Fiber-related digestive processes in three different ...€¦ · SeO 3, 0.86 and 0.70 mg of Co as 2CoCO 3 ·3Co(OH) 2 ·H O, 12,800 and 10,400 IU of vitamin A, 1,920 and 1,560 IU

E. von Heimendahl, G. Breves and Hj. AbelFiber-related digestive processes in three different breeds of pigs

doi: 10.2527/jas.2009-2370 originally published online November 20, 20092010, 88:972-981.J ANIM SCI

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ABSTRACT: The hypothesis examined in this experi-ment was that, because of intensive selection for greater daily BW gains and efficient utilization of concentrated low-fiber diets, modern pig breeds differ from old local breeds in their physiological ability to respond to sol-uble dietary fiber. Thus, the old local breeds, Schwae-bisch Haellisches Schwein (SH) and Bunte Bentheimer (BB), and a modern crossbred pig (CB) were used in metabolism trials to study fiber-related digestion, in-cluding microbial hindgut fermentation, by applying a colon simulation technique (Cositec) and measuring in-testinal glucose transport in Ussing chambers. A basal diet or basal plus 20% dried sugar beet pulp (SBP) as a soluble fiber source was fed to 6 pigs/breed in a 2 × 3 factorial arrangement of treatments. Four pigs of each breed per treatment were used for intestinal anatomi-cal measurements at the end of the metabolism trials. The pigs had an initial average BW of 33.9 ± 3.7 kg. The basal diet was formulated to meet 80% of energy and 100% of nutrient requirements for pigs with 700 g of ADG. Feeding the SBP diet reduced total intestinal tract, but it increased colon length, water-holding ca-pacity of the digesta, and fecal bulk (P < 0.01). The

digestibility of OM, CP, and ether extract decreased, whereas that of NDF and ADF increased, by SBP (P = 0.001). Pigs receiving SBP excreted less urinary N and retained more N (P = 0.001). The fecal proportions of undigested dietary and water soluble N increased and those of bacterial and endogenous debris N decreased (P < 0.05) in SBP-fed pigs. The SH pigs had lighter empty cecum weight, shorter colons, and less NDF digestibil-ity than BB and CB pigs (P < 0.05). Fecal N excretion did not differ (P = 0.659) among breeds, but SH pigs excreted more urinary N (P = 0.001) than the other breeds. In Cositec, OM, NDF, and ADF disappearance rates from cecal chyme of SBP-fed pigs increased (P < 0.05) irrespective of pig breed. Cecal chyme of SBP-fed BB pigs produced more VFA with a smaller proportion of propionate and a larger acetate to propionate ratio than chyme of SBP-fed SH and CB pigs. The intestinal epithelial glucose transport was greater for ileal than for jejunal tissues (P < 0.001) but was not influenced by diet and pig breed. In conclusion, the modern and intensely selected pig breed can utilize SBP fiber as efficiently as the old pig breeds under the present ex-perimental conditions.

Key words: colon simulation technique, fiber digestion, hindgut fermentation, pig breed

©2010 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2010. 88:972–981 doi:10.2527/jas.2009-2370

INTRODUCTION

Many experiments have shown the large physiolog-ical potential of pigs for fiber utilization (Dierick et al., 1989; Wenk, 2001; Dégen et al., 2007). However, modern breeds selected for greater daily BW gain and

efficient feed utilization, when fed high-concentrate, low-fiber diets, may have lost intestinal processes re-quired to adapt to high-fiber diets. Significant interac-tions between diet and genotype on nutrient digestibil-ity were found after feeding diets containing small or large quantities of insoluble fiber to genetically unim-proved Asian/Chinese free-range pigs or modern Euro-pean pigs with conventional animal breeding (Kemp et al., 1991; Fevrier et al., 1992; Morel et al., 2006). We hypothesized that soluble fiber exerts similar interac-tive effects and is more efficiently used by old local pig breeds traditionally consuming less concentrated feed than pigs of a modern crossbred origin because of the difference in the microbial hindgut digestion. To make comparisons between breeds, a test of the aforemen-tioned hypothesis should ensure that all pigs used for

Fiber-related digestive processes in three different breeds of pigs1,2

E. von Heimendahl,* G. Breves,† and Hj. Abel*3

*Institute of Animal Physiology and Nutrition, Georg-August-University of Goettingen, D-37077 Goettingen, Germany; and †Department of Physiology, School of Veterinary Medicine Hannover,

D-30173 Hannover, Germany

1 Supported by the National Program of Organic Farming, Federal Ministry of Food, Agriculture and Consumer Protection (BMELV), Bonn, Germany.

2 The authors thank G. Das (Department of Animal Science, Georg-August-University of Goettingen, Goettingen, Germany) for his contribution to the statistical analysis of the results.

3 Corresponding author: [email protected] August 5, 2009.Accepted November 11, 2009.

972



the study consume the same amount of a control diet. Therefore, unlike other investigations where feed mix-tures or single feed components were replaced by a fiber source, dried sugar beet pulp (SBP) was added to a basal feed ration as a source of soluble fiber in the pres-ent study. Differences between basal diet- and SBP-fed pigs in digestive physiology should thus be exclusively attributable to the effect of SBP. The objective of the current study was to determine the effect of feeding SBP on gastrointestinal anatomy, nutrient digestion, microbial hindgut metabolism, and intestinal epithelial transport function in 3 pig breeds to test if genetically less improved breeds and modern conventionally bred genotypes differ in their ability to digest soluble fiber.

MATERIALS AND METHODS

The metabolism trials and slaughtering of the ani-mals, as well as the procedures used in vitro-techniques, were not subject to approval but were registered ac-cording to governmental regulations and local animal care and use regulations of the Georg-August-Universi-ty of Goettingen and the School of Veterinary Medicine Hannover.

