Poult. Sci.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Poult Sci 2008. 87:759-767. doi:10.3382/ps.2007-00437
© 2008 Poultry Science Association OPEN ACCESS ARTICLE
This Article
Free Via Open Access
Right arrow Abstract
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by del Alamo, A. G.
Right arrow Articles by Villamide, M. J.
Right arrow Search for Related Content
PubMed
Right arrow Articles by del Alamo, A. G.
Right arrow Articles by Villamide, M. J.

METABOLISM AND NUTRITION

Effect of Wheat Cultivar and Enzyme Addition to Broiler Chicken Diets on Nutrient Digestibility, Performance, and Apparent Metabolizable Energy Content

A. Gutierrez del Alamo*,1, M. W. A. Verstegen{dagger}, L. A. Den Hartog*,{dagger}, P. Perez de Ayala* and M. J. Villamide{ddagger}

* Nutreco Poultry and Rabbit Research Centre, 45950 Casarrubios del Monte, Toledo, Spain; {dagger} Wageningen University, Animal Nutrition Group, PO Box 338, 6700 AH Wageningen, the Netherlands; and {ddagger} Departamento de Producción Animal, Escuela Ténica Superior de Ingenieros Agrónomos, Universidad Politécnica de Madrid, 28040 Madrid, Spain

1 Corresponding author: a.gutierrez{at}nutreco.com


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
A total of 5,000 one-day-old male broiler chickens were assigned to 8 different treatments in a 4 x 2 factorial design. Four wheat cultivars (Amiro, Guadalupe, Isengrain, and Horzal) and 2 levels (0 or 1 kg/t of feed) of an enzyme cocktail (Avizyme 1300, xylanase, 2,500 U/kg and protease, 800 U/kg) were used. Nutritionally complete mash diets contained 65 and 70% of the test wheat for the starter and grower period, respectively. Test wheats were used in diets for broilers, and growth performance and AME contents were measured. Broiler performance was measured in 4,800 broilers allocated to floor pens with 75 birds each and fed from 1 to 42 d of age. Digestibilities and AME contents of diets were measured in 200 broilers from 6 to 27 d of age individually allocated to battery cages. Chromic oxide (Cr2O3) at an inclusion rate of 0.5% in the diet was used as an indigestible marker. Apparent metabolizable energy was corrected by zero N balance to obtain AMEn. Wheat cultivar strongly influenced animal performance during the starter period (1 to 21 d of age). During the grower period (21 to 42 d of age), only BW and daily feed intake were influenced by wheat cultivar. Differences in daily feed intake were associated with differences in AMEn intake during the starter period, but not during the grower period. Nutrient digestibility was higher with the use of enzyme. Animal performance was not affected (i.e., wheat cultivar differences were not eliminated by using enzymes). During the grower period, significant interactions were detected with regard to nutrient digestibility and AMEn. Differences in AMEn content of wheat could not be explained by digestible starch.

Key Words: broiler • wheat • metabolizable energy • broiler performance • enzyme


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Wheat is an important ingredient in broiler diets because of its high starch (ST) and CP content, and is often the only cereal in grower and finisher diets. However, the chemical composition and energy availability of wheat can vary (Mollah et al., 1983; Kim et al., 2003). In a survey of 18 wheat cultivars, Kim et al. (2003) reported that ST content ranged between 58.5 and 73.7%, CP between 9.7 and 19.1%, and nonstarch polysaccharides (NSP) between 7.8 and 11.0% (on a DM basis). Mollah et al. (1983) found AME ranging between 11.0 and 15.9 MJ/kg of DM when 22 wheat samples were fed to growing broiler chickens. Several physical and chemical factors influence wheat AMEn and animal performance, including specific weight (McCracken and Quintin, 2000), viscosity and hardness (Carré et al., 2002), pelleting, (Scott, 2000), ST, CP, NSP, and ether extract content (Steenfeldt, 2001; Svihus and Gullord, 2002; Pirgozliev et al., 2003). However, the relationship between the physicochemical properties of wheat and its AMEn content has not been fully defined. Moreover, some wheat cultivars considered to be of high quality have produced unexpectedly low broiler performance.

