Ileal digestibility and endogenous flow of minerals and amino acids: responses to dietary phytic acid in piglets

Still no direct evidence of postprandial hyperkalemia with plant foods

Although St-Jules et al have presented the case for postprandial hyperkalemia with food, including plant foods, there (still) is little to no direct evidence supporting the occurrence of postprandial hyperkalemia, mostly due to a lack of studies performed exclusively using food. Food is different than salts or supplements, and it is likely that a banana behaves differently than potassium salts. A growing body of evidence supports the use of plant foods without causing hyperkalemia in patients with kidney disease. Currently, only 1 study has reported on the postprandial effects of hyperkalemia. In this study, there was a substantial reduction in the instances of postprandial hyperkalemia in participants consuming a diet that included more plant foods and more fiber. At the time of this writing, there is no evidence to support risk or safety of certain foods with regard to postprandial hyperkalemia, and additional research is warranted.

Basis for the diversity and extent in loss of digestible nutrients created by dietary phytin: Emphasis on fowl and swine

Phytin is the Ca2+-Mg2+-K+ salt of phytic acid that is created and deposited in the aleurone layer and/or germ of grains and legumes. Its high presence in feedstuffs for fowl and swine diets results in it being a universal and significant impediment to optimum performance. Phytin impairs gastrointestinal recovery of a wide array of nutrients, the effect varying with the nutrient concerned. On exposure to low pH during gastric digestion, phytin dissociates into phytic acid and solubilized Ca2+. Even at low gastric pH, phytic acid is negatively charged which forms the basis of its anti-nutritive behavior. Pepsinogen has extensive basic amino acids on its activation peptide that are presented as cations at low pH which are targeted by pepsin for activation. Partially crystalized Ca2+ near the enzyme's active site further stabilizes its newly formed structure. Thus, phytic acid appears to interfere with gastric digestion by several mechanisms; interfering with pepsinogen activation by binding to the polypeptide's basic amino acids; coordinating free Ca2+, destabilizing pepsin; binding some dietary proteins directly, further compromising gastric proteolysis. Upon digesta attaining neutrality in the duodenum, Ca2+ and other cations re-bind with accessible anions, phytic acid being a significant contender. Phytate not only binds free cations but can also strip them from enzymes (e.g. Ca2+, Zn2+) which reduces their structural resistance to autolysis and ability as co-factors (e.g. Zn2+) to increase enzyme activity. Goblet cells initially employ Ca2+ as an electronic shield between mucin layers enabling granule formation and cell storage. After mucin granule release, Ca2+ is progressively displaced by Na+ to free the viscous mucins enabling its translocation. Mucin entangles with the glycocalyx of adjacent enterocytes thereby constructing the unstirred water layer (USWL). Excessive removal of Ca2+ from mucin by phytic acid increases its fluidity facilitating its loss from the USWL with its associated Na+. This partly explains increased mucin and Na+ losses noted with high phytate diets. This review suggests that phytic acid binding of Ca2+ and less so Zn2+ is the basis for the diversity in nutrient losses encountered and that such losses are in proportion to dietary phytate content.

Apparent digestibility of energy and nutrients and efficiency of microbial phytase is influenced by body weight of pigs

An experiment was conducted to test the hypothesis that regardless of pig body weight (BW), increasing dietary phytase results in increased phytate degradation and improved digestibility of minerals, amino acids (AA), and gross energy (GE). Eighteen pigs were equipped with a T-cannula in the distal ileum and allotted to a triplicated 6 × 3 Youden square design with six diets and three collection periods of 7 d, for a total of nine replicate pigs per diet. This design was repeated four times to simulate four production phases, and there was a 7-d resting period before each collection phase started (BW at start of collections: 29.3, 53.6, 85.1, and 114.4 kg for phases 1, 2, 3, and 4, respectively). Six corn-soybean meal diets were formulated by including 0, 250, 500, 1,000, 2,000, or 4,000 phytase units/kg feed (FTU). The six diets were used throughout the experiment. Samples of feces and ileal digesta were collected in each period. Results indicated that regardless of pig BW, increasing inclusion of phytase increased (quadratic; P < 0.05) apparent ileal digestibility (AID) of crude protein (CP) and most AA, increased apparent total tract digestibility (ATTD) of Ca, P, K, Mg (linear and quadratic; P < 0.05), and Na (linear; P < 0.05), but decreased (linear and quadratic; P < 0.05) AID and ATTD of GE. In all phases, ileal concentrations of inositol phosphate (IP) 6, IP5, IP4, and IP3 decreased (linear and quadratic; P < 0.05), whereas ileal inositol increased (linear and quadratic; P < 0.05) with increasing dietary phytase. However, as pig BW increased, AID of GE, CP, and AA increased (linear, P < 0.05), and the AID of a few AA (Met, Phe, Thr, Trp, Ala, Asp, Gly, and Ser) also increased quadratically (P < 0.05). The ATTD of GE, K, and Mg increased (linear and quadratic; P < 0.05), but ATTD of Ca and Na (linear; P < 0.05) and of P (linear and quadratic; P < 0.05) decreased as pig BW increased. Ileal IP6 and IP3 (linear and quadratic; P < 0.05) and ileal IP5 and IP4 (linear; P < 0.05) increased, whereas ileal inositol decreased (linear; P < 0.05) as pig BW increased. In conclusion, regardless of pig BW, increasing dietary phytase increased phytate degradation and inositol release in the small intestine, and consequently increased mineral and AA digestibility. Older pigs have reduced Ca, P, and Na digestibility, but increased K, Mg, AA, and GE digestibility compared with younger pigs. The efficiency of dietary phytase to degrade phytate appears to decrease as pigs get older.

Effect of Microbial Phytase on Ileal Digestibility of Minerals, Plasma and Urine Metabolites, and Bone Mineral Concentrations in Growing-Finishing Pigs

