Effect of dietary phytate and phytase on proteolytic digestion and growth regulation of broilers

Effects of removing phytic acid on the bioaccessibility of Ca/Fe/Zn and protein digestion in soymilk

BACKGROUND

Soymilk is a high-quality source of protein and minerals, such as calcium (Ca), iron (Fe), and zinc (Zn). However, phytic acid in soymilk restricts mineral and protein availability. We here investigated the effects of removing phytic acid on the physicochemical properties, mineral (Ca, Fe, and Zn) bioaccessibility, and protein digestibility of soymilk.

RESULTS

Physicochemical property analysis revealed that the removal of phytic acid reduced protein accumulation at the gastric stage, thereby facilitating soymilk matrix digestion. The removal of phytic acid significantly increased Zn bioaccessibility by 18.19% in low-protein soymilk and Ca and Fe bioaccessibility by 31.20% and 30.03%, respectively, in high-protein soymilk.

CONCLUSION

Removing phytic acid was beneficial for the hydrolysis of high-molecular-weight proteins and increased the soluble protein content in soymilk, which was conducive to protein digestion. This study offers a feasible guide for developing plant-based milk with high nutrient bioaccessibility. © 2024 Society of Chemical Industry.

Supplemental phosphorus can be completely replaced with microbial phytase in White Leghorn layer diets

1. A study was conducted to assess the possibility of totally replacing supplemental phosphorus sources in White Leghorn (WL) layer diets (aged 28 to 45 weeks of age) with microbial phytase supplementation. One thousand commercial layers (HyLine White) of 28 weeks of age were housed in California cages fitted in open-sided poultry shed at the rate of 20 layers in each replicate. Ten replicates were randomly allotted to each treatment, and the respective diet was fed from 28 to 45 weeks of age.2. A control diet (CD) containing the recommended levels of non-phytate phosphorus (3.6 g/kg NPP) and four other test diets (2-5) having sub-optimal levels of NPP (2.4, 2.0, 1.6 and 1.2 g/kg), but with supplemental microbial phytase (600 FTU/kg) were prepared and fed for the trial duration.3. The layers fed with lower levels of NPP with phytase had the same laying performance as the group fed the CD. Egg production, feed efficiency, egg mass, shell defects, egg density, shell weight, shell thickness, ash content and breaking strength of the tibia and sternum were not affected by feeding the lowest concentration of NPP (1.2 g/kg) plus microbial phytase.4. Phytase supplementation in diets with sub-optimal levels of NPP (2.4, 2 and 1.6 g/kg) significantly improved the Haugh unit score compared to those fed the CD.5. It was concluded that supplemental phosphorus can be completely replaced with microbial phytase (600 FTU/kg) in a diet without affecting egg production, shell quality or bone mineral variables in WL layers (28 to 45 weeks).

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.

The Contribution of Phytate-Degrading Enzymes to Chicken-Meat Production

The contribution that exogenous phytases have made towards sustainable chicken-meat production over the past two decades has been unequivocally immense. Initially, their acceptance by the global industry was negligible, but today, exogenous phytases are routine additions to broiler diets, very often at elevated inclusion levels. The genesis of this remarkable development is based on the capacity of phytases to enhance phosphorus (P) utilization, thereby reducing P excretion. This was amplified by an expanding appreciation of the powerful anti-nutritive properties of the substrate, phytate (myo-inositol hexaphosphate; IP₆), which is invariably present in all plant-sourced feedstuffs and practical broiler diets. The surprisingly broad spectra of anti-nutritive properties harbored by dietary phytate are counteracted by exogenous phytases via the hydrolysis of phytate and the positive consequences of phytate degradation. Phytases enhance the utilization of minerals, including phosphorus, sodium, and calcium, the protein digestion, and the intestinal uptakes of amino acids and glucose to varying extents. The liberation of phytate-bound phosphorus (P) by phytase is fundamental; however, the impacts of phytase on protein digestion, the intestinal uptakes of amino acids, and the apparent amino acid digestibility coefficients are intriguing and important. Numerous factors are involved, but it appears that phytases have positive impacts on the initiation of protein digestion by pepsin. This extends to promoting the intestinal uptakes of amino acids stemming from the enhanced uptakes of monomeric amino acids via Na⁺-dependent transporters and, arguably more importantly, from the enhanced uptakes of oligopeptides via PepT-1, which is functionally dependent on the Na⁺/H⁺ exchanger, NHE. Our comprehension of the phytate-phytase axis in poultry nutrition has expanded over the past 30 years; this has promoted the extraordinary surge in acceptance of exogenous phytases, coupled with the development of more efficacious preparations in combination with the deflating inclusion costs for exogenous phytases. The purpose of this paper is to review the progress that has been made with phytate-degrading enzymes since their introduction in 1991 and the underlying mechanisms driving their positive contribution to chicken-meat production now and into the future.