Animals and Diets in Metabolism Trials

Male castrated pigs of 3 breeds, each with 12 ani-mals, were used. The German local breeds Schwaebisch Haellisches Landschwein (SH) and Buntes Bentheimer (BB) were purchased from the farmers association, Baeuerliche Erzeugergemeinschaft Schwaebisch Hall, Wolpertshausen, Germany, and the breeding asso-ciation, Verein zur Erhaltung des Bunten Bentheimer Schweines, Stadland, Germany, respectively. Pigs of a modern crossbreed (CB) were obtained from the exper-imental pig breeding station (Relliehausen, Georg-Au-gust-University of Goettingen, Goettingen, Germany) and corresponded to a 3-line cross with crossbred dams (German Landrace × Large White) and stress-negative Piétrain as sires.

The pigs were raised according to established nursing and feeding programs at the breeding farms before they were adapted to the experimental diets in their wk 13 to 14 of life at an initial average BW of 33.9 ± 3.7 kg. Upon arrival, they were first kept in pens with gradual change to the experimental diets during the first 3 d. After 1 wk, piglets were housed individually in metabo-lism cages. A 7-d adaptation period was followed by a 5-d collection period. Thus, the animals were fed the experimental diets for 20 d. The room temperature dur-ing the metabolism trial was kept constant at 22°C.

The metabolism trials were accomplished using 3 identical runs with 12 animals each. Within each run, 2 experimental diets (Table 1), a basal diet and basal plus 20% SBP, were fed to 2 animals per diet and breed according to a 2 × 3 factorial arrangement of treat-ments. The basal diet was fed at a rate of 0.076 kg

and the SBP diet at a rate of 0.095 kg·d−1·kg−0.75, thus providing the same amount of basal diet for all animals. The individual BW of the pigs was determined before the morning feeding at the beginning of the collection period (Table 2) to calculate the metabolic BW. The daily amount of basal diet was calculated to meet ap-proximately 80% of the energy requirements and 100% of nutrients for pigs with 700 g of ADG (GfE, 2006). The daily feed ration was divided into 2 equal por-tions mixed with water and offered at 0800 and 1600 h. Drinking water was made available ad libitum.

Feces were collected quantitatively twice daily after feeding and stored frozen at −20°C. At the end of the collection period, total feces of each animal were thawed and homogenized. Aliquots of fresh samples from the collection period were collected to determine DM and N (Kjeldahl) contents. For the determination of all other nutrients, feces were oven-dried at 60°C for 24 h. Samples of dried feed and feces were ground through a sieve with 1-mm pore size and analyzed for DM, ash,

Table 1. Composition and analysis of the experimental diets

Item Basal diet SBP diet1

Ingredient, g/kg (as-fed basis) Wheat 400 320 Barley 298 238 Soybean meal, extracted 200 160 Potato protein 50 40 Premix2 32 26 Soybean oil 20 16 Dried sugar beet pulp — 200Analyzed composition DM, g/kg 886.0 885.0 Nutrient, g/kg of DM Ash 48.7 54.8 OM 837.7 830.4 CP 241.3 211.3 Ether extract 38.8 32.6 Starch 439.9 358.8 Sugar 42.3 59.9 NDF 132.9 186.0 ADF 44.8 79.4 Ca 8.38 8.71 P 5.11 4.20Calculated energy ME, MJ/kg of DM 16.96 14.24

1Sugar beet pulp (SBP) diet; each kilogram made up of 800 g of basal diet plus 200 g of SBP.

2Supplemented per kilogram of basal and SBP diets, respectively: 1.66 and 1.35 g of l-lysine·HCl, 0.58 and 0.47 g of dl-methionine, 0.38 and 0.31 g of l-threonine, 7.84 and 6.37 g of Ca, 1.60 and 1.30 g of P, 1.76 and 1.43 g of Na, 0.32 and 0.26 g of Mg, 128 and 104 mg of Fe as FeSO4·H2O, 16 and 13 mg of Cu as CuSO4·5H2O, 85 and 69 mg of Mn as Mn2O3, 107 and 87 mg of Zn as ZnO, 2.1 and 1.7 mg of I as Ca(IO3)2·6H2O, 0.43 and 0.35 mg of Se as Na2SeO3, 0.86 and 0.70 mg of Co as 2CoCO3·3Co(OH)2·H2O, 12,800 and 10,400 IU of vitamin A, 1,920 and 1,560 IU of vitamin D3, 80 and 65 mg of vitamin E, 1.60 and 1.30 mg of vitamin B1, 4.96 and 4.03 mg of vitamin B2, 4.00 and 3.25 mg of vitamin B6, 32 and 26 µg of vitamin B12, 3.20 and 2.60 mg of vitamin K3, 20.00 and 16.25 mg of nicotinic acid, 12.00 and 9.75 mg of Ca-pantothenate, 0.80 and 0.65 mg of folic acid, and 240 and 195 mg of choline chloride.

Fiber digestion in pigs 973



CP, ether extract, starch, sugar, calcium, and phos-phorous according to standard methods (Naumann and Bassler, 1976). The fiber fractions constituting NDF and ADF were analyzed according to Van Soest et al. (1991) with a fiber analyzer (Ankom220-Fiber Analyzer, Macedon, NY) using a heat-stable α-amylase and were expressed exclusive of residual ash. For fecal N frac-tionation, the procedure of Mason (1969) adapted to pig feces by Kreuzer et al. (1989) was used. In this procedure, fresh fecal samples are suspended in distilled water and centrifuged (20,000 × g for 20 min at 4°C) for the determination of water soluble N (WSN) in the supernatant and sedimented N (Kjeldahl) in the pellet. Another fresh fecal sample was cooked (1 h) in neutral detergent (ND) solution (Van Soest et al., 1991) us-ing a fiber analyzer (Ankom220-Fiber Analyzer). The ND-insoluble residue was thoroughly washed with hot distilled water and analyzed for undigested dietary N (UDN). Bacterial and endogenous debris N (BEDN) is calculated as difference between sedimented N and UDN. Urine was collected quantitatively twice daily at 0730 and 1630 h in 150 mL of 30% H2SO4, and stored frozen at −20°C until analyzed for N in aliquot samples of each animal.