The study was conducted to evaluate the effects of added phytase in the diet of pigs on utilization of minerals and to determine the essential levels of this supplement in compound feed. An additional aim of the study was a critical assessment of current recommendations regarding the level of phosphorus in the diet of pigs, taking into account the use of phytase. A total of 432 pigs were allotted to six dietary treatments, with nine replicate pens per treatment according to body weight (BW) and sex. The treatments included a negative control (NC) with reduced content of digestible phosphorus; the NC diet supplemented with 6-phytase produced by a genetically modified strain of Aspergillus oryzae in the amount of 250 (NC + 250), 500 (NC + 500), 1000 (NC + 1000), or 1500 (NC + 1500) FTU/kg of feed; and a positive control (PC) diet formulated to meet NCR nutrient requirements for pigs. The results showed that, the higher the phytase activity in the diet (NC+), the lower the concentration of P, Ca, and Mg in the chyme (p < 0.05). Pigs fed the PC and NC+ diets had higher plasma levels of P and Ca than group NC in both fattening periods (p < 0.05). The content of phosphorus in the femur of pigs increased with the level of phytase added to the diet (p < 0.05). The content of Cu and Zn in the femur of pigs in the growing period was higher in groups NC + 500 and NC + 1000 than in the remaining experimental groups (p < 0.001). The content of P and Ca in the feces was higher in pigs fed the PC diet in comparison to the remaining experimental groups in both fattening periods (p < 0.001). There was a decrease in the content of P, Ca, and Mg in the excreta of pigs fed NC+ diets in both fattening periods (p < 0.05). A linear decrease in excretion of zinc in the feces was noted in the case of high levels of phytase, i.e., 1000 and 1500 FTU (p < 0.001). Increasing the level of phytase decreased the Cu (p < 0.001) content in the urine of growing−finishing pigs. In conclusion, the analysis of the effects of the use of phytase in a range of 0−1500 FTU/kg in low-phosphorus diets for fattening pigs indicates that 1000 FTU is the most effective level of phytase for increasing utilization of minerals and reducing excretion of elements into the environment.

Contribution of purified soybean trypsin inhibitor and exogenous protease to endogenous amino acid losses and mineral digestibility

The primary objective of the current study was to evaluate the impact of trypsin inhibitor (TI) and exogenous protease supplementation on endogenous loss of amino acids (AA) in broiler chickens. A total of 384 Cobb-500 broiler chicks were allocated to 4 nitrogen-free diets, each with 8 replicate cages and 12 birds per replicate. The diets were arranged as a 2 × 2 factorial with factors being dietary TI (0 or 8,000 TIU/g) and exogenous protease (0 or 15,000 PROT/kg). Desired dietary TI concentration was achieved by addition of commercially available, purified soybean TI. There was no effect of TI or exogenous protease or their interaction on growth performance of birds. However, the endogenous loss of nitrogen (N) and all AA increased (P < 0.05) due to dietary TI concentration except for Cys. The increase in endogenous AA due to TI ranged from 17% for Thr to 52.2% for Trp. Exogenous protease had no effect on endogenous loss of N and all AA. There was no effect of TI or exogenous protease or their interaction on the AID of P, however AID of Ca, Fe, Mg, Mn, and Cu was reduced (P < 0.05) due to dietary TI. The AID of Cu (P < 0.01) and K (P < 0.05) improved with exogenous protease supplementation. Significant interactions (P < 0.05) between exogenous protease and TI existed for Zn, Mg, Cu, and Na. The concentration (g/kg DM intake) of crude mucin and sialic acid increased (P < 0.05) with increased dietary TI. Decreased trypsin (P < 0.001) and increased chymotrypsin (P < 0.001) activity in the pancreas were observed as a result of exogenous protease supplementation. In conclusion, the current study showed that TI increases the endogenous loss of AA and reduced the digestibility of minerals in broiler chickens. Furthermore, exogenous protease did not affect endogenous AA flow, irrespective of added purified dietary TI.

Comparative Effects of Compound Enzyme and Antibiotics on Growth Performance, Nutrient Digestibility, Blood Biochemical Index, and Intestinal Health in Weaned Pigs

This experiment aims to explore the effects of compound enzyme preparation substituting chlortetracycline on growth performance, serum immune markers, and antioxidant capacity and intestinal health in weaned piglets. A total of twenty-four 28-day-old “Duroc × Landrace × Yorkshire” weaned piglets with an average initial weight of 7.25 ± 0.25 kg were randomly divided into three groups according to their body weight, with eight replicates in each group and one pig in each replicate. The three dietary treatments were basal diet (CON), basal diet + 1,000 mg/kg compound enzyme preparation (cellulase 4,000 IU/g, α-amylase 1,000 IU/g, β-glucanase 150 IU/g, and neutral protease 3,000 IU/g, CE), and basal diet + 75 mg/kg chlortetracycline (CTC). The animal experiment lasted for 28 days and was divided into two stages: the early stage (0–14 days) and the late stage (15–28 days). The results showed that (1) compared with the CON, the CE and CTC significantly increased the ADG of weaned piglets during the early and whole period of experiment (p < 0.05), decreased the F:G in the whole experiment period (p < 0.05), and diarrhea rate in the early stage (p < 0.01). (2) Compared with the CON, the apparent total tract digestibility of ADF and NDF was significantly increased in pigs fed the CE diet in the early and late stages of experiment (p < 0.05) with no significant difference compared with the CTC. (3) Compared with the CON, the concentrations of serum IgA and SOD in weaned piglets were significantly increased in the CE group in the early stage of the experiment (p < 0.05). (4) Compared with the CON group, the acetic acid, propionic acid, and total VFA contents in cecum and colon segments were elevated in the CE group (p < 0.05) with no significant difference compared with the CTC. (5) Compared with the CON group, the villus height of duodenum and jejunum and the ratio of villus height to recess depth of ileum were increased in the CE and CTC group (p < 0.05). (6) Compared with the CON group, the abundance of Lactobacillus significantly increased (p < 0.01) while the abundance of Escherichia coli decreased in the CE group and CTC group (p < 0.01). In conclusion, CE preparation instead of CTC can significantly improve the nutrient digestibility, the immunity, antioxidant capacity, and intestinal health of pigs, which may contribute to the improved growth performance of piglets.

The effect of dietary phosphorus load and food matrix on postprandial serum phosphate in hemodialysis patients: a pilot study

Background: Potential dietary strategies for controlling hyperphosphataemia include the use of protein sources with lower phosphorus bioavailability such as pulses and nuts, focus on phosphorus to protein ratios and the avoidance of all phosphate additives. Methods: We conducted a controlled crossover feeding study in 8 haemodialysis (HD) patients to investigate the acute postprandial effect of a modified versus standard low phosphorus diet for one day on serum phosphate, potassium and intact parathyroid levels in prevalent HD patients. Each participant consumed the modified diet on one day and the standard diet on a second day one week apart. The modified diet included beef and less dairy, with a lower phosphorus to protein ratio, as well as plant-based protein, whole grains, pulses and nuts containing phytates which reduces phosphorus bioavailability. Both diets were tailored for each participant to provide 1.1g protein/kg ideal body weight. Participants provided fasting bloods before breakfast, a pre-prandial sample before the lunch time main meal and samples at one-hour intervals for the four hours after the lunch time main meal, for analysis of phosphate, potassium and intact parathyroid hormone (iPTH). Results: At four hours post the lunch time main meal on each study day, individuals on the modified diet had serum phosphate readings 0.30 mmol/l lower than when on the standard diet (p-value = 0.015, 95% confidence interval [CI] -0.57, -0.04). The corresponding change in serum potassium at four hours was a decrease of 0.675 mmol/l (p-value = 0.011, CI -1.25, -0.10). Conclusions: Decreases in both serum phosphate and serum potassium readings on a modified low phosphorus diet encourage further larger studies to explore the possibility of greater food choice and healthier plant-based diets in HD patients.  ClinicalTrials.gov registration: NCT04845724 (15/04/2021).