Most trials measure 1 or 2 physicochemical factors with animals housed in battery cages and fed experimental diets for a limited period of time. In addition, the determination of AMEn in raw materials is commonly done by using broilers at one fixed age. Most animals used for testing are less than 20 d old (Scott, 2002; Scott and Silversides, 2003) or slightly older (Carré et al., 2002). Until now, only moderate correlations between wheat AMEn and animal performance have been found (Rose and Bedford, 1995; Steenfeldt, 2001).

Much information exists on the use of NSP-degrading enzymes and their beneficial effect on nutrient digestibility (Steenfeldt et al., 1998; Marron et al., 2001; Meng et al., 2005) and on animal performance (Choct et al., 2004; Wang et al., 2005). The use of NSP-degrading enzymes in poultry diets is therefore a common practice. However, much less information is available on the efficacy of the enzymes to equalize the nutritional values of different wheats. In addition, the characteristics of the wheats that are improved by the use of enzymes are not well known.

Our objectives were to determine the effect of wheat cultivar on animal performance and AMEn with or without enzyme addition and to study the relationship between wheat AMEn and performance on animals grown on the floor throughout the fattening period.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Feeds
The experimental design was 4 x 2 with 4 wheat cultivars (Isengrain, Amiro, Guadalupe, and Horzal) and 2 levels of enzyme addition (0 and 1 kg/t of feed). The diets contained high levels of the experimental wheat (65 and 70% in the starter and grower diets, respectively) and diets met or exceeded broiler requirements (NRC, 1994). The ingredients and the average determined chemical compositions of the experimental diets are shown in Table 1Go. All wheat cultivars used in the study came from the same growing region of Torrijos (Spain). They were selected to have different ST and CP contents (Table 2Go). Wheats were milled separately and passed through a 3-mm screen in a hammer mill (40 CV, Roxal, Barcelona, Spain) and then mixed with the other ingredients. The exogenous enzyme was a commercial powdered preparation containing xylanase derived from Trichoderma longibrachiatum and protease derived from Bacillus subtilis (Avizyme 1300, Danisco Animal Nutrition, Marlborough, UK; EC 3.2.1.8, 2,500 IU and EC 3.4.21.6 [EC] 2, 800 IU, respectively). The enzyme was added to the feed by first mixing it with the premix and a small proportion of ground cereal. The amount of enzyme added was based on guaranteed product activities (Danisco Animal Nutrition). In each experimental period, the wheat-based diets were split into 2 portions. One portion was fed as is, whereas in the other portion the recommended dose of the commercial powdered enzyme (1 kg/t of feed) was added on top.


View this table:
[in this window]
[in a new window]

  		Table 1. Ingredient profile and determine analysis of starter and grower diets
 

View this table:
[in this window]
[in a new window]

  		Table 2. Chemical and physical properties of the different wheat1 cultivars
 
Animals and Experimental Design
One-day-old male broiler chickens (Ross 308) were obtained from a commercial hatchery (Cazalegas, Toledo, Spain). Animals were randomly assigned to the 8 dietary treatments. Feed and water were provided ad libitum during the whole trial. Light was on continuously during the first day and for 16 h/d afterward. Broiler chickens were kept at 32°C during the first week of age. Thereafter, temperatures were decreased by 3°C/wk to reach 22°C by 23 d of age. After that, they were maintained at approximately 22°C until the end of the experiments, which was 42 d for the growth assay and 27 d for the metabolic assay.

Experiment 1: Growth Assay.
A total of 4,800 one-day old male broiler chickens were assigned randomly to 64 pens (7.5 m2). Each contained 75 broiler chickens. Each pen was equipped with 1 hanging feeder, a nipple drinker, and wood shavings (6 cm deep) as litter. The experimental treatment diets were randomly assigned to 8 pens each.

The experimental period lasted 42 d. Animals were weighed at the beginning (d 0), when the experimental diets changed from the starter to the grower diet (d 21), and at the end, before slaughtering (d 42). The chickens were inspected daily and dead birds were removed (date of death and BW were recorded). To calculate the feed conversion ratio (FCR), the BW of dead birds was considered. Sixteen animals per treatment on d 7 and 8 animals per treatment on d 13, 20, 27, and 34 were randomly selected and euthanized following the principles for care of animals in experimentation (Spanish Royal Decree 1201/2005, 2005). Immediately afterward, the small intestine was removed. The ileum, defined as the area between Meckel’s diverticulum and the ileocecal junction, was dissected and the digesta from this area was collected by gentle finger-stripping. After collection, the samples were immediately centrifuged at 2,777 x g for 10 min (Mixtasel, Selecta, Barcelona, Spain), the supernatant was collected, and the ileal viscosity was measured.

