Effect of soluble and insoluble fiber on energy digestibility, nitrogen ...

Published February 9, 2015

Effect of soluble and insoluble fiber on energy digestibility, nitrogen retention, and fiber digestibility of diets fed to gestating sows1 J. A. Renteria-Flores,* L. J. Johnston,†2 G. C. Shurson,‡ and D. D. Gallaher‡ *Centro Nacional de Investigación Disciplinaria en Fisiología Animal–Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias, Ajuchitlán, Qro., México C. P. 76280; †University of Minnesota, Morris 56267; and ‡University of Minnesota, St. Paul 55108.

ABSTRACT: Twenty-four sows (12 nulliparous, 12 multiparous) were used to determine soluble fiber (SF) and insoluble fiber (ISF) effects on energy digestibility, N balance, and SF and ISF digestibility. Experimental diets included a corn-soybean meal control (C; 1.20% SF, 9.78% ISF), a 34% oat bran diet high in SF (HS; 3.02% SF, 10.11% ISF), a 12% wheat straw diet high in ISF (HIS; 1.11% SF, 17.86% ISF), and a 16% sugar beet pulp diet (HS + HIS; 2.32% SF, 16.08% ISF). Sows were assigned randomly to diets within parity group and individually fed to meet their energy requirements according to the NRC model assuming 10 pigs per litter and 40 kg of gestation gain. Total feces and urine were collected in 5-d periods at wk 5, 10, and 14 of gestation. There were no interactions between dietary treatments and parity group for any of the response criteria evaluated. Dietary energy digestibility was greatest (P < 0.01) for females fed C (87.9%) and HS (89.3%) diets compared with females fed diets high in ISF (HIS, 82.9; HS + HIS, 86.8%). Energy digestibility was not affected by stage of gestation. Dietary N digestibility was similar between C and HS (86.1 and 86.2%) but greater (P < 0.01) than HIS and HS + HIS (82.8 and

82.8%, respectively). Nitrogen digestibility declined (P < 0.05) as gestation progressed for sows fed HS only. Nitrogen retention as a percentage of N intake was not affected by diet (C, 51.8; HS, 44.0; HIS, 42.0; HS + HIS, 48.6). Soluble fiber digestibility was different (P < 0.01) among experimental diets (C, 85.8; HS, 89.5; HIS, 77.7; HS + HIS, 80.3%). Sows fed HS + HIS (61.8%) and HS (58.4%) had greater (P < 0.05) ISF digestibility than sows fed C (53.5%), whereas sows fed HIS (38.3%) had lower (P < 0.01) ISF digestibility than sows fed the other experimental diets. Greater digestibility of dietary energy (87.1 vs. 86.2%; P < 0.05), N (85.7 vs. 83.2%; P < 0.01), and ISF (54.5 vs. 51.2%; P < 0.06) was observed in multiparous vs. nulliparous sows. In conclusion, increased intake of ISF decreased energy digestibility, whereas increasing SF intake improved energy digestibility. Diet had no effect on N retention. Insoluble fiber digestibility improved when SF intake increased, suggesting that knowledge of specific dietary fiber components is necessary to accurately predict effects of dietary fiber on digestibility. Multiparous sows demonstrated a greater ability to digest fibrous diets than nulliparous sows.

Key words: digestibility, energy, fiber, nitrogen, sow ©2008 American Society of Animal Science. All rights reserved.

INTRODUCTION Inclusion of fiber in swine diets is not a common practice in the United States. Most swine diets in the United States are formulated based on corn and soybean meal because of the great availability, low cost, and complementary nutrient composition of these 2 feed ingredients. However, the usage of fibrous ingre-

1 This study was supported by the Minnesota Agricultural Experiment Station. 2 Corresponding author: [email protected] Received June 22, 2007. Accepted May 27, 2008.

J. Anim. Sci. 2008. 86:2568–2575 doi:10.2527/jas.2007-0375

dients in sow diets may increase, because dietary fiber can improve litter size (Farmer et al. 1996; Grieshop et al., 2001) and decrease stereotypic behaviors (Robert et al., 1993, 1997) that can develop in limit-fed gestating sows (Meunier-Salaün et al., 2001). In contrast to its beneficial effects, fiber addition to swine diets decreases nutrient digestibility (Noblet and Le Goff, 2001). The effect of dietary fiber addition on nutrient digestibility is influenced by several factors, such as fiber composition (Kritchevsky, 1988), fiber processing after harvest (McDougall et al., 1996), and age and physiological status of the animal (Noblet and Shi, 1993). Nutritionists must understand the effects of dietary fiber on nutrient digestibility of diets to properly feed high-fiber diets to sows.