Influence of a novel consensus bacterial 6-phytase variant on mineral digestibility and bone ash in young growing pigs fed diets with different concentrations of phytate-bound phosphorus

A 20-d experiment was conducted to test the hypothesis that phytase increases nutrient digestibility, bone ash, and growth performance of pigs fed diets containing 0.23%, 0.29%, or 0.35% phytate-bound P. Within each level of phytate, five diets were formulated to contain 0, 500, 1,000, 2,000, or 4,000 phytase units (FTU)/kg of a novel phytase (PhyG). Three reference diets were formulated by adding a commercial Buttiauxella phytase (PhyB) at 1,000 FTU/kg to diets containing 0.23%, 0.29%, or 0.35% phytate-bound P. A randomized complete block design with 144 individually housed pigs (12.70 ± 4.01 kg), 18 diets, and 8 replicate pigs per diet was used. Pigs were adapted to diets for 15 d followed by 4 d of fecal collection. Femurs were collected on the last day of the experiment. Results indicated that diets containing 0.35% phytate-bound P had reduced (P < 0.01) digestibility of Ca, P, Mg, and K compared with diets containing less phytate-bound P. Due to increased concentration of total P in diets with high phytate, apparent total tract digestible P and bone ash were increased by PhyG to a greater extent in diets with 0.29% or 0.35% phytate-bound P than in diets with 0.23% phytate-bound P (interaction, P < 0.05). At 1,000 FTU/kg, PhyG increased P digestibility and bone P more (P < 0.05) than PhyB. The PhyG increased (P < 0.01) pig growth performance, and pigs fed diets containing 0.35% or 0.29% phytate-bound P performed better (P < 0.01) than pigs fed the 0.23% phytate-bound P diets. In conclusion, the novel phytase (i.e., PhyG) is effective in increasing bone ash, mineral digestibility, and growth performance of pigs regardless of dietary phytate level.

Effects of Exogenous 6-Phytase (EC 3.1.3.26) Supplementation on Performance, Calcium and Phosphorous Digestibility, and Bone Mineralisation and Density in Weaned Piglets

Phosphorus (P) is an essential mineral for growing piglets, which is poorly accessible in vegetable feedstuffs as it is stored as phytates. Thus, phytase supplementation is essential to increase P availability. Two experiments were conducted to evaluate a novel 6-phytase (EC 3.1.3.26) in weaned pigs fed low-P diets. In each experiment, one hundred and twenty piglets were fed a positive control (PC; adequate in Ca and P), a negative control (NC; limiting in Ca and P), or NC supplemented with 125, 250, or 500 FTU/kg of phytase (NC125, NC250, and NC500, respectively). P content was lower in diets of Experiment 1 than diets of Experiment 2. In Experiment 1, piglets offered PC or phytase diets had higher growth and efficiency compared with NC diets. In Experiment 2, similar effects were obtained, but the effects were less significant. In both experiments, P and Ca ATTD and bone density were significantly increased with phytase supplementation. Moreover, PC and NC500 had higher P concentrations and lower alkaline phosphatase activity in plasma than NC. To conclude, supplementation with the new 6-phytase at doses up to 500 FTU/kg enhanced P utilization, growth performance, and bone density in piglets fed P-limiting diets.

Growth performance, nutrient digestibility, and fecal microbial composition of weaned pigs fed multi-enzyme supplemented diets

A study determined the effects of supplementing corn-based diets for weaned pigs with multi-enzymes on growth performance, apparent total tract digestibility (ATTD) of nutrients, fecal score, and fecal microbial composition. A total of 132 pigs (initial body weight = 7.23 kg) that had been weaned at 21 d of age and fed a drug-free nursery diet for 7 d were housed in 33 pens of 4 barrows or gilts, blocked by body weight and gender, and fed 3 experimental diets at 11 pens per diet. The diets were corn-based diet without or with multi-enzyme A or B. Multi-enzyme A supplied 4,000 U of xylanase, 150 U of β-glucanase, 3,500 U of protease, and 1,500 U of amylase per kilogram of diet. Multi-enzyme B was the same as multi-enzyme A except that it supplied amylase at 150 U/kg, and that its source of amylase was different from that of multi-enzyme A. All diets contained phytase at 1,000 U/kg. The diets were fed for 35 d in 2 phases; phase 1 for the first 14 d and phase 2 for the last 21 d of the trial. Fecal score was determined daily during the first 7 d of the trial. Fecal samples were collected from rectum of 1 pig per pen on days 2, 7, 14, and 35 of the trial for determining bacterial composition. Also, fresh fecal samples were collected from each pen on days 41 and 42 to determine ATTD of nutrients. Multi-enzyme B increased (P < 0.05) average daily gain (ADG) for phases 1 and 2. For the overall study period, multi-enzyme B increased (P < 0.05) ADG from 262 to 313 g, and average daily feed intake (ADFI) from 419 to 504 g. Multi-enzyme A increased (P < 0.05) overall ADG from 262 to 290 g, but did not affect ADFI. Multi-enzyme A or B did not affect ATTD of gross energy, but increased (P < 0.05) the ATTD of ether extract from 30% to 36% or 37%, respectively. Multi-enzyme A did not affect fecal score; however, multi-enzyme B tended to decrease (P = 0.09) fecal score, implying that it tended to decrease diarrhea. Firmicutes were the most abundant phylum of fecal bacteria (its relative abundance ranged from 58% to 72%). Bacteroidetes and Actinobacteria were the 2nd and 3rd most abundant phyla of fecal bacteria. Neither multi-enzyme affected fecal bacterial composition. In conclusion, the addition of multi-enzyme A or B to phytase-supplemented corn-based diet for weaned pigs can improve their growth performance and fat digestibility. However, multi-enzyme B was more effective than multi-enzyme A in terms of improving the growth performance of weaned pigs fed corn-based diet.

