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METABOLISM AND NUTRITION |
* Institute of Animal Nutrition and Feed Technology, University of Agriculture, Faisalabad, Pakistan-38040; Shamim Feed Industries, Bahawalpur, Pakistan-63100; and Department of Zoology and Fisheries, University of Agriculture, Faisalabad, Pakistan-38040
2 Corresponding author: tmmirza{at}fsd.paknet.com.pk
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Key Words: enzyme supplementation • broiler • carcass response • digestible lysine • canola meal
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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-galacto-oligosaccharides and 18% NSP of which 1.5% is soluble (Bell, 1993) as compared with 23% insoluble NSP and 4.5% soluble polysaccharides in sunflower meal (Irish and Balnave, 1993). The soluble NSP tends to increase the digesta viscosity and reduce nitrogen digestion and absorption (Annison, 1991), subsequently resulting in poor growth performance. Canola meal has been reported to replace up to 100% of the dietary soybean meal without any negative effect on bird performance provided the diets are supplemented with Lys (Leeson et al., 1987; Kocher et al., 2000). The successful use of enzymes in cereal-based diets has stimulated interest in the application of enzymes to target the vegetable protein components of poultry diets. A multicarbohydrase supplement was effective in depolymerizing cell wall polysaccharides of SBM, CM, and peas in vitro (Meng et al., 2005). The addition of the same enzyme supplement to a broiler diet based on wheat, SBM, CM, and peas resulted in a significant improvement in digestibility of protein, starch, and NSP and, consequently, improved growth performance. Growth performance was not affected when enzymes were added to broiler diets with high levels of CM (Simbaya et al., 1996; Kocher et al., 2000, 2001). However, the literature is not clear about the effect of enzyme addition in CM-based diets.
The high prices of SBM in this country make its use limited in poultry diets. Canola meal, on the other hand, is available at a much cheaper price. The present study was conducted to evaluate the response of broilers on low nutrient density canola meal-based diets supplemented with enzyme, Lys, or both.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Animal Husbandry
A total of 2,448 1-d-old male Hubbard broiler chicks were obtained from a local hatchery and were randomly allotted to 1 of 48 floor pens (51 birds in each replicate) with rice straw as bedding material over a concrete floor. A floor space of 0.074 m2 (0.80 feet2) was allotted for one bird in an open-sided house with sidewall curtains. Each pen was equipped with a separate tube feeder and a manual drinker. On d 15, tube feeder was replaced with round bottom feeders, and manual drinkers were replaced with automatic drinkers. The house temperature was maintained at 32°C during the first week of age, and a weekly reduction of 3°C was practiced until a temperature of 25°C was attained. Birds were vaccinated against infectious bronchitis and Newcastle disease (ND) at 1 d, for infectious bursal disease (IBD) at 15 d of age, and against hydro-pericardium syndrome at 19 d. Birds were revaccinated against ND at 23 d and for IBD at 29 d. The experiment lasted for 42 d, and 24 h of light was provided throughout the experiment.
