TY - JOUR
AU - Carciofi, A. C.
AB - Abstract The influence of rice, maize, and sorghum raw material particle size in extruded dry dog food on the digestibility of nutrients and energy and the fecal concentration of fermentation products was investigated. Three diets with similar nutrient compositions were formulated, each with 1 starch source. Before incorporation into diets, the cereals were ground into 3 different particle sizes (approximately 300, 450, and 600 µm); therefore, a total of 9 diets were in a 3 × 3 factorial arrangement (3 cereals and 3 particle sizes). Fifty-four beagle dogs (12.0 ± 0.1 kg BW) were randomly assigned to the diets, with 6 dogs per diet. The digestibility was measured with the chromium oxide method. The data were evaluated with ANOVA considering the carbohydrate source, grinding effect, and interactions. The means were compared with the Tukey test and polynomial contrasts (P < 0.05). With the same grinding procedure, rice was reduced to smaller particles than other cereals. The cereal mean geometric diameter (MGD) was directly related to starch gelatinization (SG) during extrusion. For rice diets, the MGD and SG did not change nutrient digestibility (P > 0.05); only GE digestibility was reduced at the largest MGD (P < 0.01). For maize and sorghum diets, the total tract apparent nutrient digestibility was reduced for foods with greater MGD and less SG (P < 0.01). A linear reduction in nutrient digestibility according to cereal particle size was observed for sorghum (r2 < 0.72; P < 0.01). Higher concentrations of fecal total short-chain fatty acids (SCFA) were observed for sorghum diets (P < 0.05) than for other diets. The rice diets led to the production of feces with less lactate (P < 0.05). The increase in raw material MGD did not influence fecal SCFA for rice diets, but for the dogs fed maize and sorghum foods, an increase in propionate and butyrate concentrations were observed as MGD increased (P < 0.05). In conclusion, for dogs fed different particle sizes of the cereal starches in the extruded diets, the digestibility and fecal characteristics were affected, and this effect was ingredient dependent. INTRODUCTION The primary ingredients for most standard kibble foods for dogs are cereal grains, which may be more than 40% of the formulation. The endosperm of cereals is primarily starch, organized in granules of concentric layers of semicrystalline or amorphous formations (Svihus et al., 2005). Starch is important for proper extrusion, helping to generate viscosity, mechanical energy transference from screw to dough, adequate kibble expansion rate, cellular structure formation, and kibble crispness (Crane et al., 2000). In addition to extrusion processing traits (Sitohy et al., 2000), depending on the botanical origin, the granular structure and the amylose:amylopectin proportion of starches vary (Tester et al., 2004), which affects the digestibility and postprandial glycemic response of dogs (Murray et al., 1999; Carciofi et al., 2008). During the processing of cereals, grinding is an important concern. In poultry and swine, raw material particle size influences nutrient digestibility (Wondra et al., 1995; Amerah et al., 2007), and in humans, particle size affects satiety, insulinemia, and postprandial glycemia (Holt and Miller, 1994; Pereira et al., 2002). However, little information exists on the influence of raw material particle size on extruded dog foods, and in published studies, the raw material particle size was imprecisely determined or not described (Twomey et al., 2002; Twomey et al., 2003; Carciofi et al., 2008; Fortes et al., 2010). The assumption is that small raw material particle sizes increase the gelatinization of starch during extrusion, which increases nutrient digestibility and leads to better fecal formation. However, studies on the interactions among the starch source, the raw material particle size, and the extrusion process for kibble dog foods were not found. Because of this lack of information, this study investigated the influence of the particle size of rice, maize, and sorghum on nutrient and energy digestibility and on fecal concentrations of some fermentation products of dogs fed extruded diets. MATERIALS AND METHODS Animals, Diets, and Experimental Design Fifty-four beagle dogs, 36 females and 18 males, with BCS between 4 and 6 (Laflamme, 1997) and a mean BW of 12.0 ± 0.1 kg, were used to evaluate diet digestibility. The animals were maintained in the Laboratory of Research on Nutrition and Nutritional Diseases of Dogs and Cats at Sao Paulo State University (Jaboticabal, Brazil). All animals were healthy at the beginning of the study on the basis of clinical and hematological examination and biochemical serum profiles, which included those of urea, creatinine, alkaline phosphatase, alanine aminotransferase, total plasma protein, and albumin. The dogs lived in 3.5 × 1.5 m kennels, with daily access to an outside playground for exercise and socialization, where they were adapted to the experimental diets. For feces collection during the digestibility tests, dogs were housed individually in 1 × 1 × 1 m metabolic cages. The metabolizable energy of the diets was estimated from their chemical composition, and the quantity of diet provided was determined with standard equations for the proper energy requirements of kennel dogs (ME, kcal = 130 × kg BW0.75), in accordance with the NRC (2006) guidelines. Water was available ad libitum. The Ethics Committee for Animal Well-Being at the College of Agrarian and Veterinarian Sciences, Sao Paulo State University, approved all experimental procedures. The experiment followed a completely randomized design in a 3 × 3 factorial arrangement of treatments, with 3 starches (rice, maize, and sorghum) and 3 particle sizes (fine, medium, and coarse) for a total of 9 different diets with 6 dogs per diet. The diets were formulated according to the American Association of Feed Control Officials (2008) nutritional recommendations for adult dogs. The formulations differed depending on which starch source, rice, maize, or sorghum, was used. Chromium oxide was added as a digestibility marker (Table 1). The diets were prepared in the extruder facility of the College of Agrarian and Veterinarian Sciences, Sao Paulo State University. All ingredients were purchased, sampled, and analyzed for DM, ash, CP, fat, and dietary fiber before formulation, according to the AOAC (1995) methods described below. On the basis of the results of chemical analyses, cellulose was added to the diets to equalize fiber contents. Each formulation was then separated into 3 diets according to the particle size of the starch used in the preparation. The starch sources were ground separately from the other ingredients and were further mixed to obtain the final diet. The starch sources were ground in a hammer mill (model 4, D'Andrea, Limeira, Brazil) fitted with screen sieves with mesh sizes to produce raw material mean geometric diameters (MGD) of approximately 300 µm (fine), 450 µm (medium), and 600 µm (coarse). To obtain these particular sizes, the hammer mill was fitted with screen sieves with 0.8-, 1.5-, and 3.0-mm meshes. After grinding, the obtained MGD of the starch were determined according to the procedure described by Zanotto and Bellaver (1996), using a set of screen sieves with meshes of 1.4, 1.2, 1.0, 0.7, 0.5, 0.35, and 0.125 mm, with the bottom plate. The calculations were performed with the software package Gransuave (Embrapa-CNPSA, Concordia, Brazil). Table 1. Chemical composition of the starch sources and ingredient composition of the experimental diets for dogs Item  Broken rice  Maize  Sorghum  Chemical composition (as-fed basis), %      DM  90.5  88.3  88.8      Ash  1.2  1.1  1.2      CP  9.9  8.0  9.1      Fat  3.3  5.6  3.4      Starch  74.5  63.5  63.7      Total dietary fiber  1.2  9.9  11.2  Ingredient composition of the experimental diets, %      Starch source  47.1  53.3  53.4      Poultry by-product meal  29.2  29.1  28.2      Poultry fat  5.1  4.5  6.1      Powdered liver  4.0  4.0  4.0      Soybean hulls  2.0  2.0  2.0      Cellulose1  6.8  1.5  0.8      Brewer's yeast  2.5  2.5  2.5      Flavor enhancer2  1.5  1.5  1.5      Dicalcium phosphate  0.3  0.1  0.0      Potassium chloride  0.4  0.4  0.4      Sodium chloride  0.4  0.4  0.4      Chromium oxide3  0.25  0.25  0.25      Vitamin-mineral premix4  0.2  0.2  0.2      Mold inhibitor 5  0.1  0.1  0.1      L-lysine  0.06  0.06  0.06      DL-methionine  0.05  0.05  0.05      Antioxidant 6  0.04  0.04  0.04  Item  Broken rice  Maize  Sorghum  Chemical composition (as-fed basis), %      DM  90.5  88.3  88.8      Ash  1.2  1.1  1.2      CP  9.9  8.0  9.1      Fat  3.3  5.6  3.4      Starch  74.5  63.5  63.7      Total dietary fiber  1.2  9.9  11.2  Ingredient composition of the experimental diets, %      Starch source  47.1  53.3  53.4      Poultry by-product meal  29.2  29.1  28.2      Poultry fat  5.1  4.5  6.1      Powdered liver  4.0  4.0  4.0      Soybean hulls  2.0  2.0  2.0      Cellulose1  6.8  1.5  0.8      Brewer's yeast  2.5  2.5  2.5      Flavor enhancer2  1.5  1.5  1.5      Dicalcium phosphate  0.3  0.1  0.0      Potassium chloride  0.4  0.4  0.4      Sodium chloride  0.4  0.4  0.4      Chromium oxide3  0.25  0.25  0.25      Vitamin-mineral premix4  0.2  0.2  0.2      Mold inhibitor 5  0.1  0.1  0.1      L-lysine  0.06  0.06  0.06      DL-methionine  0.05  0.05  0.05      Antioxidant 6  0.04  0.04  0.04  1Microcrystalline cellulose (Vittacell, JRS, Rosemberg, Germany). 