2568

2569

Soluble and insoluble fiber in sow diets 1

Table 1. Composition and nutrient analysis of experimental diets (as-fed basis) Item Ingredient, % Corn Soybean meal, 47% CP Oat bran Wheat straw Sugar beet pulp Dicalcium phosphate Limestone Salt Mineral-vitamin premix2 Total Calculated analysis SF,3 % ISF,3 % NDF, % ADF, % Starch, % Crude fat, % Lignin, % Laboratory analysis CP, % Lysine, % Ca, % P, % SF, % ISF, %

C

HS

HIS

HS + HIS

83.26 13.40 — — — 1.47 1.07 0.40 0.40 100.00

54.00 8.50 34.32 — — 1.35 1.03 0.40 0.40 100.00

71.72 13.36 — 11.64 — 1.63 0.85 0.40 0.40 100.00

68.36 12.68 — — 15.92 1.65 0.59 0.40 0.40 100.00

1.59 7.67 9.18 3.05 52.24 3.65 0.83

3.19 8.95 12.53 1.97 48.70 4.49 1.47

1.46 15.36 17.97 9.01 45.10 3.41 2.34

3.19 15.32 15.65 7.37 42.99 3.15 1.00

12.45 0.43 0.57 0.40 1.20 9.78

12.03 0.48 0.66 0.52 3.02 10.11

12.37 0.55 0.59 0.47 1.11 17.86

12.11 0.52 0.67 0.54 2.32 16.08

1 C = control diet; HS = high soluble fiber diet; HIS = high insoluble fiber diet; HS + HIS = high soluble and insoluble fiber diet. 2 Provided (per kg of diet): 0.6 mg of I, 0.01 mg of Se, 100 mg of Zn, 100 mg of Fe, 6.6 mg of Cu, 30 mg of Mn, 6,608 IU of vitamin A, 1,652 IU of vitamin D3, 27.5 IU of vitamin E, 4.4 mg of vitamin K, 6.6 mg of riboflavin, 39.6 mg of niacin, 26.4 mg of pantothenic acid, 33 µg of vitamin B12, 0.8 mg of pyridoxine, 1.1 mg of folic acid, 0.22 mg of biotin, 583 mg of choline, and 0.66 mg of thiamine. 3 SF = soluble fiber; ISF = insoluble fiber.

This study was designed to test the hypothesis that type of fiber fed to gestating sows influences digestibility of the diet. The primary objective of this study was to evaluate the effect of increased levels of soluble fiber (SF) and insoluble fiber (ISF) in diets for gestating sows on digestibility of energy, and SF and ISF in the diet, and on N balance.

MATERIALS AND METHODS The study protocol was reviewed and approved by the University of Minnesota’s Institutional Animal Care and Use Committee before initiation of the study. Twenty-four sows, 12 multiparous (Imperial Swine Genetics-Line 442, Nicollet, MN) and 12 nulliparous (Duroc × Imperial Swine Genetics-Line 442), were used in this study. Two weeks before mating, sows were weighed and assigned randomly within parity to 1 of 4 experimental diets. Sows were divided into 3 blocks based upon day of mating. Sows were inseminated artificially with terminal-line Duroc semen (D-100, Compart’s Boar Store Inc., Nicollet, MN) on the day of estrus and 24 h later. From d 16 to 21 after insemination, sows were checked daily for signs of estrus using a mature boar. Pregnancy was confirmed ultrasonically 30 d after insemination. Sows found not pregnant were excluded from the experiment.

The experimental diets (Table 1) were as follows: a control diet (C) based on corn and soybean meal; a diet high in SF (HS) containing oat bran; a diet high in ISF (HIS) containing wheat straw; and a diet high in both SF and ISF (HS + HIS), which contained sugar beet pulp. The HS diet was formulated to contain approximately twice the amount of SF contained in the C diet, with a similar amount of ISF. The HIS diet was formulated to contain an amount of SF similar to the control diet but twice the concentration of ISF. The HS + HIS diet was formulated to contain almost twice the concentrations of SF and ISF found in the control diet. All diets were fed to sows in mash form. The oat bran was Diamond Brand #8 Coarse Oat Bran (LaCrosse Milling Co., Cochrane, WI). Wheat straw was ground twice through a 16-mm screen in a commercial hammer mill. Dried, unpelleted sugar beet pulp shreds were used in the HS + HIS diet. Values used in diet formulations for ME concentration (kcal/kg as-fed basis) of ingredients were as follows: 3,420 (corn), 3,380 (soybean meal), 3,400 (oat bran), 808 (wheat straw), and 2,495 (sugar beet pulp). Sows were fed individually once daily to meet their energy requirements according to the NRC (1998) gestation model assuming 40 kg of maternal gain during gestation and a litter size of 10 pigs at farrowing. Daily feed allowance was calculated for each sow based on

2570

Renteria-Flores et al.

