Growth performance and nutrient digestibility in pigs fed wheat distillers dried grains with solubles-based diets supplemented with a multicarbohydrase enzyme

Alternatives to antibiotics as growth promoters for use in swine production: a review

In the past two decades, an intensive amount of research has been focused on the development of alternatives to antibiotics to maintain swine health and performance. The most widely researched alternatives include probiotics, prebiotics, acidifiers, plant extracts and neutraceuticals such as copper and zinc. Since these additives have been more than adequately covered in previous reviews, the focus of this review will be on less traditional alternatives. The potential of antimicrobial peptides, clay minerals, egg yolk antibodies, essential oils, eucalyptus oil-medium chain fatty acids, rare earth elements and recombinant enzymes are discussed. Based on a thorough review of the literature, it is evident that a long and growing list of compounds exist which have been tested for their ability to replace antibiotics as feed additives in diets fed to swine. Unfortunately, the vast majority of these compounds produce inconsistent results and rarely equal antibiotics in their effectiveness. Therefore, it would appear that research is still needed in this area and that the perfect alternative to antibiotics does not yet exist.

Effects of feeding fiber-fermenting bacteria to pigs on nutrient digestion, fecal output, and plasma energy metabolites

Inclusion of feedstuffs with higher plant cell wall (fiber) content in swine diets has increased in recent years due to greater availability and lower cost, especially coproduct feeds, such as corn distillers dried grains with soluble (DDGS). Limitations of feeding higher fiber diets include increased fecal output, which can exceed manure storage volumes, and decreased energy density, which can decrease growth performance; dietary treatments that ameliorate these limitations would benefit pork producers. Grower pigs (n = 48; 61.1 kg initial BW) were used to establish the effects of supplementation of fiber-fermenting bacteria in a 2 × 4 factorial, consisting of 2 diets (standard and high fiber) and 4 bacterial treatments (A, no bacteria; and B, C, and D bacterial supplements). Increased fiber came from inclusion of soybean hulls (10%) and corn DDGS (20%) in the diet. The 3 bacterial supplements (all Bacteroides strains) were isolated from fecal enrichment cultures and selected for their fiber-fermenting capacity. The high fiber diet increased fecal output, blood cholesterol, and triglyceride concentrations, and digestibility of NDF, ADF, and S; CP digestibility decreased (P ≤ 0.10). The improved fiber digestibility and altered energy status of pigs fed the high fiber diet was primarily due to fermentation of soybean hulls, resulting in increased short-chain fatty acid production and absorption, and decreased dietary starch content. Overall, pigs fed the bacterial treatments had only increased blood cholesterol concentrations (P = 0.10). When individual bacterial treatments were compared, pigs fed Bacteria B had decreased fecal output (P ≤ 0.10) and both blood glucose and cholesterol concentrations were increased (P ≤ 0.10) compared with the other 3 treatments, indicating an improved energy status. Pigs fed Bacteria B increased both CP and ADF (P ≤ 0.10), and tended (P = 0.16) to have increased NDF digestibilities compared with pigs fed no bacteria (Treatment A), whereas pigs fed the other 2 bacterial treatments did not differ from pigs fed Bacteria B for nutrient digestibility. Both had similar fecal outputs to pigs fed no bacteria. This is the first report of reduction in fecal output and increased fiber digestibility with pigs fed live bacteria. Successful application of this bacterial treatment could result in improved pig performance and decreased manure volumes, both of which would improve profitability of producers.

Crucial role of Pro 257 in the thermostability of Bacillus phytases: biochemical and structural investigation

We have previously cloned and characterized the thermostable phytase (PHY US417) from Bacillus subtilis US417. It differs with PhyC from B. subtilis VTTE-68013 by the R257P substitution. PHY US417 was shown to be more thermostable than PhyC. To elucidate the mechanism of how the Pro 257 changes the thermostability of Bacillus phytases, this residue was mutated to Arg and Ala. The experimental results revealed that the thermostability of the P257A mutants and especially P257R was significantly decreased. The P257R and P257A mutants recovered, respectively, 64.4 and 81.5% of the wild-type activity after incubation at 75 °C for 30 min in the presence of 5mM CaCl(2). The P257R mutation also led to a severe reduction in the specific activity and catalytic efficiency of the enzyme. Structural investigation, by molecular modeling of PHY US417 and PhyC focused on the region of the 257 residue, revealed that this residue was present in a surface loop connecting two of the six characteristic β sheets. The P257 residue is presumed to reduce the local thermal flexibility of the loop, thus generating a higher thermostability.

