and semiseriated cuts. The blades were stained with hematoxylin and eosin and then mounted on microscope slides with Entellan resin (Merck, Darmstadt, Germany) between the blade and the coverslip. The morphometry of the intestinal villus was investigated using optical image capture and measurement with Image Pro-Plus 4.5 software (Media Cybernetics, Silver Spring, MD).
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the average weight of the birds; these responses both decreased thereafter. It is, therefore, possible to predict that every 1% of inclusion of canola meal produces a corresponding increase of 5.55 g in the weight of the birds up to the inclusion level of 15.9%. No significant effect (P < 0.05) was found for feed consumption and feed conversion. The observed decrease in weight gain can be related to the imbalance of lysine:arginine in diets with high levels of canola meal (Taraz et al., 2006). The use of canola meal in large quantities is limited due to a low energy content and high fiber content relative to SBM. As a result, the CF content negatively affects the metabolizable energy of poultry, decreasing bird growth performance (Bell, 1993; Chibowska et al., 2000). The results of this experiment are consistent with the findings of Naseem et al. (2006), who showed that canola meal can be used at levels up to 25% without affecting the growth performance of broilers. The current results are also consistent with Payvastagan et al. (2012) because the inclusion of the meal did not affect feed consumption. However, the results of Min et al. (2011) are not consistent with the results of the current study. Min et al. (2011) found no significant effect of the level of canola meal on broiler growth performance with the inclusion of up to 25% of the ingredient. Mikulski et al. (2012) tested 60, 120, and 180 g/kg of canola meal in diets for growing turkeys and found that the inclusion of 60 and 120 g/kg of canola meal did not affect the average weight of birds. The decrease in weight gain and average weight of birds found in the current study at levels of canola meal inclusion greater than 16.7 and 15.9%, respectively, can be explained by the increase in CF content in the diets, causing a decrease in protein nutrient digestibility and thus resulting in lower BW gain (Khajali and Slominski, 2012). Because of this negative effect, the inclusion of canola meal in place of SBM is limited to a level of up to 20% in diets for broilers. Moreover, the decrease in growth performance at inclusion levels of canola meal of 20% and higher was most likely due to the presence of glucosinolates, tannins, and sinapine, antinutritional factors present in canola. Tannins might not only give a meal a dark unattractive color, but also form complexes with protein and proteolytic enzymes in the gastrointestinal tract, thereby negatively affecting protein digestion and growth performance (Khajali and Slominski, 2012).
Nutrient Digestibility The increase in the level of canola meal in the broiler diet significantly (P < 0.05) affected the apparent nutrient digestibility coefficient (Table 3) of DM, CP, and NFE. The nutrient digestibility of DM decreased linearly. The quadratic response of the nutrient digestibility of CP increased up to the 20% level and decreased
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inclusion of 16.4% of canola meal and decreased thereafter. The average daily consumption, feed conversion ratio, and average bird weight showed no statistically significant differences. In the period from 14 to 21 d, the level of inclusion of canola meal showed a statistically significant effect (P < 0.05) on daily feed consumption. The quadratic response increased to a maximum corresponding to the inclusion of 22.9% of canola meal and decreased thereafter. The response to daily weight gain, feed conversion, and average bird weight was not significant, as shown in Table 2. The presence of sinapine and others antinutritional factors, including glucosinolates in canola meal may have caused a reduction in feed consumption (Mushtaq et al., 2007; Min et al., 2011). In addition, an increase in the level of inclusion of canola meal results in an increase in the level of fiber in the diet. In turn, this increase decreases the protein digestibility and the consumption of feed by the birds, producing decreased weight gain, as noted in the present study at 7 to 14 d of age. From 14 to 21 d of age, a statistically significant decrease in feed consumption resulted from the inclusion of a 22.9% level of canola meal. Analysis of the experimental diets showed that the increase in CF content from 3.7 to 4.4, 5.3, 5.6, and 6.7% following the addition of 10, 20, 30, and 40% of canola meal, respectively, may have caused the observed decrease in feed consumption (Bell, 1993; Chibowska et al., 2000). A regression analysis of the data for 21 to 28 d of age showed that the effects of the substitution of canola meal for SBM on daily weight gain were statistically significant (P < 0.05). An increased quadratic response was observed up to the 30% level of inclusion. Feed conversion improved up to the 20% level of inclusion of canola meal and decreased thereafter. Average BW increased up to the 19.1% level of canola meal and decreased thereafter. For 28 to 35 d of age, the bird weight showed an increasing quadratic response (P < 0.05) up to a maximum level of 15.9% of inclusion of canola meal and decreased thereafter. The effect of the levels of replacement of canola meal for SBM on daily weight gain, feed consumption, and feed conversion was not significant (P < 0.05). The results of this study differ from those found by Nascimento et al. (1998), who observed a decrease in feed consumption in response to an increase in the inclusion of canola meal in the final phase. The results of the current study are not consistent with the findings of de Brum et al. (1998), who found the lowest BW at the 40% level of inclusion of canola meal. A regression analysis of the period from 7 to 35 d of age showed that the substitution levels of canola meal for SBM significantly affected (P < 0.05) the daily weight gain and average weight of the birds. An increasing quadratic response was observed up to the level of 16.7% of inclusion of canola meal for daily weight gain and up to the level of 15.9% of canola meal for
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GROWTH PERFORMANCE OF BROILERS FED CANOLA MEAL Table 3. Apparent digestibility coefficients (ADC) of DM, CP, ether extract (EE), crude fiber (CF), and nitrogen-free extract (NFE) of broilers fed diets containing different levels of canola meal Item Level of canola meal (%) 0 10 20 30 40 SEM P-value1 Linear Quadratic Cubic
DM (%)
CP (%)
EE (%)
CF (%)
NFE (%)
81.0 80.6 79.5 78.0 75.1 0.45
79.6 79.6 79.7 78.0 74.2 0.54
92.7 92.3 93.4 93.4 92.2 0.36
29.4 30.3 30.9 27.3 28.7 1.29
90.7 88.6 87.1 85.7 83.3 0.40