Progress in ileal endogenous amino acid flow research in poultry

The progress in our understanding of the endogenous protein concept over the past century is reviewed. Non-dietary proteins found in the digesta at the terminal ileum of poultry, known as endogenous protein loss, are comprised of digestive secretions, mucus and sloughed gut epithelial cells. The measurement of this loss is of fundamental importance because it is an indicator of gut metabolism and is essential to adjust apparent estimates of ileal amino acid digestibility. The ileal endogenous amino acid losses comprise of two components, namely basal and specific losses. The basal losses are fixed and associated with feed dry matter intake, whereas the specific losses are variable and induced by the presence of dietary components such as fibre and anti-nutrients. Currently there is no methodology available to directly measure the specific endogenous losses and these losses are calculated by determining the basal and total (basal plus specific) losses and, then subtracting the basal losses from total losses. The seminal features, specific applications and shortcomings of available methodologies are briefly outlined as well as the practical challenges faced in using the published endogenous amino acid loss values for true digestibility corrections. The relevance of taurine as a component of endogenous protein flow in poultry is identified for the first time.

Effect of phytase on nutrient digestibility and expression of intestinal tight junction and nutrient transporter genes in pigs

The study was conducted to determine the effects of high levels of phytase on growth performance, nutrient digestibility, phytate breakdown, and expression of mucosal tight junction and nutrient transporter genes in weanling pigs. A total of 128 barrows were penned in groups of four and used in a randomized completely block design and assigned to four treatments for a 28-d study. A two-phase feeding was implemented (phase 1: day 1 to 14; phase 2: day 15 to 28). The diets differed in dietary calcium (Ca) and phosphorus (P) levels (positive control [PC]: 8.1 to 7.1 g/kg Ca and 6.5 to 6.8 g/kg P; negative control [NC]: 6.6 to 5.5 g/kg Ca and 5.6 to 5.3 g/kg P) from phase 1 to phase 2, respectively. NC diets were supplemented with phytase at 0 (NC), 1,500 (NC + 1,500), or 3,000 (NC + 3,000) phytase units (FTU)/kg. Blood was collected after fasting (day 27) or feeding (day 28) for the measurement of plasma inositol concentrations. On day 28, two pigs per pen were euthanized. Duodenal-jejunal and ileal digesta samples and feces were collected to determine inositol phosphates (InsP3-6) concentrations. Phytase supplementation increased the body weight on days 14 and 28 (P < 0.05). Average daily gain and feed efficiency compared with NC were increased by phytase with the majority of its effect in phase 1 (P < 0.05). The apparent ileal digestibility and apparent total tract digestibility of P were increased in piglets fed phytase-supplemented diets (P < 0.01) compared with NC piglets. Disappearance of InsP6 and total InsP3-6 up to the duodenum-jejunum, ileum, and in feces was increased by both phytase application rates (P < 0.01). Plasma concentrations of myo-inositol were higher (P < 0.001) in the phytase-supplemented diets than PC and NC diets, irrespective of whether pigs were fed or fasted. Expression of claudin 3 was higher in pigs fed both phytase-supplemented diets in the duodenum and jejunum compared with PC and NC. Mucin 2 expression was lower in the ileum of NC + 3,000 fed piglets compared with PC (P < 0.05), whereas expression of GLUT2 (solute carrier family 2-facilitated glucose transporter member 2) was increased (P < 0.05) by the NC + 3,000 treatment in all sections. In summary, high phytase supplementation increased the growth performance of nursery pigs. The increased expression of GLUT2 by phytase may indicate an upregulation of glucose absorption from the intestine by phytase.

Ileal digestibility and endogenous protein losses of milk replacers based on whey proteins alone or with an enzyme-treated soybean meal in young dairy calves

Our objective was to measure and compare apparent ileal digestibility, standard ileal digestibility, and true ileal digestibility of crude protein (CP) and amino acids (AA) in milk replacers (MR) containing all milk proteins (WPC) or with 50% of the CP provided by an enzyme-treated soybean meal (ESBM). A T-cannula was placed in the ileum of 9 Holstein calves (8 males and 1 freemartin female) at approximately 15 d of age. After 2 wk postsurgery, calves were randomly assigned to a 3 × 3 replicated Latin square with 5-d periods. Calves were fed twice daily at a rate of 2% (dry matter) of body weight (1.25 kg/d on average), reconstituted to 15% solids, and adjusted weekly. No starter was offered to minimize rumen development. Digesta samples were collected continuously during 12 h on d 4 and 5 of each period. Basal endogenous losses of AA and CP were estimated by feeding an N-free MR to each calf during 1 period. Total endogenous losses (basal + specific; ENDtotal) were estimated by multivariate regression of the chi-squared distances between digesta and reference protein AA profiles. Ileal digesta pH with the ESBM diet was lower than that with the WPC diet. According to the piecewise nonlinear model of pH fluctuation, digesta pH during ESBM decreased more slowly after feeding and reached its nadir later than with the WPC diet. Diet did not affect average daily gain, but calves on the ESBM diet showed a bigger increment of withers height and lower mean fecal scores. The basal endogenous losses of AA and CP were 13.9 ± 1.1 and 22.4 ± 1.1 g/kg of dry matter intake, respectively. The estimated ENDtotal of AA and CP was higher with ESBM than with WPC. Accordingly, apparent ileal digestibility and standard ileal digestibility of most AA, CP, and total AA were lower or tended to be lower with ESBM. However, true ileal digestibility did not differ between diets for CP and all AA except Ala and Ile, which were greater with WPC, and Arg, which tended to be greater with ESBM. In agreement with the estimated differences in ENDtotal, we found that flows of digesta DNA and crude mucin were greater with ESBM. Substitution of 50% of the protein from whey with enzymatically treated soybean meal did not affect major nutrient digestibility or calf growth and even improved fecal consistency. Adjusting digestibilities of CP and AA in MR by endogenous protein losses is crucial when comparing bioavailability of alternative proteins and milk proteins.

Effect of Phytase Derived from the E. coli AppA Gene on Weaned Piglet Performance, Apparent Total Tract Digestibility and Bone Mineralization

Simple Summary

Plants store phosphorus mainly in a form that is indigestible to pigs: phytate. Unabsorbed minerals excreted into the environment are considered to be environmental pollutants. Our study focuses on the effects of novel types of phytase enzymes in diets deficient in external phosphorus on the performance, digestibility of crude protein, dry matter and minerals, and bone mineralization of weaned piglets. Using novel phytases, we noted a positive impact on body weight gain, feed conversion ratio, the digestibility of phosphorus and calcium, and phosphorus and calcium content in bones. There was no significant improvement in the content of dry matter or digestion of crude protein. This study reveals novel phytases to be useful additives for weaned piglet diets because of their superior performance results and phosphorus absorption.

