Effects of ß-mannanase supplementation on intestinal health and growth of nursery pigs.

Two experiments were conducted using 120 pigs to test the hypothesis that supplementation of ß-mannanase could reduce digesta viscosity, enhance nutrient digestion, and improve intestinal health and growth of nursery pigs. In experiment 1, 48 crossbred barrows were randomly allotted to four treatments with increasing levels of ß-mannanase at 0, 200, 400, and 600 U/kg in feeds. All pigs were euthanized on day 12 to collect jejunal digesta to measure digesta viscosity and ileal digesta to measure apparent ileal digestibility (AID) of dry matter (DM), gross energy (GE), neutral detergent fiber (NDF), and acid detergent fiber (ADF). In experiment 2, 72 nursery pigs were randomly allotted to three treatments with increasing levels of ß-mannanase at 0, 400, and 600 U/kg in feeds. Plasma collected on day 9 was used to measure tumor necrosis factor-α (TNF-α), immunoglobulin G (IgG), malondialdehyde (MDA), and protein carbonyl (PC). All pigs were euthanized on day 10 to collect duodenal and jejunal tissues to evaluate the production of TNF-α, IL-6, and MDA, morphology, crypt cell proliferation, and expression of tight junction proteins in the jejunum. Data were analyzed using the MIXED procedure for polynomial contrasts and the NLMIXED procedure for broken-line analysis of SAS. In experiment 1, ß-mannanase supplementation tended to have quadratic effects on digesta viscosity (P = 0.085) and AID of GE (P = 0.093) in the pigs. In experiment 2, jejunal digesta viscosity of the pigs was reduced (P < 0.05) when ß-mannanase was supplemented at 360 U/kg of feed. ß-Mannanase supplementation linearly reduced (P < 0.05) TNF-α, IgG, MDA, and PC in the duodenum, and TNF-α, IgG, and MDA in the jejunum of the pigs. ß-Mannanase supplementation linearly increased (P < 0.05) villus height to crypt depth ratio and crypt cell proliferation in the jejunum. ß-Mannanase supplementation tended to linearly improve (P = 0.083) expression of zonula occludens-1 in the jejunum. In conclusion, supplementation of ß-mannanase at 360 U/kg reduced the digesta viscosity and up to 600 U/kg positively affected intestinal health and growth of pigs by reducing inflammation and oxidative stress whilst enhancing structure and barrier function in the jejunum.

Nursery pigs face challenges in digesting complex carbohydrates in their feeds, which can negatively affect their growth and intestinal health. In particular, ß-mannans can increase digesta viscosity and hinder nutrient digestion of nursery pigs. ß-Mannanase, an enzyme that breaks down ß-mannans, has been used in nursery feeds to alleviate negative impacts on nutrient utilization and intestinal health of nursery pigs. This study investigated the effects of increasing supplementation levels of ß-mannanase on intestinal health, nutrient utilization, and growth of nursery pigs. The results showed that supplementation of ß-mannanase at 360 U/kg in the feed reduced the digesta viscosity in the jejunum and up to 600 U/kg positively had beneficial effects on the intestinal health and growth of nursery pigs by reducing inflammation and oxidative stress through improving structure and barrier function in the jejunum.

Growth performance, nutrient digestibility, fecal microbial diversity and volatile fatty acid, and blood biochemical indices of suckling donkeys fed diets supplemented with multienzymes.