initial sow BW and diet to provide equivalent energy and similar total Lys intake among experimental diets. Daily feed intake of sows was not adjusted as gestation progressed. Daily feed intake for nulliparous sows ranged from 1.56 to 1.73 kg and for multiparous sows from 1.95 to 2.28 kg. Sows were housed in a temperature-controlled confinement barn in individual gestation stalls with free access to water through nipple drinkers during the entire experiment. Room temperature was maintained at 21 ± 1°C throughout the experiment. During wk 5, 10, and 14 of gestation, sows were moved, within the same barn, to a modified gestation stall to permit total collection of feces and urine during a 5-d period. During the first collection period, 1 nulliparous sow fed the HIS diet was removed from the experiment due to a rectal prolapse. Feces were collected at 0700, 1000, 1300, 1600, and 1800 h daily, weighed, stored in plastic bags, and frozen at −20°C until the end of the collection period. At the end of the collection period, feces were dried in aluminum trays at 60°C in a forced-draft oven for 3 consecutive days. Dried feces were weighed, ground through a 1-mm screen, and a subsample was retained for N, GE, SF, and ISF determination. To facilitate urine collection, a Foley catheter (18, 20, or 22°F; size depended on sow BW) was inserted into the bladder of each sow and was connected to a plastic vessel containing 40 mL of 3.6 N H2SO4. Urine volume and weight were measured daily to determine quantity and density of urine excreted. A 500-mL aliquot from the collection each day was frozen. At the end of the collection period, aliquots of urine were thawed and pooled proportional to the daily urine volume excreted by each sow. A 50-mL subsample of pooled urine was frozen for N determination, and approximately 500 mL was freeze-dried for energy determination. After the 5-d collection period, sows were moved to their original gestation stalls. Gross energy content of feed, feces, and freeze-dried urine were determined in an isoperibol bomb calorimeter (model 1281, Parr Instrument Company, Moline IL). Total N content of feed, feces, and urine was determined by the Kjeldahl method using a 2300 Kjeltec Analyzer Unit (ANKOM200, ANKOM Technology Corporation, Fairport, NY). Soluble fiber and ISF content of feed and feces was measured by a modification (Prosky et al., 1988) to the total dietary fiber procedures described by Prosky et al. (1985). Data were analyzed by least squares ANOVA with repeated measures in time (Gill, 1986) using the GLM procedure (SAS Inst. Inc., Cary, NC). The statistical model included the effects of diet, parity, sow nested within diet, stage of gestation, and the diet × parity and diet × stage of gestation interactions. Effects of diet were tested using sow nested within diet as the error term. Mean separation was accomplished using the PDIFF procedure of SAS. The REG procedure of SAS was used to conduct simple linear and multiple linear regression analyses that evaluated the effects

of SF intake or ISF intake, or both, on digestibility of energy, N, and fiber. Pooled SEM were calculated using the mean squared error and the harmonic mean number of replications because of unequal replication among experimental diets (Steel et al., 1997). Statistically significant differences were assumed with P < 0.05. Probability values between 0.06 and 0.10 were considered trends.

RESULTS AND DISCUSSION No significant interactions between diet and parity for any response criteria were observed; consequently, only main effects of diet and parity are presented.

Diet Effects Initial BW was similar among sows fed the 4 experimental diets (Table 2). Sows were fed to satisfy their daily energy requirement; consequently, sows fed HIS had greater feed intake than sows fed the C and HS diet (P < 0.05) but similar to sows fed the HS + HIS diet due to the relatively low energy density of the HIS diet. In this experiment, gestation BW gain was not affected by the inclusion of fiber, indicating that sows can consume high-fiber diets and realize the desired pregnancy BW gain. Other authors (Calvert et al., 1985) reported that concentration of dietary fiber from alfalfa during gestation was related inversely to BW gain, but these authors did not attempt to compensate for differences in the calculated ME density among experimental diets. Declining ME intake plus the observation that dietary fiber decreases digestibility of energy and other nutrients (Noblet and Le Goff, 2001) may explain the differences in gestation BW gain reported by Calvert et al. (1985). Results of this study demonstrate that high-fiber diets fed to gestating sows can support desired gains in sow BW if appropriate adjustments to daily feed intake are instituted. Differences in ADFI were reflected in the amount of feces excreted daily. Sows fed the HIS diet excreted the greatest (P < 0.01) quantity of fecal DM followed by sows fed the HS + HIS diet. Urinary excretion was highly variable and not significantly different among sows fed the 4 diets. Nitrogen retention and N retained as a percentage of intake were similar among sows fed the experimental diets (Table 3). Kennelley and Aherne (1980) reported that addition of 22% oat hulls to the diet did not influence N excretion or N retention of growing barrows or gilts. Apparent N digestibility was decreased (P < 0.01) for sows fed HIS and HS + HIS diets compared with sows fed C. The HS diet supported apparent N digestibility similar to C. Increasing ISF of diets by adding wheat straw or sugar beet pulp depressed apparent N digestibility. Chabeauti et al. (1991) observed a 9.7 and 12.0% decline in N digestibility in growing pigs fed diets containing sugar beet pulp (16%) or wheat straw