The pigs of the first 2 experimental runs (i.e., 4 pigs of each feeding group and breed), were used for ana-tomical measurements at the end of the metabolism trials. After overnight fasting, the pigs were slaughtered by stunning with subsequent carotid artery bleeding. The intestines, exclusive of esophagus and stomach, were removed within 3 min after exsanguination and separated by ligatures into small intestines, cecum, and colon. The ceca were weighed both filled and emptied, and the lengths of the emptied segments of the small intestines, cecum, and colon were measured. The water-holding capacity (WHC) of the contents of the jeju-num, cecum, and colon was determined according to Johansen et al. (1996).

Colon Simulation Technique

The colon simulation technique (Cositec) is a semi-continuous long-term incubation procedure resem-bling the rumen simulation technique (Rusitec) of Czerkawski and Breckenridge (1977). It allows the in-vestigation of the microbial digestive processes in the hindgut of pigs and has been described in detail (Breves et al., 2000a). At the beginning of the experiment, 125 mL of gauze-filtered cecal fluid were introduced into each fermentation vessel containing a perforated inner container filled with 2 nylon bags (50-µm mesh size), one introducing the fresh solid inoculum on d 1 and the second supplying freeze-dried cecal particles, which had been obtained from pigs of the same breeds, and similar BW kept on the same experimental diet for the same periods as the inoculum donor pig. On d 2, the nylon bag with the inoculum of the previous day was replaced with a nylon bag containing freeze-dried cecal particles. The next day, the bags were changed alter-nately every 24 h. The fermentation vessels were kept in a water bath set at 39°C and continuously infused with an isotonic buffer (302 mosm/kg; pH, 7.38) at a rate of 625 mL/d.

Using 9 fermenter vessels operating simultaneously, 2 experimental runs each consisting of a 5-d system equilibration period and 5-d collection period were car-ried out. The inoculum for the first run was obtained from 3 pigs of each breed adapted to the basal diet, with each pig serving as a donor for an individual fer-mentation vessel. In the second run, the inoculum was taken from pigs adapted to the SBP diet. The diet- and breed-specific freeze-dried cecal particles had been pre-pared earlier from the cecal contents of the slaughtered pigs of the metabolism trials.

After incubation, the nylon bags were carefully squeezed in a prewarmed buffer and the liquid poured back into the fermentation vessel. The solid residues in

Table 2. Body weight development, feed intake, and feed efficiency (G:F) of the pigs during the collection pe-riod1

Item

Diet2 (n = 18) Breed3 (n = 12)Interaction

P-valueBasal SBP SE4 P-value SH BB CB SE P-value

BW,5 kg d 1 37.1 38.6 0.8 0.232 38.3 36.7 38.7 1.0 0.353 0.646 d 5 40.0 42.4 0.9 0.079 41.2 40.0 42.4 1.1 0.318 0.672ADG, g/d 576 757 29 0.001 585a 665ab 748b 36 0.012 0.218Feed intake, as-fed basis g·d−1 1,181 1,514 22 0.001 1,358 1,311 1,373 27 0.258 0.628 g·d−1·kg−0.75 76.4 93.2 0.2 0.001 85.8a 84.4b 84.3b 0.3 0.003 0.0496

G:F, g/g 0.48 0.50 0.02 0.616 0.42a 0.50ab 0.55b 0.02 0.003 0.075a,bWithin a row, means without a common superscript differ (P < 0.05).1Pigs were prefed the experimental diets for 14 d before the start of the 5-d collection period.2Basal diet was fed to meet 80% of ME and 100% of nutrient requirements for pigs with 700 g of ADG; SBP (sugar beet pulp) diet: 200 g of

SBP and 800 g of basal diet/kg.3SH = Schwaebisch Haellisches Landschwein, BB = Buntes Bentheimer, and CB = modern crossbreed.4Pooled SE.5Pigs were weighed before the morning feeding.6Greater intake (g·d−1·kg−0.75) of SH (94.8) compared with BB (92.6; P = 0.012) and CB (92.3; P = 0.003) on the SBP diet.

von Heimendahl et al.974



the bags were collected over 5 d and pooled for each fermentation vessel. The pH values of each vessel were measured daily at feeding time using a pH electrode (type 408, Mettler Toledo, Steinbach, Germany) con-nected to a pH meter (digital pH meter 646, Knick, Berlin, Germany). The OM apparently degraded (OMAD) was calculated by noting the difference be-tween OM input and output.

The volume of the daily effluent of each fermentation vessel was collected quantitatively and aliquot portions were kept frozen at −20°C. An aliquot of the pooled effluent of each fermentation vessel was centrifuged at 40,000 × g for 20 min at 4°C. From the supernatant, 1.0 mL was acidified with 0.1 mL of 98% HCOOH and then centrifuged again at 4,000 × g for 10 min at 4°C. The supernatant was analyzed for VFA by gas chromatogra-phy (GC; model 5890 II, Hewlett Packard, Böblingen, Germany) equipped with a 1.8 × 2 mm glass column (packed with Chromosorb WAW, mesh 80/100, Analyt, Mülheim, Germany) with 20% neopentyl glycol succi-nate and 2% H3PO4. Helium was used as the carrier gas with a flow rate of 25 mL/min. The injection port, detector, and oven temperatures were 220, 250, and 120°C, respectively. The daily production rates of VFA were estimated by multiplying the respective concen-tration by the volume of effluent collected.