Abstract

The objective of this study was to assess the effect of novel appAT1 and appAT2 phytase inclusion at 250 phytase units (FTU)/kg on weaned piglet performance, the apparent total tract digestibility of P and Ca, and bone mineralization. Piglets (48 males) were randomly divided into four treatment groups: a positive control (PC), with recommended levels of phosphorus (P) and calcium (Ca), a negative control (NC) deficient in P and Ca, and two experimental groups with NC diets supplemented with phytase derived from the appA gene of Escherichia coli. Diets fed in a mashed form were divided into prestarter (0–21 days) and starter (22–42 days) periods. During the whole period of the study, the experimental diets improved (p < 0.05) the body weight gain (BWG) and feed conversion ratio (FCR) compared to the NC diet. The apparent total tract digestibility (ATTD) of the dry matter and crude protein was not significantly different among the diets. Phytase-supplemented diets improved the ATTD of P (p < 0.05) and the ATTD of Ca (p < 0.05). Bone ash content in the third metacarpal and P and Ca content were improved among the phytase supplemented diets compared to the NC diet.

Effect of phytase on intestinal phytate breakdown, plasma inositol concentrations, and glucose transporter type 4 abundance in muscle membranes of weanling pigs1

The objective of this present study was to determine the effects of phytase dosing on growth performance, mineral digestibility, phytate breakdown, and the level of glucose transporter type 4 (GLUT4) in muscle plasma membranes of weanling pigs. A total of 160 barrows were used in a randomized completely block design and assigned to 4 treatments for a 7-wk study. Depending on the feeding phase, diets differed in dietary calcium (Ca) and phosphorus (P) levels (positive control [PC]: 8 to 6.8g/kg Ca; 7.3 to 6.3 g/kg P; negative control [NC]: 5.5 to 5.2 g/kg Ca; 5.4 to 4.7 g/kg P). NC diets were supplemented with phytase at 0 (NC); 500 (NC + 500 FTU); or 2,000 FTU/kg (NC + 2,000 FTU) phytase units/kg. Blood was collected after fasting (day 48) or feeding (day 49) for measurement of plasma inositol concentrations. On day 49, 2 pigs per pen were euthanized, and duodenal and ileal digesta samples were collected to determine inositol phosphates (InsP6-2) concentrations. High phytase supplementation increased BW on days 21, 35, and 49 (P < 0.05). Over the entire feeding period, ADG, ADFI, and feed efficiency were increased by NC + 2,000 FTU compared with the other treatments (P < 0.05). Postprandial plasma inositol concentration was increased in NC + 2,000 (P < 0.01), but there was only a tendency (P = 0.06) of a higher fasting plasma inositol concentration in this group. Inositol concentrations in the portal vein plasma (day 49) were not different among treatments. Duodenal digesta InsP5 and InsP6 concentrations were similar in PC and NC, but higher in these 2 treatments (P < 0.05) than those supplemented with phytase. Phytase supplementation decreased InsP6-4, resulting in increased InsP3-2 and myo-inositol concentrations. Similar effects were found in ileal contents. Compared with NC, phytase supplementation resulted in greater cumulative InsP6-2 disappearance (93.6% vs. 72.8% vs. 25.0%, for NC + 2,000 FTU, NC + 500 FTU and NC, respectively, P < 0.01) till the distal ileum. Longissimus dorsi muscle plasma membrane GLUT4 concentration was increased by NC + 2,000 FTU (P < 0.01) compared with NC. In summary, high phytase supplementation increased growth performance of nursery pigs. The higher myo-inositol release from phytate could contribute to the increased expression of GLUT4 in muscle plasma membranes. Further investigation is needed to determine whether this is associated with enhanced cellular glucose uptake and utilization.

Phytic acid disrupted intestinal immune status and suppressed growth performance in on-growing grass carp (Ctenopharyngodon idella)

Phytic acid (PA) is one of the most common anti-nutritional factors in plant-derived protein feeds, and it poses considerable threats to aquaculture production. However, little is known about the effects of PA on fish intestinal health. This study aimed to investigate the impacts of PA on intestinal immune function in on-growing grass carp. To achieve this goal, a growth trial was conducted for 60 days by feeding 540 fish (120.56 ± 0.51 g) with six semi-purified diets containing graded levels of PA (0, 0.8, 1.6, 2.4, 3.2 and 4.0%). Then fish were challenged with Aeromonas hydrophila for 6 days. The results indicated that, compared with the control group (0% PA), PA did the following: (1) suppressed fish growth performance (percentage weight gain and feed efficiency) and reduced their ability to resist enteritis; (2) decreased fish intestinal antimicrobial ability by reducing intestinal lysozyme (LZ) activities, the contents of complement 3 (C3), C4 and immunoglobulin M (IgM), and downregulating the mRNA levels of hepcidin, liver-expressed antimicrobial peptide 2A (LEAP-2A), LEAP-2B, and β-defensin-1; and (3) aggravated fish intestinal inflammation responses by upregulating the mRNA levels of pro-inflammatory cytokines including tumour necrosis factor α (TNF-α), interleukin 1β (IL-1β) (except in the DI), interferon γ2 (IFN-γ2), IL-8, IL-12p40, IL-15 (except in the DI) and IL-17D, which is partly related to the nuclear factor kappa B (NF-κB) signalling pathway, whereas downregulating the mRNA levels of anti-inflammatory cytokines including transforming growth factor β1 (TGF-β1), IL-4/13A, IL-4/13B, IL-10 and IL-11, which is partially associated with the target of rapamycin (TOR) signalling pathway. The possible reasons for some distinctive gene expression patterns in fish three intestinal segments were discussed. Finally, based on the percent weight gain, enteritis morbidity, IgM content and LZ activity in the PI, the maximum tolerance levels of PA for on-growing grass carp were estimated to be 2.17, 1.68, 1.47 and 1.18% of the diet, respectively.

Increasing the dosing of a Buttiauxella phytase improves phytate degradation, mineral, energy, and amino acid digestibility in weaned pigs fed a complex diet based on wheat, corn, soybean meal, barley, and rapeseed meal1

