Effect of Gelatinizing Dietary Starch Through Feed Processing on Zeroto Three-Week Broiler Performance and Metabolism

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1 2005 Poultry Science Association, Inc. Effect of Gelatinizing Dietary Starch Through Feed Processing on Zeroto Three-Week Broiler Performance and Metabolism J. S. Moritz,*,1 A. S. Parsons,* and N. P. Buchanan,* W. B. Calvalcanti, K. R. Cramer, and R. S. Beyer *Division of Animal and Veterinary Sciences, West Virginia University, Morgantown, West Virginia 26506; and Department of Animal Science and Industry, Kansas State University, Manhattan, Kansas Primary Audience: Feed Mill Managers, Nutritionists, Broiler Producers, Researchers SUMMARY Feed manufacturing produces physical and chemical changes in ingredients, including the gelatinization of starch. The effect of gelatinized starch on animal metabolism and subsequent performance has been inconsistent in past research. In the current study, corn was processed through different procedures (pelleting and extrusion) and substituted for unprocessed corn at varying levels (one-third, two-thirds, and three-thirds) in complete diets. Complete diets were not further processed. The objective of the study was to evaluate different levels of starch gelatinization produced by different processes on broiler performance through 3 wk of age. Pelleted and extruded corn had analyzed starch gelatinizations of 29 and 92%, respectively. Each of the 6 processed corn diets and a control diet (ground unprocessed corn) was fed to 8 replicate pens of 10 male broilers. A second experiment determined AME n of each diet. Broilers fed diets containing pelleted corn had lower feed intake (P = ) and higher gain to feed (G:F, P = ) than broilers fed diets containing extruded corn. Gain-to-feed ratio was not affected when pelleted or extruded corn was increased in diets. The AME n of diets increased as pelleted or extruded corn inclusion increased (P = and , respectively). Diets containing pelleted or extruded corn pooled by inclusion level did not improve AME n or G:F compared with the control diet. However, diets containing pelleted or extruded corn pooled by inclusion level increased live weight gain (LWG, P = 0.04 and , respectively) compared with the control in part due to increased feed intake. Key words: broiler performance, extrusion, feed manufacturing, starch gelatinization, pelleting 2005 J. Appl. Poult. Res. 14:47 54 DESCRIPTION OF PROBLEM Typical US broiler diets contain high percentages of corn and, therefore, high proportions of starch. Under processing conditions using heat and moisture, starches gelatinize and help bind feed particles together [1]. Hoover [2] defines starch gelatinization as an order-disorder phase transition that includes the diffusion of water into a granule, hydration and swelling, uptake of heat, loss of crystallinity, and amylose leaching. Leached amylose immediately forms 1 To whom correspondence should be addressed: jsmoritz@mail.wvu.edu.

2 48 double helices that may aggregate (hydrogen bond) to each other and create semicrystalline regions [3]. Lund [4] speculates that as the gelatinized starch cools, the dispersed matrix forms a gel or pastelike mass that may function as an adhesive or binding agent. Past research has associated dietary gelatinized starch both positively and negatively with pellet quality and broiler performance [5, 6, 7]. However, it has been speculated that gelatinized starch per se may affect broiler performance aside from its contribution to pellet binding. Gelatinizing cereal starch has generally been thought to improve enzymatic access to glucosidic linkages and consequent digestibility [8, 9]. Allred et al. [10] reported a significant improvement in weight gain and feed conversion in chicks fed pelleted and reground corn that was incorporated into a complete diet over chicks fed similar diets with unprocessed corn (UC). However, later research examining processed and reground corn-based diets concluded there was no nutritional benefit to broilers despite increased diet starch gelatinization [11, 12]. Moreover, Plavnik et al. [13] found that feeding broilers pelleted and reground corn-based diets resulted in decreased bird performance compared with broilers fed similar unprocessed diets. One strategy for producing high-quality pellets has been to gelatinize as much ingredient starch as possible. High-quality pellets are desirable as their feeding is correlated with improved broiler performance. However, improving pellet quality through increasing starch gelatinization may negatively affect nutrient utilization, thus antagonizing performance enhancements of pelleting. In the current study, corn was processed using typical feed industry practices