| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
METABOLISM AND NUTRITION |
Institute of Food, Nutrition and Human Health, Massey University, Private Bag 11 222, Palmerston North, New Zealand
1 Corresponding author: v.ravindran{at}massey.ac.nz
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Key Words: particle size • wheat • corn • digestive tract • digesta parameter
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Grain type is known to influence the particle size spectra of milled products. Passing different grains through the same screen size opening in a hammer mill will give different particle size distributions (Amerah et al., 2007a). This suggests that, during hammer mill grinding, different screen sizes may have to be used for different grains to obtain the desired particle size distribution. Nir et al. (1995) reported that grinding wheat with the same hammer mill under the same conditions gave a greater geometric mean diameter (GMD) compared with sorghum.
Available evidence suggests grain particle size to be more critical in mash feeds and less so in pelleted or crumbled feeds (Amerah et al., 2007a). This is surprising, because the effect of particle size on broiler performance may be expected to be maintained even after pelleting, given that pellets dissolve in the crop after consumption. Studies examining the effect of pelleting on the particle size distribution of wheat-based diets have produced inconsistent results. Peron et al. (2005) and Lentle et al. (2006) reported that the particle size distribution in wheat-based diets remained after pelleting, with positive effects on performance and gizzard development. In contrast, Engberg et al. (2002), Svihus et al. (2004b), and Amerah et al. (2007b) reported that pelleting evened out the differences in particle size distribution of wheat-based diets, with no effects observed on performance and gizzard development. On the other hand, the effect of pelleting on the particle size distribution of corn-based diets has not been previously reported. The objectives of the present study were to compare the effects of particle size on the performance, energy utilization, digestive tract development, intestinal villus morphology, and duodenal and colonic di-gesta particle size spectra of broilers fed pelleted diets based on wheat and corn.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
One-day-old male broilers (Ross 308) were obtained from a commercial hatchery, individually weighed, and assigned to 24 cages (8 birds per cage) in electrically heated battery brooders so that the average weight per cage was similar. The birds were transferred to grower cages on d 12 and maintained on the same dietary treatments until d 21. The battery brooders and grower cages were housed in an environmentally controlled room. The birds had no access to litter material. The temperature was maintained at 31°C on d 1 and was subsequently gradually decreased to 22°C by 21 d of age. Light was provided continuously throughout the study. Body weights and feed intake by cage were recorded weekly, and the mortality was recorded daily. Feed per gain values were calculated by dividing total feed intake by weight gain of live plus dead birds.
Diets
A 2 x 2 factorial arrangement of treatments was employed and tested 2 grain types (wheat vs. corn) and 2 particle sizes (fine vs. coarse). The 2 particle sizes were achieved by grinding the wheat and corn in a hammer mill (Bisley’s Farm Machinery, Auckland, New Zea-land) to pass through 1- and 7-mm sieves, respectively. The GMD and geometric standard deviation (GSD) of the ground grains were then determined as described by Baker and Herrman (2002). Four diets (Table 1
), based on one of the milled grades of wheat or corn, were formulated to meet or exceed the NRC (1994) recommendations for major nutrients for broiler starters. All diets were pelleted using a pellet mill (Rich-ard Size Limited Engineers, Orbit 15, Kingston-upon-Hull, UK) capable of manufacturing 180 kg of feed/h and equipped with a die ring (3-mm holes and 35-mm thickness). Conditioning time of the mash was 90 s to a temperature of 70°C. All diets and water were provided for ad libitum consumption. The experimental procedures were approved by the Massey University Animal Ethics Committee.
|
On d 15, feed was withdrawn from each cage for 2 h, and identical experimental diets containing chromic oxide (1.0 g/kg) were then offered for 15 min before being replaced with the original diet. Transit time was determined as the lapsed time from the introduction of the diets to the time of first appearance in the droppings of green coloration from chromic oxide.
AME Determination
From d 17 to 20 posthatching, feed intake and total excreta output were measured quantitatively per cage over 4 consecutive days for the determination of AME. Daily excreta collections were pooled within a cage, mixed in a blender, and subsampled. Each sub-sample was lyophilized, ground to pass through a 0.5-mm sieve, and stored in airtight plastic containers at -4°C pending analysis.