Experiment 2: Metabolic Assay.
A total of 200 one-day-old male broiler chickens were housed in the same room as in experiment 1 and fed on a mash starter diet for the first week. At d 6, all the birds were weighed; 80 were selected for the experiment (BW 101 ± 16 g) and moved to another room prepared with metabolic cages (19.5 x 38.5 x 35 cm, width x length x height). Animals were randomly assigned to 1 of the 8 dietary treatments and individually allocated to cages (10 replicates/treatment). This allowed for total collection of excreta from each individual separately. Each cage was fitted with a metal feeder and a drinker.

Experimental diets were the same as in experiment 1, except that 0.5% of chromic oxide (Cr2O3) was added and mixed to facilitate determination of nutrient digestibility. The experimental period lasted 21 d (from d 6 to d 27). Excreta was collected for 3 consecutive days: from d 10 (BW 177 ± 29 g) to d 13 for the starter feed and from d 24 (BW 694 ± 97 g) to d 27 for the grower feed. Contamination (e.g., down and feathers) was carefully removed and the excreta was stored in containers at –20°C. Afterward, excreta was dried at 70 ± 0.5°C for 48 h. Samples collected from each bird during the 3 d of excreta collection were blended, ground through a 0.75-mm sieve (ZM 200 UltraCentrifugal Mill, Retsch GmbH & Co. KG, Haan, Germany), and stored in plastic tins until analysis. Samples were analyzed for ST, N, and gross energy (GE) to determine ST digestibility, N retention, and AME. The AME was corrected to zero N balance (AMEn) according to Hill and Anderson (1958).

At the end of the experiment (d 27), all birds were killed by cervical dislocation, and immediately afterward the small intestine was removed. The ileal content was collected as explained previously and was freeze-dried. Ileal contents of 2 animals from the same treatment were pooled, ground through a 0.75 mm sieve, and stored in plastic bags until analysis. Samples were analyzed for ST, N, and chromium.

Chemical Analysis
All analyses, except Cr2O3 in feed (9 times/treatment), were carried out in duplicate and the results are reported on a DM basis. Chemical analysis of the wheats, diets, and excreta were conducted according to the methods of AOAC (1995) for DM (930.15), N (954.01), crude fiber (962.09), ether extract (960.39), and ash (942.05). Neutral detergent fiber, acid detergent fiber, and acid detergent lignin were determined sequentially following the procedures described by Van Soest et al. (1991). Starch content was analyzed following the {alpha}-amylogluclosidase method (996.11). Total, soluble, and insoluble NSP and their constituent sugars were determined by using the method described by Bach Knudsen (1997), with the exception that the polysaccharides in ST-free residues were treated with 12 mol/L of H2SO4 and hydrolyzed to monosaccharides with 2 mol/L (100°C, 60 min) instead of with 1 mol/L (100°C, 120 min). Physical properties of the wheat flour were determined according to the method of the International Association for Cereal Science and Technology (1998) for alveograph (121) by using a model MA82 Chopin alveograph (Chopin Technologies, Villeneuve-la-Garenne Cedex, France). Chromium oxide content in feed and excreta was determined according to Fenton and Fenton (1979). Ileal viscosity was measured according to Bedford and Classen (1993). Gross energy values were determined by bomb calorimeter with a Parr 6100 adiabatic calorimeter (Parr Instrument Company, Moline, IL).

Calculations and Statistical Analysis
In the metabolic assay, the following equations were used for calculation of apparent total tract digestibility (using ST digestibility as an example), apparent ileal digestibility, and AMEn content of the experimental diets (Hill and Anderson, 1958):


Formula


Formula


Formula

where GE is gross energy, Cr2O3 is chromic oxide, ST is starch, N is nitrogen, and 8.22 is the energy equivalent of 1 g of uric acid N.