2571

Soluble and insoluble fiber in sow diets 1

Table 2. Sow BW, daily feed and nutrient intake, and excretions of sows fed the experimental diets Trait Sows, n Initial BW at mating, kg Final BW at wk 14, kg Daily feed intake, kg Gestation BW gain, kg SF intake, as-fed g/d ISF intake, as-fed g/d Fecal excretion, g/d wet wt. Fecal excretion, g of DM/d Urine excretion, L/d

C

HS

HIS

HS + HIS

Pooled SEM

6 161.6 195.7 1.83c 34.2 21.9z 178.6z 293.5z 180.1z 5.7

6 173.5 206.3 1.87bc 32.8 56.5x 189.0z 286.6z 175.3z 7.4

5 169.4 201.0 1.96a 31.5 21.8z 350.6x 564.9x 343.4x 3.2

6 162.7 198.7 1.92ab 36.0 44.4y 307.9y 356.0y 217.1y 7.0

— 3.71 5.45 0.02 5.00 0.46 3.56 16.09 9.84 2.30

a–c

Means within a row with uncommon superscripts differ (P < 0.05). Means within a row with uncommon superscripts differ (P < 0.01). 1 C = control diet; HS = high soluble fiber diet; HIS = high insoluble fiber diet; HS + HIS = high soluble and insoluble fiber diet; SF = soluble fiber; ISF = insoluble fiber. Data represent main effects of diets across stages of gestation. x–z

(22%), respectively. Results of this study highlight the important effect that fiber composition has on digestibility of the diet. When SF was included in the diet (i.e., HS diet), N digestibility was similar to that obtained for the C diet. Inclusion of ISF (i.e., HIS and HS + HIS diets) decreased digestibility of N about 3 percentage units compared with the control diet. The relatively small decline in N digestibility caused by inclusion of ISF observed in the current study compared with that of Chabeauti et al. (1991) likely is due to differences in maturity of the pigs studied. Chabeauti et al. (1991) used growing pigs, which experience the negative effects of dietary fiber on nutrient digestibility to a greater degree than sows (Noblet and Shi, 1993). The larger and more developed gastrointestinal tract of adult sows facilitates more extensive fermentation of fibrous ingredients (Fernandez et al., 1986; Noblet and Shi, 1993; Noblet and Bach Knudsen, 1997). Stage of gestation had no effect on apparent N digestibility for sows fed C, HIS, and HS + HIS diets (Table 4). In contrast, apparent N digestibility was greater during wk 5 of gestation compared with later periods for sows fed HS [standard error of conditional (intraperiod) treatment differences = 1.02], which resulted in the diet × stage of gestation interaction (P < 0.01). There was no interaction between diet and stage of gestation for energy digestibility. Daily feed allowance

was designed to provide similar energy intake among sows fed the experimental diets. However, GE and ME intake tended (P < 0.10) to be different among sows fed the experimental diets (Table 5). Apparent energy digestibility was different among sows fed the 4 experimental diets (P < 0.01). Sows fed the HS diet had greater apparent energy digestibility compared with sows fed the C diet. Diets containing elevated levels of ISF (HIS, HS + HIS) had lower energy digestibility than the control diet. Using the ME density of diets reported in Table 5, the recorded DM content of diets (C, 89.39%; HS, 89.64%; HIS, 89.39%; HS + HIS, 89.68%), and the prediction equations of Noblet et al. (1994), the NE concentrations of the experimental diets on an asfed basis were as follows: 2,397 (C), 2,501 (HS), 2,215 (HIS), and 2,343 (HS + HIS) kcal/kg. Simple and multiple linear regression analyses were used to explore the effect of SF and ISF intake on energy digestibility. Apparent energy digestibility was related positively (P < 0.01; R2 = 0.36) to SF intake, whereas ISF intake was related negatively (P < 0.01; R2 = 0.50) to energy digestibility (Figure 1). Almost 80% of the variation in apparent energy digestibility of the experimental diets fed to gestating sows can be explained by the SF and ISF intake (P < 0.01; R2 = 0.78) expressed in the following equation: apparent energy digestibility = 88.74 + 0.083 (SF intake) − 0.02 (ISF intake).

Table 3. Nitrogen intake, excretion, and retention in sows fed the experimental diets1,2 Trait Sows, n N intake, g/d N excreted in feces, g/d N excreted in urine, g/d Total N excreted, g/d N retained, g/d N retained as % intake Apparent N digestibility, % y,z

C

HS

HIS

HS + HIS

Pooled SEM

6 36.4 5.0y 12.5 17.5 18.8 51.8 86.1y

6 36.0 4.9y 15.1 20.0 15.9 44.0 86.2y

5 38.6 6.6z 16.0 22.4 16.1 42.0 82.8z

6 37.1 6.3z 12.9 19.3 17.8 48.6 82.8z

— 0.28 0.25 1.63 1.64 1.68 4.21 0.67

Means within a row with uncommon superscripts differ (P < 0.01). C = control diet; HS = high soluble fiber diet; HIS = high insoluble fiber diet; HS + HIS = high soluble and insoluble fiber diet. 2 Means represent average of N balance determinations conducted at wk 5, 10, and 14 of gestation. 1

2572


Table 4. Apparent N digestibility (%) of diets fed to sows during different weeks of gestation1,2 Stage of gestation Wk 5 SEM Wk 10 SEM Wk 14 SEM

C

HS

85.82 0.68 86.40 0.76 86.07 0.67

y

88.05 0.68 84.50z 0.76 85.65z 0.67

HIS

HS + HIS

83.79 0.77 82.00 0.86 82.60 0.76

83.14 0.68 83.84 0.76 81.39 0.67

y,z

Means within column with uncommon superscript differ (P < 0.01). C = control diet; HS = high soluble fiber diet; HIS = high insoluble fiber diet; HS + HIS = high soluble and insoluble fiber diet. 2 Standard error of conditional (intraperiod) treatment differences = 1.02. 1

Others have reported similar effects of fiber type on apparent energy digestibility of diets fed to growing pigs (Kennelley and Aherne, 1980; Chabeauti et al., 1991) and sows (Mroz et al., 1986). Kennelley and Aherne (1980) showed that diets with increased levels of crude fiber from oat hulls had a lower energy digestibility than the control diet. These results are comparable to results reported herein for HIS and HS + HIS diets in which energy digestibility decreased with dietary inclusion of fiber. In contrast, fiber added to the HS diet from oat bran improved energy digestibility. Differences in fiber composition between oat hulls and oat bran could explain their differential effects on energy digestibility. Oat hull fiber has a greater amount of NDF (78%) and ADF (42%; NRC, 1988) compared with oat bran fiber that contains 10.4% NDF and 4.5% ADF (Fadel, 1992). These differences in fiber composition are important because they show that oat hull fiber has a greater proportion of cell wall components (i.e., cellulose, hemicellulose, and lignin) that are considered ISF and more difficult to digest. Oat bran fiber has a greater amount of SF (i.e., β glucan), which is more likely to be fermented by bacteria present in the large intestine of swine (Noblet and Le Goff, 2001). Two possible mechanisms may explain increases in energy digestibility when SF, but not ISF, is included in the diet for sows. First, SF delays gastric emptying due to its ability to swell and form a viscous material (Anderson, 1985; Schneeman, 1998). Delayed gastric

emptying improves digestive and absorptive efficiency (Davidson and McDonald, 1998). Second, increased SF intake increases bacterial populations in the large intestine as evidenced by increased excretion of bacteria in feces (Chen et al., 1998; Davidson and McDonald, 1998). The large populations of intestinal microbes likely increased fermentation and utilization of SF to a greater extent than ISF (Graham and Åman, 1991; Noblet and LeGoff, 2001). Microbial fermentation in the large intestine produces VFA (Jørgensen and Jensen, 1994; Schneeman, 1998) that can satisfy up to 30% of the maintenance energy requirement of the pig (Varel and Pond, 1985; Varel and Yen, 1997). In contrast to SF, ISF decreased energy digestibility of diets. Insoluble dietary fiber decreases intestinal transit time (Anderson, 1985), which limits nutrient digestion and absorption (Mroz et al., 1986). The primary components of ISF are cellulose, hemicellulose, and lignin, which are less likely to be utilized and fermented by gastrointestinal flora compared with SF (Graham and Åman, 1991). Low digestibility caused by ISF components explains why greater intakes of ISF increase the amount of plant material excreted in the feces and increases fecal bulk (Chen et al., 1998; Davidson and McDonald, 1998). Other researchers have demonstrated that composition of dietary fiber can affect energy digestibility of the diet. Silvio et al. (2000) reported that increasing concentrations of purified SF (pectin) and decreasing

Table 5. Energy intake, excretion, and apparent digestibility in sows fed the experimental diets1,2 Trait Sows, n GE intake, kcal/d Energy excreted in feces, kcal/d Energy excreted in urine, kcal/d DE, intake kcal/d ME, intake kcal/d Apparent energy digestibility, % DE, kcal/kg as-fed ME, kcal/kg as-fed w–z

C

HS

HIS

HS + HIS

Pooled SEM

6 6,847 820y 156 6,027 5,871 87.9x 3,296x 3,210x

6 7,184 776y 161 6,408 6,247 89.1w 3,423w 3,337w

5 7,272 1,239w 179 6,033 5,854 82.9z 3,094z 3,002z

6 7,138 940x 173 6,199 6,026 86.8y 3,236y 3,147y

— 53.30 48.4 20.5 71.3 72.4 0.7 25.0 25.2

Means within a row with uncommon superscripts differ (P < 0.01). C = control diet; HS = high soluble fiber diet; HIS = high insoluble fiber diet; HS + HIS = high soluble and insoluble fiber diet. 2 Means represent average of energy digestibility determinations conducted at wk 5, 10, and 14 of gestation. 1

2573

Soluble and insoluble fiber in sow diets

Figure 1. Effect of soluble fiber (SF; panel a) and insoluble fiber (ISF; panel b) intake on apparent energy digestibility (APEDIG) in gestating sows fed different levels of dietary fiber. Panel a: APEDIG = 83.43 + 0.093 (SF intake); r2 = 0.36; P < 0.01. Panel b: APEDIG = 92.21 + 0.021 (ISF intake); r2 = 0.50; P < 0.01.

