The contribution of digestible and metabolizable energy from high-fiber dietary ingredients is not affected by inclusion rate in mixed diets fed to growing pigs

Nutritional guide to feeding wheat and wheat co-products to swine: a review

Inclusion of wheat grain can offer feeding opportunities in swine diets because of its high starch, crude protein (CP), amino acid (AA), and phosphorus (P) content. High concentrations of starch within wheat grain makes it a good energy source for swine. Mean energy content of wheat was 4,900 and 3,785 kcal/kg dry matter (DM) for digestible energy and metabolizable energy, respectively. CP concentration can vary based on the class of wheat which include hard red winter, hard red spring, soft red winter, hard white, soft white, and durum. The average CP of all wheat data collected in this review was 12.6% with a range of 8.5% to 17.6%. The AA concentration of wheat increases with increasing CP with the mean Lys content of 0.38% with a standardized ileal digestibility (SID) of 76.8%. As CP of wheat increases, the SID of AA in wheat also increases. Mean P of wheat was 0.27% and median P was 0.30%. Off-quality wheat is often associated with sprouts, low-test weight, or mycotoxin-contamination. Sprouted and low-test weight wheat are physical abnormalities associated with decreased starch within wheat kernel that leads to reductions in energy. The assumed energy value of wheat grain may need to be reduced by up to 10% when the proportion of sprouted to non-sprouted wheat is up to 40% whereas above 40%, wheat's energy may need to be reduced by 15% to 20%. Low-test weight wheat appears to not influence pig performance unless it falls below 644 kg/m3 and then energy value should be decreased by 5% compared to normal wheat. Deoxynivalenol (DON) contamination is most common with wheat grain. When content is above the guidance level of 1 mg/kg of DON in the complete diet, each 1 mg/kg increase in a DON-contaminated wheat-based diet will result in a 11% and 6% reduction in ADG and ADFI for nursery pigs, and a 2.7% and 2.6% reduction in ADG and ADFI, in finishing pigs, respectively. Wheat co-products are produced from the flour milling industry. Wheat co-products include wheat bran middlings, millrun, shorts, and red dog. Wheat co-products can be used in swine diets, but application may change because of differences in the final diet energy concentration due to changes in the starch and fiber levels of each wheat co-product. However, feeding wheat co-products are being evaluated to improve digestive health. Overall, wheat and wheat co-products can be fed in all stages of production if energy and other nutrient characteristics are considered.

Gestating sows with a restricted feed allowance require a longer adaptation period before collecting feces compared with lactating sows in total tract digestibility assessments using index method

The objective of the present experiment was to determine the minimum adaptation period for total tract digestibility experiments in gestating and lactating sows using the indigestible index method. Five gestating and 5 lactating sows at parities 3 to 5 were used. An indigestible index of 0.5% chromic oxide was supplemented to a diet based on corn and soybean meal. The daily feed allowance for gestating sows was 2 kg and 2 equal meals were provided to the sows. Lactating sows were fed 6 kg of feed per day in 3 equal meals. After feeding a diet without supplemental chromic oxide for 5 d, index-supplemented diets were provided to the gestating and lactating sows. Feces were collected at 24-h intervals for 9 and 7 d from gestating and lactating sows, respectively. Fecal Cr concentrations increased linearly (P < 0.001) and quadratically (P < 0.001) with collection time in both gestating and lactating sows. Minimum adaptation periods were estimated by one-slope broken-line model. The break point of Cr concentrations in feces was day 7.2 (SE = 0.3) in the gestating sows and day 4.2 (SE = 0.2) in the lactating sows, respectively. Apparent total tract digestibility of dry matter, organic matter, and energy on day 4 was less (P < 0.001) than that on days 8 to 9 in gestating sows fed the experimental diet with a 2-kg feed allowance. In lactating sows fed the experimental diets with a 6-kg feed allowance, the apparent total tract digestibility of dry matter, organic matter, and energy on day 3 was less (P < 0.05) than that on days 5 to 7. In conclusion, at least 8 d of adaptation period are required for gestating sows to determine total tract digestibility using Cr as the indigestible index method whereas 5 d of adaptation period are required for lactating sows. An insufficient adaptation period results in lower digestibility values.