Data from the growth and metabolic assays were analyzed with ANOVA by using the GLM procedure of SAS (SAS Institute, 1985). The factors were 4 wheat cultivars and 2 levels of enzyme. If a significant interaction existed between the main effects, the data were reanalyzed by 1-way ANOVA. Mortality data were transformed into arcsine of the square root for statistical analysis, but the data are presented as natural numbers. Viscosity was analyzed by using 1-way ANOVA repeated measurements. Means were separated by using Duncan’s multiple-range test. Pooled SEM were calculated from the mean square error term generated by 1-way ANOVA. Relationships between wheat characteristics, and chicken performance and AMEn of the diets were estimated by using a simple Pearson correlation analysis. All statements of significance were based on a P-value of equal to or less than 0.05.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Growth Assay
The effect of the wheat cultivar and enzyme addition on BW, daily gain (DG), daily feed intake (DFI), FCR, and mortality at d 21 and d 42 are shown in Table 3Go. The wheat cultivar had a clear effect on most broiler growth parameters. At d 21 birds fed diets containing the Isen-grain cultivar had the greatest (622 g, P < 0.001) BW, followed by the animals fed diets containing Guadalupe (603 g), Amiro, and Horzal (average 580 g). The differences in BW attributable to wheat cultivar at d 42 were lower (maximum differences of 3.7%) than at d 21, but wheat cultivar ranking was maintained. Daily feed intake was greater (P ≤ 0.03) for animals fed Guadalupe than for those fed the Amiro and Horzal cultivars in both the starter (42.06 vs. 40.55 g/d, respectively) and grower period (89.00 vs. 86.55 g/d, respectively), whereas those fed Isengrain showed intermediate values (41.21 and 88.11 g/d for the starter and grower period, respectively). The FCR at d 21 was lower (P ≤ 0.001) for birds fed the Isengrain cultivar (1.490) than for those fed any other wheat cultivar (average 1.573). At d 42 there was no effect of wheat cultivar on FCR. The average value was 1.933. None of the dietary treatments affected mortality in any of the periods.


View this table:
[in this window]
[in a new window]

  		Table 3. Effect of wheat cultivar and enzyme1 addition2 on broiler performance (mean values)
 
The addition of an NSP enzyme cocktail did not have a clear effect on growth performance under the conditions tested (Table 3Go). In the grower period, DFI was greater (P = 0.037) in chicks fed diets without enzyme (131 g/d) than in those fed enzyme-supplemented diets (129 g/d).

The intestinal viscosity of chicks fed the experimental diets decreased with age (range from 11.90 to 2.83, P ≤ 0.03; Figure 1aGo). The reduction was most pronounced between d 7 and 13. The dietary exogenous enzyme cocktail reduced (P ≤ 0.001) intestinal viscosity during the whole period, up to 60% at d 7 (Figure 1aGo). No correlations between intestinal viscosity and animal performance were found except at d 7, which affected BW at d 21 (r = –0.31, P = 0.018) and DG during the starter period (r = –0.30, P = 0.018; data not shown). Wheat cultivar clearly affected intestinal viscosity at the ileum. The Horzal cultivar had the greatest viscosity at all ages (average 6.90 cP) and the Guadalupe and Isengrain cultivars had the lowest (average 5.52 and 4.19 cP, respectively). An interaction between enzyme addition and wheat cultivar was found for animals at d 20 (P ≤ 0.01; Figure 1bGo) and d 27 (P ≤ 0.03). Enzyme cocktail supplementation to the Horzal cultivar reduced ileal viscosity to a greater extent compared with the other wheat cultivars.


Figure 1
View larger version (25K):
[in this window]
[in a new window]

  		Figure 1. Digesta viscosity (centipoise, cP) of ileal contents from broilers fed diets containing different wheat cultivars and supplemented with enzyme [Avizyme 1300 added at 0 (–) or 1 kg/t of feed (+)]. a) Evolution as the bird ages. b) At d 20 of age. In panels a and b, each mean represents 32 and 8 replicates, respectively.

 
Metabolic Assay
Daily feed intake between treatments was in the same range as reported in the growth assay for both the starter (average 40.53 ± 6.9 g/d) and grower periods (average 92.85 ± 18.5 g/d). Digestibility coefficients and the AMEn content of the diets are presented in Table 4Go. Digestibility of DM, protein retention, and AMEn of the diets in both the starter and grower periods were affected by wheat cultivar (P < 0.05). During the starter period, DM digestibilities of the diets including the Isengrain and Amiro cultivars were greater (average 70.93%) than digestibilities of the diets with the other cultivars (average 69.19%). During the grower period, the Isengrain cultivar showed the greatest DM digestibility (72.44%). In both periods, the digestibility of ST was very high (99.23 and 98.53% for the starter and grower period, respectively) and was not influenced by wheat cultivar.