and incrementally incorporated into complete diets at the expense of UC. The objective was to create diets with different levels of gelatinized starch produced from different commercial processes. Corn was the only ingredient processed to avoid confounding processing effects of high-fat or high-protein ingredients. Corn was either pelleted (PC) or extruded (EC) and subsequently reground prior to diet incorporation. The PC provided dietary starch gelatinization percentages indicative of conventional pelleted feeds, while EC provided high levels of gelatinization. JAPR: Research Report Diets were fed to broilers during the 0- to 3-wk starter phase to determine effects of processingderived starch gelatinization on performance and metabolism. MATERIALS AND METHODS Diet Compositions and Feed Manufacturing Experimental starter diets utilized various ratios of 3 different corn types. Corn, originating from a similar lot, was unprocessed, pelleted, or extruded. To ensure favorable processing, it was necessary for preextruded corn to be finely ground. Accordingly, all corn was ground through a hammer mill using a 1.59 mm (4/64 in.) screen prior to any processing. Corn used for pelleting was steam conditioned using a short-term conditioner [ m (1 3 ft), 10 s retention time] set at a constant temperature of 65.6 C (150 F). Higher conditioning temperatures were avoided to prevent pellet mill roll slippage or die blockage or both. Pellets were formed using a California pellet mill [14] with a mm (3/ in.) die. Postpelleted corn was cooled for 10 min in a vertical cooler using forced ambient air. The EC was produced using a twin-screw extruder [15] with a shaft speed of 240 rpm and a feed rate of 100 kg/h. Water was injected into the conditioner and extruder at rates of 7.4 and 3.1 kg/h, respectively. The extruder included a barrel assembly with 8 chambers, each with temperature control. Barrel chamber temperatures were set at 48, 48, 90, 120, 150, 142, 142, and 152 C. Head pressure was 5.17 Pa (750 psi). The extrudate was dried for 6 min at 160 C (320 F) and subsequently cooled with ambient air for 3 min. This drying procedure was adopted to obtain an EC moisture content similar to PC. Differences in corn particle size and texture were of concern. Consequently, PC and EC were again ground through a hammer mill with a 1.59 mm (4/64 in.) screen prior to diet incorporation. Each ground corn type was analyzed for moisture [16], bulk density [17], particle size [18], and the percentage of gelatinized starch [19] (Table 1). Experimental broiler starter diets were formulated to 1994 NRC recommendations [20], using different types and percentages of processed corn. Corn comprised 57.5% of each diet

3 MORITZ ET AL.: FEEDING GELATINIZED STARCH 49 TABLE 1. Corn type descriptions Item Unprocessed corn (UC) Pelleted corn (PC) Extruded corn (EC) Bulk density, kg/m 3 (lb/ft 3 ) (33.6) (33.1) (33.8) Moisture (%) Particle size (SD) 1,2 364 (2.08) 256 (1.95) 487 (1.78) Starch gelatinization 3 (%) Peak gelatinization temperature ( C) Geometric mean particle size measured in microns. 2 Log normal geometric SD. 3 The percentage of gelatinized starch for the unprocessed corn sample was designated as zero in order to determine percentage gelatinization increase for processed samples. (Table 2). The PC or EC made up either onethird, two-thirds, or all of the corn fraction of diets. Processed corn was substituted in a 1:1 ratio for ground UC. A control diet, using only ground UC, was also made for a total of 7 different experimental diets. Each diet utilized a common mash premix, which included all ingredients less corn and soybean oil. Soybean oil was added during mixing. Complete diets were not further processed. Broiler Performance Day-old male broilers [21] were the experimental model for testing performance. Birds were randomly allotted to raised-wire grower cages [ cm (23 30 in.)] equipped TABLE 2. Broiler starter diet formulation Ingredient % Yellow corn Soybean meal (47.5%) Soybean oil Defluorinated phosphate Limestone Poultry premix Salt Methionine Calculated composition ME (kcal/kg) 3,200 CP (%) 21.5 Methionine (%) 0.5 Lysine (%) 1.2 Calcium (%) 1.0 Available phosphorus (%) Supplied per kilogram of diet: manganese, 0.02%; zinc, 0.02%; iron, 0.01%; copper, %; iodine, %; selenium, %; folic acid, 0.69 mg; choline, 386 mg; riboflavin, 6.61 mg; biotin, 0.03 mg; vitamin B 6, 1.38 mg; niacin, mg; panthothenic acid, 6.61 mg; thiamine, 2.20 mg; menadione, 0.83 mg; vitamin B 12, 0.01 mg; vitamin E, IU; vitamin D 3, 2,133 ICU; vitamin A, 7,716 IU. with nipple drinkers and trough-type feeders. An individual cage of 10 birds was the experimental unit. Experimental diets were randomly assigned among groups of 7 adjacent cages. There were 8 