Effect of a carbohydrase mixture on ileal amino acid digestibility in extruded full-fat soybeans fed to finishing pigs

Extrusion technology has been used successfully to improve the nutritive value of full-fat oilseeds via shear force and heat applied during passage through the extruder, exposing more peptide bonds to enzymatic hydrolysis. However, the fibrous portion of the seeds is largely intact after extrusion. Therefore, application of carbohydrase mixtures targeting nonstarch polysaccharides might further improve the nutritive value of extruded full-fat oilseeds. This hypothesis was investigated in a study involving 6 ileal-cannulated barrows (average initial BW = 75.0 kg) fed extruded full-fat, soybean- (FFSB) based diets, without or with a carbohydrase mixture (CM) to determine apparent ileal digestibility (AID) of energy and standardized ileal digestibility (SID) of AA. The CM supplement provided 500, 50, 400, 1200, 450, and 45 units of pectinase, cellulase, mannanase, xylanase, glucanase, and galactanase, respectively, per kilogram of diet. A basal diet was formulated to contain FFSB as the sole source of AA, whereas the CM diet was formulated by supplementing the basal diet with CM. Diets contained titanium dioxide as an indigestible marker. Diets were fed in a 2-period crossover design to give 6 observations per diet. Each experimental period lasted 7 d, including a 5-d adaptation period and 2-d ileal digesta collection period. The SID of N and AA were calculated using published values for ileal endogenous N and AA losses from our laboratory. Enzyme supplementation increased (P < 0.01) AID values of DM (68.7 vs. 65.7%), GE (74.6 vs. 70.5%), and N (64.2 vs. 58.5%). Greater (P < 0.05) AID values were recorded for Leu, Met + Cys, Thr, Cys, Ser, and Tyr in the CM diet compared with the basal diet. Compared with the basal diet, the CM diet had greater SID values for N (73.7 vs. 68.6%; P < 0.01), Met + Cys (59.9 vs. 52.2%; P < 0.05), and Thr (66.3 vs. 61.2%; P < 0.05). The average SID for indispensable and total AA increased by 3.4% and 3.8% units, respectively, after enzyme supplementation. In conclusion, enzyme supplementation increased the nutritive value of extruded FFSB for finishing pigs.

Heterologous expression and optimization using experimental designs allowed highly efficient production of the PHY US417 phytase in Bacillus subtilis 168

To attempt cost-effective production of US417 phytase in Bacillus subtilis, we developed an efficient system for its large-scale production in the generally recognized as safe microorganism B. subtilis 168. Hence, the phy US417 corresponding gene was cloned in the pMSP3535 vector, and for the first time for a plasmid carrying the pAMβ1 replication origin, multimeric forms of the resulting plasmid were used to transform naturally competent B. subtilis 168 cells. Subsequently, a sequential optimization strategy based on Plackett-Burman and Box-Behnken experimental designs was applied to enhance phytase production by the recombinant Bacillus. The maximum phytase activity of 47 U ml^-1 was reached in the presence of 12.5 g l^-1 of yeast extract and 15 g l^-1 of ammonium sulphate with shaking at 300 rpm. This is 73 fold higher than the activity produced by the native US417 strain before optimization. Characterization of the produced recombinant phytase has revealed that the enzyme exhibited improved thermostability compared to the wild type PHY US417 phytase strengthening its potential for application as feed supplement. Together, our findings strongly suggest that the strategy herein developed combining heterologous expression using a cloning vector carrying the pAMβ1 replication origin and experimental designs optimization can be generalized for recombinant proteins production in Bacillus.

Determination of energy and amino acid digestibility in growing pigs fed corn distillers' dried grains with solubles containing different lipid levels

Two experiments were conducted to estimate the digestibility of energy, nitrogen and amino acids (AA) in growing pigs fed diets containing one of five corn distillers' dried grains with solubles (DDGS), including three normal oil DDGS (NO-DDGS) and two low oil DDGS (LO-DDGS) samples. Exp. 1 was conducted to determine the digestible energy (DE) and metabolisable energy (ME) content. Six growing barrows (initial body weight [BW]: 35.1 +/- 2.2 kg) were allotted to a 6 x 6 Latin square design, with six periods and six diets. One diet was a corn soybean meal basal diet and the other five diets were based on corn, soybean meal and 28.8% DDGS. The average DE and ME values for the three NO-DDGS samples were 16.0 and 14.9 MJ/kg dry matter (DM). These values were 9 and 13% greater than the LO-DDGS values of 14.7 and 13.2 MJ/kg DM respectively. Exp. 2 was conducted to determine and compare apparent (AID) and standardised (SID) ileal digestibility for crude protein and AA in the five DDGS samples. Six growing barrows (initial BW, 32.2 +/- 1.9 kg) fitted with a simple T-cannula were allotted to a 6 x 6 Latin square design with six periods and six diets. Five of the diets were based on the five DDGS samples, and the remaining one diet was nitrogen-free diet based on cornstarch and sucrose. Titanium dioxide (0.1%) was used as inert marker. The results of the experiment showed the largest variation among the different samples in AID and SID for lysine (from 41.8 to 65.8% and 53.8 to 73.9% respectively) and threonine (from 54.3 to 73.8% and 65.2 to 79.5% respectively). Also, among the indispensable AA, the SID values for arginine, histidine, threonine and tryptophan observed in LO-DDGS were not different from the values derived from NO-DDGS. In conclusion, LO-DDGS may have decreased energy compared with NO-DDGS because of its lower fat content. However, oil removal during the production of DDGS may not affect amino acid digestibility.