Nutritional and Functional Roles of Phytase and Xylanase Enhancing the Intestinal Health and Growth of Nursery Pigs and Broiler Chickens

This review paper discussed the nutritional and functional roles of phytase and xylanase enhancing the intestinal and growth of nursery pigs and broiler chickens. There are different feed enzymes that are currently supplemented to feeds for nursery pigs and broiler chickens. Phytase and xylanase have been extensively studied showing consistent results especially related to enhancement of nutrient digestibility and growth performance of nursery pigs and broiler chickens. Findings from recent studies raise the hypothesis that phytase and xylanase could play functional roles beyond increasing nutrient digestibility, but also enhancing the intestinal health and positively modulating the intestinal microbiota of nursery pigs and broiler chickens. In conclusion, the supplementation of phytase and xylanase for nursery pigs and broiler chickens reaffirmed the benefits related to enhancement of nutrient digestibility and growth performance, whilst also playing functional roles benefiting the intestinal microbiota and reducing the intestinal oxidative damages. As a result, it could contribute to a reduction in the feed costs by allowing the use of a wider range of feedstuffs without compromising the optimal performance of the animals, as well as the environmental concerns associated with a poor hydrolysis of antinutritional factors present in the diets for swine and poultry.

Conditioning of Feed Material Prior to Feeding: Approaches for a Sustainable Phosphorus Utilization

A circular phosphorus (P) bioeconomy is not only worthwhile for conserving limited mineral P reservoirs, but also for minimizing negative environmental impacts caused by human-made alterations. Although P is an essential nutrient, most of the P in concentrates based on cereals, legumes and oilseed byproducts is organically bound to phytate. The latter cannot be efficiently utilized by monogastric animals and is therefore diluted into the environment through the manure pathway. This review examines various strategies for improved P utilization in animals and reflects the respective limitations. The strategies considered include feeding of debranned feedstuffs, pre-germinated feed, co-feeding of phytase and feeding material with high native phytase activity. All these approaches contribute to an improved P bioavailability. However, about half of the organic P content continues to be excreted and therefore remains unused by the animals. Nevertheless, technologies for an efficient utilization of P from cereal-based feed already exist; however, these are not industrially established. Conditioning feed material prior to feeding fosters P-reduced feed; meanwhile, P bound to phytate can be recovered. Based on known techniques for P separation and solubilisation from cereal products and phytate conversion, potential designs for feed material conditioning processes are proposed and evaluated.

Standardized ileal amino acid digestibility of plant-based feedstuffs and phytase supplementation in broiler chicken diets

ABSTRACT The objective was to determine the standardized ileal amino acid digestibility (SIAAD) in soybean meal (SBM), corn + SBM, wheat + SBM and a protein free diet (PFD) associated with phytase. A total of 672 Cobb 500 (493±10g) male chicks were distributed in a completely randomized design with twelve treatments (PFD, PFD + SBM, PFD + corn + SBM and PFD + wheat + SBM, supplemented with 0, 500 and 1000 FTU), eight replicates and seven birds per cage from 14 to 23 days. Phytase supplementation at 500 FTU increased the SIAAD of methionine in SBM (P<0.05) and threonine in corn + SBM (P<0.05). There was no significant effect (P>0.05) for the SIAAD of methionine, arginine and histidine in wheat + SBM as the phytase supplementation. However, the SIAAD of lysine, threonine, isoleucine, phenylalanine, valine, cystine, alanine, aspartic acid, glutamic acid, glycine, serine and tyrosine differed (P<0.05). In general, the SIAAD for SBM, corn + SBM and wheat + SBM are 90.32, 88.65 and 83.97% (0 FTU); 91.31, 88.81 and 88.36% (500 FTU); and 91.36, 87.09 and 87.87% (1000 FTU). In conclusion, the efficacy of phytase for improve the SIAAD vary according to the feedstuff and level of supplementation.