BACKGROUND: As the foal grows, the amount of breast milk produced by the donkey decreases. In such cases, early supplemental feeding is particularly important to meet the growth needs of the foal. Foals have an incompletely developed gastrointestinal tract with a homogenous microbiota and produce insufficient amounts of digestive enzymes, which limit their ability to digest and utilize forage. Improving the utilization of early supplemental feeds, promoting gastrointestinal tract development, and enriching microbial diversity are the hotspots of rapid growth research in dairy foals. Plant-based feeds usually contain non-starch polysaccharides (NSPs), including cellulose, xylan, mannan, and glucan, which hinder nutrient digestion and absorption. In addition, proteins and starch (both biomolecules) form a composite system mainly through non-covalent interactions. The proteins wrap around the surface of starch granules and act as a physical obstacle, thereby inhibiting water absorption and expansion of starch and decreasing the enzyme's catalytic effect on starch. Glyanase, ß-mannanase, ß-glucanase, cellulase, protease, and amylase added to cereal diets can alleviate the adverse effects of NSPs. The current study determined the effects of adding multienzymes (glyanase, ß-mannanase, ß-glucanase, cellulase, protease, and amylase) to the diet of 2-month-old suckling donkeys on their growth performance, apparent nutrient digestibility, fecal volatile fatty acid (VFA) and pH, fecal bacterial composition, and blood biochemical indices. RESULTS: On day 120 of the trial, fecal samples were collected from the rectum of donkeys for determining bacterial diversity, VFA content, and pH. Moreover, fresh fecal samples were collected from each donkey on days 110 and 115 to determine apparent digestibility. The multienzymes supplementations did not affect growth performance and apparent nutrient digestibility in the donkeys; however, they tended to increase total height gain (P = 0.0544). At the end of the study, the multienzymes supplementations increased (P < 0.05) the Observed species, ACE, Chao1, and Shannon indices by 10.56%, 10.47%, 10.49%, and 5.01%, respectively. The multienzymes supplementations also increased (P < 0.05) the abundance of Firmicutes, Oscillospiraceae, Lachnospiraceae, Christensenellaceae, Christensenellaceae_R-7_group, and Streptococcus in feces, whereas decreased (P = 0.0086) the abundance of Proteobacteria. CONCLUSIONS: Multienzymes supplementations added to a basal diet for suckling donkeys can increase fecal microbial diversity and abundance.

The Effects of Bacillus subtilis QST713 and ß-mannanase on growth performance, intestinal barrier function, and the gut microbiota in weaned piglets.

We investigated the effects of different Bacillus subtilis QST713 doses and a B. subtilis QST713 and ß-mannanase mix on growth performance, intestinal barrier function, and gut microbiota in weaned piglets. In total, 320 healthy piglets were randomly assigned to four groups: 1) control group (basal diet), 2) BS100 group (basal diet plus 100 mg/kg B. subtilis QST713), 3) BS200 group (basal diet plus 200 mg/kg B. subtilis QST713), and 4) a BS100XT group (basal diet plus 100 mg/kg B. subtilis QST713 and 150 mg/kg ß-mannanase). The study duration was 42 d. We showed that feed intake in weaned piglets on days 1 to 21 was increased in group BS100 (P < 0.05), and that the feed conversion ratio in group BS100XT animals decreased throughout the study (P < 0.05). In terms of microbial counts, the BS100XT group showed reduced Escherichia coli and Clostridium perfringens numbers on day 21 (P < 0.05). Moreover, no significant α-diversity differences were observed across all groups during the study (P > 0.05). However, principal coordinates analysis indicated clear separations in bacterial community structures across groups (analysis of similarities: P < 0.05) on days 21 and 42. Additionally, E-cadherin, occludin, and zonula occludens-1 (ZO-1) expression in piglet feces increased (P < 0.05) by adding B. subtilis QST713 and ß-mannanase to diets. Notably, this addition decreased short-chain fatty acid concentrations. In conclusion, B. subtilis QST713 addition or combined B. subtilis QST713 plus ß-mannanase effectively improved growth performance, intestinal barrier function, and microbial balance in weaned piglets.

The use of antibiotics in pig farming raises serious concerns in terms of antibiotic resistance. Consequently, alternative approaches such as probiotics, including Bacillus subtilis, and enzymes such as ß-mannanase, have been proposed to improve pig health and performance. In particular, B. subtilis improves gut microbiota and reduces the prevalence of harmful bacteria such as Escherichia coli and Clostridium perfringens. Similarly, ß-mannanase enhances feed digestibility and improves nutrient use in pigs. Thus, combined B. subtilis and ß-mannanase may provide synergistic effects toward pig performance and gut health. In this study, we showed that adding B. subtilis to a weaned piglet diet improved feed intake, while a B. subtilis and ß-mannanase mix reduced feed conversion ratios in weaned piglets.

Comparative effects of different enzymatic hydrolysates of konjac glucomannan on gut flora and constipation in rats.