Fermentation gases were collected as 1 pooled sample for each fermentation vessel over the whole 5-d collec-tion period in gas-proof aluminum bags and the volume quantified by the corresponding replacement of water. The CH4 content of the fermentation gases was ana-lyzed in replicate samples by GC on a packed Porapak Q-column 80/100 (Alltech GmbH, Unterhaching, Ger-many) at 80°C injection port and detector tempera-ture, and 40°C column temperature (isothermal). The GC was equipped with a thermal conductivity detec-tor (Shimadzu C-R 1B; Shimadzu Deutschland GmbH, Duisburg, Germany), and argon served as the carrier gas.

Ussing Chamber Technique

To study potential effects of diet, breed, and intes-tinal localization on epithelial glucose transport, elec-trophysiological responses to an increased luminal glu-cose concentration were quantified in mid-jejunum and ileum using the Ussing chamber technique. Four pigs of each breed adapted to the experimental diets were slaughtered as described before, and 40-cm segments were taken from the mid-jejunum and the ileum. The intestinal segments were immediately rinsed with ice-cold saline (0.9% NaCl) and kept in a modified Krebs-Henseleit buffer solution at 4°C being continuously gassed with carbogen (95% O2, 5% CO2) until being placed in Ussing chambers. Subsequent preparation of intestinal tissues, placement into Ussing chambers, and incubation were done as described in detail for porcine intestinal tissues (Breves et al., 2000b). Intestinal epi-thelial glucose transport was measured as short circuit

current (Isc) and is expressed as the difference (ΔIsc) between maximum and basal Isc response at 10 and 0 mmol of glucose·L−1 mucosal buffer solution, respec-tively.

Statistical Analysis

The data were analyzed using the GLM procedure (SAS Inst. Inc., Cary, NC). The experimental struc-ture was a 2 × 3 factorial arrangement of treatments, with diet and breed as the main factors. The data of the metabolic trials represented 2 (intestinal anatomy and digesta WHC) or 3 repetitions. The fixed effects of diet, breed, and diet × breed interaction, as well as the block effect of repetition, were included in the following model:

Yijkl = µ + αi + βj + (αβ)ij + γk + εijkl,

where Yijkl is the observation, µ is the overall mean, αi is the effect of the ith diet (i = 1,2), βj is the effect of the jth breed (j = 1, …, 3), (αβ)ij is the effect of diet × breed interaction (ij = 1–6), γk is the effect of the kth block (1, …, 3), and εijkl is the residual term. The effect of block was excluded for the statistical evaluation of the Cositec and Ussing chamber variables. The Ussing chamber data were evaluated with an extended statisti-cal model including the main effects of diet, breed, and intestinal segment as well as all possible interactions among the 3 factors.

Multiple comparisons were carried out using the Tukey’s test with a significance level of P < 0.05. The results are presented as least squares means for the ef-fects of the main experimental factors. The pooled SE were calculated from the SAS outputs as described by Pesti (1997). In the case of significant interactions be-tween the main experimental factors, the means of each factor combination are presented.

RESULTS

Performance, Anatomy of the Gastrointestinal Tract, and Digestibility

The SBP-supplemented diet was consumed in greater amounts than the basal diet (Table 2) and resulted in greater daily BW gains. The multiple comparison test revealed that the P-value for interaction (P = 0.049) on feed intake based on metabolic BW resulted from a greater feed consumption of SH (95 g·d−1 kg−0.75) in comparison with BB (93 g·d−1·kg−0.75) and CB pigs (92 g·d−1·kg−0.75) when the SBP diet was fed (P = 0.003). The SH pigs gained less BW (P = 0.012) and showed an adverse feed conversion efficiency compared with CB (P = 0.003). There was a trend for a difference in G:F between SH and BB pigs (P = 0.055).

Feeding the SBP-supplemented diet led to a reduc-tion in total intestine length (P < 0.001) but increased




colon length (P < 0.001; Table 3). The pig breeds dif-fered in their colonic length, with smaller values for SH than for CB pigs (P = 0.005). The SBP diet increased the cecum and colon contents (P = 0.019) and trend for the empty cecum (P = 0.071). The empty cecum weight of SH was lighter as compared with BB and CB pigs (P < 0.001). The WHC of the jejunum was elevated, and fecal volume almost doubled by feeding SBP.

The SBP diet resulted in reduced (P = 0.001) appar-ent total tract digestibility (ATTD) of OM, CP, and ether extract (Table 4), whereas ATTD of NDF and ADF were increased (P = 0.001). The NDF digestibil-ity was influenced by pig breed, showing less ATTD for SH than for BB and CB pigs (P = 0.006).

Nitrogen Balances

The N balances and fecal N proportions are shown in Table 5. According to multiple comparisons, the inter-

action on N intake (P = 0.040) resulted from a trend for greater feed intake by SH in comparison with BB pigs and CB pigs when the SBP diet was fed (P = 0.063). Feeding the SBP diet led to greater N intake and fecal N excretion (P = 0.001), whereas it reduced urinary N excretion (P = 0.001). This resulted in increased N retention (P = 0.001). Urinary N excretion decreased in the order of SH > BB > CB, with a difference between SH and CB pigs (P = 0.012). Correspondingly, the N retention tended to be less for SH pigs (P = 0.095).