Diverse role of phytic acid in plants and approaches to develop low-phytate grains to enhance bioavailability of micronutrients

Natural or synthetic compounds that interfere with the bioavailability of nutrients are called antinutrients. Phytic acid (PA) is one of the major antinutrients present in the grains and acts as a chelator of micronutrients. The presence of six reactive phosphate groups in PA hinders the absorption of micronutrients in the gut of non-ruminants. Consumption of PA-rich diet leads to deficiency of minerals such as iron and zinc among human population. On the contrary, PA is a natural antioxidant, and PA-derived molecules function in various signal transduction pathways. Therefore, optimal concentration of PA needs to be maintained in plants to avoid adverse pleiotropic effects, as well as to ensure micronutrient bioavailability in the diets. Given this, the chapter enumerates the structure, biosynthesis, and accumulation of PA in food grains followed by their roles in growth, development, and stress responses. Further, the chapter elaborates on the antinutritional properties of PA and explains the conventional breeding and transgene-based approaches deployed to develop low-PA varieties. Studies have shown that conventional breeding methods could develop low-PA lines; however, the pleiotropic effects of these methods viz. reduced yield, embryo abnormalities, and poor seed quality hinder the use of breeding strategies. Overexpression of phytase in the endosperm and RNAi-mediated silencing of genes involved in myo-inositol biosynthesis overcome these constraints. Next-generation genome editing approaches, including CRISPR-Cas9 enable the manipulation of more than one gene involved in PA biosynthesis pathway through multiplex editing, and scope exists to deploy such tools in developing varieties with optimal PA levels.

Increasing dietary phytate has a significant anti-nutrient effect on apparent ileal amino acid digestibility and digestible amino acid intake requiring increasing doses of phytase as evidenced by prediction equations in broilers

Cobb 400, male broilers (n = 4,752) were housed in 12 pens/diet and 33 birds/pen. There were 3 levels of phytate P (0.24, 0.345, or 0.45%) and 4 phytase doses (0, 500, 1,000 or 2,000 phytase units (FTU)/kg) to evaluate the influence of phytate and phytase dose on apparent ileal digestibility (AID) and digestible nutrient intake. Diets were formulated with reduced Ca (0.22%), available P (0.20%), energy (80 to 120 kcal/kg) and amino acids (1 to 5%). On day 21, digesta was collected from 8 birds/pen. Prediction equations determined the linear or non-linear influence of phytate P, log phytase dose, and the interaction. The AID of amino acids, Ca or P and digestible amino acid or Ca intake were influenced by linear or non-linear phytate P × log phytase dose (P < 0.0001). Increasing the dietary phytate P from 0.24 to 0.345 or 0.45% was predicted to reduce the AID of amino acids in a non-linear manner by an average of 6 to 7 percentage points, respectively. This corresponded to a non-linear decrease in digestible amino acid intake of an average of 80 to 90 mg/D. The negative effect of increasing dietary phytate P from 0.24 to 0.45% on AID was greatest for cysteine (-14 percentage points), aspartic acid or glycine (-9 percentage points) and lowest for methionine, tryptophan, serine, or glutamic acid (-5 percentage points). The predicted digestible intake of lysine (-120 mg/D), aspartic acid (-180 mg/D), or glutamic acid (-290 mg/D) were reduced in birds fed diets containing 0.345% vs. 0.24% phytate P. Phytase supplementation was predicted to increase the AID of amino acids, Ca, or P in a non-linear-log or log-linear manner at all levels of phytate P, with the greatest response at higher doses of phytase in diets containing 0.345 or 0.45% phytate P. The effect of phytase on digestible nutrient intake was less clear. Prediction equations can be useful to determine the influence of phytase and phytate P on AID and digestible nutrient intake in broilers.

Effect of a high dose of exogenous phytase and supplementary myo-inositol on mineral solubility of broiler digesta and diets subjected to in vitro digestion assay

This study was conducted to evaluate the effect of microbial phytase and myo-inositol supplementation in low non-phytate phosphorus (nPP) diets on pH and the solubility of minerals in an in vitro digestion procedure (IVDP) and to compare this with digesta from birds fed different diets (grower diets) compared to the in vitro test (starter diets). A total of 660 1-day-old broilers were randomly allotted into 11 dietary treatments and fed a corn-soybean-meal-based diet with recommended nPP (positive control; PC), an nPP-deficient diet (negative control; NC), NC diets supplemented with phytase (500; 1,000; 2,000; 3,000; 4,000; 5,000; and 6,000 FTU/kg), an NC diet plus 0.15% myo-inositol, and an NC diet with reduced Ca level (Ca: nPP ratio same as PC) from 1 to 23 D of age. The pH and Ca solubility of the NC diet was increased compared with the PC when subjected to IVDP (P < 0.05). P solubility in the gizzard and jejunal digesta was reduced in the NC compared with the PC diet and this was also reflected in the IVDP. Phytase addition to the NC diets linearly increased (P < 0.05) the pH value and Ca and P solubilities in both digesta and diets subjected to IVDP. Higher doses of microbial phytase increased (P < 0.05) Zn and Fe solubilities in both digesta and IVDP. Myo-inositol supplementation of the NC diet had no effect on mineral solubility, but decreased (P < 0.05) the pH of the IVDP. Lowering the Ca content of the NC diet decreased (P < 0.05) the pH of the in vitro digested diets and Ca solubility in both broiler digesta and IVDP and also increased (P < 0.05) P solubility in both the jejunal digesta and IVDP. Correlations were noted between the solubility of P in the in vitro assay and that in the gizzard and jejunal digesta, and also with bird performance, confirms the usefulness of in vitro assay.