This study evaluated the effects of increasing the dose of a 6-phytase from Buttiauxella on phytate degradation, mineral, energy, and AA digestibility in weaned pigs fed complex diets based on wheat, corn, soybean meal, barley, and rapeseed meal. A negative control (NC) diet containing no added inorganic phosphorus (P) and a reduction of 0.1% calcium (Ca) and 36 kcal/kg ME was supplemented with Buttiauxella phytase at 0, 250, 500, 1,000, or 2,000 FTU/kg diet and tested against a nutritionally adequate, positive control (PC) diet. One phytase units (FTU) is the amount of enzyme that liberates 1 micromole of inorganic phosphate per minute from a sodium phytate substrate at pH 5.5 and 37 °C. Barrows (Topigs × Pietrian; initial mean body weight 19.3 kg) were housed individually in metabolic crates and fed the test diets in mash form via 2 equal meals per day for 9 d (fed at 2.5 times the maintenance energy requirement), with 8 replicate pigs per treatment, in 2 experimental runs (total n = 48). After a 3-d adaptation period, urine and feces were collected over 5 d for measurements of apparent total tract digestibility (ATTD) and retention of nutrients. On day 9, pigs were euthanized and ileal digesta collected for measurements of apparent ileal digestibility (AID) of nutrients. Phytase improved (P < 0.05) digestibility of all measured AA except Trp (P < 0.1), and AID P, nitrogen, phytate, ATTD P, Ca versus NC. Increasing phytase dose from 0 (NC) to 2,000 FTU/kg increased AID Lys, Cys, Thr, Val, Ile, Leu, mean AA, P, N, phytate, ATTD P, N, Na, energy, ME, P retention (g/d), and reduced P excretion (g/d) in a linear or exponential manner (P < 0.05). Phytase at 2,000 FTU/kg improved AA digestibility by between +3.1 percentage points (Trp) and +8.8 percentage points (Cys) versus NC (average +6.3 percentage points) (P < 0.05). Phytase inclusion at 2,000 FTU/kg reduced P excretion (g/d) by 57% versus PC (P < 0.05). In conclusion, increasing Buttiauxella phytase in the range of 0 to 2,000 FTU/kg increased phytate degradation, improved AA and P digestibility, and reduced P excretion in weaned pigs fed complex diets.

A new phytase continuously hydrolyzes phytate and improves amino acid digestibility and mineral balance in growing pigs fed phosphorous-deficient diet

Ten ileal T-cannulated pigs (19.26 ± 1.06 kg) were used to evaluate the effects of a novel phytase on apparent ileal digestibility (AID) of AA and apparent total tract digestibility (ATTD) and hindgut disappearance of DM, GE, CP, crude fiber, NDF, and ADF as well as minerals balance. Pigs were fed in a duplicated 5 × 4 incomplete Latin square design (5 diets with 4 periods). Each period consisted of a 5-d adjustment period followed by a 3-d total collection of feces and urine and then a 2-d collection of ileal digesta. The 5 diets included a P-deficient basal diet (0.43% Ca and 0.38% total P) that was supplemented with 0 (negative control [NC]), 500, 1,000, or 20,000 phytase units (FTU)/kg phytase and a positive control (PC) diet that was P adequate (0.64% Ca and 0.52% total P). The addition of phytase to the NC diet improved ( < 0.05) AID of phytate from 11.1 to 62.8, 70.6, and 90.5% at the inclusion rates of 500, 1,000, and 20,000 FTU/kg, respectively. In general, phytase supplementation at a dose of 20,000 FTU/kg further increased ( < 0.05) AID of Ca, total P, and phytate and reduced ( < 0.05) the ileal phytate concentration compared with diets with 500 or 1,000 FTU/kg phytase. Pigs fed the diet with 20,000 FTU/kg phytase but not diets with 500 and 1,000 FTU/kg phytase showed improved ( < 0.05) ATTD of CP and AID of DM, GE, CP, Leu, Lys, Thr, Val, Asp, and Ser compared with pigs fed the PC or NC diet. However, hindgut disappearance of crude fiber and NDF ( < 0.05) were reduced in pigs fed the diet with 20,000 FTU/kg phytase compared with pigs fed the PC or NC diet. Pigs fed diets with 500 or 1,000 FTU/kg phytase had greater ATTD and retention of Ca and P than pigs fed the NC diet but less compared with pigs fed the diet with 20,000 FTU/kg phytase. Supplementation of 20,000 FTU/kg phytase to the NC diet improved ( < 0.05) digestibility of Na, Mn, and Zn as well as retention (%) of Zn. Increasing phytase supplementation doses from 0 to 1,000 FTU/kg linearly improved ( < 0.05) retention of Mg; meanwhile, digestibility of Mg and Mn and AID of Thr showed a linear increase trend ( = 0.084). In conclusion, supplementation of the novel phytase at doses up to 20,000 FTU/kg hydrolyzed most of the phytate (90%) and consequently further improved mineral and protein utilization.

Efficacy of New 6-Phytase from Buttiauxella spp. on Growth Performance and Nutrient Retention in Broiler Chickens Fed Corn Soybean Meal-based Diets

A total of 420 day-old male Ross chicks were weighed at d 1 of life and assigned to test diets to assess the efficacy of a new Buttiauxella spp. phytase expressed in Trichoderma reesei. Diets were: positive control (PC) adequate in nutrients and negative control (NC) diet (40% and 17% less available phosphorous (P) and calcium (Ca), respectively) supplemented with 6 levels of phytase 0, 250, 500, 750, 1,000, and 2,000 phytase units (FTU)/kg of diet. All diets had titanium dioxide as digestibility marker and each diet was allocated to ten cages (6 birds/cage). Diets were fed for 3 wk to measure growth performance, apparent retention (AR) on d 17 to 21 and bone ash and ileal digestibility (AID) on d 22. Growth performance and nutrient utilization was lower (p<0.05) for NC vs PC birds. Phytase response in NC birds was linear (p<0.05) with 2,000 FTU showing the greatest improvement on body weight gain (20%), feed conversion (7.4%), tibia ash (18%), AR of Ca (38%), AR of P (51%) and apparent metabolizable energy corrected for nitrogen (5.1%) relative to NC. Furthermore, phytase at ≥750 FTU resulted in AID of total AA commensurate to that of PC fed birds and at ≥1,000 FTU improved (p<0.05) AR of P, dry matter, and N beyond that of the lower doses of phytase and PC diet. In conclusion, the result from this study showed that in addition to increased P and Ca utilization, the new Buttiauxella phytase enhanced growth performance and utilization of other nutrients in broiler chickens in a dose-dependent manner.

Phytase in non-ruminant animal nutrition: a critical review on phytase activities in the gastrointestinal tract and influencing factors

This review focuses on phytase functionality in the digestive tract of farmed non-ruminant animals and the factors influencing in vivo phytase enzyme activity. In pigs, feed phytase is mainly active in the stomach and upper part of the small intestine, and added phytase activity is not recovered in the ileum. In poultry, feed phytase activities are mainly found in the upper part of the digestive tract, including the crop, proventriculus and gizzard. For fish with a stomach, phytase activities are mainly in the stomach. Many factors can influence the efficiency of feed phytase in the gastrointestinal tract, and they can be divided into three main groups: (i) phytase related; (ii) dietary related and (iii) animal related. Phytase-related factors include type of phytase (e.g. 3- or 6-phytase; bacterial or fungal phytase origin), the pH optimum and the resistance of phytase to endogenous protease. Dietary-related factors are mainly associated with dietary phytate content, feed ingredient composition and feed processing, and total P, Ca and Na content. Animal-related factors include species, gender and age of animals. To eliminate the antinutritional effects of phytate (IP6), it needs to be hydrolyzed as quickly as possible by phytase in the upper part of the digestive tract. A phytase that works over a wide range of pH values and is active in the stomach and upper intestine (along with several other characteristics and in addition to being refractory to endogenous enzymes) would be ideal.