Standardized ileal digestibility of amino acids in soybean meal fed to non-pregnant and pregnant sows

BACKGROUND

Two studies were designed to determine standard ileal crude protein (CP) and amino acid (AA) digestibility of soybean meal (SBM) from different origins fed to non-pregnant and pregnant sows. Seven solvent-extracted SBMs from soybeans produced in the USA, Brazil, and China were selected. In Exp. 1, eight different diets were created: a nitrogen (N)-free diet and 7 experimental diets containing SBM from different origins as the only N source. Eight non-pregnant, multiparous sows were arranged in an 8 × 8 Latin square design (8 periods and 8 diets). In Exp. 2, the diet formula was the same as in Exp. 1. Eight gestating sows (parity 3) were assigned to 4 different diets in a replicated 4 × 3 Youden square design (three periods and four diets) in mid-gestation and again in late-gestation stages.

RESULTS

When fed to non-pregnant and late-gestating sows, the standardized ileal digestibility (SID) of CP and most AAs from different SBM were not significantly different (P > 0.05). When fed to mid-gestating sows, the SID values for Arg, His, Lys, Phe, Cys, Gly, Ser, and Tyr in SBM 1 were lower than in SBM 4 and 5 (P < 0.05), whereas SID for Leu from SBM 5 was higher than in SBM 1 and 4 (P < 0.05). SID values for Ile, Ala, and Asp from SBM 4 were lower than in SBM 1 and 5 (P < 0.05). Sows had significantly greater SID values for Lys, Ala, and Asp during mid-gestation when compared with late-gestation stages (P < 0.05). Mid-gestating sows had greater SID value for Val and lower SID value for Tyr when compared with non-pregnant and late-gestating sows (P < 0.01), whereas non-pregnant sows had significantly greater SID value for Met when compared with gestating sows (P < 0.01).

CONCLUSIONS

When fed to mid-gestating sows, the SID values for most AAs varied among SBM samples. The SID values for Lys, Met, Val, Ala, Asp, and Tyr in SBM were affected by sow gestation stages. Our findings provide a cornerstone for accurate SBM use in sow diets.

Time-course effects of different fiber-rich ingredients on energy values, microbiota composition and SCFA profile in growing pigs

This study was to investigate time-course effects of different types of dietary fiber on the energy values, fecal microbiota and short-chain fatty acid (SCFA) concentration in growing pigs. A total of 24 barrows (initial body weight, 19.8 ± 0.5 kg) were assigned to 4 dietary treatments based on body weight (BW) in a completely randomized design, including a basal diet (CON) and 3 fiber-rich diets replacing corn, soybean meal and soybean oil in the CON diet with 20% sugar beet pulp (SBP), defatted rice bran (DFRB) or soybean hull (SBH), respectively. Fresh feces were sampled on d 7, 14 and 21, followed by 5 d total feces and urine collections. The results showed that there were no differences in DE and ME between any of the fiber ingredients on d 7, 14 or 21. However, fiber inclusion decreased the DE and ME of the diet (P < 0.05) regardless of the time effect. Principal coordinate analysis (PCoA) revealed distinctly different microbial communities on the DFRB diet and SBH diet across different times (P < 0.05) and the fecal microbiota of the 4 diet groups demonstrated notably distinct clusters at each time point (P < 0.05). With adaptation time increased from 7 to 21 d, cellulose-degrading bacteria and SCFA-producing bacteria (e.g., Ruminococcaceae _UCG-014, Rikenellaceae _RC9_gut_group and Bifidobacterium) increased in the fiber inclusion diets, and pathogenic genera (e.g., Streptococcus and Selenomonas) were increased in the basal diet (P < 0.05). Furthermore, the gut microbiota of growing pigs adapted more easily and quickly to the SBP diet compared to the DFRB diet, as reflected by the concentration of propionate, butyrate, isovalerate and total SCFA which increased with time for growing pigs fed the DFRB diet (P < 0.05). Collectively, our results indicated at least 7 d adaptation was required to evaluate the energy values of fiber-rich ingredients, as the hindgut microbiota of growing pigs may need more time to adapt to a high fiber diet, especially for insoluble dietary fiber.

Fiber digestibility in growing pigs fed common fiber-rich ingredients: a systematic review

The application of high-fiber ingredients in the swine feed industry has some limitations considering that high amounts of fiber are resistant to endogenous enzymatic degradation in the pig’s gut. However, there is growing interest in fiber fermentation in the intestine of pigs due to their functional properties and potential health benefits. Many strategies have been applied in feed formulations to improve utilization efficiency of fiber-rich ingredients and stimulate their prebiotic effects in pigs. This manuscript reviews chemical compositions, physical properties, and digestibility of fiber-rich diets formulated with fibrous ingredients for growing pigs. Evidences presented in this review indicate there is a great variation in chemical compositions and physical properties of fibrous ingredients, resulting in the discrepancy of energy and fiber digestibility in pig intestine. In practice, fermentation capacity of fiber components in the pig’s intestine can be improved using strategies, such as biological enzymes supplementation and feed processing technologies. Soluble dietary fiber (SDF) and insoluble dietary fiber (IDF), rather than neutral detergent fiber (NDF) and acid detergent fiber (ADF), are recommended in application of pig production to achieve precise feeding. Limitations of current scientific research on determining fiber digestibility and short chain fatty acids (SCFA) production are discussed. Endogenous losses of fiber components from non-dietary materials that result in underestimation of fiber digestibility and SCFA production are discussed in this review. Overall, the purpose of our review is to provide a reference for feeding the pig by choosing the diets formulated with different high-fiber ingredients.

Evaluation of energy values of high-fiber dietary ingredients with different solubility fed to growing pigs using the difference and regression methods

The objective of this study was to compare the energy values of high-fiber dietary ingredients with different solubility (sugar beet pulp [SBP] and defatted rice bran [DFRB]) in growing pigs using the difference and the regression methods. A total of 21 barrows (initial BW, 40.5 ± 1.2 kg) were assigned to 3 blocks with BW as a blocking factor, and each block was assigned to a 7 × 2 incomplete Latin square design with 7 diets and two 13-d experimental periods. The 7 experimental diets consisted of a corn-soybean meal basal diet and 6 additional diets containing 10%, 20%, or 30% SBP or DFRB in the basal diet, respectively. Each of the experimental periods lasted 12 d, with a 7 d dietary adaptation period followed by 5-d total fecal and urine collection. Results showed that the digestible energy (DE) and metabolizable energy (ME) of the SBP determined by the difference method with different inclusion levels (10%, 20%, or 30%) were 2,712 and 2,628 kcal/kg, 2,683 and 2,580 kcal/kg, and 2,643 and 2,554 kcal/kg DM basis, respectively. The DE and ME in the DFRB evaluated by the difference method with 3 different inclusion levels were 2,407 and 2,243 kcal/kg, 2,687 and 2,598 kcal/kg, and 2,630 and 2,544 kcal/kg DM basis, respectively. Different inclusion levels had no effects on the energy values of each test ingredient estimated by the difference method. The DE and ME of the SBP and the DFRB estimated by the regression method were 2,562 and 2,472 kcal/kg and 2,685 and 2,606 kcal/kg DM basis, respectively. The energy values of each ingredient determined by the regression method were similar to the values estimated by the difference method with the 20% or 30% inclusion level. However, the energy values of the SBP and DFRB estimated by the difference method with the 10% inclusion level were inconsistent with the values determined by the regression method (P < 0.05). In conclusion, the regression method was a robust indirect method to evaluate the energy values for high-fiber ingredients with different solubility in growing pigs. If the number of experimental animals was limited, the difference method with a moderate inclusion level (at least 20%) of the test high-fiber ingredient in the basal diet could be applied to substitute the regression method.

Physiological function and application of dietary fiber in pig nutrition: A review

Dietary fiber (DF), divided into soluble dietary fiber (SDF) and insoluble dietary fiber (IDF), has attracted increasing attention in the field of pig nutrition. Although DF reduces nutrient digestibility and inhibits energy deposition in most cases, fiber-rich feeds have been widely used in pig diets. This is not only because of lower feed costs, but also from the continuous discovery about the nutritional value of DF, mainly including the improvement of piglet intestinal health and sow reproductive performance. The addition timing has also been further considered, which potentially enables the nutritional value of DF to be accurately used in applicable pig models. Furthermore, fiber degrading enzymes have been shown to alleviate the anti-nutritional effects of DF and have ensured the improvement effect of fiber on intestinal health in young piglet models. However, the regulatory effect of fiber on pork quality is still unclear, which requires consideration of the wide range of fiber sources and the complexity of the basic diet composition, as well as the impact of pig breeds. Taken together, future research needs to gain more insight into the combined effects of SDF and IDF, processing methods, and addition timing to improve the nutritional value of DF, and further explore the physiological functions and regulatory mechanisms of DF fermentation products short-chain fatty acids in pigs.

Adding Appropriate Fiber in Diet Increases Diversity and Metabolic Capacity of Distal Gut Microbiota Without Altering Fiber Digestibility and Growth Rate of Finishing Pig

The digestion ability of pigs to dietary fiber is derived from their intestinal microbiota, especially hindgut microbiota. However, tolerance of pigs to high dietary fiber and the changes of microbiota profile with fiber levels are still unclear. To investigate the changes of gut microbiota with dietary fiber and its relationship with fiber digestibility, we conducted comparative analyses of growth rate, apparent fiber digestibility, gut microbiota and volatile fatty acid (VFA) profiles in Chinese Suhuai pigs feeding diets with different defatted rice bran (DFRB) fiber levels. We found that dietary fiber level had no effect on the growth rate of Suhuai pigs. Although the apparent digestibility of Cellulose, insoluble dietary fiber (IDF) and total dietary fiber (TDF) decreased with dietary fiber level, we found that the apparent digestibility of Cellulose, IDF and TDF of Suhuai pigs was not changed when provided with diet containing 19.10% TDF (as feed basis). The pigs provided with diet containing 19.10% TDF had higher microbial richness, proportions of several fiber-degrading bacteria taxa at genus level and predicted microbial functions (such as carbohydrate metabolism, energy metabolism) in cecum compared to those fed with basal diet. In addition, the fiber-induced increasing of fiber-degrading bacteria promoted the VFAs metabolism, which potentially helped Suhuai pigs to maintain growth rate. However, as TDF reached to 24.11% (as feed basis), the apparent digestibility of fiber decreased and the positive effect on intestine microbiota in caecum were absent. Together, our data suggest that appropriate fiber level could increase the diversity and metabolic capacity of distal gut microbiota to improve the utilization efficiency of fiber resources without altering the growth rate of pigs.

At least 3 days of adaptation are required before indigestible markers (chromium, titanium, and acid insoluble ash) are stabilized in the ileal digesta of 60-kg pigs, but values for amino acid digestibility are affected by the marker

An experiment was conducted to 1) test the hypothesis that a minimum adaptation period to diets used in ileal amino acid (AA) digestibility experiments with pigs is needed and 2) to test the null-hypothesis that ileal digestibility and basal endogenous losses of AA are not affected by the indigestible marker used. Eight ileal-cannulated barrows with an initial BW of 58.1 ± 4.3 kg were randomly allotted to a 2-period crossover design with 2 diets and 4 pigs per diet in each period. A soybean meal-based diet and an N-free diet were prepared. Both diets contained 0.4% chromium oxide, 0.4% titanium dioxide, and 0.4% Celite (a source of acid insoluble ash; AIA). Pigs were provided feed in a daily amount of 3 times the maintenance requirement for metabolizable energy, and 2 equal meals were provided each day. Ileal digesta samples were collected from 0800 to 2000 h on each day during the two 9-d collection periods. There was no period by diet interactions observed. Marker concentrations in ileal digesta were analyzed separately for each day, and the point where the concentration of each marker was stabilized in the digesta was determined using a linear broken-line analysis. For pigs fed the soybean meal diet, the breakpoints for Cr, Ti, and AIA in ileal digesta were 2.70, 2.45, and 3.77 d, respectively. In pigs fed the N-free diet, the breakpoints for Cr, Ti, and AIA in ileal digesta were 2.52, 2.39, and 2.29 d, respectively. Based on the pooled data, the basal endogenous losses of most AA calculated using Cr as an indigestible marker were less (P < 0.05) than the values calculated using Ti, but greater (P < 0.05) compared with values calculated based on AIA. The standardized ileal digestibility of most AA in soybean meal calculated using Cr or Ti as a digestibility marker were greater (P < 0.05) than the digestibility values calculated using AIA. In conclusion, 3 d of adaptation is required before markers are stabilized in the ileal outflow if Cr or Ti is used as an indigestible marker and 4 d of adaptation is required if AIA is the marker. Values for AA digestibility calculated using Cr or Ti as the marker are not different, but greater compared with values calculated using AIA as the marker.

Effects of Collection Durations on the Determination of Energy Values and Nutrient Digestibility of High-Fiber Diets in Growing Pigs by Total Fecal Collection Method

Simple Summary

The total fecal collection method is the gold standard to estimate the energy values and nutrient digestibility of the swine diet. However, there is no standard collection duration for animals that should be sampled in swine research using the total fecal collection method. Thus, this study aimed to investigate the effects of different collection durations (3-day, 5-day, or 7-day) on energy values and nutrient digestibility of high-fiber diets in growing pigs by time-based total fecal collection method. The results showed that the digestible energy (DE), metabolizable energy (ME), and apparent total tract digestibility (ATTD) of gross energy (GE) and most nutrients in diets decreased linearly as the collection duration increased from a 3-day to a 7-day collection. However, there were no differences in the ATTD of GE and nutrient between the 5-day and 7-day collection durations. In addition, the energy values and the ATTD of GE and nutrient of high-fiber ingredients (sugar beet pulp (SBP) or defatted rice bran (DFRB)) were also not affected by the collection durations. Therefore, the results of this research suggest that a 5-day collection duration is adequate to determine the energy values and the ATTD of nutrient in diets containing high-fiber ingredients for growing pigs by time-based total fecal collection method.

Abstract

This study was conducted to evaluate the effect of collection durations on the energy values and nutrient digestibility of high-fiber diets in growing pigs with a time-based total fecal collection method. A total of 24 barrows (body weight (BW): 31.1 ± 1.5 kg) were allotted to a completely randomized design with three diets. Diets included a corn–soybean meal (CSM) basal diet and two additional diets containing 20% sugar beet pulp (SBP) or defatted rice bran (DFRB) by replacing corn, soybean meal, and soybean oil in the CSM diet, respectively. Each diet was fed to eight barrows for a 7-day adaptation period followed by a 7-day total feces and urine collection period. The 7-day collection duration was divided into three collection phases, namely, phase 1 (days 8 to 11), phase 2 (days 11 to 13), and phase 3 (days 13 to 15). Then, similar portions of feces and urine from the different collection phases were composited into three additional samples (days 8 to 11, days 8 to 13, and days 8 to 15, respectively). The results showed that the digestible energy (DE), metabolizable energy (ME), and apparent total tract digestibility (ATTD) of gross energy (GE) and nutrient in experimental diets decreased linearly as the collection durations increased from a 3-day to a 7-day collection (p < 0.05). However, there were no differences in the energy values, GE, and nutrient digestibility of diets and of high-fiber ingredients between the 5-day and 7-day collection durations. In conclusion, this study suggests that a 5-day collection duration is adequate to determine the energy values and nutrient digestibility of high-fiber diets containing SBP or DFRB in growing pigs by the time-based total fecal collection method.