Ingredients, Experimental Diets, and Bird Performance
The analyzed values for CM used in the present study were 38.8, 7.17, 0.58, and 6.74% for CP, CF, ether extract, and ash, respectively (AOAC, 2000). A value of 1,500 kcal of ME·kg–1 was assigned to the CM used in the present study. Two levels of CM (i.e., 20 and 30%) were used with 3 levels of digestible Lys (i.e., 0.8, 0.9, and 1.0%) in a factorial design of 2 x 3 in 6 dietary combinations in equinitrogenous and equicaloric diets (Table 1
). Total and digestible AA were calculated from analyzed DM and CP contents of each ingredient using AminoDat 2.0 (Degussa AG, Hanau-Wolfgang, Germany). The feed formulation was based on digestible AA. The ME value of each ingredient was calculated by regression equation of NRC (1994). Diets were formulated by linear formulation method using WinFeed 2.8 (WinFeed Ltd., Cambridge, UK). The nutrient specifications were lower than those proposed by NRC (1994) for broiler starter diets (for 0 to 21 d). The digestible AA met or exceeded ideal AA ratio (Baker and Han, 1994). Digestible Lys was used as reference AA to calculate other indispensable AA (Table 2). Each diet was divided into 2 portions. One portion was mixed with vitamin and mineral premix, whereas the other portion was mixed with vitamin and mineral premix plus enzyme at 0.5 g·kg–1 (Rovabio Excel AP 10%; Adisseo, Asia Pacific Pte Ltd., Singapore) of finished feed. Cane molasses and oil was added thereafter. The supplemental enzyme activities reported by the supplier were 2,200 visco units·g–1 (equivalent to 1,400 xylanase units·g–1) for endo-1,4-ß xylanase (EC 3.2.1.8) and 200 glucanase units·g–1 for endo-1,3-ß glucanase (EC 3.2.1.6
[EC]
). The aliphatic glucosinolates of the CM used in the study were assayed by gravimetric method (McGhee et al., 1965). Each of the experimental diets (total of 12 dietary combinations) was offered to 4 replicates in mash form throughout the experimental period of 42 d. Feed and water were provided ad libitum.
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Carcass and Immunity Responses
At the end of d 42, two birds from each replicate were randomly selected for eviscerated carcass yield. The carcass responses were evaluated as described by Mushtaq et al. (2005). For determining the antibody titer against infectious bronchitis virus, IBD virus, and ND virus (NDV), one bird from each replicate was randomly selected at 37 d and blood was collected by puncturing the wing vein. The antibody titers against infectious bronchitis virus and NDV were detected by hemagglutination-inhibition tests in which titer against NDV was tested using 16 hemagglutinin units of the ND antigen (G. D. Animal Health Service, Deventer, Holland) as described by Richtzenhain et al. (1993), whereas for IBD virus, antibody titer was determined using commercially available ELISA kits (Biochek, Gouda, Holland) as described by Thayer et al. (1987).
Digestibility Study
Diets containing 0.3% chromic oxide (Cr2O3) as digestibility marker were offered from 1 d. At the end of 43 d, ileal digesta from each of the pens was collected by the method described by Scott and Boldaji (1997). Briefly, 4 birds from each of the replicate were slaughtered. The intestinal tract was excised, and the contents of the tract from Meckel’s diverticulum to 40 mm above the ileocecal junction were gently squeezed directly into 200-mL plastic cups and kept in an ice container. During digesta collection, few drops of formalin were also added to avoid bacterial activity. The digesta samples within a pen were pooled and dried in hot air oven at 65°C until the constant weight was obtained. They were ground to pass through 0.5-mm sieve and stored at –10°C to avoid further contamination until analyses.
Diets and ileal digesta samples were analyzed for N (AOAC, 2000) and gross energy (GE) by adiabatic oxygen bomb calorimeter (Parr Instrument Co., Moline, IL). The Cr2O3 content in the ashed samples of the diets and digesta was analyzed spectrophotometrically after acid digestion (Divakaran et al., 2002). The AME of the diets was not corrected for endogenous energy losses, and therefore TME was not calculated. The AME of the diet was calculated by the following formula:
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The apparent digestibility coefficient of N (ADCN) was calculated by the following equation (Ravindran et al., 1999):
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where (N/Cr2O3)dietis the ratio of N to Cr2O3 in diet and (N/Cr2O3)digesta is the ratio of N to Cr2O3 in digesta.