cage groups designated according to their location within the house, and these were used as the blocking criterion. Broilers were fed experimental mash diets during the 0- to 3-wk starter period. Feed and water were provided for ad libitum consumption throughout the period. Temperature was regulated thermostatically by starting chicks at 35 C (95 F) and decreasing the temperature 2.8 C (5 F) weekly to maximize bird comfort. Dead birds were removed and weighed as necessary. At 3 wk, feed was removed and weighed. After a 12-h fasting period, broiler pen number and weight were recorded. From these measurements, broiler live weight gain (LWG), feed intake, and gain to feed (G:F) were calculated. Gain-to-feed ratios included mortality weight. Broiler Metabolism A modified energy metabolism procedure [22] was used to determine AME n. The procedure used multiple birds per pen and ad libitum feeding that ensured adequate excreta for analysis and satisfied West Virginia University animal care requirements. Straight-run commercial broilers [23] were raised in floor pens from 0 to 1 wk. Birds were then randomly assigned to raised-wire cages (3 birds per cage) equipped with feed troughs and nipple drinkers. The room containing these cages utilized forced-air brooders and crosscurrent ventilation. Birds were given a 1.5-wk cage adaptation period prior to experimentation. The pretest diet was formulated to NRC specifications and contained finely ground corn (complete diet particle size = 545

4 50 µm). On d 17 (2.5 wk of age), feed was withheld from birds for 24 h. Experimental diets were then randomly assigned among groups of 7 adjacent cages. There were 6 cage groups designated according to their location within the room, and these were used as the blocking criterion. Birds were given the same experimental diets as used in the performance experiment ad libitum for a 12-h period, and excreta were collected. The diets were then removed, and excreta collection continued for an additional 24 h. Gross energy of feed and excreta were determined using bomb calorimetry [24]. Nitrogen content of feed and excreta were determined with Kjeldahl analysis [25]. Retained nitrogen was calculated and corrected for eventual uric acid formation and oxidation [26]. The AME n was calculated using the weight of feed consumed, total excreta, gross energy, and retained nitrogen oxidation values. All procedures followed protocols established by the West Virginia University Animal Care and Use Committee ( ). Statistical Analysis Due to the application of a control treatment, 2 separate analyses were performed to describe dietary effects on broiler performance. A processed corn type corn inclusion level factorial analysis was run to explore main effects and their interaction. Additionally, linear regression was conducted for each series of diets containing PC and EC. A second analysis was run that included all 7 treatments. This analysis enabled comparisons between each diet containing processed corn and the control diet. Preplanned orthogonal contrasts were also performed to explore specific comparisons. Statistics were calculated using either the GLM or REG procedure of the Statistical Analysis System [27]. Significant effects were further explored using Fisher s least significant difference test to determine differences among treatment means. In all cases, α was designated as RESULTS AND DISCUSSION Descriptive data concerning the 3 corn types are presented in Table 1. Unprocessed and processed corn types had numerically similar bulk density postgrinding (Table 1). Creating this similarity was important since dietary starch JAPR: Research Report density may influence broiler feed intake [12]. Moisture content of diets may also influence feed intake [5, 6]. However, moisture percentages among corn types were relatively similar, and moisture from corn accounted for a percentage of dietary moisture (Tables 1 and 2). Despite grinding unprocessed and processed corn through the same hammer mill screen, particle size among corn types differed (Table 1). Standard deviations among corn-type particle size were similar. Starch gelatinization percentages were calculated relative to UC [19]. Pelleting and extruding corn increased starch gelatinization 29 and 92%, respectively (Table 1). The diet containing three-thirds PC had a similar percentage of calculated gelatinized starch as the diet containing one-third EC. Peak gelatinization temperatures were similar among corn types. Treatment effects on broiler performance and AME n are presented in Tables 3 and 4, respectively. Processed corn type and inclusion level effects were significant; however, interactions were not. Feeding broilers diets that utilized PC resulted in lower feed intake and higher