Comparison of endogenous loss and maintenance need for minerals in rainbow trout (Oncorhynchus mykiss) fed fishmeal or plant ingredient-based diets

Mineral needs as affected by changes in dietary protein and oil sources were studied in rainbow trout. Duplicate groups (n = 30 fish per replicate) of rainbow trout (initial BW: 37 g) were fed either a fish meal/fish oil-based (M) or a complete plant ingredient (V)-based diet at four graded ration (R) levels [apparent satiation (AS), R75, R50 and R25 % of AS]; one treatment group was maintained under starvation. The feeding trial lasted 12 weeks at a water temperature of 17 °C. Dietary intake, apparent digestibility and initial and final whole-body composition data were used to calculate mineral gain which was regressed against digestible mineral intake (both expressed as mg or µg kg(-0.8) day(-1)). Starvation loss (SL), endogenous loss of fed fish (ELF, y-intercept at x = 0) and point of intake for zero balance (PZB, x-intercept at y = 0) were used as estimates of maintenance requirements. SL provided the lowest estimate, ELF provided the net requirement of a mineral for maintenance and PZB provided the digestible dietary intake required to meet maintenance (SL < ELF < PZB). Dietary ingredient composition did not significantly affect the digestible mineral supply required for maintenance (PZB) for any of the minerals (P, Mg, K, Cu and Zn) studied. However, ELF of micro-minerals such as Cu and Zn were significantly affected. The ELF of Cu was significantly lower and that of Zn was significantly higher in V group compared with M-fed fish. Further studies on the effects of such changes in dietary formulations on micro-mineral metabolism are warranted.

Effects of Adding Super Dose Phytase to the Phosphorus-deficient Diets of Young Pigs on Growth Performance, Bone Quality, Minerals and Amino Acids Digestibilities

Two experiments were conducted to evaluate the efficacy of feeding an Escherichia coli (E. coli) derived phytase to pigs fed P deficient, corn-soybean meal diets. In Exp. 1, one hundred and twenty crossbred piglets (9.53±0.84 kg) were allocated to one of five treatments which consisted of four low P diets (0.61% Ca, 0.46% total P and 0.24% non-phytate P) supplemented with 0, 500, 1,000, or 20,000 FTU/kg E. coli phytase as well as a positive control formulated to be adequate in all nutrients (0.77% Ca, 0.62% total P and 0.42% non-phytate P). The treatments were applied to six pens with four pigs per pen for 28 days. In Exp. 2, ten crossbred pigs (19.66±1.16 kg) fitted with ileal T-cannula were used in a nutrient balance study. The pigs were assigned to treatments similar to those used in Exp. 1 in a doubly replicated 5×4 incomplete Latin square design (5 diets with 4 periods). Each period consisted of a 5-d adjustment period followed by a 3-d total collection of feces and urine and then a 2-d collection of ileal digesta. Supplementation with phytase linearly increased (p<0.05) weight gain, feed intake, feed efficiency, bone breaking strength and fat-free dry and ash bone weight. There were linear increases (p<0.01) in the apparent ileal digestibility (AID) of DM, GE, CP, Ca, total P, inositol hexaphosphate (IP6) and some AA with increasing dose of E. coli phytase. Pigs fed 20,000 FTU/kg had a greater (p<0.05) AID of IP6 (80% vs 59% or 64%, respectively) than pigs fed diets with 500 or 1,000 FTU/kg phytase. There were linear increases (p<0.05) in the total tract digestibility of Ca, total P, Na, K, Mg, and Zn as well as in the retention of Mg and Zn with increased phytase dose. The retention and utilization of Cu, and the total tract digestibility of CP and Cu quadratic increased (p<0.05) with increased phytase dose. In conclusion, supplementation of 500 FTU of phytase/kg and above effectively hydrolyzed phytate in low-P corn-soybean diets for pigs. In addition, a super dose of phytase (20,000 FTU/kg) hydrolyzed most of the IP6 and consequently further improved mineral use, protein utilization and performance.

Review: Anti-nutritional effects of phytic acid in diets for pigs and poultry – current knowledge and directions for future research

Woyengo, T. A. and Nyachoti, C. M. 2013. Review: Anti-nutritional effects of phytic acid in diets for pigs and poultry – current knowledge and directions for future research. Can. J. Anim. Sci. 93: 9–21. Plant feedstuffs contain phytic acid (PA), which is a storage form of phosphorus. Phytic acid is, however, poorly hydrolyzed by pigs and poultry, and it has a capacity to complex dietary nutrients, thereby reducing nutrient digestibility. Reduced nutrient digestibility by PA implies reduced efficiency of utilization of the nutrients and increased discharge of the unabsorbed nutrients to the environment. Phytic acid has also recently been shown to increase the endogenous nutrient losses (ENL) in pigs and poultry. Because the increased ENL in the gastrointestinal tract are associated with increased maintenance requirement for the lost nutrients and of energy spent on their secretion, an increase in ENL due to PA implies that there are other adverse effects of PA on nutrient utilization in addition to reducing nutrient digestibility. In this review, the effects of PA on performance of pigs and poultry, and on the digestibility and ENL in these animals are discussed in detail. Also, the mechanisms by which PA reduces nutrient digestibility and increases gastrointestinal ENL in pigs and poultry are discussed, and areas that need further research to gain more insight into these mechanisms are suggested.

Influence of a microbial phytase and zinc oxide on young pig growth performance and serum minerals