Experimental Design and Data Analyses
The experiment was conducted using completely randomized design with factorial structure. Pen mean was an experimental unit. Effect of enzyme addition (with and without), CM (20 and 30%), and digestible Lys (0.8, 0.9, and 1.0%) were statistically analyzed as 2 x 2 x 3 factorial design by GLM method of ANOVA using Minitab 14.1 (Minitab Inc., State College, PA). The level of significance was 0.05 unless otherwise stated. In case of significance, Tukey’s honestly significant difference test was used to detect the differences in means (Mead et al., 1993).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Performance During 1 to 21 d
The birds fed diets containing 30% CM had 9.40% less BW gain than those fed diets containing 20% CM (Table 3). The feed:gain was depressed by the addition of CM in the diet without affecting the feed intake. The mortality was also higher in diets having 30% CM than that of 20% CM (4.27 vs. 2.29%). No effect of enzyme addition or varying the digestible Lys level was observed on BW gain, feed:gain, feed intake, and mortality during the starter phase (1 to 21 d). No interaction effects were observed for any of the growth performance parameter at this stage.
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). The effects of enzyme, CM, and digestible Lys or their interactions were not significant for other responses.
Carcass and Immunity Characteristics
A depression in breast weight was observed due to 30% CM or 0.8 and 0.9% digestible Lys (Table 4). This depression was more when 30% CM was used with 0.8 or 0.9% digestible Lys. Enzyme failed to improve the breast weight in diets having high CM or low digestible Lys. Leg weights were significantly depressed by the enzyme addition at 0.8% digestible Lys. No effect of experimental diets was observed on abdominal fat weights (Tables 4 and 5). No response in terms of antibody titers against ND and IBD was observed with higher levels of CM and enzyme supplementation or change in dietary Lys level.
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). The ADCN determined by ileal digestibility was not significantly different among the dietary treatments (Table 5). |
DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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). It is, in general, believed that glucosinolates in poultry diets must be less than 2.5 µmol·g–1. The phytic acid content of CM is also fairly high. Over 70% of the canola phosphorus is in phytic acid form (Summers et al., 1983). A significant reduction in performance parameters of broiler chicks during 1 to 21 d may be the result of high glucosinolate content of the experimental diets. The tolerance to glucosinolates in younger birds is less, which impairs thyroid functions. As the birds grow, the thyroid develops and mature birds can tolerate a fairly high amount of glucosinolates.
Canola meal is also low in sodium (Bell and Keith, 1991). March (1984) corrected the depression in the performance of broilers by increasing dietary NaCl from 0.25 to 0.5% in CM-based diet. In the present study, the dietary sodium was higher than the NRC (1994) recommended for broiler chickens. Lack of effect of adding 30% CM on growth performance during 1 to 42 d may be due to addition of dietary sodium, potassium, and chloride at similar dietary electrolyte balance (DEB) to a level that ensures optimum performance (Mushtaq et al., 2005; Ahmad et al., 2006). Leeson and Summers (2001) were of the view that a high level of sulfur in the CM might cause leg abnormality in broiler chickens. However, not a single bird with leg abnormality was observed in the present study. Generally sulfur is not included in DEB calculation (Ahmad and Sarwar, 2006); the increasing sulfur may affect the cation-anion difference and ultimately bird performance. In the present study, the DEB was fixed at 210 mEq·kg–1, and if it is assumed that the sulfur being the cation may increase DEB, then the resultant DEB will be in an acceptable range as reported by various authors (Oviedo-Rondon et al., 2001; Murakami et al., 2001; Borges et al., 2003; Mushtaq et al., 2005, 2007).
The inclusion of CM at 20% had no effect on performance of broilers at any age (Ahmad et al., 2007). Increase in dietary CM to 30% resulted in reduced performance only during 1 to 21 d only (Table 3). Reduced performances were also reported by Cowan et al. (1999) and Szczurek et al. (2000) with high levels of rapeseed meal in young broilers. Kocher et al. (2001) demonstrated no adverse effect of low glucosinolates in CM when it was added at 35% of the broilers’ diet. Shires et al. (1981) and Baloch et al. (2003) reported no effect of inclusion of extracted dehulled CM up to 20% of the diet on the performance of broilers.