G:F compared with broilers fed diets containing EC (P = and , respectively, Table 3). Broiler LWG and mortality were not affected by processed corn type (P > 0.05, Table 3). The AME n was significantly affected by inclusion level but not processed corn type. Increasing dietary inclusions of PC, thus gelatinized starch, resulted in a linear decrease in broiler feed intake and weight gain (P = and , respectively, Table 3) that coincided with an increase in AME n (P = , Table 4). Increasing PC inclusion did not effect G:F (P = ). Increased dietary inclusions of EC, thus gelatinized starch, did not significantly affect broiler performance (Table 3). However, broilers fed diets containing increased amounts of EC showed a numerical trend of decreased G:F (P = , Table 3), despite an increase in AME n (P = , Table 4). The AME n may have been increased due to increased gelatinized starch with increased inclusions of PC or EC. However, the increase in AME n may not have offset potential nonstarch nutrient destruction associated with thermal processing. This effect seems most probable for diets containing EC. Decreased starch availability was unlikely, since differential scanning calorimetry did not illus-

5 MORITZ ET AL.: FEEDING GELATINIZED STARCH 51 TABLE 3. Treatment effects on 0- to 3-wk broiler performance Live weight gain Feed intake (pen) 1 Gain:feed Mortality 2 Item (g) (g) (g/g) (%) Unprocessed corn 579 c 8,328 bc a 0 Pelleted corn, 1/3 624 a 8,843 ab a 3.8 Pelleted corn, 2/3 613 ab 8,630 abc a 2.5 Pelleted corn, 3/3 585 bc 8,137 c a 5.0 Extruded corn, 1/3 618 a 8,965 a ab 1.3 Extruded corn, 2/3 620 a 8,718 ab ab 5.0 Extruded corn, 3/3 621 a 8,893 a b 5.0 LSD Comparison of all treatments; P-value P-values generated for main effects and the interaction Processed corn type Inclusion level Interaction Orthogonal contrast P-values Unprocessed corn vs. pelleted Unprocessed corn vs. extruded P-values generated for linear regression within each processing series Pelleted diets, 1/3 3/ Extruded diets, 1/3 3/ a c Means within a column without a common superscript differ significantly (P 0.05). 1 Pens contained 10 birds each on d 1. 2 Means are provided for mortality percentages; however, P-values are based on the arc sine transformation of mortality percentages. 3 Fisher s least significant difference. TABLE 4. Treatment effects on 2.5-wk broiler energy metabolism Item AME n kcal/kg (SD) Unprocessed corn 3,099 b (104) Pelleted corn, 1/3 3,076 b (100) Pelleted corn, 2/3 3,022 b (39) Pelleted corn, 3/3 3,192 a (47) Extruded corn, 1/3 3,031 b (104) Extruded corn, 2/3 3,095 b (58) Extruded corn, 3/3 3,198 a (43) LSD Comparison of all treatments; P-value P-values generated for main effects and the interaction Processed corn type Inclusion level Interaction Orthogonal contrast P-values Unprocessed corn vs. pelleted treatments Unprocessed corn vs. extruded treatments P-values generated for linear regression within each processing series Pelleted diets, 1/3 3/ Extruded diets, 1/3 3/ a,b Means within a column without a common superscript differ significantly (P 0.05). 1 Fisher s least significant difference.

6 52 trate temperature peaks indicative of retrograded starch. Performance differences may, in part, be explained by variations among corn-type particle size. Corn particle size of mash diets has been shown to influence feed preference, growth efficiency, and metabolism of broilers. Past research suggests that reduced particle size increases surface area and digestive enzyme accessibility [28, 29, 30, 31]. Particle size difference among feeds has also been suggested to influence anatomical and physiological characteristics of digestive tissues and organs [29, 30, 31]. In general, decreased particle size increases G:F by increasing dietary metabolizable energy and decreasing feed intake. In addition, decreased particle size decreases digestive organ weight and energy requirement associated with digestion. Increasing the PC fraction, which decreased complete diet particle size, increased AME n (P = , Table 4). In contrast, increasing the EC fraction, which increased complete diet particle size, also increased AME n (P = , Table 4). Hence, performance effects cannot be explained by particle size or AME n alone. Live weight gain of broilers fed the control diet were lower than LWG produced by diets containing either pelleted or extruded corn pooled by inclusion level (P = and , respectively, Table 3). Feed intake and G:F were similar among diets containing PC and the control (P = and , respectively, Table 3). In contrast, feed intake increased (P = ) and G:F decreased (P = ) when broilers were fed diets containing EC as compared with the control (Table 3). The AME n of the control did not differ from diets containing