Compared with pigs fed the basal diet, the greater total fecal N excretion of pigs fed SBP was associated with increased UDN (P = 0.001) and WSN (P = 0.018), whereas the proportion of BEDN was reduced in the SBP-fed pigs (P = 0.001). The pig breeds did not differ in their total fecal N excretion, but there was a trend toward increased UDN in the order of SH < BB < CB. The WSN was less for SH than for CB pigs (P = 0.005). An inverse order between the breeds was observed for

Table 3. Effect of diet and pig breed on gastrointestinal tract (GIT) anatomy, water-holding capacity (WHC) of digesta, and fecal bulk1

Item



Length,5 cm/kg0.75 GIT 88.93 70.40 1.84 <0.001 78.03 79.66 81.30 2.26 0.600 0.874 Cecum 1.23 1.20 0.06 0.783 1.06a 1.18ab 1.40b 0.08 0.020 0.617 Colon 15.02 20.61 0.44 <0.001 16.48a 17.55ab 19.41b 0.54 0.005 0.330Weight, g/kg0.75 Cecum empty 5.58 6.14 0.21 0.071 4.86a 5.96b 6.75b 0.25 <0.001 0.529 Cecum content 18.58 26.09 2.05 0.019 17.81 24.25 24.94 2.52 0.117 0.964WHC, g of H2O/g Jejenum 4.44 6.61 0.19 0.001 5.54 5.52 5.51 0.24 0.995 0.142 Cecum 4.29 6.94 0.16 0.001 5.67 5.72 5.46 0.19 0.595 0.378 Colon 2.98 3.94 0.07 0.001 3.37 3.52 3.50 0.09 0.439 0.796Fecal bulk, g/kg0.75 159 310 10 0.001 217 236 251 12 0.159 0.216

a,bWithin a row, means without a common superscript differ (P < 0.05).1Four pigs of each breed and feeding group were slaughtered after an overnight fast. Intestines were removed immediately after slaughter and

separated by ligatures into small intestines, cecum, and colon.2Basal diet was fed to meet 80% of ME and 100% of nutrient requirements for pigs with 700 g of ADG; SBP (sugar beet pulp) diet: 200 g of

SBP and 800 g of basal diet/kg.3SH = Schwaebisch Haellisches Landschwein, BB = Buntes Bentheimer, and CB = modern crossbreed.4Pooled SE.5Measured for emptied intestine segments.

Table 4. Effect of diet and pig breed on apparent total tract digestibility (%) of nutrients

Item



OM 87.9 85.1 0.3 0.001 86.2 86.5 86.7 0.4 0.793 0.159CP 87.3 79.8 0.6 0.001 84.1 83.0 83.6 0.7 0.518 0.382EE4 64.5 55.1 1.1 0.001 59.5 58.4 61.4 1.3 0.276 0.154NDF 58.2 64.1 0.7 0.001 58.7a 62.3b 62.5b 0.9 0.006 0.621ADF 36.0 52.7 1.6 0.001 42.2 45.8 45.1 1.9 0.389 0.190

a,bWithin a row, means without a common superscript differ (P < 0.05).1Basal diet was fed to meet 80% of ME and 100% of nutrient requirements for pigs with 700 g of ADG; SBP (sugar beet pulp) diet: 200 g of

SBP and 800 g of basal diet/kg.2SH = Schwaebisch Haellisches Landschwein, BB = Buntes Bentheimer, and CB = modern crossbreed.3Pooled SE.4Ether extract.




the proportion of BEDN, resulting in a greater value for SH than for CB pigs (P = 0.002).

Microbial Hindgut Fermentation

Because the same amount of freeze-dried cecal par-ticles was supplied in Cositec for each diet/breed com-bination (Table 6), the input data were not evaluated statistically. The OMAD and the degradation rates of NDF and ADF were greater with the substrate from the SBP-fed pigs as compared with the basal diet sub-strate (P = 0.001). The smallest disappearance rates were observed with the substrate from the SH pigs, but this was not statistically significant (P > 0.123).

Diet and breed influenced the VFA production in Cositec, and both factors partly interacted with each

other (Table 7). Particularly greater amounts of VFA associated with the smallest proportion of propionate and the largest acetate to propionate ratio were pro-duced in fermenter vessels being supplied with cecal substrate of SBP-fed BB pigs. On the other hand, ce-cal substrate of basal diet-fed CB pigs led to greater proportions of propionate and the smallest acetate to propionate ratio (P < 0.05). The average molar pro-portions of acetate and butyrate were not influenced by interaction. Fermentation vessels receiving the SBP- instead of the basal diet-adapted substrate produced more acetate (61.74 vs. 57.54%; P = 0.001) and less butyrate (7.97 vs. 10.00%; P = 0.001). The acetate pro-portion was less for CB (58.27%) than for SH and BB (60.30 and 60.36%, respectively; P < 0.05). Butyrate reached a greater proportion with cecal substrate of BB

Table 5. Effect of diet and pig breed on the N balances of the pigs and on the proportions of fecal N fractions

Item



N intake, g/kg0.75 2.69 2.89 0.01 0.001 2.81 2.78 2.78 0.01 0.193 0.0404

N excretion, g/kg0.75 Feces 0.34 0.58 0.02 0.001 0.45 0.48 0.46 0.02 0.659 0.395 Urine 1.12 0.84 0.03 0.001 1.08a 0.96ab 0.91b 0.04 0.012 0.472N retention, g/kg0.75 1.23 1.46 0.03 0.001 1.28 1.35 1.41 0.04 0.095 0.145Fecal N fractions, % UDN5 13.86 24.62 1.17 0.001 16.74 19.18 21.80 1.44 0.061 0.145 BEDN6 66.83 52.48 1.65 0.001 65.48a 59.31ab 54.16b 2.02 0.002 0.462 WSN7 19.32 22.90 1.01 0.018 17.78a 21.51ab 24.04b 1.24 0.005 0.954

a,bWithin a row, means without a common superscript differ (P < 0.05).1Basal diet was fed to meet 80% of ME and 100% of nutrient requirements for pigs with 700 g of ADG; SBP (sugar beet pulp) diet: 200 g of

SBP and 800 g of basal diet/kg.2SH = Schwaebisch Haellisches Landschwein, BB = Buntes Bentheimer, and CB = modern crossbreed.3Pooled SE.4Trend for greater intake (g/kg0.75) of SH (2.93) compared with CB (2.86; P = 0.063) on the SBP diet.5Undigested dietary nitrogen.6Bacterial and endogenous debris nitrogen.7Water soluble nitrogen.

Table 6. Effect of diet and pig breed on disappearance coefficients for OM, NDF, and ADF in the colon simula-tion technique (Cositec)

Item

Diet1 (n = 9)2 Breed3 (n = 6)Interaction


Substrate input,5 g/d DM 2.20 2.20 — — 2.20 2.20 2.20 — — — OM 2.05 2.02 — — 2.05 2.04 2.02 — — — NDF 1.31 1.35 — — 1.34 1.35 1.31 — — — ADF 0.64 0.83 — — 0.74 0.74 0.73 — — —Disappearance coefficient6 OM 0.37 0.42 0.01 0.013 0.37 0.42 0.40 0.02 0.135 0.074 NDF 0.19 0.30 0.02 0.001 0.23 0.26 0.25 0.02 0.376 0.176 ADF 0.09 0.26 0.02 0.001 0.14 0.21 0.18 0.02 0.123 0.077

1Basal diet was fed to meet 80% of ME and 100% of nutrient requirements for pigs with 700 g of ADG; SBP (sugar beet pulp) diet: 200 g of SBP and 800 g of basal diet/kg.

2Cecal contents of 3 pigs of each breed adapted to the basal diet and the SBP diet were used as substrates, respectively.3SH = Schwaebisch Haellisches Landschwein, BB = Buntes Bentheimer, and CB = modern crossbreed.4Pooled SE.5The input data were not evaluated statistically because the fermenters received the same amounts of substrate DM.6[(Input – output)/input].




(9.86%) as compared with SH and CB (8.45 and 8.65%, respectively; P = 0.010).

The total SCFA production was more efficient in the fermentation vessels receiving SBP- instead of basal di-et-adapted substrate (8.11 vs. 7.57 mmol/g of OMAD; P = 0.017) and reached 8.37 (SH), 7.86 (BB), and 7.30 (CB) mmol/g of OMAD, with a difference between the SH and CB substrate (P = 0.003). Methane release tended to be influenced by a feed × breed interaction (P = 0.086) and was greater in the fermentation ves-sels supplied with the cecum content of SBP-adapted BB pigs.

Electrophysiology in the Mid-Jejunum and Ileum

There were no interactions between diet, breed, and intestinal location on ΔIsc using Ussing chambers or differences between breeds and diets for epithelial glu-cose transport in the 2 intestinal segments (Table 8). However, under both dietary conditions, ΔIsc in ileal tissues was greater (P < 0.001) compared with jejunal tissues.

DISCUSSION

The SBP diet consisted of 80% basal plus 20% SBP and was fed in 20% greater amounts as compared with the basal diet. Even though the SBP-supplemented pigs consumed on average 2% less DM than planned, the observed differences between the 2 feeding groups can be ascribed to the influence of SBP.

The pigs of the 3 breeds are routinely fattened and slaughtered at BW around 100 to 115 kg. The BB pigs originate from the marshland of northwest Germany and were genetically improved by crossbreeding with British Berkshire and Cornwall pigs in the middle of the 19th century. The SH pigs are derived from a tradi-tional local breed of the low mountain range of south-

west Germany and were genetically improved by cross-breeding with imported Chinese pigs from the central province of Jinhuha in the early 19th century. Both breeds greatly increase fat deposition in late fattening. They are mainly fattened under conditions of organic farming and are slaughtered around 200 d of age. Their meat is characterized by larger intramuscular fat con-tent (Baulain et al., 2000). The experimental period consisted of an early phase of development, where gut size is closely related to the increasing BW (Whitte-more et al., 2003). The pigs were prefed the experi-mental diets for 14 d before beginning the metabolism trials. This should have been sufficient for complete adaptation to fiber-rich feeding in the supplemental groups. In agreement with other studies (Longland and Low, 1988; Anguita et al., 2007), the greater BW gain

Table 7. Effect of diet and pig breed on fermentation variables in the colon simulation technique (Cositec)1

Item

Basal diet2 Diet SBP2

SE3Interaction

P-valueSH4 BB4 CB4 SH BB CB

pH 6.60ab 6.63ab 6.57abc 6.46ac 6.44c 6.62b 0.029 0.005Total VFA, mmol/d 5.88a 5.44a 5.78a 6.71ab 7.88b 6.08a 0.284 0.007Acetate, % 58.92 57.79 55.90 61.68 62.92 60.63 0.544 0.109Propionate, % 31.27a 31.13a 34.92b 31.22a 28.43c 31.25a 0.536 0.015Butyrate, % 9.76 11.02 9.24 7.15 8.70 8.07 0.405 0.213Acetate/propionate 1.88a 1.86a 1.60b 1.98a 2.21c 1.94a 0.049 0.033mmol of VFA/g of OMAD5 8.17 7.42 7.13 8.56 8.29 7.47 0.236 0.494CH4, mmol/d 0.06 0.05 0.07 0.05 0.25 0.05 0.050 0.086

a–cMeans within a row without a common superscript differ (P < 0.05).1n = 3 (cecal contents of 3 pigs of each breed adapted to the basal diet and the SBP diet were used as substrates, respectively).2Basal diet was fed to meet 80% of ME and 100% of nutrient requirements for pigs with 700 g of ADG; SBP (sugar beet pulp) diet: 200 g of

SBP and 800 g of basal diet/kg.3Pooled SE.4SH = Schwaebisch Haellisches Landschwein, BB = Buntes Bentheimer, and CB = modern crossbreed.5OM apparently disappeared.