The DM content, nitrogen, and gross energy were determined in replicate samples of diets and excreta. Dry matter content was determined using standard procedures (method 930.15; AOAC, 1990). Nitrogen was determined by combustion (method 968.06; AOAC, 1990) using a CNS-200 carbon, nitrogen, and sulfur auto analyzer (Leco Corporation, St. Joseph, MI). Gross energy was determined by adiabatic bomb calorimetry (Gallenkamp Autobomb, London, UK) standardized with benzoic acid. The AME values were calculated using the following formula with appropriate corrections made for differences in DM content:
Nitrogen-corrected AME was calculated by correction for zero nitrogen retention by simple multiplication with 8.73 kcal/g of nitrogen retained in the body as described by Hill and Anderson (1958).
Digestive Tract and Intestinal Morphology Measurements
On d 21, four birds from each replicate cage, with body weights closest to the mean weight of the pen, were killed by cervical dislocation. Two of these birds were used for measurements of the digestive tract and the other 2 birds for the microscopic study of intestinal morphology.
The live weight and weight of digestive tract segments from crop to ceca of each bird was determined. The length of each intestinal segment was determined with a flexible tape on a glass surface to prevent inadvertent stretching. The length (±0.1 mm) of the duodenum (from the pyloric junction to the distalmost point of insertion of the duodenal mesentery), the length of the jejunum (from the distalmost point of insertion of the duodenal mesentery to the junction with Meckel’s diverticulum), the length of the ileum (from the junction with Meckel’s diverticulum to ileocecal junction), and the sum of the lengths from ostium to the tip of each ceca were determined. After division and freeing of each of these components from any adherent mesentery, their full and empty weights (±0.1 g) were determined along with those of the crop, proventriculus, and gizzard.
For intestinal morphological examinations, sections from the middle of the duodenum and jejunum (about 5 cm in length) were excised, flushed with ice-cold saline, and immediately placed in Bouin’s fluid. Samples were transferred into 70% ethanol after 24 h. Each fixed sample was then embedded into wax and sectioned at a thickness of 7 µm, stained with alcian blue-hema-toxylin-eosin, and examined by light microscopy. Four intestinal segments were fixed in each slide, and the slides were viewed on a Zeiss Axiophot microscope (Carl Zeiss, Oberkochen, Germany). Visual measurements of villus height and crypt depth were made on 10 villi at 100x and 200x magnifications using imaging software (Image Pro Plus, Version 4.1.0.9 [EC] , Media Cybernetics, Silver Spring, MD). The variables measured were villus height (the distance from the apex of the villus to the junction of the villus and crypt), crypt depth (the distance from the junction to the basement membrane of the epithelial cell at the bottom of the crypt), and the total extent of the mucosal layer (the distance from the apex of the villus to the basement membrane of the epithelial cell at the bottom of the crypt).
Determination of Particle Size Distribution in the Diets and Duodenal and Colonic Digesta
Two more birds per cage were killed by intravenous injection of sodium pentobarbitone (50 mg/kg of body weight) on d 21. Digesta were removed from the duodenum by simple drainage and from the colon by manual expression. Samples from the 2 birds within each pen were then pooled, giving a total of 6 digesta samples per segment per dietary treatment. The particle size spectra of the samples were determined by wet-sieving using the method described by Lentle et al. (2006). Briefly, weighed samples of the diet and duodenal and colonic digesta samples were each divided into 2 sub-samples. One was dried at 80°C in a forced-draft oven to constant weight to determine the DM content, and the other was suspended in 50 mL of water before it was washed through a set of sieves (Endocot, London, UK) sized 2, 1, 0.5, 0.25, 0.106, and 0.075 mm. The diet samples were suspended in 50 mL of water and left to stand for 30 min before sieving to ensure adequate hydration. The contents of each of the sieves were subsequently washed onto dried, preweighed filter papers, dried for 24 h in a forced-draft oven at 80°C for 3 d, and reweighed. The dry weight of particles retained by each sieve and of fines remaining in the bottom pan was expressed as percentage of total DM recovered.
Pellet Durability
Pellet durability was determined in a Holmen Pellet Tester (New Holmen Pellet Tester, TekPro Ltd., Norfolk, UK) using the method described by Svihus et al. (2004b). The pellet samples (100 g) were circulated pneumatically through a closed pipe for 30 s before being passed through a 3-mm sieve. The pellet durability index (PDI) was calculated as the relative proportion by weight of pellets retained on the 3-mm sieve.
Data Analysis
The performance data were analyzed by 2-way ANO-VA using the GLM procedure of SAS (1997) using cage as the experimental unit. Differences were considered to be significant at P < 0.05. When a significant F-test was detected, means were separated using the least significant difference test (Snedecor and Cochran, 1967).