The poor growth performance in younger birds in the present study may be due to high phytate content of CM. Phytate has the ability not only to chelate cations, such as iron, sodium, sulfur, sialic acid, calcium, zinc, copper, etc., but also other nutrients such as nitrogen and AA (Cowieson et al., 2003). Phytate is also known to inhibit a number of digestive enzymes, such as pepsin and trypsin (Pallauf and Rimbach, 1997). Digestive enzyme activities (units·kg–1 of BW) in the pancreas and intestinal contents increase with age (Nitsan et al., 1991). The development of secretion of digestive enzymes in the posthatched chick due to the high phytate could also be a limiting factor in digestion leading to inefficient growth by birds and poor feed:gain and liveability in younger birds. Lack of effect of CM on performance during 1 to 42 d may be due the development of sufficient enzyme activities as the birds mature.
The effect of enzyme supplementation on growth performance or on digestibility was not significant in the present study. Meng and Slominski (2005) reported depressed protein digestibility by enzyme cocktail in corn-CM diet. Similarly, carbohydrase addition did not influence the growth performance, starch digestibility, or ME content of sunflower- or CM-based diets (Simbaya et al., 1996; Kocher et al., 2000; Mushtaq et al., 2006). Meng and Slominski (2005) indicated that the enzyme effects were not always beneficial in CM-based diet. Some low-molecular weight NSP hydrolysis products may adversely affect protein digestion by chickens (Irish and Balnave, 1993; Acamovic, 2001). It has been suggested by Moran (1982) that poultry are not able to produce and use any significant amount of energy deriving from volatile fatty acids products, which may explain the lack of enzyme effect on AME content and chick performance in a CM-based diet. The AME of the diets were calculated as 2,750 kcal·kg–1 (Table 2). The AME determined from ileal digesta showed on an average 2,885 kcal·kg–1. The CM used in the present study was assigned 1,500 kcal of ME·kg–1, and it seems that the CM had high ME as used in this study.
Lysine is the first limiting AA in the CM-based diet, and Lys supplementation could be an appropriate strategy to lower the negative effects of CM. However, no significant advantage of Lys supplementation was observed on the growth performance, but it increased the breast weight in present study. Breast meat was depressed when diets containing 30% CM had only 0.8% digestible Lys (Table 4 and 5). It has been reported that CM can replace up to 100% of the dietary SBM without any negative effect on birds’ performance provided the diets are supplemented with Lys (Leeson et al., 1987). The nonsignificant results due to Lys supplementation in the present study may be due to increased feed intake as commonly noted in lower energy diets (Leeson et al., 1996). The response to low Lys during the present study may be due to the marginal CP contents of the experimental diets (Table 2). Increased breast yield by Lys supplementation may be due to the fact that Lys requirements are higher for carcass characteristics than for growth. Several authors have shown that the dietary Lys required by broilers to achieve maximum feed:gain (Han and Baker, 1993; Baker et al., 2002) and maximum breast meat yield (Kerr et al., 1999) was higher than that required for maximum BW gain in the order of BW < breast meat < feed:gain (Leclerq, 1998). An improvement in breast yield has been reported previously by increasing sulfur containing AA of the diets (Schutte and Pack, 1995). Increased breast yield has also been reported with increasing dietary Lys in sunflower meal based diets (T. Mushtaq, unpublished data). Garcia et al. (2006) and Corzo et al. (2002), however, noted no difference in breast, fillet, or abdominal fat yield by the dietary Lys. Although the CM used in the present study had 80% KOH solubility, there are still chances of Maillard reaction. Previous work (Newkirk and Classen, 1999; Newkirk et al., 2000) has shown that the desolventization and toasting of pre-press solvent extracted canola reduced the content and digestibility of AA, particularly that of Lys. Because breast yield has higher Lys requirements, the depression in breast yield in low-Lys diets was obvious.
In conclusion, the CM may be used up to 30% of the diets during the finishing phase. The digestible Lys can be lowered to 0.8% when amino acids in proportion to digestible Lys follow the ideal AA ratio. The glucanase and xylanase cocktail has no pronounced effect on the growth performance, nutrient digestibility, and carcass characteristics.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Received for publication January 23, 2007. Accepted for publication May 24, 2007.
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