View this table:
[in this window]
[in a new window]

  		Table 4. Effect of wheat cultivar and enzyme1 addition2 on excreta digestibility and AMEn of broilers (mean values)
 
Protein retention during the starter period was lower (P ≤ 0.001) for diets with the Horzal cultivar (57.41%) than for the other cultivars (average 60.84%). During the grower period, protein retention was similar to that during the starter period (1% less), but differences among the cultivars remained.

The diet that contained the Guadalupe cultivar showed the lowest (P < 0.001) AMEn during both the starter (2,876 kcal/kg of DM) and grower periods (2,930 kcal/kg of DM). During the grower period, the Isengrain and Amiro cultivars differed (P < 0.001) by 71 kcal/kg of DM (3,071 vs. 3,000 kcal/kg of DM, respectively), whereas the Horzal cultivar presented an intermediate value (3,015 kcal/kg of DM).

The addition of an exogenous enzyme cocktail increased (P = 0.03) the digestibility of the DM, ST, and AMEn of the diets by 1% in the starter period, but not in the grower period (Table 4Go). During the grower period, an interaction between wheat cultivar and enzyme supplementation was found for DM digestibility (P = 0.008) and AMEn (P < 0.001) of the diets. Enzyme supplementation increased excreta DM digestibility (from 67.3 to 71.6%) and AMEn (from 2,913 to 3,108 kcal/kg of DM) in diets based on the Horzal cultivar, but not in those based on the other cultivars.

There were no differences among wheat cultivars (Table 5Go) for ileal DM, ST, and protein digestibilities (average 70.8, 97.9, and 79.5%, respectively). Addition of the exogenous enzyme cocktail did not increase ileal digestibilities.


View this table:
[in this window]
[in a new window]

  		Table 5. Effect of wheat cultivar and enzyme1 addition2 on ileal digestibility of broilers at d 27 (mean values)
 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
According to our results, wheat cultivar type can affect animal performance and nutrient availability and should be taken into account in diet formulations. Daily feed intake was affected by wheat cultivar in both the starter and grower periods, but it was not fully related to wheat AMEn. Energy consumption during the starter period and DFI during the grower period were the parameters mainly related to DG. Scott (2000, 2002) observed that DG is better explained by feed intake than by AMEn in animals allocated to cages from 4 to 17 d of age. This agrees with our data. Nevertheless, none of the wheat physicochemical parameters or diet digestibilities analyzed was highly related to DFI in our study with 4 wheat cultivars.

Excreta digestibility of DM, N retention, and AMEn of the diets were affected by wheat cultivar, contrary to the ileal digestibilities analyzed. Starch digestibility measured with excreta was nearly 100% for all cultivars. Starch is the most important energy-yielding nutrient in wheat grain, and it contributes the most to its AMEn. In this study, the differences among wheat cultivars in ST content were low (2.6%), but those in dietary AMEn were approximately 5%, and there was no relationship between total ST or ST digestibility and AMEn content. In a study (Mollah et al., 1983) with 22 samples of wheat in which ST content ranged from 59 to 72%, there was no relationship between ST and AMEn. However, in the same study, ST digestibility was different among wheat cultivars (from 80 to 99%) and was correlated with AMEn. The amount of digestible ST is what contributes most to AME (Longstaff and McNab, 1986; Wiseman, 2006). This contribution ranged from 73 to 79% in the current study, but its variation explained less than 22% of the variation in dietary AMEn. When diets were not supplemented with enzyme, dietary AMEn mainly related to the total NSP content of the wheat cultivars (r = –0.42, r = –0.53, P < 0.02, for the starter and grower period, respectively). However, dietary AMEn mainly related to the insoluble NSP content (r = –0.7, r = –0.47, P < 0.005) in enzyme-supplemented diets.

The beneficial effect of the use of exogenous enzymes in the present study was observed only in some variables and depended on the wheat cultivar used. Daily feed intake was not increased in animals fed enzyme-supplemented diets. This indicates that enzymes cannot eliminate the differences in DFI among wheat cultivars. This is in concordance with Scott et al. (1998), who observed that DFI variability among animals fed different wheat cultivars could not be eliminated by enzyme supplementation, although its addition increased DFI.