Gross and microscopic measurements of the digestive tract of individual birds were first subjected to log transformation to achieve near normal distribution on graphic analysis in SYSTAT (Wilkinson, 1990). Two-way ANOVA was used to identify any interaction between grain type and feed particle size on the microscopic morphometric parameters of gut components. For gross digestive tract measurements, a 3-way ANO-VA was used to identify any interaction between grain type, feed particle size, and the various digestive tract components (crop to ceca) so as to understand how grain type and particle size influence the overall tract development. A similar model was used for analysis of (log-transformed) digesta content, with the digesta content of the various segments of the small intestine being the third factor. In each case, the significance of individual components within the 3 levels was explored by post hoc testing with Bonferroni correction.
The effects of treatments on particle size distribution in the duodenal and colonic digesta were compared by discriminant analysis using SYSTAT (Wilkinson, 1990). Pellet durability data were compared by 1-way ANOVA using the GLM procedure of SAS (1997).
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Particle size distributions of the ground grains are shown in Figure 1. The GMD of wheat ground through 1- and 7-mm screen sizes were determined to be 0.284 and 0.890 mm, respectively, with corresponding GSD values of 1.95 and 2.19. The GMD of corn ground through 1- and 7-mm screen sizes were determined to be 0.297 and 0.528 mm, respectively, with corresponding GSD values of 1.81 and 2.33. Comparisons of the particle size distributions of the pelleted diets showed that the differences in particle size distribution persisted in both diets after pelleting, notably in the proportion of coarse particles (1 mm and over; Figure 2).
|
|
Grain type influenced (P = 0.06) weight gain, with birds fed wheat-based diets having a greater gain than those fed corn-based diets (Table 2). A grain type x particle size interaction was observed, with coarse grinding increasing (P = 0.07) the gains only in birds fed corn-based diets. Feed intake was influenced (P < 0.001) by grain type, with the intake of wheat-based diets being greater than those of corn-based diets. Feed intake was also influenced (P < 0.05) by particle size, with the intake of fine ground diets being greater than those of coarse ground diets. Birds fed corn-based diets had a lower (P < 0.001) feed per gain compared with those fed wheat-based diets. Coarse grinding lowered (P < 0.0001) feed per gain of broilers compared with fine grinding. No grain type x particle size interaction (P > 0.05) was observed for feed intake and feed per gain.
|
Pellet durability was influenced by grain type and particle size (Table 2
). Pellets made with corn had better (P < 0.0001) pellet durability than those made with wheat. Fine grinding resulted in a better (P < 0.05) pellet durability than coarse grinding. No treatment interaction (P > 0.05) was observed for pellet durability.
Digestive Tract Measurements
Although there were no significant (P > 0.05) main effects of particle size and grain type on the relative weight of gut components, an interaction (P < 0.05) was noted between individual gut components and grain type due to the greater gizzard weight in birds fed corn-based diet (Table 3). There was an interaction (P < 0.05) between individual gut components and particle size. This was due to the greater gizzard weight in birds fed coarse particle size diets. A 3-way interaction (P < 0.05) between particle size, grain type, and the weights of the various gut segments was also found due to birds fed coarse particle size having heavier gizzards in birds fed corn-based diets, but this effect was not found in birds fed wheat-based diets.
|
The relative length of all gut components was generally shorter (P < 0.05) in birds fed wheat-based diets compared with those fed corn-based diets. An interaction (P < 0.05) between particle size and grain type was noted for the relative length of gut components. All gut components were shorter in birds fed coarse particle sizes compared with those fed fine particle sizes in corn-based diets, but there was no difference between different particle sized wheat-based diets.
Intestinal Morphology
Total extent of the mucosal layer, villus height, and epithelial cell thickness in the duodenum were not influenced (P > 0.05) by grain type and particle size (Table 4). Birds fed corn-based diets had deeper (P = 0.06) crypts compared with those fed wheat-based diets.
|
Discriminant analysis failed to show any distinction between particle size distributions of the duodenal digesta of birds fed fine and coarse particle-sized wheat- and corn-based diets (Table 5). Similarly, the discriminant analysis failed to show distinction between particle size distributions of the colonic digesta of birds fed fine and coarse particle-sized wheat- and corn-based diets.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Wet-sieving of the pelleted diets indicated differences in particle size distribution between diets after pelleting, especially in the proportion of coarse particles over 1 mm. The coarse wheat diet consisted of 46.8% of particles over 1 mm compared with 26.6% in the fine wheat diet. Similarly, the coarse corn diet had 33.7% of particles over 1 mm compared with 19.2% in the fine corn diet. Similar findings have been reported by Peron et al. (2005) in wheat-based diets. In contrast, Amerah et al. (2007b) showed that pelleting evened out the differences in particle size distribution of diets consisting of medium or coarse ground wheat. The inconsistency between research results may be due to differences in wheat cultivars used and endosperm hardness.
In the present study, particle size influenced both feed intake and feed per gain, with coarse grinding decreasing feed intake and improving feed per gain in both wheat- and corn-based diets. In contrast, Lott et al. (1992) found that corn ground through a hammer mill screen opening of 9.59 mm, which resulted in coarse particles (GMD, 1.20 mm), significantly decreased 21-d body weights and increased feed per gain compared with corn ground through a screen opening of 3.18 mm (GMD, 0.68 mm). Kilburn and Edwards (2001) also reported improvements in feed per gain and true metabolizable energy when the diet included medium ground corn (GMD, 0.87 mm) compared with that made from very coarse corn (GMD, 2.90 mm). Reece et al. (1985, 1986a,b), however, found that the corn particle size (GMD, 0.68 vs. 1.29 mm) had no effect on the performance of broilers fed crumbled or pelleted diets. The results of the current study suggest that grinding corn using a 7-mm hammer mill screen size will have beneficial effects on broiler performance compared with those fed corn ground using a 3-mm screen size.
With regard to pelleted wheat-based diets, previous research findings on the effect of particle size on broiler performance are conflicting. Peron et al. (2005) reported a tendency for lower feed per gain in birds given coarse wheat (GMD, 0.96 mm) vs. those fed fine ground wheat (GMD, 0.39 mm), and this enhancement was associated with a greater relative gizzard weight. Similarly, using 3 wheat cultivars, which resulted in different particle size distributions, Lentle et al. (2006) found that the diet with the greatest relative proportion of coarser particles resulted in the lowest feed per gain in broiler chickens. Both Peron et al. (2005) and Lentle et al. (2006) found that the differences in particle size distribution between treatments still existed even postpelleting. On the other hand, Engberg et al. (2002) and Amerah et al. (2007b) reported that pelleting evened out the differences in particle size distribution in pelleted diets, which resulted in a lack of a wheat particle size effect on broiler performance. It can be suggested, therefore, that the effect of wheat particle size on broiler performance in pelleted diets may depend on particle size distribution postpelleting, with coarse particles remaining postpelleting having beneficial effects.
Three different explanations may be provided for the improvement in feed efficiency in birds fed diets with coarse particles. First, a greater proportion of coarse particulate matter resulted in a longer residence time within the gizzard, leading to enhanced digestion and thus better feed efficiency. Second, a greater proportion of coarse particulate matter might stimulate greater gizzard activity, leading to more efficient grinding with production of greater quantities of finer particles that are more readily digested. Third, the converse of the second, that with greater requirement for gizzard action to decrease particle size, efficiency is decreased, a greater proportion of coarser material enters the small intestine and that this coarser particulate material in some way stimulates digestive efficiency and is itself digested more readily. However, the results of the current study do not support the third possibility, because discriminant analysis failed to show any distinction between particle size distribution in the duodenal digesta of birds fed fine and coarse particles of both wheat- and corn-based diets. The improvement in feed per gain found in the birds fed coarse particle diets in the current study may be explained, in part, by the larger relative gizzard observed in these birds. The greater digesta content observed in the gizzard of the birds fed coarse particles may have stimulated an increase in the size of the gizzard. A well-developed gizzard has been reported to improve gut motility (Ferket, 2000) through increased levels of cholecystokinin release (Svihus et al., 2004a), which in turn stimulates the secretion of pancreatic enzymes and the gastroduodenal refluxes (Duke, 1992; Li and Owyang, 1993). Coarse particles may slow the passage rate of digesta through the gizzard (Nir et al., 1994), increasing the exposure time of nutrients to digestive enzymes, which in turn may improve energy utilization and nutrient digestibility (Carre, 2000). Furthermore, it has been reported that a lower pH of gizzard contents may increase pepsin activity (Gabriel et al., 2003) and improve protein digestion.
In the present study, birds fed corn-based diets had a lower feed per gain compared with those fed wheat-based diets. These results may be explained, in part, by the lower AMEn determined for wheat-based diets. Coarse grinding of wheat tended to increase AMEn, but corn particle size had no effect on AMEn. In contrast, Peron et al. (2005) found that fine grinding of wheat improved starch digestibility and the AME compared with coarse grinding. Svihus et al. (2004b) found no effect of wheat particle size on the AME.
In the current study, there was an interaction between grain type and the weights of the various gut segments due to birds fed corn-based diets having a relatively heavier gizzard than those fed wheat-based diets. Nir et al. (1994) also found that the relative weights of gizzard and its contents were greater in birds fed corn-based diets compared with those fed wheat-based diet in mash feeds. The reasons for these findings are unclear.
The lack of difference in duodenal digesta particle size distribution between treatments in the birds suggests that the grinding activity of gizzard evened out the differences in particle size distribution of the diets. Similar results also observed by Amerah et al. (2007b) suggest that the gizzard is efficient in grinding large particles.
In general, it is believed that there is an inverse relationship between particle size and pellet durability (Angulo et al., 1996), which is based on the fact that smaller particles have more contact points with each other because of their larger surface area per unit volume ratio (Behnke, 2001). This is in agreement with the findings of the current study, in which pellets made from fine particles gave better durability compared with those made from coarsely ground grains. These results are consistent with those of Svihus et al. (2004b), who reported a tendency for better pellet durability in diets made from fine particles. This finding was attributed to greater starch gelatinization in fine ground wheat. Reece et al. (1986b), in contrast, found that pellets made from coarse particles gave significantly more durable pellets than those made from fine particles. However, the lower PDI of the coarse diets observed in the current study did not adversely influence feed per gain of broilers, which may be explained by the good pellet durability in all diets, PDI >90%.
In summary, under the conditions of the current study, grinding wheat and corn under the same milling conditions resulted in different particle size distributions. Coarse grinding lowered feed per gain when compared with fine grinding regardless of the grain type. This improvement in feed efficiency with coarse ground diets was concomitant with greater relative gizzard weights. The gizzard evened out dietary particle size differences, which resulted in a similar particle size distribution in the duodenal digesta of the birds fed fine and coarse particles. Birds fed corn-based diets had a relatively heavier gizzard than those fed wheat-based diets. The duodenal morphometry was not influenced by either grain type or particle size. Pellets made from fine particle sizes were more durable than those made from coarse ground grains. Overall, the results of the present study suggest that the effects of feed particle size vary depending on grain type and that coarse grinding of wheat and corn is advantageous in terms of broiler performance.
Received for publication April 10, 2008. Accepted for publication July 8, 2008.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Amerah, A. M., V. Ravindran, R. G. Lentle, and D. G. Thom-as. 2007b. Influence of feed particle size and feed form on the performance, energy utilization, digestive tract development and digesta parameters of broiler starters. Poult. Sci. 86:2615–2623.
Angulo, E., J. Brufau, and E. Esteve-Garcia. 1996. Effect of a sepiolite product on pellet durability in pig diets differing in particle size and in broiler starter and finisher diets. Anim. Feed Sci. Technol. 63:25–34.[CrossRef]
AOAC. 1990. Official Methods of Analysis. 15th edition. Association of Official Analytical Chemists, Washington, DC.
Baker, S., and T. Herrman. 2002. Evaluating particle size. MF-2051 Feed Manufacturing. Kansas State University, Manhattan.
Behnke, K. C. 2001. Factors influencing pellet quality. Feed Technol. 5:19–22.
Carre, B. 2000. Effets de la taille des particules alimentairessur les processus digestifs chez les oiseaux d’élevage. Prod. Anim. 13:131–136.
Dobraszczyk, B. J., M. B. Whitworth, J. F. V. Vincent, and A. A. Khan. 2002. Single kernel wheat hardness and fracture properties in relation to density and the modelling of fracture in wheat endosperm. J. Cereal Sci. 35:245–263.[CrossRef]
Dozier, W. A. III. 2002. Reducing utility cost in the feed mill. Watt Poult. USA. 53:40–44.
Duke, G. E. 1992. Recent studies on regulation of gastric motility in turkeys. Poult. Sci. 81:1–8.
Engberg, R. M., M. S. Hedemann, and B. B. Jensen. 2002. The influence of grinding and pelleting of feed on the microbial composition and activity in the digestive tract of broiler chickens. Br. Poult. Sci. 43:569–579.[CrossRef][Web of Science][Medline]
Ferket, P. 2000. Feeding whole grains to poultry improves gut health. Feedstuffs 72:12–14.