Crossbred pigs (n=288; average age=21±3 d and BW=7.1±0.2 kg) were used in a 42-d trial to determine the influence of a microbial phytase and various doses of ZnO on growth performance and serum minerals. Pigs (6 castrated males or females/pen) were randomly allotted to treatments in a 2×3 factorial arrangement with 2 dietary levels of a microbial phytase (0 or 2,500 phytase units/kg) and 3 dietary levels of supplemental ZnO [0, 1750, or 3,500 mg/kg ZnO (72% Zn)] with 4 pens of castrated males and 4 pens of females per treatment. Diets were formulated to exceed all nutrient requirements, including Ca and P from d 0 to 21 (phase 1) and d 22 to 42 (phase 2). Growth performance, serum Zn, and serum P were not influenced (P>0.05) by a ZnO×phytase interaction during phase 1, phase 2, or overall (d 0 to 42). Phytase increased (P=0.01) ADFI and improved (P=0.02) ADG in phase 1 and improved (P=0.01) overall ADG, regardless of the level of ZnO supplemented. Zinc oxide supplementation linearly reduced (P=0.05) ADG, and ZnO at 3,500 mg/kg reduced (quadratic, P=0.04) G:F in pigs (phase 2). During phase 1, phytase increased serum Ca, but only in the absence of ZnO supplementation, which resulted in a ZnO×phytase interaction (P=0.02). Serum Zn was increased (linear, P<0.001) and serum P was decreased (linear, P=0.05) as ZnO supplementation increased in the diet (phase 1). In phase 2, serum Ca was reduced (linear, P=0.04) and serum Zn was increased (linear, P=0.02) as ZnO supplementation increased in the diet. Phytase supplementation increased (P=0.009) serum Zn and increased (P=0.003) serum P (phase 1). There was no influence of phytase supplementation on serum minerals in phase 2. In summary, supplemental ZnO reduced growth performance in this experiment. Phytase supplementation improved ADG in Ca- and P-adequate diets regardless of the level of ZnO supplemented, which may be attributed to the reduction of phytate as an antinutrient. In addition, through phytate hydrolysis, phytase reduced phytate-Zn interactions and increased serum Zn, Ca, and P. However, supplementing ZnO increased serum Zn, which reduced serum P and Ca, indicating Ca-Zn-P precipitation. In addition, phytase increased serum Ca, but only in the absence of Zn, further indicating a complex interaction between Zn, Ca, and P in the blood.

Effect of dietary phytic acid on performance and nutrient uptake in the small intestine of piglets

An experiment was conducted with piglets to determine the effect of dietary phytic acid supplementation on performance, electrophysiological properties of jejunum mounted in Ussing chambers, sodium-dependent glucose transporter 1 (SGLT1) protein expression in jejunum, and plasma glucose and Na concentrations. Sixteen piglets with an average initial BW of 7.40 ± 0.36 kg were randomly assigned to 2 experimental diets with 8 piglets per diet. The diets were casein-cornstarch-based and were either unsupplemented or supplemented with 2% phytic acid (as Na phytate). The basal diet was formulated to meet the recommendation of NRC (1998) for energy, AA, minerals, and vitamins for piglets. The experiment lasted for 21 d, and at the end, BW gain and feed consumption were determined, and blood samples were collected for determination of plasma glucose and Na concentrations. The piglets were then euthanized to determine jejunal electrophysiological properties (transmural potential difference and short-circuit current) and SGLT1 protein expression. Phytic acid supplementation reduced ADG (P = 0.002), ADFI (P = 0.017), and G:F (P = 0.001) from 316.1 to 198.2 g, 437.4 to 360.3 g, and 0.721 to 0.539 g/g, respectively. Phytic acid supplementation also tended to reduce (P = 0.088) potential difference (-3.80 vs. -2.23 mV) and reduced (P = 0.023) short-circuit current from 8.07 to 0.1 μA/cm(2). However, phytic acid supplementation did not affect SGLT1 protein, and blood plasma glucose and Na concentrations. In conclusion, dietary phytic acid reduced growth performance and transmural short-circuit current in the jejunum of piglets. The reduced transmural short-circuit current in the jejunum by phytic acid implies reduced active Na transport in the jejunum by the phytic acid. Therefore, it seems that dietary phytic acid reduces growth performance of pigs partly through reduced capacity of the small intestine to absorb Na.

Review: Supplementation of phytase and carbohydrases to diets for poultry

Woyengo, T. A. and Nyachoti, C. M. 2011. Review: Supplementation of phytase and carbohydrases to diets for poultry. Can. J. Anim. Sci. 91: 177–192. Feedstuffs of plant origin contain anti-nutritional factors such as phytic acid (PA) and non-starch polysaccharides (NSP), which limit nutrient utilization in poultry. Phytic acid contains phosphorus, which is poorly digested by poultry, and has the capacity to bind to and reduce the utilisation of other nutrients, whereas NSP are indigestible and have the capacity to reduce nutrient utilisation by encapsulation. Supplemental phytase and NSP-degrading enzymes (carbohydrases) can, respectively, hydrolyze PA and NSP, alleviating the negative effects of these anti-nutritional factors. In feedstuffs of plant origin, PA is located within the cells, whereas NSP are located in cell walls, and hence it has been hypothesized that phytase and carbohydrases can act synergistically in improving nutrient utilization because the carbohydrases can hydrolyze the NSP in cell walls to increase the accessibility of phytase to PA. However, the response to supplementation of a combination of these enzymes is variable and dependent on several factors, including the type of carbohydrase supplement used, dietary NSP composition, calcium and non-phytate phosphorus contents, and endogenous phytase activity. These factors are discussed, and areas that need further research for optimising the use of a combination of phytase and carbohydrases in poultry diets are suggested.

Histomorphology and small intestinal sodium-dependent glucose transporter 1 gene expression in piglets fed phytic acid and phytase-supplemented diets

An experiment was conducted to determine the effect of dietary phytic acid (PA) and phytase supplementation on small intestinal histomorphology and Na-dependent glucose transporter 1 (SGLT1) gene expression in piglets. Twenty-four piglets with an average initial BW of 7.60 ± 0.73 kg were randomly assigned to 3 experimental diets, to give 8 piglets per diet. The diets were a casein-cornstarch-based diet that was supplemented with 0 or 2% PA, or 2% PA (as Na phytate) plus an Escherichia coli-derived phytase at 500 phytase units/kg. The basal diet was formulated to meet the 1998 NRC energy, digestible AA, mineral, and vitamin requirements for piglets. After 10 d of feeding, the piglets were killed to determine small intestinal histomorphology and small intestinal SGLT1 gene expression. Phytic acid supplementation did not affect (P > 0.1) villus height (VH) and the VH-to-crypt depth (CD) ratio, but did decrease (P < 0.05) CD in the jejunum. Phytase supplementation did not affect (P > 0.1) VH, CD, and the VH-to-CD ratio. Phytic acid supplementation reduced SGLT1 gene expression in the duodenum, jejunum, and ileum by 1.1-, 5.4-, and 2.4-fold, respectively. Phytase supplementation increased SGLT1 gene expression in the jejunum by 2.6-fold, but reduced SGLT1 gene expression in the duodenum and ileum by 2.0- and 4.0-fold, respectively. In conclusion, PA reduced CD in the jejunum and SGLT1 gene expression in the duodenum, jejunum, and ileum, whereas phytase supplementation increased the expression of SGLT1 in the jejunum. The reduced SGLT1 gene expression by PA implies that PA reduces nutrient utilization in pigs partly through reduced expression of SGLT1, which is involved in glucose and Na absorption. The increased expression of SGLT1 in the jejunum by phytase supplementation implies that phytase alleviated the negative effects of PA partly through increased expression of SGLT1.