2Hydrolyzed chicken liver. 399% (wt/wt) chromium oxide powder (Merck, Darmstadt, Germany). 4Provided per kilogram of diet: vitamin A, 22,000 IU; vitamin D, 2,200 IU; vitamin E, 90 IU; vitamin B1, 3 mg/kg; vitamin B2, 7 mg/kg; pantothenic acid, 22 mg/kg; niacin, 14 mg/kg; vitamin B6, 4 mg/kg; folic acid, 0.3 mg/kg; vitamin B12, 33 µg/kg, choline, 1,200 mg/kg; zinc, 140 mg/kg; iron, 80 mg/kg; copper 9.5 mg/kg; iodine 1.5 mg/kg; selenium, 0.25 mg/kg. 5Mold Zap: ammonium dipropionate, acetic acid, sorbic acid, and benzoic acid (Alltech do Brasil Agroindustrial Ltda, Curitiba, Brazil). 6Banox: butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), , propyl gallate and calcium carbonate (Alltech do Brasil Agroindustrial Ltda). View Large Table 1. Chemical composition of the starch sources and ingredient composition of the experimental diets for dogs Item  Broken rice  Maize  Sorghum  Chemical composition (as-fed basis), %      DM  90.5  88.3  88.8      Ash  1.2  1.1  1.2      CP  9.9  8.0  9.1      Fat  3.3  5.6  3.4      Starch  74.5  63.5  63.7      Total dietary fiber  1.2  9.9  11.2  Ingredient composition of the experimental diets, %      Starch source  47.1  53.3  53.4      Poultry by-product meal  29.2  29.1  28.2      Poultry fat  5.1  4.5  6.1      Powdered liver  4.0  4.0  4.0      Soybean hulls  2.0  2.0  2.0      Cellulose1  6.8  1.5  0.8      Brewer's yeast  2.5  2.5  2.5      Flavor enhancer2  1.5  1.5  1.5      Dicalcium phosphate  0.3  0.1  0.0      Potassium chloride  0.4  0.4  0.4      Sodium chloride  0.4  0.4  0.4      Chromium oxide3  0.25  0.25  0.25      Vitamin-mineral premix4  0.2  0.2  0.2      Mold inhibitor 5  0.1  0.1  0.1      L-lysine  0.06  0.06  0.06      DL-methionine  0.05  0.05  0.05      Antioxidant 6  0.04  0.04  0.04  Item  Broken rice  Maize  Sorghum  Chemical composition (as-fed basis), %      DM  90.5  88.3  88.8      Ash  1.2  1.1  1.2      CP  9.9  8.0  9.1      Fat  3.3  5.6  3.4      Starch  74.5  63.5  63.7      Total dietary fiber  1.2  9.9  11.2  Ingredient composition of the experimental diets, %      Starch source  47.1  53.3  53.4      Poultry by-product meal  29.2  29.1  28.2      Poultry fat  5.1  4.5  6.1      Powdered liver  4.0  4.0  4.0      Soybean hulls  2.0  2.0  2.0      Cellulose1  6.8  1.5  0.8      Brewer's yeast  2.5  2.5  2.5      Flavor enhancer2  1.5  1.5  1.5      Dicalcium phosphate  0.3  0.1  0.0      Potassium chloride  0.4  0.4  0.4      Sodium chloride  0.4  0.4  0.4      Chromium oxide3  0.25  0.25  0.25      Vitamin-mineral premix4  0.2  0.2  0.2      Mold inhibitor 5  0.1  0.1  0.1      L-lysine  0.06  0.06  0.06      DL-methionine  0.05  0.05  0.05      Antioxidant 6  0.04  0.04  0.04  1Microcrystalline cellulose (Vittacell, JRS, Rosemberg, Germany). 2Hydrolyzed chicken liver. 399% (wt/wt) chromium oxide powder (Merck, Darmstadt, Germany). 4Provided per kilogram of diet: vitamin A, 22,000 IU; vitamin D, 2,200 IU; vitamin E, 90 IU; vitamin B1, 3 mg/kg; vitamin B2, 7 mg/kg; pantothenic acid, 22 mg/kg; niacin, 14 mg/kg; vitamin B6, 4 mg/kg; folic acid, 0.3 mg/kg; vitamin B12, 33 µg/kg, choline, 1,200 mg/kg; zinc, 140 mg/kg; iron, 80 mg/kg; copper 9.5 mg/kg; iodine 1.5 mg/kg; selenium, 0.25 mg/kg. 5Mold Zap: ammonium dipropionate, acetic acid, sorbic acid, and benzoic acid (Alltech do Brasil Agroindustrial Ltda, Curitiba, Brazil). 6Banox: butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), , propyl gallate and calcium carbonate (Alltech do Brasil Agroindustrial Ltda). View Large The protein sources (poultry by-product meal, powdered liver, and brewer's yeast), fiber sources (cellulose and soybean hulls), and minor ingredients were weighed and mixed before being ground in a hammer mill (model 4, D'Andrea) fitted with a 0.8-mm screen sieve. The diets were extruded under identical processing conditions with a single screw extruder (Mab 400S, Extrucenter, Monte Alto, Brazil), with an average extrusion capacity of 150 kg/h. A laboratory-scale complete extrusion system was used, with the same components and standards of operation as extruders for commercial production. To control the manufacturing process, the kibble density out of the extruder was adjusted to between 420 and 440 g/L (on an as-is basis) every 15 min to ensure consistent cooking and kibble quality (size and expansion). The extruder feed rate was approximately 90 kg/h, the extruder screw speed was 450 rpm, and the die open area was 63.9 mm2. The extruder preconditioning temperature was maintained above 90°C through direct steam injection. Water addition in the preconditioner was adjusted according to diet formulation, with an in-barrel moisture of approximately 29%. The dough temperature at the end of the extruder varied between 125°C and 135°C. After extrusion, the kibbles were dried in a forced-air dryer at 105°C for 30 min and coated with poultry fat and liquid flavor enhancer. The chemical composition and quality characteristics of the diets are presented in Table 2. The particle size distribution of the cereal starches is presented in Table 3. Table 2. Chemical composition and starch gelatinization degree of the experimental diets for dogs   Broken rice  Maize  Sorghum  Item  Fine1  Medium2  Coarse 3  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Chemical composition (DM basis)                        DM, %  92.9  93.2  92.3  92.9  92.6  93.2  92.2  92.3  93.1      CP, %  26.4  26.0  25.8  26.8  27.1  27.3  28.2  27.7  27.9      Acid-hydrolyzed fat, %  11.6  11.6  12.0  12.0  12.8  12.1  13.0  12.6  13.8      Total dietary fiber, %  7.1  7.8  7.6  7.5  7.8  8.0  7.8  7.3  7.5      Starch, %  42.7  41.6  42.7  44.3  42.9  43.1  41.4  42.7  41.0      GE, kcal/g  4.45  4.47  4.44  4.46  4.50  4.51  4.45  4.49  4.49  Food starch gelatinization degree, %  90.6  80.1  76.8  79.9  73.8  63.2  86.7  71.7  62.4  Density after extruder, g/L  423  422  433  428  428  438  441  444  443    Broken rice  Maize  Sorghum  Item  Fine1  Medium2  Coarse 3  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Chemical composition (DM basis)                        DM, %  92.9  93.2  92.3  92.9  92.6  93.2  92.2  92.3  93.1      CP, %  26.4  26.0  25.8  26.8  27.1  27.3  28.2  27.7  27.9      Acid-hydrolyzed fat, %  11.6  11.6  12.0  12.0  12.8  12.1  13.0  12.6  13.8      Total dietary fiber, %  7.1  7.8  7.6  7.5  7.8  8.0  7.8  7.3  7.5      Starch, %  42.7  41.6  42.7  44.3  42.9  43.1  41.4  42.7  41.0      GE, kcal/g  4.45  4.47  4.44  4.46  4.50  4.51  4.45  4.49  4.49  Food starch gelatinization degree, %  90.6  80.1  76.8  79.9  73.8  63.2  86.7  71.7  62.4  Density after extruder, g/L  423  422  433  428  428  438  441  444  443  1Screen sieve with 0.8-mm mesh. 2Screen sieve with 1.5-mm mesh. 3Screen sieve with 3.0-mm mesh. View Large Table 2. Chemical composition and starch gelatinization degree of the experimental diets for dogs   Broken rice  Maize  Sorghum  Item  Fine1  Medium2  Coarse 3  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Chemical composition (DM basis)                        DM, %  92.9  93.2  92.3  92.9  92.6  93.2  92.2  92.3  93.1      CP, %  26.4  26.0  25.8  26.8  27.1  27.3  28.2  27.7  27.9      Acid-hydrolyzed fat, %  11.6  11.6  12.0  12.0  12.8  12.1  13.0  12.6  13.8      Total dietary fiber, %  7.1  7.8  7.6  7.5  7.8  8.0  7.8  7.3  7.5      Starch, %  42.7  41.6  42.7  44.3  42.9  43.1  41.4  42.7  41.0      GE, kcal/g  4.45  4.47  4.44  4.46  4.50  4.51  4.45  4.49  4.49  Food starch gelatinization degree, %  90.6  80.1  76.8  79.9  73.8  63.2  86.7  71.7  62.4  Density after extruder, g/L  423  422  433  428  428  438  441  444  443    Broken rice  Maize  Sorghum  Item  Fine1  Medium2  Coarse 3  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Chemical composition (DM basis)                        DM, %  92.9  93.2  92.3  92.9  92.6  93.2  92.2  92.3  93.1      CP, %  26.4  26.0  25.8  26.8  27.1  27.3  28.2  27.7  27.9      Acid-hydrolyzed fat, %  11.6  11.6  12.0  12.0  12.8  12.1  13.0  12.6  13.8      Total dietary fiber, %  7.1  7.8  7.6  7.5  7.8  8.0  7.8  7.3  7.5      Starch, %  42.7  41.6  42.7  44.3  42.9  43.1  41.4  42.7  41.0      GE, kcal/g  4.45  4.47  4.44  4.46  4.50  4.51  4.45  4.49  4.49  Food starch gelatinization degree, %  90.6  80.1  76.8  79.9  73.8  63.2  86.7  71.7  62.4  Density after extruder, g/L  423  422  433  428  428  438  441  444  443  1Screen sieve with 0.8-mm mesh. 2Screen sieve with 1.5-mm mesh. 3Screen sieve with 3.0-mm mesh. View Large Table 3. Particle size distribution of the rice, maize, and sorghum after grinding with different screen sieve sizes to produce the experimental diets for dogs   Broken rice  Maize  Sorghum  Item  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Particle retention, %        1.400-mm screen sieve  0.0  0.4  2.4  0.3  0.9  2.4  0.0  0.8  1.2      1.200-mm screen sieve  0.1  0.6  2.7  0.2  0.7  2.7  0.2  0.8  2.3      1.000-mm screen sieve  0.2  1.9  10.0  0.2  1.4  12.1  0.3  3.0  11.9      0.710-mm screen sieve  0.3  4.2  18.2  0.3  4.0  16.3  0.4  7.6  19.8      0.500-mm screen sieve  34.7  34.7  34.8  37.5  48.2  41.8  36.4  46.3  41.3      0.350-mm screen sieve  4.7  6.2  5.5  14.9  15.6  7.3  8.2  7.0  5.4      0.125-mm screen sieve  38.3  31.7  18.4  43.3  27.4  16.0  42.5  26.6  12.4      0.0-mm screen sieve  21.7  20.3  8.0  3.2  1.9  1.6  12.0  7.9  5.6  Mean geometric diameter, µm  277  311  521  360  451  619  314  439  594  Geometric standard device, µm  2.6  2.6  2.5  2.4  2.4  2.3  2.2  2.1  2.2    Broken rice  Maize  Sorghum  Item  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Particle retention, %        1.400-mm screen sieve  0.0  0.4  2.4  0.3  0.9  2.4  0.0  0.8  1.2      1.200-mm screen sieve  0.1  0.6  2.7  0.2  0.7  2.7  0.2  0.8  2.3      1.000-mm screen sieve  0.2  1.9  10.0  0.2  1.4  12.1  0.3  3.0  11.9      0.710-mm screen sieve  0.3  4.2  18.2  0.3  4.0  16.3  0.4  7.6  19.8      0.500-mm screen sieve  34.7  34.7  34.8  37.5  48.2  41.8  36.4  46.3  41.3      0.350-mm screen sieve  4.7  6.2  5.5  14.9  15.6  7.3  8.2  7.0  5.4      0.125-mm screen sieve  38.3  31.7  18.4  43.3  27.4  16.0  42.5  26.6  12.4      0.0-mm screen sieve  21.7  20.3  8.0  3.2  1.9  1.6  12.0  7.9  5.6  Mean geometric diameter, µm  277  311  521  360  451  619  314  439  594  Geometric standard device, µm  2.6  2.6  2.5  2.4  2.4  2.3  2.2  2.1  2.2  1Screen sieve with 0.8-mm mesh. 2Screen sieve with 1.5-mm mesh. 3Screen sieve with 3.0-mm mesh. View Large Table 3. Particle size distribution of the rice, maize, and sorghum after grinding with different screen sieve sizes to produce the experimental diets for dogs   Broken rice  Maize  Sorghum  Item  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Particle retention, %        1.400-mm screen sieve  0.0  0.4  2.4  0.3  0.9  2.4  0.0  0.8  1.2      1.200-mm screen sieve  0.1  0.6  2.7  0.2  0.7  2.7  0.2  0.8  2.3      1.000-mm screen sieve  0.2  1.9  10.0  0.2  1.4  12.1  0.3  3.0  11.9      0.710-mm screen sieve  0.3  4.2  18.2  0.3  4.0  16.3  0.4  7.6  19.8      0.500-mm screen sieve  34.7  34.7  34.8  37.5  48.2  41.8  36.4  46.3  41.3      0.350-mm screen sieve  4.7  6.2  5.5  14.9  15.6  7.3  8.2  7.0  5.4      0.125-mm screen sieve  38.3  31.7  18.4  43.3  27.4  16.0  42.5  26.6  12.4      0.0-mm screen sieve  21.7  20.3  8.0  3.2  1.9  1.6  12.0  7.9  5.6  Mean geometric diameter, µm  277  311  521  360  451  619  314  439  594  Geometric standard device, µm  2.6  2.6  2.5  2.4  2.4  2.3  2.2  2.1  2.2    Broken rice  Maize  Sorghum  Item  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Fine1  Medium2  Coarse3  Particle retention, %        1.400-mm screen sieve  0.0  0.4  2.4  0.3  0.9  2.4  0.0  0.8  1.2      1.200-mm screen sieve  0.1  0.6  2.7  0.2  0.7  2.7  0.2  0.8  2.3      1.000-mm screen sieve  0.2  1.9  10.0  0.2  1.4  12.1  0.3  3.0  11.9      0.710-mm screen sieve  0.3  4.2  18.2  0.3  4.0  16.3  0.4  7.6  19.8      0.500-mm screen sieve  34.7  34.7  34.8  37.5  48.2  41.8  36.4  46.3  41.3      0.350-mm screen sieve  4.7  6.2  5.5  14.9  15.6  7.3  8.2  7.0  5.4      0.125-mm screen sieve  38.3  31.7  18.4  43.3  27.4  16.0  42.5  26.6  12.4      0.0-mm screen sieve  21.7  20.3  8.0  3.2  1.9  1.6  12.0  7.9  5.6  Mean geometric diameter, µm  277  311  521  360  451  619  314  439  594  Geometric standard device, µm  2.6  2.6  2.5  2.4  2.4  2.3  2.2  2.1  2.2  1Screen sieve with 0.8-mm mesh. 2Screen sieve with 1.5-mm mesh. 3Screen sieve with 3.0-mm mesh. View Large Digestibility Protocol and Fecal Traits The digestibility assay was conducted using the marker method with chromium oxide. A 5-d test diet adaptation phase preceded 5 d of feces collection. The dogs were fed once per day (0800), the bowls were removed after 20 min, and any remaining food was weighed and recorded. Feces were collected twice daily, weighed, and frozen (−15°C) until analysis (Carciofi et al., 2007). The fecal samples were scored according to the following system: 0 = watery with liquid that can be poured; 1 = soft and unformed; 2 = soft and malformed, and stool assumed shape of container; 3 = soft, formed, and moist with softer stool that retained shape; 4 = well-formed and consistent stool that did not adhere to the floor; and 5 = hard and dry pellets with small and hard mass. The dogs were confined in the cages an additional 3 d for sample collection of fresh feces (maximum 15 min after elimination) for fermentation product analysis. For these samples, the pH was measured in a mixture of 5 mL of distilled water and 5 g of feces with a pH meter (model Q-400-Bd, Quimis, Brazil). Additionally, immediately after collection, the fecal samples (approximately 10 g) were mixed with 30 mL of 16% (vol/vol) formic acid solution and precipitated at 4°C for 72 h. The supernatant was centrifuged (5804R, Eppendorf, Hamburgo, Brazil) 3 times at 4,500 × g at 15°C for 15 min. These extracts were frozen (−15°C) until short-chain fatty acid (SCFA) and lactic acid analyses. Laboratory Analyses At the end of the collection period, the fecal samples were thawed, homogenized, and pooled for each dog. Before laboratory analyses, the fecal samples were dried in a forced-air oven at 55°C for 72 h (320-SE, FANEM, Sao Paulo, Brazil). Both feces and food samples were ground in a cutting mill fitted with a 1-mm screen sieve. The diets and feces were analyzed according to the AOAC (1995) standards for dry matter with oven-drying of the sample (934.01), converting to ash with muffle furnace incineration (942.05), measuring the CP with the Kjeldahl method (954.01), and measuring the acid-hydrolyzed fat (954.02). Organic matter was calculated by difference (OM = DM – ash). The total dietary fiber was measured according to Prosky et al. (1992), and the total starch was measured according to Miller (1959) and Hendrix (1993). The GE contents of diets and fecal matter were determined using a bomb calorimeter (model 1261, Parr Instrument Co., Moline, IL). The procedure proposed by Fenton and Fenton (1979) was used to quantify chromium oxide, and the analytical calibration curve was constructed using standard solutions prepared by digesting known amounts of chromium oxide (4, 10, 15, 25, and 35 mg). The chromium concentrations were measured by visible spectrophotometry (Labquest Bio 2000, Labtest Diagnóstica S.A., Lagoa Santa, Brazil) at 450 nm. To assess the quality of extrusion, the degree of starch gelatinization was measured in all diets with the amyloglucosidase method as described by Sá et al. (2013). The fecal SCFA were analyzed by gas chromatography (model 9001, Finnigan, San Jose, CA) according to Erwin et al. (1961) with a glass column 2 m in length and 3.17 mm in width covered with 80/120 Carbopack B-DA/4% Carbowax 20M. The carrier gas was nitrogen with a flow rate of 25 mL/min. The working temperatures were 220°C at injection, 210°C in the column, and 250°C in the flame ionization detector. The lactic acid was measured according to Pryce (1969) using a colorimetric method (Spectrophotometer Quick–Lab, Drake, São José do Rio Preto, Brazil). All analyses were conducted in duplicate and were repeated when the coefficient of variation was greater than 5%. Calculations The total tract apparent digestibility coefficients of DM, OM, CP, acid-hydrolyzed fat, GE, and starch were calculated for each experimental diet using chromium as an indigestible marker, according to Lloyd and McCay (1954), using the following formula:  Statistical Analyses The data were analyzed as a completely randomized design using the General Linear Model procedures of the SAS statistical software package (version 8, SAS Inst. Inc., Cary, NC). The experimental unit was 1 dog. The model sums of squares were separated into diet and animal effects and the interactions. The interactions among the variables (starch source and particle size) were analyzed with the SLICE statement. When significant differences were detected in ANOVA, F tests for multiple comparisons of the means were performed using the Tukey test for nutrient intake, feces characteristic, total tract apparent nutrient digestibility, and SCFA concentration. Additionally, polynomial regressions were performed to describe the relationships between particle size or degree of starch gelatinization and each evaluated criterion. The values of P < 0.05 were significant. All data complied with the assumptions of the ANOVA models. RESULTS Rice grinds differently than other grains, and rice was reduced to smaller particle sizes than maize and sorghum (Table 2). In general, coarse grinding resulted in more than 10% of the particles retained on a 1-mm sieve, but these very large particles did not occur after fine and medium grinding. However, a large proportion of particles smaller than 0.35 mm were observed after the fine grinding. The chemical composition of the foods were similar among both starch sources and particle sizes. Because rice contained less fiber than maize and sorghum, 6.6% cellulose was added to the rice formulation to provide a similar amount of fiber. The degree of starch gelatinization appeared to be greater for rice-based foods than for sorghum- and maize-based diets. The relation between MGD (x axis) of cereals and degree of starch gelatinization (y axis) was explored with linear regression analyses for the 9 experimental diets (Fig. 1), and the foods with the smaller particle sizes exhibited greater starch gelatinization than foods with larger MGD (P < 0.001). Figure 1. View largeDownload slide Relationship among the cereal mean geometric diameter (µm) and the starch gelatinization degree (%) of extruded dog diets with different carbohydrate sources and raw material particle sizes (n = 9): Starch gelatinization degree = 106.32 − (0.0699 × cereal mean geometric diameter); r2 = 0.85; P < 0.001. Figure 1. View largeDownload slide Relationship among the cereal mean geometric diameter (µm) and the starch gelatinization degree (%) of extruded dog diets with different carbohydrate sources and raw material particle sizes (n = 9): Starch gelatinization degree = 106.32 − (0.0699 × cereal mean geometric diameter); r2 = 0.85; P < 0.001. The diets were readily consumed by the dogs, without episodes of diarrhea or vomiting. Body weights did not change during the trial and did not differ among diets (P > 0.05). An interaction between the starch source and the raw material particle size was observed for the total tract apparent digestibility of all nutrients (Table 4). For the rice-based diets, the raw material particle size did not change the digestibility of DM, fat, CP, or starch (P > 0.05), and only the GE digestibility was lower for the large MGD rice-based food (P < 0.01). For maize- and sorghum-based diets, total tract apparent nutrient digestibility was dependent on the particle size of the cereal, and foods with larger starch source MGD had lower digestibility, as shown by the contrasts for each cereal source (P < 0.01). Therefore, the mean nutrient digestibility of starch, protein, and fat in the rice-based foods was higher than the mean values for maize- and sorghum-based foods (P < 0.05), but these differences among diets were not observed for the finely ground maize- and sorghum-based diets. For sorghum, a linear response was observed (Table 5), and the sorghum diet with smaller particle size had greater nutrient digestibility than the other diets (r2 < 0.72; P < 0.01). Table 4. Apparent total tract digestibility of extruded diets for dogs with different carbohydrate sources and raw material particle sizes   Apparent total tract digestibility, %  Item  DM  Starch  CP  Fat  GE  Broken rice (MGD)1      Fine (277 µm)  79.6  99.5  84.1  94.9  84.8      Medium (311 µm)  79.0  99.6  84.0  94.9  84.1      Coarse (521 µm)  79.8  99.5  81.9  95.3  81.9      Ingredient mean2  79.5  99.5a  83.3a  95.0a  83.7  Maize (MGD)1      Fine (360 µm)  80.5  99.5  81.0  93.7  85.0      Medium (451 µm)  82.1  99.9  82.8  94.1  86.2      Coarse (619 µm)  75.9  97.4  76.2  91.0  80.4      Ingredient mean2  79.5  98.8b  80.0b  92.9b  83.9  Sorghum (MGD)1      Fine (314 µm)  83.2  99.7  83.6  94.3  86.7      Medium (439 µm)  79.9  99.1  80.1  92.8  84.4      Coarse (594 µm)  75.9  97.8  74.9  91.4  80.2      Ingredient mean2  79.7  98.9b  79.5b  92.8b  83.7      SEM3  0.9  0.4  1.4  0.6  0.9  Effects (P-values)4      Ingredients  NS  <0.01  <0.01  <0.01  NS      Grinding  <0.01  <0.01  <0.01  <0.01  <0.01      Interaction  <0.01  <0.01  <0.01  <0.01  <0.01  Contrasts4      Grinding × rice  NS  NS  NS  NS  <0.05      Grinding × maize  <0.01  <0.01  <0.01  <0.01  <0.01      Grinding × sorghum  <0.01  <0.01  <0.01  <0.01  <0.01    Apparent total tract digestibility, %  Item  DM  Starch  CP  Fat  GE  Broken rice (MGD)1      Fine (277 µm)  79.6  99.5  84.1  94.9  84.8      Medium (311 µm)  79.0  99.6  84.0  94.9  84.1      Coarse (521 µm)  79.8  99.5  81.9  95.3  81.9      Ingredient mean2  79.5  99.5a  83.3a  95.0a  83.7  Maize (MGD)1      Fine (360 µm)  80.5  99.5  81.0  93.7  85.0      Medium (451 µm)  82.1  99.9  82.8  94.1  86.2      Coarse (619 µm)  75.9  97.4  76.2  91.0  80.4      Ingredient mean2  79.5  98.8b  80.0b  92.9b  83.9  Sorghum (MGD)1      Fine (314 µm)  83.2  99.7  83.6  94.3  86.7      Medium (439 µm)  79.9  99.1  80.1  92.8  84.4      Coarse (594 µm)  75.9  97.8  74.9  91.4  80.2      Ingredient mean2  79.7  98.9b  79.5b  92.8b  83.7      SEM3  0.9  0.4  1.4  0.6  0.9  Effects (P-values)4      Ingredients  NS  <0.01  <0.01  <0.01  NS      Grinding  <0.01  <0.01  <0.01  <0.01  <0.01      Interaction  <0.01  <0.01  <0.01  <0.01  <0.01  Contrasts4      Grinding × rice  NS  NS  NS  NS  <0.05      Grinding × maize  <0.01  <0.01  <0.01  <0.01  <0.01      Grinding × sorghum  <0.01  <0.01  <0.01  <0.01  <0.01  a,bIngredient means in the same column without a common superscript differ (P < 0.05). 1MGD = mean geometric diameter of the carbohydrate source (in µm). 2Ingredient means, considering the 3 particle sizes. 3n = 6 per diet. 4NS = nonsignificant (P > 0.05). View Large Table 4. Apparent total tract digestibility of extruded diets for dogs with different carbohydrate sources and raw material particle sizes   Apparent total tract digestibility, %  Item  DM  Starch  CP  Fat  GE  Broken rice (MGD)1      Fine (277 µm)  79.6  99.5  84.1  94.9  84.8      Medium (311 µm)  79.0  99.6  84.0  94.9  84.1      Coarse (521 µm)  79.8  99.5  81.9  95.3  81.9      Ingredient mean2  79.5  99.5a  83.3a  95.0a  83.7  Maize (MGD)1      Fine (360 µm)  80.5  99.5  81.0  93.7  85.0      Medium (451 µm)  82.1  99.9  82.8  94.1  86.2      Coarse (619 µm)  75.9  97.4  76.2  91.0  80.4      Ingredient mean2  79.5  98.8b  80.0b  92.9b  83.9  Sorghum (MGD)1      Fine (314 µm)  83.2  99.7  83.6  94.3  86.7      Medium (439 µm)  79.9  99.1  80.1  92.8  84.4      Coarse (594 µm)  75.9  97.8  74.9  91.4  80.2      Ingredient mean2  79.7  98.9b  79.5b  92.8b  83.7      SEM3  0.9  0.4  1.4  0.6  0.9  Effects (P-values)4      Ingredients  NS  <0.01  <0.01  <0.01  NS      Grinding  <0.01  <0.01  <0.01  <0.01  <0.01      Interaction  <0.01  <0.01  <0.01  <0.01  <0.01  Contrasts4      Grinding × rice  NS  NS  NS  NS  <0.05      Grinding × maize  <0.01  <0.01  <0.01  <0.01  <0.01      Grinding × sorghum  <0.01  <0.01  <0.01  <0.01  <0.01    Apparent total tract digestibility, %  Item  DM  Starch  CP  Fat  GE  Broken rice (MGD)1      Fine (277 µm)  79.6  99.5  84.1  94.9  84.8      Medium (311 µm)  79.0  99.6  84.0  94.9  84.1      Coarse (521 µm)  79.8  99.5  81.9  95.3  81.9      Ingredient mean2  79.5  99.5a  83.3a  95.0a  83.7  Maize (MGD)1      Fine (360 µm)  80.5  99.5  81.0  93.7  85.0      Medium (451 µm)  82.1  99.9  82.8  94.1  86.2      Coarse (619 µm)  75.9  97.4  76.2  91.0  80.4      Ingredient mean2  79.5  98.8b  80.0b  92.9b  83.9  Sorghum (MGD)1      Fine (314 µm)  83.2  99.7  83.6  94.3  86.7      Medium (439 µm)  79.9  99.1  80.1  92.8  84.4      Coarse (594 µm)  75.9  97.8  74.9  91.4  80.2      Ingredient mean2  79.7  98.9b  79.5b  92.8b  83.7      SEM3  0.9  0.4  1.4  0.6  0.9  Effects (P-values)4      Ingredients  NS  <0.01  <0.01  <0.01  NS      Grinding  <0.01  <0.01  <0.01  <0.01  <0.01      Interaction  <0.01  <0.01  <0.01  <0.01  <0.01  Contrasts4      Grinding × rice  NS  NS  NS  NS  <0.05      Grinding × maize  <0.01  <0.01  <0.01  <0.01  <0.01      Grinding × sorghum  <0.01  <0.01  <0.01  <0.01  <0.01  a,bIngredient means in the same column without a common superscript differ (P < 0.05). 1MGD = mean geometric diameter of the carbohydrate source (in µm). 2Ingredient means, considering the 3 particle sizes. 3n = 6 per diet. 4NS = nonsignificant (P > 0.05). View Large Table 5. Polynomial contrasts between the apparent total tract digestibility (y) of the nutrients and the raw material mean geometric diameter (MGD) and starch gelatinization degree (x) of extruded diets based on sorghum for dogs     P-value1    Correlation  r2  L  Q  Equation  Starch source MGD      DM  0.82  <0.01  NS  y = 91.2 − 0.026x      CP  0.77  <0.01  NS  y = 89.9 − 0.01x      Fat  0.72  <0.01  NS  y = 99.4 − 0.02x      Starch  0.78  <0.01  NS  y = 102 − 0.007x      GE  0.83  <0.01  NS  y = 94.2 − 0.023x  Food starch gelatinization degree      DM  0.82  <0.01  NS  y = 58.3 + 0.29x      CP  0.76  <0.01  NS  y = 67.6 + 0.27x      Fat  0.77  <0.01  NS  y = 53.8 + 0.35x      Starch  0.83  <0.01  NS  y = 64.9 + 0.25x      P-value1    Correlation  r2  L  Q  Equation  Starch source MGD      DM  0.82  <0.01  NS  y = 91.2 − 0.026x      CP  0.77  <0.01  NS  y = 89.9 − 0.01x      Fat  0.72  <0.01  NS  y = 99.4 − 0.02x      Starch  0.78  <0.01  NS  y = 102 − 0.007x      GE  0.83  <0.01  NS  y = 94.2 − 0.023x  Food starch gelatinization degree      DM  0.82  <0.01  NS  y = 58.3 + 0.29x      CP  0.76  <0.01  NS  y = 67.6 + 0.27x      Fat  0.77  <0.01  NS  y = 53.8 + 0.35x      Starch  0.83  <0.01  NS  y = 64.9 + 0.25x  1L = linear; Q = quadratic; NS = nonsignificant (P > 0.05). View Large Table 5. Polynomial contrasts between the apparent total tract digestibility (y) of the nutrients and the raw material mean geometric diameter (MGD) and starch gelatinization degree (x) of extruded diets based on sorghum for dogs     P-value1    Correlation  r2  L  Q  Equation  Starch source MGD      DM  0.82  <0.01  NS  y = 91.2 − 0.026x      CP  0.77  <0.01  NS  y = 89.9 − 0.01x      Fat  0.72  <0.01  NS  y = 99.4 − 0.02x      Starch  0.78  <0.01  NS  y = 102 − 0.007x      GE  0.83  <0.01  NS  y = 94.2 − 0.023x  Food starch gelatinization degree      DM  0.82  <0.01  NS  y = 58.3 + 0.29x      CP  0.76  <0.01  NS  y = 67.6 + 0.27x      Fat  0.77  <0.01  NS  y = 53.8 + 0.35x      Starch  0.83  <0.01  NS  y = 64.9 + 0.25x      P-value1    Correlation  r2  L  Q  Equation  Starch source MGD      DM  0.82  <0.01  NS  y = 91.2 − 0.026x      CP  0.77  <0.01  NS  y = 89.9 − 0.01x      Fat  0.72  <0.01  NS  y = 99.4 − 0.02x      Starch  0.78  <0.01  NS  y = 102 − 0.007x      GE  0.83  <0.01  NS  y = 94.2 − 0.023x  Food starch gelatinization degree      DM  0.82  <0.01  NS  y = 58.3 + 0.29x      CP  0.76  <0.01  NS  y = 67.6 + 0.27x      Fat  0.77  <0.01  NS  y = 53.8 + 0.35x      Starch  0.83  <0.01  NS  y = 64.9 + 0.25x  1L = linear; Q = quadratic; NS = nonsignificant (P > 0.05). View Large The relationship between the degree of dietary starch gelatinization and nutrient digestibility was also explored. For rice-based diets, no correlation was found (P > 0.05), and thus, changes in starch gelatinization did not cause changes in nutrient digestibility (data not shown). For dogs fed the maize-based diets, less starch gelatinization resulted in reduced digestibility of DM, CP, fat, and starch (data not shown; P < 0.05). For sorghum, a linear response was observed for DM, CP, fat, and starch, and as the degree of gelatinization of the starch increased, the digestibility of nutrients increased (r2 < 0.76; P < 0.01), as can be seen in Table 5. The fecal traits were also influenced by starch source and raw material particle size (Table 6). The dogs fed the rice-based foods had higher fecal DM (P < 0.05) than the dogs fed maize or sorghum. For the 3 grains, the fecal DM decreased with an increase in the starch source MGD (P < 0.05). The fecal score was lower (for all 3 starch sources), and the fecal pH was reduced (only for maize and sorghum diets) with the increase in raw material MGD (P < 0.05). For the SCFA, lower fecal concentrations of butyrate were observed for rice-based diets, and higher concentrations of total SCFA were observed for dogs fed sorghum-based diets (P < 0.05). The rice-based diet also resulted in the production of feces with less lactate (P < 0.05). The increase in raw material MGD did not influence fecal SCFA for rice-based diets, but dogs fed sorghum-based foods with high MGD exhibited reductions in acetate and propionate concentrations and an increase in butyrate concentration (P < 0.05). For dogs fed maize-based foods, a reduction in propionate and an increase in butyrate concentrations were observed with increased MGD (P < 0.05). Table 6. Fecal characteristics and concentration of some fermentation products of dogs fed extruded diets with different carbohydrate sources and raw material particle sizes Item  DM, %  pH  Score1  Acetate, mmol/kg DM  Butyrate, mmol/kg DM  Propionate, mmol/kg DM  SCFA,2 mmol/kg DM  Lactate, mmol/kg DM  Broken rice (MGD)3          Fine (277 µm)  43.0  6.4  3.8  236  35  110  362  7.8          Medium (311 µm)  45.0  6.3  3.1  246  52  138  437  8.5          Coarse (521 µm)  40.0  6.5  3.0  233  52  127  414  8.6          Ingredient mean4  42.7a  6.4  3.3  239  46a  126  402a  8.3a  Maize (MGD)3          Fine (360 µm)  38.0  6.6  3.5  231  61  140  433  11.2          Medium (451 µm)  39.6  6.2  3.5  272  44  150  491  15.1          Coarse (619 µm)  36.0  5.8  2.8  157  147  119  389  18.1          Ingredient mean4  37.9b  6.2  3.3  220  84b  137  435a,b  14.8b  Sorghum (MGD)3          Fine (314 µm)  38.9  6.7  3.3  305  88  212  605  11.9          Medium (439 µm)  36.2  5.9  3.3  214  53  133  390  16.1          Coarse (594 µm)  35.8  6.0  2.6  239  154  119  514  14.2          Ingredient mean4  37.0 b  6.2  3.1  286  98b  166  547b  14.2b  Grinding effect (mean of starch sources)      Fine  40.0a  6.6a  3.5a  257a  61b  168a  467  10.3      Medium  40.3a  6.1b  3.3a  244a,b  50b  140a,b  439  13.2      Coarse  37.7b  6.2b  2.8b  210b  118a  121b  439  13.6  SEM 5  1.3  0.12  0.1  16.4  18.1  12.3  31.1  1.5  Effects (P-values)6      Ingredients  <0.01  NS  NS  NS  <0.05  NS  <0.05  <0.01      Grinding  <0.01  <0.01  <0.01  <0.05  <0.01  <0.01  NS  NS      Interaction  NS  NS  NS  <0.05  NS  NS  NS  NS  Contrasts6          Grinding × rice  <0.05  NS  <0.05  NS  NS  NS  NS  NS          Grinding × maize  <0.05  <0.05  <0.05  NS  <0.01  <0.05  NS  NS          Grinding × sorghum  <0.05  <0.05  <0.05  <0.05  <0.05  <0.01  NS  NS  Item  DM, %  pH  Score1  Acetate, mmol/kg DM  Butyrate, mmol/kg DM  Propionate, mmol/kg DM  SCFA,2 mmol/kg DM  Lactate, mmol/kg DM  Broken rice (MGD)3          Fine (277 µm)  43.0  6.4  3.8  236  35  110  362  7.8          Medium (311 µm)  45.0  6.3  3.1  246  52  138  437  8.5          Coarse (521 µm)  40.0  6.5  3.0  233  52  127  414  8.6          Ingredient mean4  42.7a  6.4  3.3  239  46a  126  402a  8.3a  Maize (MGD)3          Fine (360 µm)  38.0  6.6  3.5  231  61  140  433  11.2          Medium (451 µm)  39.6  6.2  3.5  272  44  150  491  15.1          Coarse (619 µm)  36.0  5.8  2.8  157  147  119  389  18.1          Ingredient mean4  37.9b  6.2  3.3  220  84b  137  435a,b  14.8b  Sorghum (MGD)3          Fine (314 µm)  38.9  6.7  3.3  305  88  212  605  11.9          Medium (439 µm)  36.2  5.9  3.3  214  53  133  390  16.1          Coarse (594 µm)  35.8  6.0  2.6  239  154  119  514  14.2          Ingredient mean4  37.0 b  6.2  3.1  286  98b  166  547b  14.2b  Grinding effect (mean of starch sources)      Fine  40.0a  6.6a  3.5a  257a  61b  168a  467  10.3      Medium  40.3a  6.1b  3.3a  244a,b  50b  140a,b  439  13.2      Coarse  37.7b  6.2b  2.8b  210b  118a  121b  439  13.6  SEM 5  1.3  0.12  0.1  16.4  18.1  12.3  31.1  1.5  Effects (P-values)6      Ingredients  <0.01  NS  NS  NS  <0.05  NS  <0.05  <0.01      Grinding  <0.01  <0.01  <0.01  <0.05  <0.01  <0.01  NS  NS      Interaction  NS  NS  NS  <0.05  NS  NS  NS  NS  Contrasts6          Grinding × rice  <0.05  NS  <0.05  NS  NS  NS  NS  NS          Grinding × maize  <0.05  <0.05  <0.05  NS  <0.01  <0.05  NS  NS          Grinding × sorghum  <0.05  <0.05  <0.05  <0.05  <0.05  <0.01  NS  NS  a,bMeans in the same column without a common superscript differ (P < 0.05). 1Fecal score based on the following scale: 0 = watery (liquid that can be poured); 1 = soft, unformed; 2 = soft, malformed (stool assumes shape of container); 3 = soft, formed, moist (softer stool that retains shape); 4 = well-formed and consistent stool that does not adhere to the floor; 5 = hard, dry pellets (small, hard mass). 2Total SCFA= total short-chain fatty acids, the sum of acetic acid, butyric acid, and propionic acid. 3MGD = mean geometric diameter of the carbohydrate source (in µm). 4Ingredient means, considering the 3 particle sizes. 5n = 6 per diet. 6NS = nonsignificant (P > 0.05). View Large Table 6. Fecal characteristics and concentration of some fermentation products of dogs fed extruded diets with different carbohydrate sources and raw material particle sizes Item  DM, %  pH  Score1  Acetate, mmol/kg DM  Butyrate, mmol/kg DM  Propionate, mmol/kg DM  SCFA,2 mmol/kg DM  Lactate, mmol/kg DM  Broken rice (MGD)3          Fine (277 µm)  43.0  6.4  3.8  236  35  110  362  7.8          Medium (311 µm)  45.0  6.3  3.1  246  52  138  437  8.5          Coarse (521 µm)  40.0  6.5  3.0  233  52  127  414  8.6          Ingredient mean4  42.7a  6.4  3.3  239  46a  126  402a  8.3a  Maize (MGD)3          Fine (360 µm)  38.0  6.6  3.5  231  61  140  433  11.2          Medium (451 µm)  39.6  6.2  3.5  272  44  150  491  15.1          Coarse (619 µm)  36.0  5.8  2.8  157  147  119  389  18.1          Ingredient mean4  37.9b  6.2  3.3  220  84b  137  435a,b  14.8b  Sorghum (MGD)3          Fine (314 µm)  38.9  6.7  3.3  305  88  212  605  11.9          Medium (439 µm)  36.2  5.9  3.3  214  53  133  390  16.1          Coarse (594 µm)  35.8  6.0  2.6  239  154  119  514  14.2          Ingredient mean4  37.0 b  6.2  3.1  286  98b  166  547b  14.2b  Grinding effect (mean of starch sources)      Fine  40.0a  6.6a  3.5a  257a  61b  168a  467  10.3      Medium  40.3a  6.1b  3.3a  244a,b  50b  140a,b  439  13.2      Coarse  37.7b  6.2b  2.8b  210b  118a  121b  439  13.6  SEM 5  1.3  0.12  0.1  16.4  18.1  12.3  31.1  1.5  Effects (P-values)6      Ingredients  <0.01  NS  NS  NS  <0.05  NS  <0.05  <0.01      Grinding  <0.01  <0.01  <0.01  <0.05  <0.01  <0.01  NS  NS      Interaction  NS  NS  NS  <0.05  NS  NS  NS  NS  Contrasts6          Grinding × rice  <0.05  NS  <0.05  NS  NS  NS  NS  NS          Grinding × maize  <0.05  <0.05  <0.05  NS  <0.01  <0.05  NS  NS          Grinding × sorghum  <0.05  <0.05  <0.05  <0.05  <0.05  <0.01  NS  NS  Item  DM, %  pH  Score1  Acetate, mmol/kg DM  Butyrate, mmol/kg DM  Propionate, mmol/kg DM  SCFA,2 mmol/kg DM  Lactate, mmol/kg DM  Broken rice (MGD)3          Fine (277 µm)  43.0  6.4  3.8  236  35  110  362  7.8          Medium (311 µm)  45.0  6.3  3.1  246  52  138  437  8.5          Coarse (521 µm)  40.0  6.5  3.0  233  52  127  414  8.6          Ingredient mean4  42.7a  6.4  3.3  239  46a  126  402a  8.3a  Maize (MGD)3          Fine (360 µm)  38.0  6.6  3.5  231  61  140  433  11.2          Medium (451 µm)  39.6  6.2  3.5  272  44  150  491  15.1          Coarse (619 µm)  36.0  5.8  2.8  157  147  119  389  18.1          Ingredient mean4  37.9b  6.2  3.3  220  84b  137  435a,b  14.8b  Sorghum (MGD)3          Fine (314 µm)  38.9  6.7  3.3  305  88  212  605  11.9          Medium (439 µm)  36.2  5.9  3.3  214  53  133  390  16.1          Coarse (594 µm)  35.8  6.0  2.6  239  154  119  514  14.2          Ingredient mean4  37.0 b  6.2  3.1  286  98b  166  547b  14.2b  Grinding effect (mean of starch sources)      Fine  40.0a  6.6a  3.5a  257a  61b  168a  467  10.3      Medium  40.3a  6.1b  3.3a  244a,b  50b  140a,b  439  13.2      Coarse  37.7b  6.2b  2.8b  210b  118a  121b  439  13.6  SEM 5  1.3  0.12  0.1  16.4  18.1  12.3  31.1  1.5  Effects (P-values)6      Ingredients  <0.01  NS  NS  NS  <0.05  NS  <0.05  <0.01      Grinding  <0.01  <0.01  <0.01  <0.05  <0.01  <0.01  NS  NS      Interaction  NS  NS  NS  <0.05  NS  NS  NS  NS  Contrasts6          Grinding × rice  <0.05  NS  <0.05  NS  NS  NS  NS  NS          Grinding × maize  <0.05  <0.05  <0.05  NS  <0.01  <0.05  NS  NS          Grinding × sorghum  <0.05  <0.05  <0.05  <0.05  <0.05  <0.01  NS  NS  a,bMeans in the same column without a common superscript differ (P < 0.05). 1Fecal score based on the following scale: 0 = watery (liquid that can be poured); 1 = soft, unformed; 2 = soft, malformed (stool assumes shape of container); 3 = soft, formed, moist (softer stool that retains shape); 4 = well-formed and consistent stool that does not adhere to the floor; 5 = hard, dry pellets (small, hard mass). 2Total SCFA= total short-chain fatty acids, the sum of acetic acid, butyric acid, and propionic acid. 3MGD = mean geometric diameter of the carbohydrate source (in µm). 4Ingredient means, considering the 3 particle sizes. 5n = 6 per diet. 6NS = nonsignificant (P > 0.05). View Large DISCUSSION For proper starch gelatinization during the extrusion process and for nutrient digestibility, fecal formation, and amount of fermentation products in the feces of dogs, the raw material particle size was important. The grinding process had different effects for different starch sources, and with the same grinding conditions, rice was reduced to smaller particles than maize and sorghum. For the extrusion cooking, the geometry of the cereal was the primary factor, and the starch gelatinization of the 3 starch sources responded similarly to particle size. Thus, the raw material particle size, more than the starch source, was responsible for the differences in degree of gelatinization observed among the diets. However, for digestibility, fecal formation, and fermentation in the gut, other factors related to the starch granule structure of the cereal were also important because sorghum- and maize-based diets required a greater reduction of particle size and degree of starch gelatinization for proper digestibility. In rice-based diets, the digestibility was high and was not dependent on particle size of raw material or extent of cooking. For several animal species, the processing characteristics of feed, including particle size of the raw material and degree of starch gelatinization, are known to affect nutrient digestibility (Owsley et al., 1981; Fadel et al., 1988; Kienzle, 1993; Healy et al., 1994; Amerah et al., 2007). The particle size is a crucial point in the production of animal feeds, determining both the efficiency of processing and the nutritional quality of the diet (Wondra et al., 1995). However, these aspects are little studied for dogs (Hilcko et al., 2009), and the data on the optimum particle size to extrude cereal-based dog foods are lacking. The differences in the cereals with particle size reduction might be explained by the starch granule structure and the protein matrix associated with the starch granules. Sorghum has a hard outer endosperm, and the protein matrix closely surrounds the starch, restricting digestibility (Rooney and Pflugfelder, 1986). These characteristics might explain the linear response in nutrient digestibility of sorghum-based diets to particle size reduction in the present study. Comparing maize and sorghum in swine, for example, Healy et al. (1994) observed greater weight gain for animals fed maize with 700-µm MGD and sorghum with 500-µm MGD than other particle sizes, which also demonstrated the greater requirement for particle size reduction for proper use of sorghum. By contrast, rice has a small starch granular structure, with a larger surface area for digestive enzyme action during digestion (Svihus et al., 2005). These are important features for the pet food processing industry because the cereal grains in the formula must be accounted for to establish appropriate processing standards, including the mill configuration, raw material MGD, and extruder conformation. Because the extruder configuration and processing conditions did not change among treatments in the present study, the cereal MGD was the factor most likely responsible for the differences in degree of starch gelatinization observed among diets. Starch is particularly altered during extrusion (Zeng et al., 1997); the granules are progressively compressed and transformed into a dense, solid, and compact material that loses crystalline and granular structure. With the combination of water, heat, pressure, and shear force, the starch granules are transformed, creating a homogeneous mass of molten starch (Svihus et al., 2005). This transformation can be partial or complete, depending on the conditions of the extrusion process; the intrinsic characteristics of the raw material, including the amylose to amylopectin ratio and fiber, lipid, and protein contents (Cheftel, 1986); and the particle size of the ingredients, which together ultimately determine the extent of dough cooking in the extruder barrel (Lin et al., 1997). Although not measured for the cereal samples used in the present study, the amylose to amylopectin ratios of Brazilian cultivars of rice, sorghum, and maize were not very different (de-Oliveira et al., 2008); thus, this ratio was unlikely to explain the differences among starch sources in the present study. Following a review of the literature, only imprecise information was available regarding the extent of cooking (degree of starch gelatinization) or the appropriate MGD required for extruded dog foods to achieve adequate digestibility and proper fecal formation. Without information on starch gelatinization from previous studies on dog foods, no direct comparison of the present findings with those in the literature was possible. On the basis of the present results for rice, 76% starch gelatinization was sufficient to achieve greater digestibility, except for GE, which required greater gelatinization and smaller MGD for high digestibility. For maize-based diets, high gelatinization and small cereal particle sizes were required to obtain high digestibility and good fecal formation. For sorghum, nutrient digestibility increased linearly in response to both factors. Additionally, the degree of starch gelatinization was effective to evaluate the efficacy of extruded dog food processing, although further studies are required with different extrusion conditions and raw material MGD. The nutrient digestibility of extruded diets based on sorghum, maize, and rice in dogs was examined in some studies (Twomey et al., 2002; Twomey et al., 2003; Carciofi et al., 2008), and generally, these studies found greater digestibility of rice-based diets, but some discrepancies were found. The raw material particle size and degree of starch gelatinization were not described in these studies, and the discrepancies could be related to starch processing conditions. In the present study, for the finely ground foods (screen sieve with 0.8-mm mesh), nutrient digestibility was high and was comparable among cereal sources. However, whereas the nutrient digestibility was similar for coarsely ground rice and more finely ground rice, the digestibility was reduced for maize- and sorghum-based diets with greater MGD. Therefore, under proper processing conditions, these 3 cereals had similar digestibilities, but when the particle size was not sufficiently reduced, maize- and sorghum-based diets had reduced nutrient digestibility. However, 2 important aspects require attention in the interpretation of the present results. First, because rice had a low fiber content, 6.8% cellulose was added to the rice-based diet and only 1.5% and 0.8% were added to the maize- and sorghum-based diets, respectively, to produce foods with similar nutrient composition. Because fiber reduces nutrient and energy digestibility (NRC, 2006; Kawauchi et al., 2011), this added fiber could explain the similar digestibility of the rice-based diet in comparison to the other cereals when finely ground. In previous publications, the diets did not always have similar fiber contents. Second, only total tract apparent digestibility was measured in the present study. Studying barley fed to swine, Fadel et al. (1988) observed increased DM, energy, and ileal starch digestibility after extrusion. However, when total tract apparent digestibility was measured, no differences were found, which exemplified the importance of nutrient fermentation in the hindgut. Other differences related to MGD and starch gelatinization of maize, sorghum, and rice could possibly be verified if ileal and total tract digestibility were evaluated separately for the dogs. In this study, fermentation in the colon was indirectly evaluated with fermentation products because the dietary starch that escapes digestion and absorption in the small intestine could be fermented by intestinal microbiota, causing higher production of SCFA and lactate with a consequent lower luminal pH (Cummings and Englyst, 1995; Kienzle et al., 2001). The use of fecal concentrations of SCFA to estimate the fermentation activity of the microbiota of the large intestine of dogs has been practiced for many years (Swanson et al., 2002b), and the rectum microbiotas of dogs are active and have fermentation profiles similar to those of the transversal colon (Bosch et al., 2008). Thus, in the present study, the results reinforced that for rice diets starch was primarily digested in the small intestine because rice particle size and degree of starch gelatinization did not change fecal SCFA and pH values, regardless of processing conditions. One important metabolite generated by starch fermentation is lactate (Macfarlane and Englyst, 1986), and its lower concentration in the feces of dogs fed rice-based diets also supported the greater starch digestibility of rice in the small intestine. By contrast, maize and sorghum were fermented to a greater degree by saccharolytic bacteria when cooked less or ground coarsely in the present study. A reduction in total tract apparent starch digestibility was verified for coarsely ground maize- and sorghum-based diets, and starch fermentation resulted in lower fecal pH values but did not result in higher amounts of total SCFA, but alterations in the molar proportions led to reduced acetate and propionate and increased butyrate fecal concentrations. The fermentation of carbohydrates is important for proper gut function and health, and to increase fermentation, fiber and prebiotics were studied and used in dog foods (Vickers et al., 2001; Swanson et al., 2002a; Zentek et al., 2002). The present research opened the opportunity to use less processed starch for the promotion of gut health. This form of nondigestible starch, or resistant starch, has been studied extensively in humans (Topping and Clifton, 2001). The resistant starch is classified by at least 3 types: physically inaccessible starch, as in coarsely ground cereals; resistant starch granules, as in maize grain with high amylose content; and retrograded starch, as in cooled cooked potato starch (Englyst and Hudson, 1996). Thus, the physically inaccessible starch of coarsely ground and less gelatinized maize or sorghum could be of value for dog gut health and should be studied further. As verified in the present study by the consumption of these diets, this observation was primarily reinforced by the increase in fecal concentrations of butyrate, a fermentation product with important functions in gut mucosa physiology and health (Hamer et al., 2008). Butyrate production has received special attention because of the important physiological actions of butyrate in the colon, which may inhibit the growth of malignant cells in colon tissue (Cunningham-Rundles and Lin, 1998; Hamer et al., 2008). Attempts to increase the fecal concentrations of butyrate in dogs have included fiber and prebiotic additions to diets, but positive results were not always obtained (Sunvold et al., 1995; Strickling et al., 2000; Propst et al., 2003; Middelbos et al., 2007; Biagi et al., 2010). In the present study, the fecal concentration of butyrate in dogs fed coarsely ground maize- and sorghum-based diets exceeded the concentration of propionate, a substantial increase with potential physiological consequences to be explored in future studies. Fecal quality is an important index in the evaluation of dog foods. Similar to the results of Belay et al. (1997) and Murray et al. (1999), the results of the present experiment showed that dogs fed rice-based diets produced feces with low water content. However, this observation needs to be interpreted considering the addition of cellulose to the rice formula, a fiber source that might increase the fecal dry matter content. Additionally, for the 3 cereals, the consumption of foods based on coarsely ground cereals led to higher content of water in the dog feces, with poorly formed stools. In conclusion, the particle size of cereals affected starch gelatinization during the extrusion process, nutrient digestibility, fecal formation, and the concentration of SCFA in the feces of dogs. These effects, however, were ingredient dependent; whereas sorghum- and maize-based diets required a greater reduction in particle size for an increased degree of gelatinization for proper digestibility and for adequate feces formation, rice-based diets were more easily digested even when the rice was more coarsely ground and, subsequently, less gelatinized. The coarsely ground and less gelatinized maize- and sorghum-based diets promoted the formation of butyrate in the colon, an aspect that may be related to gut health that deserves further study. Footnotes 1 The authors acknowledge the financial support of Mogiana Alimentos (Guabi). LITERATURE CITED Amerah A. M. Ravindran V. Lentle R. G. Thomas D. G. 2007. Feed particle size: Implication on the digestion and performance of poultry. Worlds Poult. Sci. J.  63: 439– 455. doi: https://doi.org/10.1017/S0043933907001560. Google Scholar CrossRef Search ADS   AOAC 1995. Official methods of analysis. 15th ed. Assoc. Off. Anal. Chem., Arlington, VA. Association of American Feed Control Officials 2008. Association of American Feed Control Officials: Official publication. Assoc. Am. Feed Control. Off., Atlanta, GA. Belay T. Shields R. O. Jr Wiernusz C. J. Kigin P. D. Brayman C. A. 1997. Evaluation of nutrient digestibility and stool quality of rice (Oryza sativa) based canine diets. Vet. Clin. Nutr.  4: 122– 129. Biagi G. Cipollini I. Grandi M. Zaghini G. 2010. Influence of some potential prebiotics and fibre-rich foodstuffs on composition and activity of canine intestinal microbiota. Anim. Feed Sci. Technol.  159: 50– 58. doi: https://doi.org/10.1016/j.anifeedsci.2010.04.012. Google Scholar CrossRef Search ADS   Bosch G. Pellikaan W. F. Rutten P. G. P. van der Poel A. F. B. Verstegen M. W. A. Hendriks W. H. 2008. Comparative in vitro fermentation activity in the canine distal gastrointestinal tract and fermentation kinetics of fiber sources. J. Anim. Sci.  86: 2979– 2989. doi: https://doi.org/10.2527/jas.2007-0819. Google Scholar CrossRef Search ADS PubMed  Carciofi A. C. Takakura F. S. De-Oliveira L. D. Teshima E. Jeremias J. T. Brunetto M. A. Prada F. 2008. Effects of six carbohydrate sources on dog diet digestibility and post-prandial glucose and insulin response. J. Anim. Physiol. Anim. Nutr.  92: 326– 336. doi: https://doi.org/10.1111/j.1439-0396.2007.00794.x. Google Scholar CrossRef Search ADS   Carciofi A. C. Vasconcellos R. S. de-Oliveira L. D. Brunetto M. A. Valério A. G. Bazolli R. S. Carrilho E. N. V. M. Prada F 2007. Chromic oxide as a digestibility marker for dogs—A comparison of methods of analysis. Anim. Feed Sci. Technol.  134: 273– 282. doi: https://doi.org/10.1016/j.anifeedsci.2006.12.005. Google Scholar CrossRef Search ADS   Cheftel J. C. 1986. Nutritional effects of extrusion cooking. Food Chem.  20: 263– 283. doi: https://doi.org/10.1016/0308-8146(86)90096-8. Google Scholar CrossRef Search ADS   Crane S. W. Griffin R. W. Messent P. R. 2000. Introduction to commercial pet foods. In: Hand M. S. Thatcher C. D. Remillard R. L. Roudebush P. Lewis L. D. editors, Small animal clinical nutrition.  4th ed. Mark Morris Inst., Topeca, KS. p. 111– 126. Cummings J. H. Englyst H. N. 1995. Gastrointestinal effects of food carbohydrate. Am. J. Clin. Nutr.  61( Suppl. 4): 938– 945. Google Scholar CrossRef Search ADS   Cunningham-Rundles S. Lin D. H. 1998. Nutrition and the immune system of the gut. Nutr.  14: 573– 579. doi:http://dx.doi.org/10.1016/S0899-9007(98)00029-X. Google Scholar CrossRef Search ADS   de-Oliveira L. D. Carciofi A. C. Oliveira M. C. C. Vasconcellos R. S. Bazolli R. S. Pereira G. T. Prada F. 2008. Effects of six carbohydrate sources on diet digestibility and postprandial glucose and insulin responses in cats. J. Anim. Sci.  86: 2237– 2246. doi: https://doi.org/10.2527/jas.2007-0354. Google Scholar CrossRef Search ADS PubMed  Englyst H. N. Hudson G. J. 1996. The classification and measurement of dietary carbohydrates. Food Chem.  57: 15– 21. doi: https://doi.org/10.1016/0308-8146(96)00056-8. Google Scholar CrossRef Search ADS   Erwin W. S. Marco G. J. Mery E. M. 1961. Volatile fatty acids analyses of blood an rumen fluid by gas chromatography. J. Dairy Sci.  44: 1768– 1771. doi: https://doi.org/10.3168/jds.S0022-0302(61)89956-6. Google Scholar CrossRef Search ADS   Fadel J. G. Newman C. W. Newman R. K. Graham H. 1988. Effects of extrusion cooking of barley on ileal and fecal digestibilities of dietary components in pigs. Can. J. Anim. Sci.  68: 891– 897. doi: https://doi.org/10.4141/cjas88-098. Google Scholar CrossRef Search ADS   Fenton T. W. Fenton M. 1979. An improved procedure for the determination of chromic oxide in feed and feces. Can. J. Anim. Sci.  59: 631– 634. doi: https://doi.org/10.4141/cjas79-081. Google Scholar CrossRef Search ADS   Fortes C. M. L. S. Carciofi A. C. Sakomura N. K. Kawauchi I. M. Vasconcellos R. S. 2010. Digestibility and metabolizable energy of some carbohydrate sources for dogs. Anim. Feed Sci. Technol.  156: 121– 125. doi: https://doi.org/10.1016/j.anifeedsci.2010.01.009. Google Scholar CrossRef Search ADS   Hamer H. M. Jonkers D. Venema K. Vanhoutvin S. Troost F. J. Brummer R. J. 2008. Review article: The role of butyrate on colonic function. Aliment. Pharmacol. Ther.  27: 104– 119. doi: https://doi.org/10.1111/j.1365-2036.2007.03562.x. Google Scholar CrossRef Search ADS PubMed  Healy B. J. Hancock J. D. Kennedy G. A. Bramel-Cox P. J. Behnke K. C. Hines R. H. 1994. Optimum particle size of corn and hard and soft sorghum for nursery pigs. J. Anim. Sci.  72: 2227– 2236. Google Scholar CrossRef Search ADS PubMed  Hendrix D. L. 1993. Rapid extraction and analysis of nonstructural carbohydrates in plant tissues. Crop Sci.  25: 984– 989. Hilcko K. P. Félix A. P. Oliveira S. G. Bortolo M. Maiorka A. Brito C. B. M. Alves P. F. 2009. Different milling in diets for dogs. Cienc. Rural  39: 2511– 2515. doi: https://doi.org/10.1590/S0103-84782009000800037. Google Scholar CrossRef Search ADS   Holt S. H. A. Miller J. B. 1994. Particle size, satiety and glycaemic response. Eur. J. Clin. Nutr.  48: 496– 502. Google Scholar PubMed  Kawauchi I. M. Sakomura N. K. Vasconcellos R. S. de-Oliveira L. D. Gomes M. O. S. Loureiro B. A. Carciofi A. C. 2011. Digestibility and metabolizable energy of maize gluten feed for dogs as measured by two different techniques. Anim. Feed Sci. Technol.  169: 96– 103. doi: https://doi.org/10.1016/j.anifeedsci.2011.05.005. Google Scholar CrossRef Search ADS   Kienzle E. 1993. Carbohydrate metabolism of the cat: 1. Activity of amylase in the gastrointestinal tract of the cat. J. Anim. Physiol. Anim. Nutr.  69: 92– 101. doi: https://doi.org/10.1111/j.1439-0396.1993.tb00793.x. Google Scholar CrossRef Search ADS   Kienzle E. Dobenecker B. Eber S. 2001. Effect of cellulose on the digestibility of high starch versus high fat diets in dogs. J. Anim. Physiol. Anim. Nutr.  6: 51– 72. Laflamme D. 1997. Development and validation of a body condition score system for dogs. Canine Pract.  22: 13– 18. Lin S. Hsieh F. Huff H. E. 1997. Effects of lipids and processing conditions on degree of starch gelatinization of extruded dry pet food. Lebensm. Wiss. Technol.  30: 754– 761. doi: https://doi.org/10.1006/fstl.1997.0271. Google Scholar CrossRef Search ADS   Lloyd L. E. McCay C. M. 1954. The use of chromic oxide in digestibility and balance studies with dogs. J. Nutr.  53: 613– 622. Google Scholar CrossRef Search ADS PubMed  Macfarlane G. T. Englyst H. N. 1986. Starch utilization by the human large intestinal microflora. J. Appl. Bacteriol.  60: 195– 201. doi: https://doi.org/10.1111/j.1365-2672.1986.tb01073.x. Google Scholar CrossRef Search ADS PubMed  Middelbos I. S. Godoy M. R. Fastinger N. D. Fahey G. C. Jr 2007. A dose-response evaluation of spray-dried yeast cell wall supplementation of diets fed to adult dogs: Effects on nutrient digestibility, immune indices, and fecal microbial populations. J. Anim. Sci.  85: 3022– 3032. doi: https://doi.org/10.2527/jas.2007-0079. Google Scholar CrossRef Search ADS PubMed  Miller G. L. 1959. Use of dinitrosalicylic acid reagent for determination of reducing sugar. Anal. Chem.  31: 426– 428. doi: https://doi.org/10.1021/ac60147a030. Google Scholar CrossRef Search ADS   Murray S. M. Fahey G. C. Jr Merchen N. R. Sunvold G. D. Reinhart G. A. 1999. Evaluation of selected high-starch flours as ingredients in canine diets. J. Anim. Sci.  77: 2180– 2186. Google Scholar CrossRef Search ADS PubMed  NRC 2006. Nutrient requirements of dogs and cats. Natl. Acad. Press, Washington, DC. Owsley W. F. Knabe D. A. Tanksley T. D. Jr 1981. Effect of sorghum particle size on digestibility of nutrients at the terminal ileum and over the total digestive tract of growing-finishing pigs. J. Anim. Sci.  52: 557– 566. Google Scholar CrossRef Search ADS PubMed  Pereira M.A. Jacobs D. R. Jr Pins J. J. Raatz S. K. Gross M. D. Slavin J. L. Seaquist E. R. 2002. Effect of whole grains on insulin sensitivity in overweight hyperinsulinemic adults. Am. J. Clin. Nutr.  75: 848– 855. Google Scholar CrossRef Search ADS PubMed  Propst E. L. Flickinger E. A. Bauer L. L. Merchen N. R. Fahey G. C. Jr 2003. A dose-response experiment evaluating the effects of oligofructose and inulin on nutrient digestibility, stool quality, and fecal protein catabolites in healthy adult dogs. J. Anim. Sci.  81: 3057– 3066. Google Scholar CrossRef Search ADS PubMed  Prosky L. Asp N. G. Schweizer T. F. De Vries J. W. Furda I. 1992. Determination of insoluble and soluble dietary fiber in foods and food products: Collaborative study. J. AOAC Int.  75: 360– 367. Pryce J. D. A. 1969. Modification of the Barker-Summerson method for the determination of lactic acid. Analyst  94: 1151– 1152. doi: https://doi.org/10.1039/an9699401151. Google Scholar CrossRef Search ADS PubMed  Rooney L. W. Pflugfelder R. L. 1986. Factors affecting starch digestibility with special emphasis on sorghum and corn. J. Anim. Sci.  63: 1607– 1623. Google Scholar CrossRef Search ADS PubMed  Sá F. C. Vasconcellos R. S. Brunetto M. A. Filho F. O. R. Gomes M. O. S. Carciofi A. C. 2013. Enzyme use in kibble diets formulated with wheat bran for dogs: Effects on processing and digestibility. J. Anim. Physiol. Anim. Nutr.  97( Suppl. 1): 51– 59. doi: https://doi.org/10.1111/jpn.12047. Google Scholar CrossRef Search ADS   Strickling J. A. Harmon D. L. Dawson K. A. Gross K. L. 2000. Evaluation of oligosaccharide addition to dog diets: Influences on nutrient digestion and microbial populations. Anim. Feed Sci. Technol.  86: 205– 219. doi: https://doi.org/10.1016/S0377-8401(00)00175-9. Google Scholar CrossRef Search ADS   Sitohy M. Z. El-Saadany S. S. Labib S. M. Ramadan M. F. 2000. Physicochemical properties of different types of starch phosphate monoestrers. Starke  52: 101– 105. Google Scholar CrossRef Search ADS   Sunvold G. D. Fahey G. C. Jr Merchen N. R. Titgemeyer E. C. Bourquin L. D. Bauer L. L. Reinhart G. A. 1995. Dietary fiber for dogs: IV. In vitro fermentation of selected fiber sources by dog fecal inoculum and in vivo digestion and metabolism of fiber-supplemented diets. J. Anim. Sci.  73: 1099– 1109. Google Scholar CrossRef Search ADS PubMed  Svihus B. Uhlen A. K. Harstad O. M. 2005. Effect of starch granule structure, associated components and processing on nutritive value of cereal starch: A review. Anim. Feed Sci. Technol.  122: 303– 320. doi: https://doi.org/10.1016/j.anifeedsci.2005.02.025. Google Scholar CrossRef Search ADS   Swanson K. S. Grieshop C. M. Flickinger E. A. Bauer L. L. Healy H. P. Dawson K. A. Merchen N. R. Fahey G. C. Jr 2002b. Supplemental fructooligosaccharides and mannanoligosaccharides influence immune function, ileal and total tract nutrient digestibilities, microbial populations and concentrations of protein catabolites in the large bowel of dogs. J. Nutr.  132: 980– 989. Google Scholar CrossRef Search ADS   Swanson K. S. Grieshop C. M. Flickinger E. A. Healy H. P. Dawson K. A. Merchen N. R. Fahey G. C. Jr 2002a. Effects of supplemental fructooligosaccharides plus mannanoligosaccharides on immune function and ileal and faecal microbial populations in adult dogs. Arch. Anim. Nutr.  56: 309– 318. Tester F. Karkalas J. Qi X. 2004. Starch composition, fine structure and architecture. J. Cereal Sci.  39: 151– 165. doi: https://doi.org/10.1016/j.jcs.2003.12.001. Google Scholar CrossRef Search ADS   Topping D. L. Clifton P. M. 2001. Short-chain fatty acids and human colonic function: Roles of resistant starch and nonstarch polysaccharides. Physiol. Rev.  81: 1031– 1064. Google Scholar CrossRef Search ADS PubMed  Twomey L. N. Pethick D. W. Rowe J. B. Choct M. Pluske J. R. Brown W. Laviste M. C. 2002. The use of sorghum and corn as alternative to rice in dog foods. J. Nutr.  132: 1704S– 1705S. Google Scholar CrossRef Search ADS PubMed  Twomey L. N. Pluske J. R. Rowe J. B. Choct M. Brown W. Mcconnell M. F. Pethick D. W. 2003. The replacement value of sorghum and maize with or without supplemental enzymes for rice in extruded dog foods. Anim. Feed Sci. Technol.  108: 61– 69. doi: https://doi.org/10.1016/S0377-8401(03)00168-8. Google Scholar CrossRef Search ADS   Vickers R. J. Sunvold G. D. Kelley R. L. Reinhart G. A. 2001. Comparison of fermentation of selected fructooligosaccharides and other fiber substrates by canine colonic microflora. Am. J. Vet. Res.  62: 609– 615. doi: https://doi.org/10.2460/ajvr.2001.62.609. Google Scholar CrossRef Search ADS PubMed  Wondra K. J. Hancock J. D. Behnke K. C. Hines R. H. Stark C. R. 1995. Effects of particle size and pelleting on growth performance, nutrient digestibility, and stomach morphology in finishing pigs. J. Anim. Sci.  73: 757– 763. Google Scholar CrossRef Search ADS PubMed  Zanotto D. L. Bellaver C. 1996. Método de determinação da granulometria de ingredientes para uso em rações de suínos e aves. Comunicado Técnico EMBRAPA–Suíno e Aves No. CT 215.  EMBRAPA, Concordia, SC. p. 1– 5. Zeng M. Morris C. F. Batey I. L. Wrigley C. W. 1997. Sources of variation for starch gelatinization, pasting, and gelation properties in wheat. Cereal Chem.  74: 63– 71. doi: https://doi.org/10.1094/CCHEM.1997.74.1.63. Google Scholar CrossRef Search ADS   Zentek J. Marquart B. Pietrzak T. 2002. Intestinal effects of mannanoligosaccharides, transgalactooligosaccharides, lactose and lactulose in dogs. J. Nutr.  132: 1682S– 1684S. Google Scholar CrossRef Search ADS PubMed  American Society of Animal Science
TI - Effect of the particle size of maize, rice, and sorghum in extruded diets for dogs on starch gelatinization, digestibility, and the fecal concentration of fermentation products
JF - Journal of Animal Science
DO - 10.2527/jas.2014-8409
DA - 2015-06-01
UR - https://www.deepdyve.com/lp/oxford-university-press/effect-of-the-particle-size-of-maize-rice-and-sorghum-in-extruded-CJierEynWc
SP - 2956
EP - 2966
VL - 93
IS - 6
DP - DeepDyve
ER -