BOARD-INVITED REVIEW: opportunities and challenges in using exogenous enzymes to improve nonruminant animal production

Diets fed to nonruminant animals are composed mainly of feed ingredients of plant origin. A variety of antinutritional factors such as phytin, nonstarch polysaccharides, and protease inhibitors may be present in these feed ingredients, which could limit nutrients that may be utilized by animals fed such diets. The primary nutrient utilization-limiting effect of phytin arises from the binding of 6 phosphate groups, thus making the P unavailable to the animal. The negative charges allow for formation of insoluble phytin-metal complexes with many divalent cations. Furthermore, phytin and protein can form binary complexes through electrostatic links of its charged phosphate groups with either the free amino group on AA on proteins or via formation of ternary complexes of phytin, Ca(2+), and protein. The form and extent of de novo formation of binary and ternary complexes of phytin and protein are likely to be important variables that influence the effectiveness of nutrient hydrolysis in plant-based diets. Nonstarch polysacharides reduce effective energy and nutrient utilization by nonruminant animals because of a lack of the enzymes needed for breaking down the complex cell wall structure that encapsulate other nutrients. Enzymes are used in nonruminant animal production to promote growth and efficiency of nutrient utilization and reduce nutrient excretion. The enzymes used include those that target phytin and nonstarch polysaccharides. Phytase improves growth and enhances P utilization, but positive effects on other nutrients are not always observed. Nonstarch polysaccharide-hydrolyzing enzymes are less consistent in their effects on growth and nutrient utilization, although they show promise and it is imperative to closely match both types and amounts of nonstarch polysaccharides with appropriate enzyme for beneficial effects. When used together with phytase, nonstarch polysaccharide-hydrolyzing enzymes may increase the accessibility of phytase to phytin encapsulated in cell walls. The future of enzymes in nonruminant animal production is promising and will likely include an understanding of the role of enzyme supplementation in promoting health as well as how enzymes may modulate gene functions. This review is an attempt to summarize current thinking in this area, provide some clarity in nomenclature and mechanisms, and suggest opportunities for expanded exploitation of this unique biotechnology.

Effect of phytase and xylanase supplementation or particle size on nutrient digestibility of diets containing distillers dried grains with solubles cofermented from wheat and corn in ileal-cannulated grower pigs

Nutrient digestibility in distillers dried grains with solubles (DDGS) is limited by physical constraints such as particle size and by biochemical limitations such as phytate and fiber or nonstarch polysaccharides (NSP). To determine the separate effects of these limitations on nutrient digestibility, ground DDGS (383 µm) supplemented with phytase (0 or 250 units/kg of feed) and xylanase (0 or 4,000 units/kg of feed) was evaluated in a 2 × 2 factorial arrangement of treatments together with unground DDGS (517 µm) and an N-free diet in a 6 × 6 Latin square. Cofermented wheat and corn DDGS contained 8.6% moisture, 31.0% CP, 1.04% Lys, 8.0% ether extract, 2.0% starch, 40% NDF, and 0.85% P (as-is basis). Diets contained 43.7% DDGS as the sole source of AA; the digesta from pigs fed the N-free diet served to subtract basal endogenous AA losses and as control for energy digestibility. Six ileal-cannulated barrows (37.1 ± 0.8 kg of BW) were fed 6 diets at 2.8 × maintenance for DE in six 9-d periods. Feces and ileal digesta were collected for 2 d each. The apparent ileal digestibility (AID) of GE and apparent total tract digestibility (ATTD) of GE and NDF were 2.3, 0.5, and 5.1%-units greater (P < 0.05) for the ground than unground DDGS diet, respectively. Consequently, the ATTD of GE was 1.3%-units greater (P < 0.05) and the DE content was 0.06 Mcal/kg greater (P < 0.05) for ground than unground DDGS, respectively. Grinding of DDGS did not affect (P > 0.05) the ATTD of crude fiber, ADF, P, and Ca in diets. Grinding of DDGS increased (P < 0.05) the AID of most AA in diets including Lys, Met, and Thr by 6.9, 1.1, and 1.7%-units, respectively. Grinding of DDGS increased (P < 0.05) the SID of Lys by 6.2%-units and SID content of Lys and Thr by 0.06 and 0.02%-units, respectively. Phytase and xylanase did not interact (P > 0.05) to affect nutrient digestibility. Phytase increased (P < 0.001) the ATTD of P by 10.5%-units, but did not affect (P > 0.05) AA digestibility. Xylanase did not affect nutrient digestibility. In conclusion, particle size is an important physical characteristic affecting digestibility of energy and AA, but not P in DDGS. Phytate in DDGS limits digestibility of P, but not energy and AA. The substrate for xylanase in DDGS did not hinder energy and AA digestibility.