This study aimed to compare the effects of different hydrolysates (named GKOS and MKOS) on constipated rats, which were obtained by degradation from konjac glucomannan by ß-glucanase and ß-mannanase, respectively. GKOS and MKOS were characterized and administered by gavage at 100 mg kg-1 to constipated rats. The variation of the gut flora, content of short-chain fatty acids (SCFAs), defecation function, gastrointestinal motility, and intestinal mucus secretion were determined to evaluate their regulatory effects on constipation. The results revealed the more prominent augmentation of species richness in MKOS than with GKOS. They also possessed diverse modulatory effects on different genera, such as Prevotella and Parabacteroides. Unexpectedly, there was no statistical divergence between GKOS and MKOS in defecation parameters, gastrointestinal transit, serum parameters, and mucous secretion. Overall, MKOS and GKOS exhibited differential regulatory function on gut microbiota in vivo, but with nearly consistent therapeutic effects on constipation.

Exogenous ß-mannanase supplementation improved immunological and metabolic responses in lactating dairy cows.

Exogenous enzymes have been used to improve nutrient utilization in several species of livestock, particularly swine and poultry. In addition, improved immunological and metabolic traits have been reported in nonruminants. The objective of this study was to determine the effects of ß-mannanase supplementation on milk yield and composition, and immunological and metabolic responses in lactating Holstein dairy cows. Two weeks after calving, 20 Holstein cows (10 multiparous and 10 primiparous) were blocked by parity and assigned to 1 of 2 diets for 182 d. All cows were housed in the same environment and fed the same basal diet. The basal diet of the treatment group was supplemented with ß-mannanase (CTCBio Inc., Seoul, South Korea) at 0.1% of concentrate dry matter. No differences were detected between the control and enzyme supplement groups in milk yield parameters or milk composition. Supplementation of ß-mannanase enzyme reduced blood haptoglobin levels in supplemented multiparous cows compared with controls. Furthermore, nonesterified fatty acid concentration levels tended to be lower in cows fed ß-mannanase, regardless of parity. Neither immunoglobulin G nor milk somatic cell count was affected by ß-mannanase supplementation, regardless of parity. The number of insemination services tended to be lower in cows fed diets supplemented with ß-mannanase. Results from this study suggest that supplementation of ß-mannanase exogenous enzyme could help to reduce instances of systemic inflammation and decrease fat mobilization in lactating Holstein cows. Multiparous cows are considered susceptible to acute infections and inflammation; thus, the enzyme had a greater effect in multiparous cows.

Effects of mannan level and ß-mannanase supplementation on growth performance, apparent total tract digestibility and blood metabolites of growing pigs.

The exogenous enzymes are less consistent in their effects as their beneficial effects depend upon the types and level non-starch polysaccharides (NSP) present in the diets. Therefore, exogenous enzymes should be selected on the basis of types and amount of the NSP in the pig diets. The objectives of the present experiments were to investigate the effects of dietary level of mannan and ß-mannanase supplementation on growth performance, apparent total tract digestibility (ATTD) of energy and nutrients, and blood metabolites of growing pigs. In Exp. 1, 96 barrows were randomly allotted to four treatments on the basis of BW. There were four replicates in each treatment with six pigs per replicate. The dietary treatments were a corn-soybean meal (SBM)-based control diet and three other diets consisted of the control diet supplemented with 400, 800 or 1600 U of ß-mannanase/kg diet. The final BW, average daily gain (ADG) and blood glucose increased (linear, P0.05) on the concentrations of blood total cholesterol, triacylglycerides and blood urea nitrogen. These results indicate that supplementation of ß-mannanase to low- or high-mannan diets have potential to improve the performance of growing pigs. In addition, palm kernel meal may partially replace corn and SBM without reducing pig performance if ß-mannanase is added to diet.

Purification and Characterization of a Thermostable ß-Mannanase from Bacillus subtilis BE-91: Potential Application in Inflammatory Diseases.

ß-mannanase has shown compelling biological functions because of its regulatory roles in metabolism, inflammation, and oxidation. This study separated and purified the ß-mannanase from Bacillus subtilis BE-91, which is a powerful hemicellulose-degrading bacterium using a "two-step" method comprising ultrafiltration and gel chromatography. The purified ß-mannanase (about 28.2 kDa) showed high specific activity (79, 859.2 IU/mg). The optimum temperature and pH were 65°C and 6.0, respectively. Moreover, the enzyme was highly stable at temperatures up to 70°C and pH 4.5-7.0. The ß-mannanase activity was significantly enhanced in the presence of Mn2+, Cu2+, Zn2+, Ca2+, Mg2+, and Al3+ and strongly inhibited by Ba2+ and Pb2+. Km and Vmax values for locust bean gum were 7.14 mg/mL and 107.5 µmol/min/mL versus 1.749 mg/mL and 33.45 µmol/min/mL for Konjac glucomannan, respectively. Therefore, ß-mannanase purified by this work shows stability at high temperatures and in weakly acidic or neutral environments. Based on such data, the ß-mannanase will have potential applications as a dietary supplement in treatment of inflammatory processes.