Figure 2. Effect of soluble fiber (SF; panel a) and insoluble fiber (ISF; panel b) intake on soluble fiber digestibility (SFDIG) in sows fed different levels of soluble fiber. Panel a: SFDIG = 78.40 + 0.142 (SF intake); r2 = 0.22; P < 0.03. Panel b: SFDIG = 94.90 − 0.044 (ISF intake); r2 = 0.58; P < 0.01.

concentrations of purified ISF (cellulose) were associated positively with energy digestibility of diets for dogs. Mroz et al. (1986) also showed that the inclusion of different proportions of oat hulls to a basal diet decreased energy digestibility. Chabeauti et al. (1991) showed that the inclusion of sugar beet pulp or wheat straw decreased energy digestibility by 7.9 and 18.4 percentage points, respectively. In the present experiment, a similar trend of smaller magnitude was detected. These findings, along with those of Silvio et al. (2000) and the current study, reinforce the concept that fiber composi-

tion (i.e., SF and ISF) influences energy digestibility and that composition of the fiber should be considered when fiber is included in diets for gestating sows. Digestibility of SF differed (P < 0.01; SEM = 0.84) for sows fed the 4 experimental diets (HS, 89.5%; C, 85.8%; HS + HIS, 80.3%; HIS, 77.7%). Soluble fiber intake seemed to be related positively to SF digestibility (P < 0.03; R2 = 0.22), whereas the ISF intake depressed SF digestibility (P < 0.01; R2 = 0.58; Figure 2). Soluble fiber and ISF intake considered together in a multiple linear regression analysis explained 74% of the varia-

Table 6. Body weight, feed intake, digestible energy intake, N intake, and soluble and insoluble fiber intake for nulliparous and multiparous sows Trait Sows, n Initial BW at mating, kg Final BW at wk 14, kg ADFI, kg Gestation BW gain, kg GE intake, kcal/d N intake, g/d Soluble fiber intake, g/d Insoluble fiber intake, g/d y,z

Nulliparous

Multiparous

Pooled SEM

11 141.3y 174.9y 1.7y 33.6 6,247y 32.5y 31.8y 226.0y

12 192.3z 229.0z 2.1z 33.6 7,973z 41.5z 40.5z 287.1z

— 2.62 3.84 0.02 3.52 37.6 0.20 0.33 2.51

Means within a row with uncommon superscripts differ (P < 0.01).

2574


Table 7. Apparent digestibility of dietary energy, N, soluble fiber (SF), and insoluble fiber (ISF) in nulliparous and multiparous sows Trait

Nulliparous

Multiparous

Pooled SEM

11 86.2a 83.2y 82.9 51.2e

12 87.1b 85.7z 83.8 54.5f

— 0.45 0.47 0.61 0.95

Sows, n Apparent energy digestibility, % Apparent N digestibility, % Apparent SF digestibility, % Apparent ISF digestibility, % a,b

Means within a row with uncommon superscripts differ (P < 0.05). Means within a row with uncommon superscripts tended to differ (P < 0.06). y,z Means within a row with uncommon superscripts differ (P < 0.01). e,f

tion (P < 0.01) in SF digestibility according to the following relationship: SF digestibility = 89.9 + 0.12 (SF intake) − 0.042 (ISF intake). Insoluble fiber digestibility (ISFDIG) was different (P < 0.01) among diets. Sows fed HS + HIS (61.8%) and HS (58.4%) had greater (P < 0.05) ISFDIG than sows fed C (53.5%), whereas sows fed the HIS (38.3%) had lower (P < 0.01) ISFDIG than sows fed the other experimental diets. Insoluble fiber digestibility was positively related (P < 0.01) to SF intake (Figure 3). In contrast, digestibility of ISF was not affected by ISF intake (data not shown). Results of the current study indicate a greater digestibility of both SF and ISF when SF intake increases. Soluble fiber promotes microbial growth and activity (Chen et al., 1998) and slows intestinal passage rate (Cherbut et al., 1990), which supports more extensive digestion of feed. Increased intake of ISF limits microbial utilization of fiber (Varel and Pond, 1985), increases fecal bulk (Chen et al., 1998; Davidson and McDonald, 1998; Bach Knudsen, 2001), and accelerates intestinal passage rate (Vahouny and Cassidy, 1985). These properties contribute to the negative effects of ISF on diet digestibility. Evidently, the positive attributes of SF with regard to diet digestibility are of sufficient magnitude to enable sows to more completely ferment ISF in the hindgut.