In our study, enzyme addition increased AMEn in animals fed the Horzal cultivar. Xylanase reduces the intestinal viscosity in birds by degrading soluble NSP arabinoxylans (McCracken et al., 1999; Choct et al., 2004). The Horzal cultivar had the highest concentration of soluble arabinose. When this cultivar was supplemented with enzymes, the reduction in the intestinal viscosity was larger than in the other cultivars (Figure 1bGo). Choct et al. (2004) used different enzymes on 2 wheat cultivars with low and normal ME. The enzymes that reduced ileal viscosity increased the AME value of the low-ME wheat. This may indicate that xylanase supplementation is most effective when intestinal viscosity is high, whereas there is no or little effect at medium to low viscosity values. The effect of enzyme addition was also related to the CP content of wheat (r = 0.52 to 0.79) and also to the baking strength (r = 0.74 to 89). The latter represents physical protein behavior, which can be explained by the protease activity present in the enzyme used.

In conclusion, wheat cultivar affects feed intake and animal performance, and AMEn does not appear to be involved in this effect. On the basis of the wheat cultivars used in this study, digestible ST does not explain the variations in AMEn among wheat cultivars, but no other important relationship with chemical composition was found. Further, the use of an exogenous enzyme did not eliminate the differences between cultivars, because its effect was cultivar dependent.

Received for publication October 24, 2007. Accepted for publication January 1, 2008.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
AOAC. 1995. Official Methods of Analysis, 16th. ed. Association of Official Analytical Chemists, Arlington, Virginia.

Bach Knudsen, K. E. 1997. Carbohydrate and lignin contents of plant materials used in animal feeding. Anim. Feed. Sci. Technol. 67:319–338.[CrossRef]

Bedford, M. R., and H. L. Classen. 1993. An in-vitro assay for prediction of broiler intestinal viscosity and growth when fed-rye diets in the presence of exogenous enzymes. Poult. Sci. 72:137–143.[Web of Science][Medline]

Carré, B., A. Idi, S. Maisonnier, J.-P. Melcion, F.-X. Oury, J. Gomez, and P. Pluchard. 2002. Relationships between digestibilities of food components and characteristics of wheats (Triticum aestivum) introduced as the only cereal source in a broiler chicken diet. Br. Poult. Sci. 43:404–415.[CrossRef][Web of Science][Medline]

Choct, M., A. Kocher, D. L. E. Waters, D. Pettersson, and G. Ross. 2004. A comparison of three xylanases on the nutritive value of two wheats for broiler chickens. Br. Poult. Sci. 92:53–61.

Fenton, T. W., and M. Fenton. 1979. An improved procedure for the determination of chromic oxide in feed and excreta. Can. J. Anim. Sci. 59:631–634.

Hill, F. W., and D. L. Anderson. 1958. Comparison of metabolisable energy and productive energy determinations with growing chicks. J. Nutr. 64:587–603.[Abstract/Free Full Text]

International Association for Cereal Science and Technology. 1998. Standard Methods of Analysis, 7th ed. International Association for Cereal Science and Technology, Vienna, Austria.

Kim, J. C., B. P. Mullan, P. H. Simmins, and J. R. Pluske. 2003. Variation in the chemical composition of wheats grown in Western Australia as influenced by variety, growing region, season and post-harvest storage. Austr. J. Agric. Res. 54:541–550.[CrossRef]

Longstaff, M., and J. M. McNab. 1986. Influence of site and variety on starch, hemicellulose and cellulose composition of wheats and their digestibilities by adult cockerels. Br. Poult. Sci. 27:435–449.[CrossRef][Web of Science]

Marron, L., M. R. Bedford, and K. J. McCracken. 2001. The effects of adding xylanases, vitamin C and copper sulphate to wheat-based diets on broiler performance. Br. Poult. Sci. 42:493–500.[CrossRef][Web of Science][Medline]

McCracken, K. J., S. Clegg, M. R. Bedford, and C. M. Preston. 1999. Effects of diet formulation and enzyme inclusion on apparent metabolisable energy (AME) concentration in wheat-based diets and on broiler performance. Br. Poult. Sci. 40:S37–S40.[CrossRef][Medline]