Evaluation of Mannosidase and Trypsin Enzymes Effects on Biofilm Production of Pseudomonas aeruginosa Isolated from Burn Wound Infections.

Biofilm is an important virulence factor in Pseudomonas aeruginosa and has a substantial role in antibiotic resistance and chronic burn wound infections. New therapeutic agents against P. aeruginosa, degrading biofilms in burn wounds and improving the efficacy of current antimicrobial agents, are required. In this study, the effects of α-mannosidase, ß-mannosidase and trypsin enzymes on the degradation of P. aeruginosa biofilms and on the reduction of ceftazidime minimum biofilm eliminating concentrations (MBEC) were evaluated. All tested enzymes, destroyed the biofilms and reduced the ceftazidime MBECs. However, only trypsin had no cytotoxic effect on A-431 human epidermoid carcinoma cell lines. In conclusion, since trypsin had better features than mannosidase enzymes, it can be a promising agent in combatting P. aeruginosa burn wound infections.

Effect of the addition of ß-mannanase on the performance, metabolizable energy, amino acid digestibility coefficients, and immune functions of broilers fed different nutritional levels.

Three experiments were conducted to evaluate the effect of ß-mannanase BM: supplementation on the performance, metabolizable energy, amino acid digestibility, and immune function of broilers. A total of 1,600 broilers were randomly distributed in a 4 × 2 factorial arrangement (4 nutritional levels × 0 or 500 g/ton BM), with 10 replicates and 20 broilers per pen. The same design was used in the energy and digestibility experiments with 8 and 6 replicates, respectively, and 6 broilers per pen. The nutritional levels : NL : were formulated to meet the nutritional requirements of broilers : NL1 : ; reductions of 100 kcal metabolizable energy : NL2 : ; 3% of the total amino acids (NL3); and 100 kcal metabolizable energy and 3% total amino acids (NL4) from NL1. The serum immunoglobulin (Ig) concentration was determined in two broilers per pen, and these broilers were slaughtered to determine the relative weight of spleen, thymus, and bursa of Fabricius. Throughout the experiment, the lower nutritional levels reduced (P < 0.05) body weight gain : BWG : and increased (P < 0.05) feed conversion : FCR : for the NL4 treatment. The BM increased (P < 0.05) the BWG values and improved (P < 0.05) the FCR of the broilers. The apparent metabolizable energy corrected for nitrogen balance (AMEn) values were reduced (P < 0.05) for NL2 and NL3. The BM increased (P < 0.05) the AMEn values and reduced (P < 0.05) the excreted nitrogen. NL3 and NL4 reduced (P < 0.05) the true ileal digestibility coefficients (TIDc) of the amino acids cystine and glycine, and BM increased (P < 0.05) the TIDc for all amino acids. The addition of BM reduced (P < 0.05) the relative weights of the spleen and bursa. NL2 increased (P < 0.05) the Ig values, whereas BM reduced (P < 0.05) the serum IgA, IgG, and IgM values of the broilers. This study indicates that using suboptimal nutrient levels leads to losses in production parameters, whereas BM-supplemented diets were effective in improving performance, energy values, and TIDc levels of amino acids and immune response of broilers.

Effects of wheat distillers dried grains with solubles with or without protease and ß-mannanase on the performance of turkey hen poults.