Figure 3. Effect of soluble fiber (SF) intake on insoluble fiber digestibility (ISFDIG) in sows fed different levels of insoluble fiber. ISFDIG = 38.98 + 0.398 (SF intake); r2 = 0.44; P < 0.01.

Parity Effects Daily feed intake allowance was calculated based on sow BW and predicted energy concentration of the diet (NRC, 1998). Multiparous sows had greater daily feed intake than nulliparous sows due to differences in BW (Table 6). Gestation BW gain was similar for both nulliparous and multiparous sows. Nitrogen, energy, SF, and ISF intake were greater for multiparous compared with nulliparous sows. Apparent digestibility of energy (P < 0.05) and N (P < 0.01) was greater in multiparous sows than nulliparous sows (Table 7). Several researchers (Fernandez et al., 1986; Noblet and Shi, 1993) have observed greater nutrient digestibility of high-fiber diets fed to sows compared with growing-finishing pigs. Digestibility of dietary SF between nulliparous and multiparous sows was similar, whereas multiparous sows tended to have a greater (P < 0.06) ability to digest ISF compared with nulliparous sows. Noblet and Bach Knudsen (1997) reported that older sows had greater digestibility coefficients for crude fiber, cellulose, and total nonstarch polysaccharides compared with growing-finishing pigs. This finding is not surprising given that growing-finishing pigs usually receive more feed than pregnant sows and have less fermentation capabilities compared with sows. Fernandez et al. (1986) suggested that digestibility of nutrients tends to be similar for growingfinishing pigs and adult sows when feeding level was proportional to BW. However, in the present experiment, multiparous sows demonstrated a greater ability to digest energy, N, and fiber than nulliparous sows even though feeding level was proportional to BW. This suggests that the ability of the sow to utilize fibrous feedstuffs improves with advancing age. Results reported herein demonstrated that SF and ISF have differential effects on nutrient digestibility. Increased SF intake increased digestibility of energy, SF, and ISF with no apparent effect on N utilization. In contrast, increased ISF intake decreased digestibility of energy, N, and SF, with no effect on ISF digestibility. Elevated intake of ISF increased excretion of fecal DM, whereas elevated intake of SF had no effect on fecal output. Multiparous sows demonstrated a greater ability to digest fibrous diets compared with nulliparous sows. In summary, results of the current study

Soluble and insoluble fiber in sow diets

suggest that high levels of fiber can be included in diets for gestating sows without negatively affecting diet digestibility. Fiber type (SF and ISF) has differential effects on diet digestibility and must be considered in diet formulations for sows to optimize diet digestibility. Age of sow must also be considered when formulating high-fiber diets, because multiparous sows have a greater ability to digest fibrous diets compared with nulliparous sows.

LITERATURE CITED Anderson, J. W. 1985. Physiological and metabolic effects of dietary fiber. Fed. Proc. 44:2902–2906. Bach Knudsen, K. E. 2001. The nutritional significance of “dietary fibre” analysis. Anim. Feed Sci. Technol. 90:3–20. Calvert, C. C., N. C. Steele, and R. W. Rosebrough. 1985. Digestibility of fiber components and reproductive performance of sows fed high levels of alfalfa. J. Anim. Sci. 61:595–602. Chabeauti, E., J. Noblet, and B. Carré. 1991. Digestion of plant cell walls from four different sources in growing pigs. Anim. Feed Sci. Technol. 32:207–213. Chen, H. L., V. S. Haack, C. W. Janecky, N. W. Vollendorf, and J. A. Marlett. 1998. Mechanisms by which wheat bran and oat bran increase stool weight in humans. Am. J. Clin. Nutr. 68:711– 719. Cherbut, C., E. Albina, M. Champ, J. L. Doublier, and G. Lecannu. 1990. Action of guar gums on the viscosity of digestive contents and on the gastrointestinal motor function in pigs. Digestion 46:205–213. Davidson, M. H., and A. McDonald. 1998. Fiber forms and functions. Nutr. Res. 18:617–624. Fadel, J. G. 1992. In vitro buffering capacity changes of seven commodities under controlled moisture and heating conditions. J. Dairy Sci. 75:1287–1295. Farmer, C., S. Robert, and J. J. Matte. 1996. Lactation performance of sows fed a bulky diet during gestation and receiving growth hormone releasing factor during lactation. J. Anim. Sci. 74:1298–1306. Fernandez, J. A., J. N. Jorgensen, and A. Just. 1986. Comparative digestibility experiments with growing pigs and adult sows. Anim. Prod. 43:127–132. Gill, J. L. 1986. Repeated measurement: Sensitive tests for experiments with few animals. J. Anim. Sci. 63:943–954. Graham, H., and P. Åman. 1991. Nutritional aspects of dietary fibers. Anim. Feed Sci. Technol. 32:143–158. Grieshop, C. M., D. E. Reese, and G. C. Fahey Jr. 2001. Nonstarch polysaccharides and oligosaccharides in swine nutrition. Page 107 in Swine Nutrition. A. J. Lewis and L. L. Southern, ed. CRC Press, Boca Raton, FL. Jørgensen, H., and B. B. Jensen. 1994. The effect of dietary fiber on digestibility, microbial activity, and microbial gas production in various regions of the gastrointestinal tract of pigs. Page 271 in Digestive Physiology in Pigs. Publ. 80. Eur. Assoc. Anim. Prod., Bad Doberan, Germany. Kennelley, J. J., and F. X. Aherne. 1980. The effect of fiber in diets formulated to contain different levels of energy and protein on

2575

digestibility coefficients in swine. Can. J. Anim. Sci. 60:717– 722. Kritchevsky, D. 1988. Dietary fiber. Annu. Rev. Nutr. 8:301–328. McDougall, G. J., I. M. Morrison, D. Stewart, and J. R. Hillman. 1996. Plant cell walls as dietary fibre: Range, structure, processing and function. J. Sci. Food Agric. 70:133–150. Meunier-Salaün, M. C., S. A. Edwards, and S. Robert. 2001. Effect of dietary fiber on the behaviour and health of the restricted-fed sow. Anim. Feed Sci. Technol. 90:53–69. Mroz, Z., I. G. Partridge, G. Mitchell, and H. D. Keal. 1986. The effect of oat hulls added to the basal ration for pregnant sows on reproductive performance, apparent digestibility, rate of passage and plasma parameters. J. Sci. Food Agric. 37:239–247. Noblet, J., and K. E. Bach Knudsen. 1997. Comparative digestibility of wheat, maize and sugar beet pulp non-starch polysaccharides in adult sows and growing pigs. Page 571 in Digestive Physiology in Pigs. Publ. 88. Eur. Assoc. Anim. Prod., Saint Malo, France. Noblet, J., H. Fortune, X. S. Shi, and S. Dubois. 1994. Prediction of net energy value of feeds for growing pigs. J. Anim. Sci. 72:344–354. Noblet, J., and G. Le Goff. 2001. Effect of dietary fiber on energy value of feeds for pigs. Anim. Feed Sci. Technol. 90:35–52. Noblet, J., and X. S. Shi. 1993. Comparative digestive utilization of energy and nutrients in growing pigs fed ad lib and adult sows fed at maintenance. Livest. Prod. Sci. 34:137–152. NRC. 1988. Nutrient Requirements of Dairy Cattle. 6th rev. ed. Natl. Acad. Press, Washington, DC. NRC. 1998. Nutrient Requirements of Swine. 10th rev. ed. Natl. Acad. Press, Washington, DC. Prosky, L., N. G. Asp, I. Fruda, J. W. DeVires, T. F. Schweizer, and B. F. Harland. 1985. Determination of total dietary fiber in foods and food products: Collaborative study. J. Assoc. Off. Anal. Chem. 68:677–679. Prosky, L., N. G. Asp, T. F. Schweizer, J. W. DeVires, and I. Fruda. 1988. Determination of insoluble, soluble and total dietary fiber in foods and food products: Interlaboratory study. J. Assoc. Off. Anal. Chem. 71:1017–1023. Robert, S., J. J. Matte, C. Farmer, C. L. Girard, and G. P. Martineau. 1993. High-fibre diets for sows: Effects on stereotypes and adjunctive drinking. Appl. Anim. Behav. Sci. 37:297–309. Robert, S., J. Rushen, and C. Farmer. 1997. Both energy content and bulk of food affect stereotypic behaviour, heart rate and feeding motivation of female pigs. Appl. Anim. Behav. Sci. 54:161– 171. Schneeman, B. O. 1998. Dietary fiber and gastrointestinal function. Nutr. Res. 18:625–632. Silvio, J., D. L. Harmon, K. L. Gross, and K. R. McLeod. 2000. Influence of fiber fermentability on nutrient digestion in the dog. Nutrition 16:289–295. Steel, R. G. D., J. H. Torrie, and D. A. Dickey. 1997. Principles and Procedures of Statistics: A Biometrical Approach. 3rd ed. McGraw-Hill Co., New York, NY. Vahouny, G. V., and M. M. Cassidy. 1985. Dietary fibers and absorption of nutrients. Proc. Soc. Exp. Biol. Med. 180:432–446. Varel, V. H., and W. G. Pond. 1985. Enumeration and activity of cellulolytic bacteria from gestating swine fed various levels of dietary fiber. Appl. Environ. Microbiol. 49:858–862. Varel, V. H., and J. T. Yen. 1997. Microbial perspective on fiber utilization by swine. J. Anim. Sci. 75:2715–2722.