Gabriel, I., S. Mallet, and M. Leconte. 2003. Differences in the digestive tract characteristics of broiler chickens fed on complete pelleted diet or on whole wheat added to pelleted protein concentrate. Br. Poult. Sci. 44:283–290.[CrossRef][Web of Science][Medline]
Hill, F. W., and D. L. Anderson. 1958. Comparison of metabo- lizable energy and productive energy determinations with growing chicks. J. Nutr. 64:587–603.
Kilburn, J., and H. M. Edwards. 2001. The response of broilers to the feeding of mash or pelleted diets containing corn of varying particle sizes. Br. Poult. Sci. 42:484–492.[CrossRef][Web of Science][Medline]
Lentle, R. G., V. Ravindran, G. Ravindran, and D. V. Thom- as. 2006. Influence of feed particle size on the efficiency of broiler chickens fed wheat based diets. Jpn. Poult. Sci. 43:135–142.[CrossRef]
Li, Y., and C. Owyang. 1993. Vagal afferent pathway medi- ates physiological action of cholecystokinin on pancreatic enzyme secretion. J. Clin. Invest. 92:418–424.[Web of Science][Medline]
Lott, B. D., E. J. Day, J. W. Deaton, and J. D. May. 1992. The effect of temperature, dietary energy level, and corn particle size on broiler performance. Poult. Sci. 71:618–624.[Web of Science][Medline]
NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC.
Nir, I., R. Hillel, I. Ptichi, and G. Shefet. 1995. Effect of particle size on performance 3. Grinding pelleting interactions. Poult. Sci. 74:771–783.[Web of Science][Medline]
Nir, I., G. Shefet, and Y. Aaroni. 1994. Effect of particle size on performance. 1. Corn. Poult. Sci. 73:45–49.
Peron, A., D. Bastianelli, F. X. Oury, J. Gomez, and B. Carre. 2005. Effects of food deprivation and particle size of ground wheat on digestibility of food components in broilers fed on a pelleted diet. Br. Poult. Sci. 46:223–230.[CrossRef][Web of Science][Medline]
Reece, F. N., B. D. Lott, and J. W. Deaton. 1985. The effects of feed form, grinding method, energy level, and gender on broiler performance in a moderate (21°C) environment. Poult. Sci. 64:1834–1839.[Web of Science]
Reece, F. N., B. D. Lott, and J. W. Deaton. 1986a. Effects of environmental temperature and corn particle size on response of broilers to pelleted feed. Poult. Sci. 65:636–641.[Web of Science]
Reece, F. N., B. D. Lott, and J. W. Deaton. 1986b. The effects of hammer mill screen size on ground corn particle size, pellet durability, and broiler performance. Poult. Sci. 65:1257–1261.[Web of Science]
SAS. 1997. SAS/STAT® User’s Guide: Statistics. Version 6.12. SAS Institute Inc., Cary, NC.
Snedecor, G. W., and W. G. Cochran. 1967. Statistical Meth- ods. Iowa State University Press, Ames.
Svihus, B., E. Juvik, H. Hetland, and A. Krogdahl. 2004a. Causes for improvement in nutritive value of broiler chicken diets with whole wheat instead of ground wheat. Br. Poult. Sci. 45:55–60.[Web of Science][Medline]
Svihus, B., K. H. Klovstad, V. Perez, O. Zimonja, S. Sahlstrom, and R. B. Schuller. 2004b. Physical and nutritional effects of pelleting of broiler chicken diets made from wheat ground to different coarsenesses by the use of roller mill and hammer mill. Anim. Feed Sci. Technol. 117:281–293.[CrossRef]
Wilkinson, L. 1990. Statistic Package, Version 5. SYSTAT Inc., Evanston, IL.
This article has been cited by other articles:
|
|
 |
|
  P. Biggs and C. M. Parsons The effects of whole grains on nutrient digestibilities, growth performance, and cecal short-chain fatty acid concentrations in young chicks fed ground corn-soybean meal diets Poult. Sci., September 1, 2009; 88(9): 1893 - 1905. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Frikha, H. M. Safaa, M. P. Serrano, X. Arbe, and G. G. Mateos Influence of the main cereal and feed form of the diet on performance and digestive tract traits of brown-egg laying pullets Poult. Sci., May 1, 2009; 88(5): 994 - 1002. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