A processive endoglucanase with multi-substrate specificity is characterized from porcine gut microbiota

Cellulases play important roles in the dietary fibre digestion in pigs, and have multiple industrial applications. The porcine intestinal microbiota display a unique feature in rapid cellulose digestion. Herein, we have expressed a cellulase gene, p4818Cel5_2A, which singly encoded a catalytic domain belonging to glycoside hydrolase family 5 subfamily 2, and was previously identified from a metagenomic expression library constructed from porcine gut microbiome after feeding grower pigs with a cellulose-supplemented diet. The activity of purified p4818Cel5_2A was maximal at pH 6.0 and 50 °C and displayed resistance to trypsin digestion. This enzyme exhibited activities towards a wide variety of plant polysaccharides, including cellulosic substrates of avicel and solka-Floc^®, and the hemicelluloses of β-(1 → 4)/(1 → 3)-glucans, xyloglucan, glucomannan and galactomannan. Viscosity, reducing sugar distribution and hydrolysis product analyses further revealed that this enzyme was a processive endo-β-(1 → 4)-glucanase capable of hydrolyzing cellulose into cellobiose and cellotriose as the primary end products. These catalytic features of p4818Cel5_2A were further explored in the context of a three-dimensional homology model. Altogether, results of this study report a microbial processive endoglucanase identified from the porcine gut microbiome, and it may be tailored as an efficient biocatalyst candidate for potential industrial applications.

Energy values of solvent-extracted canola meal and expeller-derived canola meal for broiler chickens and growing pigs determined using the regression method1

The energy values of solvent-extracted canola meal (SECM) and expeller-derived canola meal (EDCM) for broiler chickens and growing pigs were determined in 2 experiments using the regression method. Corn-soybean meal reference diet (RF) and 4 test diets were prepared. The test diets consisted of SECM or EDCM that partly replaced the energy sources in the RF at 100 or 200 g/kg, respectively. The ratios of all energy ingredients were kept similar across all experimental diets. In Exp. 1, a total of 300 birds were fed standard broiler starter diet from days 0 to 19 posthatching. On day 19, 240 birds (776 ± 79.3 g initial BW) were assigned into 5 experimental diets in a randomized complex block design with BW as a blocking factor. Excreta were collected from days 23 to 25 and ileal digesta were collected after birds were euthanized by CO2 asphyxiation on day 26. In Exp. 2, 40 barrows (28.4 ± 1.6 kg initial BW) were allotted to 5 experimental diets according to the randomized complete block design with BW as a blocking factor. After 5-d adaption period, the feces and urine samples were collected for 5 d by total collection method. The ileal digestible energy (IDE), apparent ME (AME), and nitrogen-corrected apparent ME (AMEn) in Exp. 1 and the DE, AME, and AMEn in Exp. 2 for experimental diets and canola meals were determined. In Exp. 1, the inclusion of canola meals to RF linearly decreased the IDE, AME, and AMEn for birds fed SECM diets (P < 0.01) and the AME and AMEn for birds fed EDCM diets (P < 0.01). Furthermore, quadratic effects were also found in the IDE, AME, and AMEn by the inclusion of EDCM to RF (P < 0.05). The IDE were 2,194 and 3,514 kcal/kg DM for SECM and EDCM in broiler chickens, respectively. The respective ME and MEn values were 1,919 and 1,695 kcal/kg DM for SECM and 3,134 and 2,937 kcal/kg DM for EDCM. In Exp. 2, the SECM or EDCM addition to RF linearly decreased the AME and AMEn for pigs (P < 0.01). The DE content was also decreased linearly with the increasing level of SECM (P < 0.01). The DE, ME, and MEn of SECM for pigs were 3,109, 2,891, and 2,655 kcal/kg DM, respectively. The EDCM contained 3,850 kcal of DE, 3,581 kcal of ME, and 3,491 kcal of MEn/kg DM for pigs. In conclusion, the energy values of EDCM are greater than those of SECM for broiler chickens and pigs, and pigs utilize more of the GE in SECM and EDCM than broiler chickens.

Neutral detergent fiber rather than other dietary fiber types as an independent variable increases the accuracy of prediction equation for digestible energy in feeds for growing pigs

Objective

The objectives were to investigate correlations between energy digestibility (digestible energy [DE]:gross energy [GE]) and various fiber types including crude fiber (CF), total dietary fiber (TDF), soluble dietary fiber (SDF), insoluble dietary fiber (IDF), neutral detergent fiber (NDF), and acid detergent fiber (ADF), and to develop prediction equations for estimating DE in feed ingredients and diets for growing pigs.

Methods

A total of 289 data with DE values and chemical composition of feeds from 39 studies were used to develop prediction equations for DE. The equations were validated using values provided by the National Research Council.

Results

The DE values in feed ingredients ranged from 2,011 to 4,590 kcal/kg dry matter (DM) and those in diets ranged from 2,801 to 4,203 kcal/kg DM. In feed ingredients, DE:GE was negatively correlated (p<0.001) with NDF (r = −0.84), IDF (r = −0.83), TDF (r = −0.82), ADF (r = −0.78), and CF (r = −0.72). A best-fitting model for DE (kcal/kg) in feed ingredients was: 1,356 + (0.704 × GE, kcal/kg) − (60.3 × ash, %) − (27.7 × NDF, %) with R² = 0.80 and p<0.001. In diets, DE:GE was negatively correlated (p<0.01) with NDF (r = −0.72), IDF (r = −0.61), TDF (r = −0.52), CF (r = −0.45), and ADF (r = −0.34). A best-fitting model for DE (kcal/kg) in diets was: 1,551 + (0.606 × GE, kcal/kg) − (22.1 × ash, %) − (25.6 × NDF, %) with R² = 0.62 and p<0.001. All variables are expressed as DM basis. The equation developed for DE in feed ingredients had greater accuracy than a published equation for DE.

Conclusion

All fiber types are reasonably good independent variables for predicting DE of swine feeds. The best-fitting model for predicting DE of feeds employed neutral detergent fiber as an independent variable.

Structures and characteristics of carbohydrates in diets fed to pigs: a review

The current paper reviews the content and variation of fiber fractions in feed ingredients commonly used in swine diets. Carbohydrates serve as the main source of energy in diets fed to pigs. Carbohydrates may be classified according to their degree of polymerization: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Digestible carbohydrates include sugars, digestible starch, and glycogen that may be digested by enzymes secreted in the gastrointestinal tract of the pig. Non-digestible carbohydrates, also known as fiber, may be fermented by microbial populations along the gastrointestinal tract to synthesize short-chain fatty acids that may be absorbed and metabolized by the pig. These non-digestible carbohydrates include two disaccharides, oligosaccharides, resistant starch, and non-starch polysaccharides. The concentration and structure of non-digestible carbohydrates in diets fed to pigs depend on the type of feed ingredients that are included in the mixed diet. Cellulose, arabinoxylans, and mixed linked β-(1,3) (1,4)-d-glucans are the main cell wall polysaccharides in cereal grains, but vary in proportion and structure depending on the grain and tissue within the grain. Cell walls of oilseeds, oilseed meals, and pulse crops contain cellulose, pectic polysaccharides, lignin, and xyloglucans. Pulse crops and legumes also contain significant quantities of galacto-oligosaccharides including raffinose, stachyose, and verbascose. Overall, understanding the structure, characteristics and measurable chemical properties of fiber in feed ingredients may result in more accurate diet formulations, resulting in an improvement in the utilization of energy from less expensive high-fiber ingredients and a reduction in reliance on energy from more costly cereal grains.