Table 8. Short-circuit currents (Isc) in porcine mid-jejunum and ileum mucosa1,2

Item ΔIsc SE3 P-value

Diet4 (n = 24) Basal diet 2.74 0.31 0.762 SBP diet 2.88 Breed5 (n = 16) SH 2.75 0.38 0.898 BB 2.95 CB 2.72 Intestinal segment (n = 24) Jejunum 1.80 0.31 <0.001 Ileum 3.82

1Short-circuit currents expressed as ΔIsc = maximum Isc response at 10 mmol glucose·L−1 mucosal buffer solution – basal Isc at 0 mmol glucose·L−1 mucosal buffer solution.

2Jejunal and ileal tissue preparations were placed into Ussing cham-bers at 0 and 10 mmol of glucose·L−1 mucosal buffer solution.

3Pooled SE.4Basal diet was fed to meet 80% of ME and 100% of nutrient require-

ments for pigs with 700 g of ADG; SBP (sugar beet pulp) diet: 200 g of SBP and 800 g of basal diet/kg.

5SH = Schwaebisch Haellisches Landschwein, BB = Buntes Ben-theimer, and CB = modern crossbreed.




of SBP-fed pigs as compared with those fed the basal diet was associated with increased size and empty BW of the hindgut, elevated WHC of the digesta, and in-creased fecal volume.

The supplementation of SBP resulted in less digest-ibility of nonfiber and greater digestibility of fiber frac-tions, thus confirming the results of several other ex-periments where SBP was fed to pigs (Chabeauti et al., 1991; Kreuzer et al., 1999; Bindelle et al., 2009). A considerable proportion of SBP fiber is degraded in the small intestine of pigs, whereas the ileal digestibil-ity of ash, protein, and fat was reduced at increased SBP intake (Graham et al., 1986; Dierick et al., 1989). Therefore, it can be assumed that SBP-supplemented pigs in this study digested greater amounts of fiber and less nonfiber nutrients (protein, AA, minerals) up to the terminal ileum. No evidence for any corresponding adaptation of intestinal glucose transport could be de-tected. Interestingly, under both dietary conditions, the electrophysiological responses were greater for ileal tis-sues as compared with jejunal tissues. Such differences have not yet been detected for the porcine intestines. This might indicate that the abundance of the elec-trogenic sodium coupled glucose transporter is greater in the ileum than the jejunum. No definite conclusion, however, may be made for the quantitative amount of glucose transport in the mid-jejunum and ileum be-cause no in vivo data are available for luminal glucose concentrations. One could speculate that when digesta retention times are decreased, ileal glucose transport might act as a compensatory site for small intestinal glucose absorption.

The N balances, apart from confirming the well-known effect of fiber on increased fecal N excretion and decreased urinary N excretion (Dierick et al., 1989; Bindelle et al., 2009), showed an elevated N retention of the SBP-supplemented pigs. This is assumed to be at least partly due to an increased N accumulation in the intestinal contents. Additionally, the extra energy from absorbed VFA, formed by SBP-induced intensi-fied hindgut fermentation, may have supported inter-mediary N retention. However, normally, AA and glu-cose absorption are reduced and more energy is lost by fiber addition to the diet in the small intestine than is recovered via VFA in the hindgut (Dierick et al., 1990). Furthermore, the greater WSN excretion observed after SBP feeding indicates an increased endogenous N ex-cretion and less intermediary N retention.

The major molecular building blocks of SBP fiber are arabinose, glucose, and uronic acids (Graham et al., 1986; Bach Knudsen, 1997). Pectin, which is composed of uronic acid molecules, is soluble in ND solution and so cannot be recovered with the NDF method (Van Soest et al., 1991). Therefore, the ratio among arabi-nose, glucose, and uronic acids is changed in the NDF fraction compared with total nonstarch polysaccharides (NSP) of SBP. Nevertheless, similar digestibility of single carbohydrates from NSP was determined in pigs fed untreated or ND-treated SBP diets (Longland and

Low, 1988). Based on the fiber content, the average feed intake, and the digestibility coefficients for the control and SBP diets, an average digestibility of 73% can be calculated by difference for NDF of SBP in the present study. A lesser value of 60% was determined in Large White pigs of about 40 kg of BW on diets containing 16% SBP (Chabeauti et al., 1991). According to these authors, the digestibility of SBP fiber cannot be ex-plained by water-solubility of NSP, but in agreement with others (Graham et al., 1986), it is related to the presence of very digestible uronic acid (or rather pectic substances) and arabinose, as well as to less digestible lignin.

The well-established method of fractionation of fecal N (Mason, 1969) was chosen to estimate the level of bacterial N, which, according to Dierick et al. (1990), has been reported to be less variable than, for exam-ple, the determination of diaminopimelic acid as an index of bacterial N in pig feces. In accordance with experiments of these authors, SBP feeding increased the levels of fecal UDN and WSN in the present study, whereas the proportion of BEDN was reduced. Howev-er, the absolute amount of BEDN increased with SBP as compared with the basal diet-fed pigs, indicating an elevated bacterial N fixation in the hindgut. The greater UDN excretion observed in SBP-fed pigs may have resulted from increased quantity of fiber-bound N, and the increased WSN excretions can be explained by the enhanced endogenous secretion of enzymes, reduced urea absorption at the end of the ileum, increased re-secretion of urea through the hindgut wall, or lysis of bacteria before excretion (Kreuzer et al., 1999).

In our metabolism study, no interactions between the feed rations and pig breeds in intestinal morphol-ogy and digestive function were observed. These results are applicable to feeding predominantly soluble fiber and agree with observations obtained by feeding alfalfa meal to genetically lean, obese, or contemporary pigs, showing only limited evidence for genetic differences in the response of the animals to that mainly insoluble dietary fiber (Varel et al., 1982). On the other hand, an enhanced digestion of predominantly insoluble fiber sources has been reported for genotypes of pigs derived from Asian or Chinese gene pools (Meishan, Kune-Kune) as compared with pigs of the Dutch Landrace (Kemp et al., 1991), Large White (Fevrier et al., 1992), and Large White × Landrace (Morel et al., 2006).

The decreased BW gain, NDF digestion, and N re-tention of SH compared with BB and CB pigs was evi-denced in association with a greater feed intake, shorter cecum, and colon lengths, as well as lighter empty ce-cum weight and a smaller proportion of WSN in the feces. These data indicate a smaller capacity for mi-crobial hindgut fermentation, less intestinal secretions, and shorter digesta transit times in SH pigs, result-ing in reduced fiber digestion. Accordingly, Pond et al. (1988) and Varel et al. (1988) observed shorter small intestines and reduced colon weights, accompanied by a faster digesta passage rate, in genetically obese pigs




compared with genetically lean or contemporary pigs. Further, the obese pigs exhibited less digestibility of plant cell walls, hemicellulose, and cellulose. It can be stated from these and the present results that, apart from the considerable ability to adapt to fiber-rich feed-ing, there may be a clear disparity in the intestinal ca-pacity among different genotypes of pigs for microbial fiber degradation.

The Cositec was selected over a discontinuous in vit-ro system, because it achieves steady-state conditions and provides results rather similar to microbial hindgut fermentation in vivo. The Cositec has been proven to degrade fiber virtually equivalent to in vivo postileal digestion in pigs (Dreyer, 1990). The known SBP-in-duced intensification of hindgut fermentation (Wang et al., 2004; Anguita et al., 2007) is confirmed in Cositec by greater disappearance rates of the fiber fractions and greater mean VFA concentrations in fermentation vessels supplied with SBP-adapted substrate. However, only SBP-fed BB pigs delivered substrate that induced increased productions of total and individual VFA, whereas SBP-adapted SH did not differ from CB in this respect. Formation of acetic acid is particularly induced by uronic acid (Salvador et al., 1993), and that of pro-pionate is closely related to the degradation of pentoses (Mortensen et al., 1988). For butyrate, fermentable xy-lose seems to be the most suitable substrate of the fiber sugars (Cheng et al., 1987). The SBP fiber contains substantial amounts of soluble uronic acid and arabi-nose (Bach Knudsen, 1997; Anguita et al., 2007), thus delivering readily fermentable substrates for acetate and propionate production. On the other hand, SBP fiber is relatively poor in xylose. It may be assumed that the basal diet predominantly contained insoluble sugars and a less fermentable fraction of polysaccha-rides (Bach Knudsen, 1997). Thus, relatively small dif-ferences in butyrate production between dietary treat-ments and breeds were observed.

According to Wang et al. (2004), changes in SBP-in-duced VFA production were derived from an increased flow of ileal substrate into the hindgut. It has also been suggested that the change in molar proportions from acetate to propionate indicates a greater availability of fermentable carbohydrates (Högberg and Lindberg, 2004). Consequently, our results indicate an increased ileal substrate flow into the cecum of the SBP-fed BB pigs, which seem to differ from the SH and CB pigs in this respect. In addition, cecal content of SBP-fed BB pigs leading to the largest acetate/propionate rela-tion may have been less in fermentable carbohydrates compared with the other breeds as well as with all the other dietary treatments. The opposite was true for the basal diet-adapted CB pigs, yielding the smallest acetate:propionate ratio. However, it cannot be said that these differences were introduced by respective changes in the flow of easily fermentable carbohydrates into the hindgut because neither dietary nor breed dif-ferences could be detected from the electrophysiological data regarding jejunal and ileal glucose transport.

About 50% of OMAD was converted to VFA in Co-sitec, which seems to be less than in the rumen, where about 70% of fermented hexoses can be recovered as SCFA (Marty and Demeyer, 1973). Because of physi-cal losses from the nylon bags during incubation and during the washing procedure after incubation, OMAD may have been overestimated. However, the VFA pro-duction per unit OMAD agrees with that reported for VFA production in the hindgut of pigs per unit appar-ently digested OM (Dierick et al., 1990).

Methane excretion by pigs has been shown to be pos-itively correlated with NSP intake, and its production rate increases steadily from the cecum over the proxi-mal colon to the successive segments of the hindgut (Jensen, 1996). In Cositec, there was no clear effect of SBP on methane production, which may have been due to the use of cecal contents with low methanogenic potential. The relatively greater methane production combined with the largest acetate:propionate ratio in the fermentation vessels supplied with cecal substrate of SBP-fed BB pigs indicates a corresponding shift of fermentatively recovered hydrogen from propionate to methane. An inverse relationship between propionate and methane production in the large intestine of pigs has been observed by others (De Graeve and Demeyer, 1988) and is well known in rumen fermentation (Marty and Demeyer, 1973). It has also been reported that methane production in the hindgut of pigs can vary extremely among animals (Shi and Noblet, 1994) and may be influenced by bile acids (Jezierny et al., 2007).

In conclusion, the anatomical capacity and microbial potential for hindgut fermentation were increased by feeding SBP in all 3 pig breeds. No clear differences in intestinal tract anatomy and digestive physiology were observed between the traditional old breeds SH and BB on the one hand and the modern CB pigs on the other hand. Under the experimental conditions used in the present study, the pigs of the modern and intensely selected breed utilized SBP fiber as efficiently as the old pig breeds.

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