Expansion in bioethanol production has resulted in distillers dried grains with solubles (DDGS) being readily available as a major protein source in the poultry industry. Two experiments were conducted to investigate effects of wheat DDGS (wDDGS) and enzyme on nutrient digestibility and performance of turkey hen poults (7 to 21 d). Two starter diets (0 or 30% wDDGS) were formulated to meet or exceed the nutrient requirements for Hybrid Converter female turkeys. These diets were then mixed in different proportions to obtain 2 additional wDDGS inclusion levels (10 and 20%). In Experiment 1, 0 and 30% wDDGS diets were each subdivided into 3 portions and supplemented with no enzyme (E-), protease (P+; 0.125 g/kg) or ß-mannanase (M+; 0.5 g/kg). A total of 144, 7-day-old poults were randomly distributed in groups of 4 in 6 replicate cages per treatment. There were no significant main effects or interactions on feed intake from 7 to 21 d. However, a positive (P<0.05) effect of 30% wDDGS was shown for weight gain and gain:feed. A significant interaction on nitrogen retention (NR) was found between enzymes and wDDGS level. There were significant main effects and interactions on the AME of the diets. The AME was higher (P<0.05) for 30% compared to 0% wDDGS. Supplementation of P+ decreased (P<0.05) AME for 0% diets as compared to 30% diets and vice versa for M+. In Experiment 2, 7-day-old poults (4 birds per 6 replications per treatment) were fed 4 levels of wDDGS (0, 10, 20, and 30%) with no enzyme. A linear (P<0.01) response was found for gain:feed with 30% wDDGS having a better response. Quadratic (P<0.01) responses were also found for NR and AME; both were highest for 10% wDDGS diets. In summary, no beneficial effects of P+ or M+ were demonstrated in diets containing 30% wDDGS. Wheat DDGS is a valuable energy source and as high as 30% can be incorporated in turkey hen poults (7 to 21 d) diets.

Effect of ß-mannanase on the digestibility of diets with different protein sources in dogs determined by different methodologies.

This experiment aimed at evaluating the effects of including the enzyme, ß-mannanase, in dog (Canis lupus familiaris) diets based on either poultry (Gallus gallus domesticus) by-product meal (PBM) or soybean [Glycine max (L.) Merr.] Meal (SBM). The second objective was to evaluate 3 methods for determining energy and nutrient digestibility values in diets fed to dogs: total fecal collection (TFC) and use of aia or crude fiber (CF) as a marker. Eight dogs were allotted to a replicated latin square (4 by 4) design. There were 2 diets based on PBM as the major protein source and 2 diets based on SBM as the major protein source. Within each protein source, 1 diet contained no ß-mannanase and 1 diet contained 0.01% ß-mannanase. Diets were fed for an adaptation period of 5 d followed by 5 d of TFC. Fecal score (1 = watery feces to 5 = dry, hard pellets), pH, DM, and fecal volume were determined. The apparent total tract digestibility (ATTD) of DM, OM, CP, ether extract (EE), N-free extract (NFE), and GE, and ME content were calculated using the methods of TFC, AIA, and CF. Data were analyzed as a 2 by 2 by 3 split-split-plot design (ß-mannanase, protein source, and digestibility calculation procedure). There were interactions between protein source and ß-mannanase (P < 0.05). Supplementation of ß-mannanase increased ATTD of nutrients and energy and ME (+ 195.3 kcal/kg) and also reduced fecal production in the diet with SBM, but not in the diet that contained PBM. There was an interaction between digestibility calculation procedure and protein source (P < 0.05). The use of AIA overestimated ATTD of the diets containing PBM, but digestibility values estimated based on TFC and CF were not different. Dogs fed diets containing SBM produced more feces with greater moisture content and lower pH compared with dogs fed the PBM diet (P < 0.05). Addition of 0.01% ß-mannanase increased (P < 0.05) the digestibility and ME content of the diets containing SBM, but did not improve (P > 0.05) fecal texture. Results indicated that values for ATTD of energy and nutrients in diets containing sbm are not different if they are calculated based on TFC, AIA, or CF, but use of AIA may result in an overestimation of values for ATTD of energy and nutrients in diets containing PBM.

The effect of a beta-mannanase-based enzyme on growth performance and humoral immune response of broiler chickens fed diets containing graded levels of whole dates.

The use of low-quality whole dates in broilers' diets was evaluated. The apparent metabolizable energy (AMEn) of whole dates and date pits was determined with or without a beta-mannanase-based enzyme (Hemicell--a registered trademark of ChemGen Corp., Gaithersburg, MD. Dried Bacillus lentus fermentation solubles with 158 million units/kg minimum enzyme activity. Recommended usage rate is 0.4 g kg(-1) of feed. ChemGen Corp., Gaithersburg, MD, USA). A 3 x 2 factorial arrangement consisting of whole dates (0, 175, and 350 g kg(-1)) and enzyme (0 or 0.4 g kg(-1)) was performed to assess the effect of the enzyme on the nutritive value of whole dates (experiment 2) in broilers' diet. Enzyme improved AMEn contents of the whole dates and date pits. The diets containing 175 or 350 g kg(-1) whole dates produced body weight gain (BWG) similar to those obtained without dates. Enzyme improved BWG and feed conversion ratio throughout the experimental period. In conclusion, whole dates can be included in broiler diets at levels up to 350 g kg(-1). In addition, beta-mannanase supplementation would have beneficial effects on performance and immunity in birds fed on corn-soy or corn-soy-whole dates diets.

[Study on release mechanism of berberine hydrochloride-loaded carboxymethyl konjac glucomannan pellets for colonic delivery].

OBJECTIVE: To study release mechanism of berberine hydrochloride (BH) from carboxymethyl konjac glucomannan pellets for colonic delivery. METHOD: The pellets were prepared by ionotropic gelation technique. The effects of the kinds of enzyme and enzyme concentration of dissolution media on the release of BH and the erosion properties of the pellets were studied. RESULT: Compared with the dissolution media without enzymes, the release of BH and the erosion of the pellets were increased obviously in the media with rat cecal and colonic content or beta-mannase, the degradation of the carrier material of pellets by enzymes was the main factor which result in the erosion of the pellets. With the increased of beta-mannase concentration, the release of BH and the erosion of the pellets increased, the amount relationships of the release of BH and the erosion of the pellets were approximately 1:1. The release of BH exhibit Peppas equation, the n value was more than 1. CONCLUSION: The release mechanism of BH from the pellets was enzymatic erosion-controlled, which indicates the potential of the pellets to serve as a colon-specific drug delivery system.

Effect of beta-mannanase (Hemicell) on growth performance and immunity of broilers.

Two hundred four broilers (1-d-old) were randomly allocated to 4 treatments, each of which had 3 pens of 17 chicks per pen and were used to investigate the effects of beta-mannanase (Hemicell) on growth performance and immunity. The chicks received the same basal diet based on corn-soybean meal and Hemicell was added to the basal diet at 0, 0.025, 0.05, and 0.075%, respectively. Weight of each replicate was determined at wk 0, 3, and 6 of age. There were no significant differences in average feed intake in the 0- to 3-wk and 0- to 6-wk periods, and no differences in serum IgA, or IgG concentrations. However, the addition of Hemicell significantly increased (P < 0.05) weight gain in the 4- to 6-wk and 0- to 6-wk periods. Feed conversion for the 0.025 and 0.05% groups was significantly greater (P < 0.05) than for the control group in the 4- to 6-wk and 0- to 6-wk periods. Hemicell significantly increased (P < 0.05) the serum IgM concentration in 3- and 6-wk-old broilers. Proliferation of T lymphocytes in 6-wk-old broilers for the 0.05% group was also improved (P < 0.05) significantly. The results indicate that Hemicell may improve growth performance and immunity of broilers.

A dose-response study with the feed enzyme beta-mannanase in broilers provided with corn-soybean meal based diets in the absence of antibiotic growth promoters.

An experiment was designed to assess the effects of graded levels of beta-mannanase on performance and body weight uniformity of male broilers provided with diets based on corn and soybean meal and devoid of antibiotic growth promoters or coccidiostats. Four dietary treatments contained 0, 50, 80, and 110 MU of Hemicell/ ton (where 1 MU = 10(6) enzyme activity units, 100 MU/ton is manufacturer's recommendation). Each treatment contained 15 pens with 40 birds/pen. Individual bird weights were determined on d 0, 21, and 42. From 21 to 42 d of age, feed intake for the 80 MU/ton treatment was significantly greater than the 50 MU/ton treatment. beta-Mannanase inclusion at 80 or 110 MU/ton induced improvements (P < 0.05) in weight gain (3.9 to 4.8%) and feed efficiency (3.5 to 3.8%) over the control, whereas inclusion of 50 MU/ton resulted in no significant benefit. There were no significant differences between 80 or 110 MU/ton. The experiment demonstrated that dietary inclusion of beta-mannanase at approximately 50 MU/ton is not sufficient for maximum response. Inclusion at 80 MU/ ton improved broiler gains and feed conversion and increasing to 110 MU/ton resulted in no significant additional response.