pelleted or extruded corn pooled by inclusion level (P = and , respectively, Table 4). Sibbald [32] found that steam pelleting various diets, which included a corn-soybean chick starter diet, did not change dietary true metabolizable energy. Bayley et al. [33] fed broilers various corn-soybean mash diets from 0 to 23 d. The authors found no significant difference in energy metabolism or performance between broilers fed diets containing pelleted and ground corn and UC. The current study demonstrates that LWG relationships between diets containing processed corn and the control were in part due to feed intake, especially for EC diets. However, typical relationships between particle size, JAPR: Research Report AME n, and feed intake as described in past research were not consistent among treatments. Diets that incorporated EC may have increased broiler feed intake through decreasing nutrient availability (Table 3). However, the proposed decrease in nutrient availability did not involve a decrease in AME n (Table 4). Hongtrakul et al. [34] found that feeding diets containing extruded cereals (corn, cornstarch, broken rice, wheat flour, and grain sorghum) to pigs from 0 to 7 d postweaning decreased G:F compared with pigs fed diets containing unprocessed cereals (P < 0.05). The authors attributed these effects to variations in extrusion processing conditions that may have generated retrograded starch, Maillard products, and loss of available amino acids or vitamins. Gelatinized starch for diets containing threethirds PC and one-third EC were calculated to be similar. However, feed intake was significantly increased, and AME n was significantly decreased for broilers fed diets containing onethird EC compared with broilers fed diets containing three-thirds PC (Tables 3 and 4). Despite differences in particle size and AME n, broilers fed each diet had LWG that reflected feed intake and statistically similar G:F (Table 3). This finding does not follow typical particle size relationships found in the literature [28, 29, 30, 31] and perhaps is more indicative of extrusion processing impairing nonstarch nutrient availability and requiring broilers to consume more feed to meet nutritional requirements. In general, variation in diet particle size confounded effects of gelatinized starch on broiler performance and AME n. However, particle size was likely influenced by starch gelatinization. The potential destruction of vitamins and amino acids contained in corn would also confound the effect of gelatinized starch on broiler performance and AME n. Feed intake seems to be the performance parameter most consistently influenced by type of corn processing and processed corn inclusion. A combined effect of particle size, gelatinized starch, and availability of nutrients other than starch likely influenced feed intake. The mechanism responsible for changes in feed intake may include variations in nutrient availability, feed passage rate, gut morphology, and maintenance energy requirements. The data additionally suggest that extrusion processing

7 MORITZ ET AL.: FEEDING GELATINIZED STARCH 53 may have reduced the availability of nonstarch nutrients in corn. Moreover, increasing gelatinized corn starch through commercial processing did not improve AME n or subsequent G:F of broilers during the 0- to 3-wk starter phase. Confounding effects of the availability of nonstarch nutrients may have been controlled if corn starch was processed instead of corn; however, the study would have been less practical. CONCLUSIONS AND APPLICATIONS 1. Gain-to-feed ratio and AME n in the 0- to 3-wk starter phase did not differ between broilers fed diets containing PC and the control that contained UC exclusively. 2. Gelatinizing starch can influence diet particle size, which may affect broiler performance. 3. Extrusion processing of corn may decrease nutrient availability of diets fed to broilers in the 0- to 3-wk starter phase. 1. Mommer, R. P., and D. K. Ballantyne Reasons for pelleting. Pages 3 6 in A Guide To Feed Pelleting Technology. Hess and Clark, Inc., Ashland, OH. 2. Hoover, R Starch retrogradation. Food Rev. Int. 11: Thomas, M., T. van Vliet, and A. F. B. van der Poel Physical quality of pelleted animal feed 3. Contribution of feedstuff components. Anim. Feed Sci. Technol. 