McCracken, K. J., and G. Quintin. 2000. Metabolisable energy content of diets and broiler performance as affected by wheat specific weight and enzyme supplementation. Br. Poult. Sci. 41:332–342.[CrossRef][Web of Science][Medline]

Meng, X., B. A. Slominski, C. M. Nyachoti, L. D. Campbell, and W. Guenter. 2005. Degradation of cell wall polysaccharides by combinations of carbohydrase enzymes and their effect on nutrient utilization and broiler chicken performance. Poult. Sci. 84:37–47.[Abstract/Free Full Text]

Mollah, Y., W. L. Bryden, I. R. Wallis, D. Balnave, and E. F. Annison. 1983. Studies on low metabolisable energy wheats for poultry using conventional and rapid assay procedures and the effects of processing. Br. Poult. Sci. 24:81–89.[CrossRef][Web of Science]

NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC.

Pirgozliev, V. R., C. L. Birch, S. P. Rose, P. S. Kettlewell, and M. R. Bedford. 2003. Chemical composition and the nutritive quality of different wheat cultivars for broiler chickens. Br. Poult. Sci. 44:464–475.[CrossRef][Web of Science][Medline]

Rose, S. P., and M. R. Bedford. 1995. Relationship between the metabolisable energies of wheat samples and the productive performances of broilers. Br. Poult. Sci. 36:864–875.

SAS Institute. 1985. SAS Users Guide: Statistics. Version 5 Edition. SAS Institute Inc., Cary, NC.

Scott, T. A. 2000. Significant variability of voluntary intake of wheat-and barley-based diets by broiler chicks. Proc. XXI World’s Poult. Congr., Montreal, Canada [CD-ROM]. World’s Poultry Science Association, Odijk, the Netherlands.

Scott, T. A. 2002. Impact of wet feeding wheat-based diets with or without enzyme on broiler chick performance. Can. J. Anim. Sci. 82:409–417.

Scott, T. A., and F. G. Silversides. 2003. Defining the effects of wheat type, water inclusion level, and wet-diet restriction on variability in performance of broilers fed wheat-based diets with added water. Can. J. Anim. Sci. 83:265–272.

Scott, T. A., F. G. Silversides, H. L. Classen, M. L. Swift, and M. R. Bedford. 1998. Effect of cultivar and environment on the feeding value of western Canadian wheat and barley samples with and without enzyme supplementation. Can. J. Anim. Sci. 78:649–656.

Spanish Royal Decree 1201/2005. 2005. Sobre protección de los animales utilizados en experimentación y otros fines cientificos. Bol. Of. Estado 252:34367–34391.

Steenfeldt, S. 2001. The dietary effect of different wheat cultivars for broiler chickens. Br. Poult. Sci. 42:595–609.[CrossRef][Web of Science][Medline]

Steenfeldt, S., M. Hammershøj, A. Müllertz, and J. F. Jensen. 1998. Enzyme supplementation of wheat-based diets for broilers. 2. Effect on apparent metabolisable energy content and nutrient digestibility. Anim. Feed Sci. Technol. 75:45–64.[CrossRef]

Svihus, B., and M. Gullord. 2002. Effect of chemical content and physical characteristics on nutritional value of wheat, barley and oats for poultry. Anim. Feed Sci. Technol. 102:71–92.[CrossRef]

Van Soest, J. P., J. B. Robertson, and B. A. Lewis. 1991. Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74:3583–3597.[Abstract]

Wang, Z. R., S. Y. Qiao, W. Q. Lu, and D. F. Li. 2005. Effects of enzyme supplementation on performance, nutrient digestibility, gastrointestinal morphology, and volatile fatty acid profiles in the hind gut of broilers fed wheat-based diet. Poult. Sci. 84:875–881.[Abstract/Free Full Text]

Wiseman, J. 2006. Variations in starch digestibility in non-ruminants. Anim. Feed Sci. Technol. 130:66–77.[CrossRef]





This Article
Free Via Open Access
Right arrow Abstract
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by del Alamo, A. G.
Right arrow Articles by Villamide, M. J.
Right arrow Search for Related Content
PubMed
Right arrow Articles by del Alamo, A. G.
Right arrow Articles by Villamide, M. J.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS