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ANIMAL NUTRITION |
Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana 61801
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Key Words: Corn Hybrid • Digestion • Dog • In Vitro
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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). During that year, the pet food industry’s U.S. retail sales totaled $11.1 billion.
Extruded pet foods are the most common types produced and sold in the United States (Case et al., 1995). Cereal grains are used in extruded pet foods because of their high nutritive value and their relatively low cost. Extrusion enhances the value of the cereal grain by cooking the starch component, thereby increasing the digestibility of the complete diet.
Corn is a commonly used ingredient in dry pet foods because there is a stable supply and it is a relatively inexpensive source of nutrients. Corn varieties have been developed for various nutritional characteristics including high protein and high lipid contents, resulting in a more nutrient-dense ingredient. Low-phytate varieties of corn have been developed to increase phosphorus bioavailability. Corn also has been developed with varying amylose:amylopectin ratios, which can affect nutrient digestibility. For example, high-amylose corn varieties processed under select heating and cooling conditions have higher amounts of carbohydrate that escape digestion in the small intestine and become available for fermentation by colonic microbes (Borchers, 1962). This decreased starch digestibility may be of benefit for pets that have been diagnosed with diabetes.
There have been few published studies on corn hybrid use in dog diets. One objective of this research was to investigate the effects of selected extruded corn hybrids on in vitro hydrolytic digestion and large bowel fermentation. The second objective was to study the effects of selected corn hybrid inclusion in canine diets on ileal and total-tract nutrient digestibilities, fecal microbial populations, and fecal characteristics.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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Donors.
Three mixed-breed purpose-bred adult female dogs with hound bloodlines were used as fecal donors. Dogs had access twice daily to a commercially available diet containing approximately 26% CP and 15% fat for 14 d before collection of feces. Major ingredients in the diet included corn, poultry by-product meal, and chicken fat. Dogs were housed in a temperature-controlled room in 1.2 x 3.1 m solid-floor pens. Free access to water was provided at all times.
Monogastric In Vitro Model.
Approximately 500 mg of substrate was placed into tubes in triplicate and exposed to pepsin/hydrochloric acid and pancreatin to simulate hydrolytic digestion (Boisen, 1991). A set of tubes without substrate was used as blanks, whereas another set of tubes did not continue into the fermentation phase of the experiment in order to measure enzymatic digestion. The substrate remaining after simulated stomach and small intestinal digestion was used for in vitro fermentation (Bourquin et al., 1993). Freshly voided feces from three dogs was diluted in a 1:10 ratio in anaerobic dilution solution for 10 s in a Waring (Torrington, CT) blender. Blended, diluted feces were filtered through four layers of cheesecloth, and the filtrate was sealed in 125-mL serum bottles under CO2. Tubes were flushed with CO2 and capped with stoppers equipped with one-way gas release valves (Nalge Nunc Int., Rochester, NY). A 4-mL portion of inoculum was added to 26 mL of medium (Table 1) and residue remaining after simulated stomach/small intestinal digestion. This inoculum was used to inoculate all residues and blanks. Tubes were placed in a forced-air incubator at 39°C for 8 h. Tubes were removed from the incubator and processed immediately. A 2-mL aliquot was removed for SCFA analysis. The remaining 28 mL was combined with 112 mL of 95% ethanol for 1 h to precipitate the soluble polysaccharide fractions. Samples were filtered through Whatman No. 541 filter paper (Whatman Inc., Clifton, NJ) and washed with 78% ethanol, 95% ethanol, and acetone. Samples were dried at 105°C, weighed, and ashed in preweighed aluminum foil boats (450°C) and weighed again to determine OM disappearance (OMD).
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Short-Chain Fatty Acid Analysis.
For short-chain fatty acid (SCFA) analysis, the 2-mL aliquot taken from the inoculated tubes was added to 0.5 mL of 25% meta-phosphoric acid, precipitated for 30 min, and centrifuged at 20,000 xg for 20 min. The supernatant fluid was decanted and frozen at –20°C in microfuge tubes. After freezing, the supernatant fluid was thawed and centrifuged in microfuge tubes at 10,000 xg for 10 min. Acetate, propionate, and butyrate concentrations were measured using a Hewlett-Packard model 5890A Series II gas-liquid chromatograph (Agilent Technologies, Palo Alto, CA) and a glass column (180 cm x4 mm i.d.) packed with 10% SP-1200/1% H3PO4 on 80/100 mesh Chromosorb WAW (Supelco Inc., Bellefonte, PA). The SCFA concentrations were corrected for by analyzing blank tube production of the SCFA.
Statistical Analyses.
Data were analyzed by ANOVA as a randomized complete block with donor animal serving as block and tube serving as the experimental unit. All of the analyses were performed according to the GLM procedure of SAS (SAS Inst., Inc., Cary, NC). Means were compared by the Tukey’s honestly significant difference method when treatment differences (P < 0.05) were detected. Individual means were considered significantly different from one another when they exceeded the minimum significant difference calculated by Tukey’s test in SAS.
Experiment 2
Treatments.
Three experimental corn hybrids (HA, HP, and HPLP) were fed along with CONV and AM. All animals consumed a poultry by-product meal-based kibbled diet (Table 2) prepared under commercial conditions (extruder model X-85, Wenger Manufacturing, Sabetha, KS) and which met or exceeded nutrient requirements for adult dogs at maintenance (AAFCO, 2003). The raw materials for the diets were preconditioned before extrusion at a shaft speed of 350 to 360 rpm, with 20 to 25 kg/h steam flow, and 14 to 18 kg/h water flow. Substrate temperature was 91°C, 3.10 min after discharge from the extruder. Extruder shaft speed ranged from 570 to 595 rpm. Steam flow to the extruder was 10 to 15 kg/h. Retention time in the extruder was approximately 25 to 30 s. Moisture concentrations of the substrates ranged between 20.2 and 23.5% out of the extruder barrel before drying in a moving belt dryer for 23 min at 80°C.
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). Dogs were individually housed in clean floor pens (1.2 x3.1 m) with slip-resistant flooring in a temperature-controlled room at the animal facility of the Edward R. Madigan Laboratory on the University of Illinois campus. The room was on a 16-h light:8-h dark cycle at an average temperature of 22°C. Animal care procedures were conducted under a research protocol approved by the Institutional Animal Care and Use Committee, University of Illinois, Urbana. The five hounds (weight ranging from 18.1 to 27.3 kg) were randomly allotted to diets in a 5 x5 Latin square design with 14 d-periods. Each dog was offered 150 g of diet (as-fed basis) at 0800 and 2000 for a total of 300 g/d. During the fourth period, food was increased to 350 g/d because several of the dogs lost BW. After the second period, one dog was removed for reasons unrelated to the study. At the beginning of the third period, the animal was replaced, and this dog was offered the same amounts of food as the other animals for each period. This dog was fed for two extra periods to substitute for the first and second periods, but at 350 g/d. Food refusals from the previous feeding were weighed and recorded at 0800 and 2000. Water was available ad libitum. Days 1 through 10 served as the diet adaptation phase, whereas d 11 through 14 were used for ileal and fecal collections. Chromic oxide was used as a digestion marker on d 6 through 14. Dogs were dosed at 0800 and 2000 with 0.5 g of chromic oxide in gelatin capsules twice daily for a total of 1 g/d.
Sampling Procedures.
Ileal effluent was collected three times per day, with an interval of 4 h between the start of collections, with individual ileal collections lasting 1 h. The sampling times on the remaining 3 d were rotated 1 h from the previous day’s collection time for a total of 12 samples per animal per 4-d collection period. For example, on d 1, sampling took place at 0800, 1200, and 1600 h; on d 2, samples were collected at 0900, 1300, and 1700 h. Ileal effluent was collected by attaching a Whirlpak bag (Pioneer Container Corp., Cedarburg, WI) to the cannula barrel and around the cannula hose clamp with a rubber band. Before bag attachment, the cannulas were cleaned with a spatula and dried digesta was discarded. The dogs wore Bite-Not collars (Bite Not Products, Inc., San Francisco, CA) to prevent chewing of the Whirlpak bags. Dogs were encouraged to move about freely during ileal collection periods while being observed to ensure that they would not remove the bag from the cannula. Feces were collected from the pen floor and were scored for each dog during each collection period according to the following system: 1 = hard, dry pellets—small, hard mass; 2 = hard, formed, dry stool—remains firm and soft; 3 = soft, formed, moist—softer than stool that retains shape; 4 = soft, unformed—stool assumes shape of container, pudding-like; 5 = watery—liquid that can be poured. On d 13 or 14 of each period, a freshly voided fecal sample was collected and processed immediately for bacterial enumeration. Total feces excreted during the collection phase of each period were collected from the floor of the pen, weighed, and then frozen at –20°C for subsequent processing. Ileal samples were frozen at –20°C in their individual bags immediately following collection.
Sample Handling.
All ileal effluent samples were composited for each dog for each period, and then frozen at –20°C. Ileal effluent was freeze-dried in a Dura-Top lyophilizer (FTS Systems, Inc., Stone Ridge, NY). Feces from the 4-d collection period were composited by dog and period before being dried at 55°C in a forced-air oven. After drying, both feces and ileal samples were ground to pass a 2-mm screen in a Wiley mill. For bacterial enumeration, a 1.0-g sample of feces was placed in a pre-weighed Carey-Blair transport media container (Meridian Diagnostics, Inc., Cincinnati, OH), plated, and enumeration was performed.
Microbial Analyses.
Bifidobacteria, lactobacilli, and Clostridium perfringens concentrations were determined by serial dilution of fresh fecal samples in anaerobic diluent and inoculation onto respective petri dishes of sterile agar. Lactobacilli were cultured on Rogosa SL agar (Difco Laboratories, Detroit, MI). Bifidobacteria (BIM 25) were cultured using prepared agar (BBL Microbiology Systems, Cockneyville, MD) according to the method of Muñoa and Pares (1988). Clostridium perfringens sp. were enumerated on a tryptose-sulfite-cycloserine agar with egg yolk (FDA, 1992). All agars were inoculated by using a repeating pipette to dispense seven 10-µL drops of the appropriate dilutions. After the drops were adsorbed onto the agar, plates were inverted and incubated at 38°C. Colony counts were made after 48 h of incubation.
Chemical Analyses.
Diets, feces, and ileal effluent were analyzed for DM, OM, and ash according to AOAC (1985) methods. Crude protein was determined using Leco N analysis (AOAC, 1995). Lipid content was determined by acid hydrolysis followed by ether extraction according to AACC (1983) and Budde (1953). Total dietary fiber (TDF) was determined as outlined by Prosky et al. (1984), with an additional 7 mL of dimethyl sulfoxide for resistant starch solubilization according to Gelroth and Ranhotra (2000). Gross energy (GE) was determined by oxygen bomb calorimetry (Parr Instruments Co., Moline, IL). Chromic oxide concentration was determined according to Williams et al. (1962). Total starch (TS) was determined using the method of Thivend et al. (1972). Digestible starch was calculated as described by Muir and O’Dea (1993). This value then was subtracted from TS values to determine resistant starch (RS) concentrations. Grains, diets, and ileal effluent were analyzed for amino acid content by hydrolyzing 150 mg of sample in 15 mL of 6 N HCl for 22 h at 110°C according to Spitz (1973). The AA concentrations were determined using ion-exchange chromatography (Speckman et al., 1958) following hydrolysis. Methionine and cystine were determined using the performic acid oxidation method as described by Moore (1963). Raw and extruded starch sources and diets were fractionated into digestible and resistant starches according to Muir and O’Dea (1993). Total P was analyzed according to AOAC (1975). Phytate and the coinciding phytate-P complex were analyzed by HPLC according to Talamond et al. (2000). Bioavailable P was calculated as the difference between the total P and phytate-P concentrations divided by the total P concentration.
Calculations.
Dry matter flow (g/d) of ileal effluent and fecal DM output were calculated by dividing Cr intake (mg/d) by ileal or fecal Cr concentration (mg of Cr/g sample). Nutrient flows were calculated by multiplying the DM flow by the concentration of the nutrient in the ileal or fecal DM. Ileal and total-tract nutrient digestibilities were calculated by subtracting the nutrient flow (g/d) from the nutrient intake (g/d). This value then was divided by nutrient intake (g/d).
Statistical Analyses.
Data were analyzed using the GLM procedure of SAS. A 5 x5 Latin square design was used. Model sums of squares included treatment, period, and animal effects. For all variables, DMI was used as a covariate. Bacterial concentrations were converted to a log10 basis before statistical analysis to decrease variation and increase the normality of the distribution. Due to missing data cells, least squares means are reported in tables. Differences were considered significant at P < 0.05, but trends of P < 0.10 also are discussed.
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Results and Discussion |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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. Dry matter and OM concentrations were similar among substrates, with AM having the highest DM (93.6%) and OM (99.8%) content. Crude protein concentrations varied between 0.7 (AM) and 11.6% for (HA). Acid-hydrolyzed fat values ranged between 1.4 (AM) and 7.2% (HA). Total dietary fiber concentrations ranged from 3.5 for AM to 18.8% for HA. Total starch concentrations ranged from 69.1% for HA to 97.6% for AM. Resistant starch ranged from 34.9 (CONV) to 57.0% (AM). Gross energy values were similar among starch sources. Total P averaged 0.28% for the four corn hybrids, and was 0.03% for AM. Total phytate ranged from 0.00 (AM) to 0.91% (HP). The calculated values of bioavailable P ranged from 0.00 (HP) to 0.19% for HPLP corn. Total essential amino acids (TEAA) for the corn hybrids ranged from 3.39 for CONV to 4.95% for HA, whereas AM contained only 0.35% TEAA. Total nonessential amino acids (TNEAA) ranged from 0.41 for AM to 6.91% for HA. Total amino acids (TAA) ranged from 8.20 (CONV) to 11.86% (HA).
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. Dry matter concentrations ranged from 83.7 to 90.0%. Organic matter concentrations were similar at 98.7% on average. Crude protein concentrations ranged from 1.8 for AM to 11.5% for HA. The extruded corn hybrids had between 10.7 and 16.6% TDF, whereas AM contained only 1.9% TDF. Total starch ranged from 68.0 to 77.1% for the corn hybrids, and 97.1% for AM. Resistant starch values ranged from 16.0 (CONV) to 63.9% (AM). The AM substrate is made up of mostly amylose, which is resistant to enzymatic digestion (Borchers, 1962). Gross energy values were similar, ranging from 4.1 to 4.6 kcal/g. Total P concentrations ranged from 0.07 (AM) to 0.31% for HA and HP. Total phytate and bioavailable P concentrations ranged from 0.00 to 0.97%, and 0.00 to 0.22%, respectively, which were similar to values obtained for raw substrates. For TEAA, TNEAA, and TAA, among the corn hybrids, lower values were noted for CONV, whereas the highest values were noted for HP.
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Organic Matter Disappearance and SCFA Concentrations.
Hydrolytic digestion values for all substrates were different (P < 0.05) from each other and ranked as follows: AM < HA < CONV < HP < HPLP (Table 5). Little fermentation occurred of the residues remaining after hydrolytic digestion, with values ranging from 1.1 to 7.6% after 8 h. The AM and HA substrates had higher (P < 0.05) OMD values as a result of fermentation compared to CONV, HP, and HPLP. Total digestion values were lowest (P < 0.05) for AM, whereas HA was lower than CONV, HP, and HPLP, and CONV, HP, and HPLP were similar.
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). No differences among substrates were detected for production of propionate, butyrate, or total SCFA. Negative values were obtained for butyrate, likely indicating a higher rate of consumption rather than production. Comparing the SCFA data to the OMD data, it is clear that the majority of the corn hybrids were hydrolytically digested, with little substrate disappearance or SCFA production occurring as a result of colonic fermentation.
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; Yoon and Lim, 2003). This differs from the starch concentration in HA, in which the starch is composed of >70% amylose, or AM (nearly 100% amylose). Extrusion cooking reduces viscosity of the starch and results in partial gelatinization to complete release of amylose and amylopectin by changing temperature, moisture, shear force, and residence time in the extruder (Camire, 1998; Murray et al., 2001). Starch generally is expected to achieve complete gelatinization, at which point the hydrogen bonds among polymers break, causing absorption of water and swelling of starch granules, and increasing susceptibility to hydrolysis by amylase. The gelatinized starch is normally highly available to hydrolysis by pancreatic amylases; however, there are exceptions, particularly high-amylose starches (Goddard et al., 1984). Cooling starches after cooking results in retrogradation, where the starch polymers recrystallize forming new hydrogen bonds with a less enzymatically digestible structure and only partial crystallinity (Annison and Topping, 1994). This leads to some starch escaping the small intestine, which is referred to as resistant starch. The AM and HA substrates behaved very similarly, with less hydrolytic digestion compared with CONV, HP, and HPLP, and approximately 7.3% residue disappearance during the fermentation stage of the digestive process. Thus, whether present in a relatively pure form as in AM or as a portion of a food/feed ingredient as in HA, high-amylose starches behave much differently than those containing a greater proportion of amylopectin.
Experiment 2
Diet Composition.
The chemical composition of the diets fed to dogs is reported in Table 7. Dry matter percent ranged from 91.6 (AM) to 94.7% (CONV). Organic matter and GE concentrations were similar across diets. The CP and acid-hydrolyzed fat values of the diets were within two percentage units of one another. The diets contained between 5.0 and 8.7% TDF. Total starch concentration was highest for AM; HP, HPLP, and CONV were intermediate; and HA was lowest. High-protein, HPLP, and CONV corn-containing diets were similar in RS concentration; values were lower than for HA- and AM-containing diets. The AM substrate was chosen due to its high concentration of amylose, and thus its high concentration of RS. Unlike AM, HA is an actual corn hybrid as opposed to a relatively purified starch source, yet the concentration of RS (13.5%), when it was included at 33% in canine diets, approached that of AM (15.3%) included at a slightly lower concentration. Diets ranged from 11.89% TEAA (AM) to 13.93% (HPLP). Total nonessential AA and TAA followed similar patterns.
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Apparent Ileal Digestibility.
Dry matter digestibilities tended to be higher (P < 0.10) for dogs fed the HP diet compared with the other treatments (Table 8). Digestibilities of OM were similar, with the exception of the HP treatment, which resulted in a higher (P < 0.05) value. Ileal CP and fat digestibilities were similar among diets. Bednar et al. (2000) fed ileal-cannulated dogs a diet containing poultry meal at 22% and corn at 34%. They reported higher ileal digestibilities (DM, 67.8%; OM, 74.4%; CP, 73.9%) than for our CONV diet. This difference may be due to our use of a higher concentration of poultry by-product meal (40% for CONV), which can be relatively variable in composition. Poultry by-product meal consists of ground, rendered, clean parts of the carcass of slaughtered poultry that is free of feathers, whereas poultry meal is further restricted to be free of heads, feet, entrails, and feathers (AAFCO, 2003). The digestibility of poultry by-product meal varies considerably, depending on its ash content and its concentration of connective tissue (Murray et al., 1997). Diets of Bednar et al. (2000) also contained other carbohydrate sources, mostly wheat and rice. Because starch is highly digestible in the ileum, their DM and OM digestibility values would be expected to be higher. Also, our diets contained higher concentrations of fat (19 vs. 14.5%), thus offering greater opportunity for formation of indigestible complexes (V-complexes) that bind with amylose present in corn and lowering digestibility values (Murray et al., 1998).
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reported that small intestinal digestibility by rats of diets containing yellow dent corn was approximately 96%, whereas only 68% of the starch in HA corn was digested. Walker et al. (1994) fed extruded corn in combination with canned meat-based supplements to dogs and found that starch digestibilities were 99.8%, higher than our results with the CONV diet. The ingredients in their diets were not added together before extrusion, preventing any possible binding of starches to other components of the diets.
Ileal TEAA digestibilities of AM diets were lower (P < 0.05) than for HP diets. Digestibilities of TNEAA were higher (P < 0.05) for dogs fed HP compared with those fed HPLP. Dogs fed HP diet tended to have higher (P < 0.10) TAA digestibilities compared with those fed the AM and HPLP diets. Amino acid digestibilities of CONV were similar to results reported by Zuo et al. (1996), who fed a diet containing 56% corn and 32% poultry meal to ileal-cannulated dogs. In that study, digestibilities of TEAA were 69.7%, TNEAA were 64.2%, and TAA were 66.5%.
Apparent Total-Tract Digestibility.
For CONV, HP, and HPLP, digestibilities were higher (P < 0.05) for DM, OM, CP, fat, starch, and GE; the AM diet was intermediate in digestibility, and HA was lowest (Table 10). In a study by Moore et al. (1980), diets fed to dogs containing 54.4% extruded corn resulted in 79.6% total-tract DM digestibility and 78.6% nitrogen digestibility. Zuo et al. (1996) fed a corn and poultry meal diet that resulted in similar total-tract digestibilities to the CONV diet of DM, OM, CP, and fat.
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). Inclusion of 6% RS 2 (high-amylose corn starch) or RS 3 (retrograded high-amylose corn starch) compared with a control diet (standard corn starch) resulted in lower apparent total-tract N digestibility by rats (67.3, 64.8, and 72.8%, respectively). Granfeldt et al. (1993) reported that resistant starch from conventional corn was approximately 63% fermentable in the large bowel, whereas fermentation of diets containing high-amylose corn was less than 11% in rats.
Lower fat digestibility by dogs fed HA may be due to the formation of amylose-lipid complexes (V-complex) produced as a result of extrusion processing. Amylose forms a helical structure around fatty acids and mono-glycerides (Holm et al., 1983; Colonna et al., 1992). Murray et al. (1998) compared nutrient digestibilities by ileal-cannulated dogs fed enteral formulas where the carbohydrate portion (60%) of the diets consisted of V-complex, RS, or maltodextrin (control). Fat digestibility was 81.8% for dogs fed the V-complex treatment compared to 95.4% for the control and 94.2% for the RS treatment.
Total-tract TDF digestibilities were slightly negative for HA and highly negative for AM. Analysis of TDF was done using a dimethyl sulfoxide solubilization step to decrease the incidence of RS being analyzed as TDF. Due to the very high concentration of RS in the AM diet compared with CONV, HP, and HPLP, it is apparent that RS was analyzed as TDF, thereby resulting in the negative value. A similar situation occurred for HA, but to a lesser degree. Also, the TDF concentrations in the diets were relatively low, but variable, increasing the analytical variation as noted by the high SEM value.
Starch digestibilities by dogs fed CONV, HP, and HPLP treatments ranged from 97.7 to 98.7%. These values were higher (P < 0.05) compared with AM and HA (76.5 and 72.8%, respectively). Total-tract starch digestibilities by dogs fed diets containing standard corn were 95.7% (Moore et al., 1980). Total-tract digestibilities of starch in extruded diets including corn have been shown to be as high as 99% or higher in dogs (Walker et al., 1994; Zuo et al., 1996). The lower ileal and total-tract starch digestibility values for the AM and HA diets is apparently due to amylose-lipid binding, causing an indigestible complex, or to the inherent characteristics of the amylose component in this hybrid. At the high temperatures of extrusion combined with the moist environment, starches will gelatinize (Cummings and Englyst, 1995). Cooling of the starches, particularly high-amylose starches, can lead to retrogradation and formation of enzymatically resistant starch. In some matrices where high concentrations of lipids are present (as in canine diets), complexing with lipids is common (Annison and Topping, 1994). Lipids can slow the gelatinization of starch due to their ability to restrict hydration, swelling, and solubilization of starch granules by forming a complex with any starch molecules that leach out of the granules themselves (Ding, 1989). Total-tract carbohydrate digestibilities reported by Murray et al. (1998) were 89.4% for dogs fed a maltodextrin control diet compared with 76.1% for V-complex and 72.6% for the same AM ingredient as used in the present study.
Stool Quality and Fecal Characteristics.
Fecal output (as-is basis, g/d) was highest (P < 0.05) for dogs fed HA compared to all other treatments (Table 10
). Fecal output on a DM basis was highest for HA and AM treatments. These data, coupled with the in vitro fermentation data, suggest that HA and AM are incompletely fermented by the colonic microflora of dogs. This result probably is due to feeding retrograded amylose that increases the digesta mass (Annison and Topping, 1994). When comparing as-is fecal output per gram of DMI across treatments, dogs fed HA and AM had higher (P < 0.05) ratios than dogs fed the remaining treatments. There were no differences in fecal score among treatments (average value = 3.0), indicating that the stools of dogs fed these diets had a desirable consistency.
Fecal Microbial Concentrations.
Bifidobacteria, lacto-bacilli, and Clostridium perfringens populations did not differ among treatments (Table 9). Dogs fed HA had numerically lower (P = 0.12) concentrations of bifidobacteria than did dogs fed HP diets. Brown et al. (1997) fed pigs high-amylose cornstarch and low amylose cornstarch and did not detect differences in bifidobacteria populations. Only when pigs were given doses of Bifidobacterium longum were significant increases in fecal bifidobacteria populations noted. Reid and Hillman (1999) did not detect any differences in coliform, bifidobacteria, or lactobacilli populations in pigs fed retrograded cornstarch compared to native cornstarch. Wang et al. (2002) reported increases in bifidobacteria concentration in feces of mice fed high-amylose starch, but only when included in diets at concentrations of 30% or more. Amylomaize starch added to diets at a concentration of 40% did not affect fecal coliform or lactobacilli concentrations in this same study.
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Implications |
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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1 Correspondence: 132 Animal Sciences Laboratory, 1207 W. Gregory Drive (phone: 217-333-2361; fax: 217-244-3169; e-mail: gcfahey{at}uiuc.edu).
Received for publication April 21, 2003. Accepted for publication September 27, 2004.
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TopAbstractIntroductionMaterials and MethodsResults and DiscussionImplicationsLiterature Cited |
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