70: Lund, D Influence of time, temperature, moisture, ingredients and processing conditions on starch gelatinization. CRC Crit. Rev. Food Sci. Nutr. 20: Moritz, J. S., R. S. Beyer, K. J. Wilson, K. R. Cramer, L. J. McKinney, and F. J. Fairchild Effect of moisture addition at the mixer to a corn-soybean based diet on broiler performance. J. Appl. Poult. Res. 10: Moritz, J. S., K. J. Wilson, K. R. Cramer, R. S. Beyer, L. J. McKinney, W. B. Cavalcanti, and X. Mo Effect of formulation density, moisture and surfactant on feed manufacturing, pellet quality and broiler performance. J. Appl. Poult. Res. 11: Moritz, J. S., K. R. Cramer, K. J. Wilson, and R. S. Beyer Effect of feed rations with graded levels of added moisture formulated to different energy densities on feed manufacturing, pellet quality, performance and energy metabolism of broilers during the growing period. J. Appl. Poult. Res. 11: Moran, E. T., Jr Effect of pellet quality on the performance of meat birds. Pages in Recent Advances in Animal Nutrition. W. Haresign and D. J. A. Cole, ed. Butterworths, London. 9. Colonna, P., V. Leloup, and A. Buleon Limiting factors of starch hydrolysis. Eur. J. Clin. Nutr. 46: Allred, J. B., R. E. Fry, L. S. Jensen, and J. McGinnis Studies with chicks on improvement in nutritive value of feed ingredients by pelleting. Poult. Sci. 36: Sloan, D. R., T. E. Bowen, and P. W. Waldroup Expansion-extrusion processing of corn, milo, and raw soybeans before and after incorporation in broiler diets. Poult. Sci. 50: Naber, E. C., and S. P. Touchburn Effect of hydration, gelatinization and ball milling of starch on growth and energy utilization by the chick. Poult. Sci. 48: Plavnik, E., E. Wax, D. Sklan, and S. Hurwitz The response of broiler chickens and turkey poults to steam-pelleted diets supplemented with fat or carbohydrates. Poult. Sci. 76: California Pellet Mill Master Model HD Series 1000, CPM Co., Crawfordsville, IN. REFERENCES AND NOTES 15. Extruder model TX-52, Wenger Manufacturing, Sabetha, KS. 16. American Association of Cereal Chemists Moisture air-oven method. AACC Method 44-15A. Approved Methods of the American Association of Analytical Chemists. Vol. II. AACC, St. Paul, MN. 17. American Society of Agricultural Engineers ASAE S Cubes, pellets, and crumbles Definitions and methods for determining density, durability, and moisture. Standards Am. Soc. Agric. Eng., St. Joseph, MI. 18. American Society of Agricultural Engineers Page 325 in ASAE S319. Method of determining and expressing fineness of feed materials by sieving. Am. Soc. Agric. Eng., St. Joseph, MI. 19. Starch gelatinization was determined by differential scanning calorimetry (DSC7, Perkin-Elmer, Norwalk, CT) and calculated on a dry matter basis. Enthalpy values were determined by a computer integrator for peaks in the approximate temperature range for corn starch. The percentage of starch gelatinization was determined by subtracting the enthalpy of the unprocessed sample from the enthalpy of the processed sample and dividing the difference by the enthalpy of the unprocessed sample. The method used for this analysis included holding the sample for 1 min at 30 C and then heating from 30 to 130 C with temperatures increasing by 10 C per min. 20. National Research Council Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC. 21. Cobb-Vantress, Inc., Siloam Springs, AR. 22. Sibbald, I. R A bioassay for true metabolizable energy in feedingstuffs. Poult. Sci. 55: Ross , Aviagen-North America, Huntsville, AL. 24. Isoperibol oxygen bomb calorimeter model 1266, Parr Instrument Co., Moline, IL. 25. Association of Official Analytical Chemists Official Methods of Analysis 15th ed. Assoc. Off. Anal. Chem., Arlington, VA. 26. Hill, F. W., and D. L. Anderson Comparison of ME and PE determinations with growing chicks. J. Nutr. 64: SAS Institute The SAS System for Windows Release 8.1. SAS Institute Inc., Cary, NC. 28. Portella, F. J., L. J. Caston, and S. Leeson Apparent feed particle size preference by broilers. Can. J. Anim. Sci. 68: Healy, B. J Nutritional value of selected sorghum grain for swine and poultry and effect of particle size on performance and intestinal morphology in young pigs and broiler chicks. M.S. Thesis. Kansas State Univ., Manhattan, KS.

8 54 JAPR: Research Report 30. Nir, I., G. Shefet, and Y. Aaroni Effect of particle size on performance. 1. Corn. Poult. Sci. 73: Nir, I., R. Hill, G. Shefet, and Z. Nitsan Effect of grain particle size on performance. 2. Grain texture interactions. Poult. Sci. 73: Sibbald, I. R The effect of steam pelleting on the true metabolizable energy values of poultry diets. Poult. Sci. 56: Bayley, H. S., J. D. Summers, and S. J. Slinger The effect of steam pelleting feed ingredients on chick performance: Effect on phosphorus availability, metabolizable energy value and carcass composition. Poult. Sci. 47: Hongtrakul, K., R. D. Goodband, K. C. Behnke, J. L. Nelseen, M. D. Tokach, J. R. Bergstrom, W. B. Nessmith, Jr., and I. H. Kim The effects of extrusion processing of carbohydrate sources on weanling pig performance. J. Anim. Sci. 76: Acknowledgments The authors acknowledge Fred Roe, Bill Miller, Myron Lawson, and Robert Resser for their assistance with animal husbandry.