Probiotic expressing heterologous phytase improves the immune system and attenuates inflammatory response in zebrafish fed with a diet rich in soybean meal

Although aquaculture is among the fastest growing food production sectors in the world, one of the bottlenecks for the continuity of its expansion is the dependence of animal protein on commercial feed formulations. Vegetable proteins are an alternative due to the low cost and high availability. However, this protein source is accompanied by a series of antinutritional and pro-inflammatory compounds, including phytate. Phytases can be added in feed for phytate degradation and increase nutrient availability. However, the use of purified phytases significantly increases the production costs. An interesting alternative is to use probiotics genetically modified as bioreactors for phytase production. In the present study, a strain of Bacillus subtilis secreting a fungal phytase was used to evaluate the effect of a feed with high content of soybean meal on zebrafish (Danio rerio). We analysed the condition factor (K) of fish, and the expression of genes related to the immune system, inflammatory response and oxidative. stress. The results obtained demonstrate that the transgenic probiotic was efficient in improving the fish condition factor, stimulating the immune system, reducing the inflammatory response and oxidative stress. Thus, probiotics acting as phytase bioreactors can be considered an interesting tool for the adaptation of commercial species to feed of lower cost.

High doses of phytase on growth performance and apparent ileal amino acid digestibility of broilers fed diets with graded concentrations of digestible lysine

Two experiments of the same design were conducted to determine the influence of phytase on performance and apparent ileal digestibility (AID) of amino acids in broilers fed graded concentrations of digestible lysine (dgLys). Cobb 400, male broilers were allocated to 1 of 16 diets consisting of 4 basal diets formulated at 80, 88, 96, or 104% of the Cobb 400 dgLys requirements for each feeding phase. Phytase was included in each basal diet at 0, 750, 1,500, or 3,000 phytase units (FTU)/kg. In Exp. 1, 33 birds/pen from hatch to day 42 were fed a 2-phase feeding program with 12 replicate pens/diet. In Exp. 2, there were 25 birds/pen from hatch to day 21 and 8 replicate pens/diet. Data were analyzed as a 4 × 4 factorial and means separated using orthogonal contrasts. In Exp. 1, feed intake (FI) increased (quadratic, P < 0.05) as dgLys increased in the diet. Body weight gain (BWG) increased (quadratic, P < 0.05) as dgLys concentration or phytase dose increased in the diet. As phytase dose increased in the diet, feed conversion ratio (FCR) was improved in a linear or quadratic (P < 0.05) manner depending on the dgLys concentration of the diet (dgLys × phytase, P<0.05). In Exp. 2, FI linearly (P < 0.05) increased as dgLys increased in the diet. Increasing the concentration of dgLys or phytase in the diet increased (quadratic, P < 0.05) BWG and improved (quadratic, P < 0.05) FCR. The AID of most amino acids was influenced by a dgLys × phytase interaction (P < 0.05), except threonine, valine, tryptophan, serine, cysteine, or leucine (linear or quadratic effect of phytase, P < 0.05), where phytase improved the AID in birds fed diets containing 80, 88, or 96% of the dgLys requirement, but not birds fed 104%. The predicted dgLys requirement to maximize performance, carcass, and digestible lysine intake was 97.6 to ≥ 104%. The predicted dose of phytase to maximize BWG or FCR was between 1,990 and 2,308 FTU/kg, regardless of the dgLys concentration in the diet. The predicted dose of phytase to maximize carcass weight was between 1,527 and 2,658 FTU/kg of diet and to maximize breast weight was 0 to ≥ 3,000 FTU/kg diet, depending on the dgLys concentration in the diet. In conclusion, optimal performance in the absence of phytase could be achieved at much lower levels of lysine in the presence of phytase.

Effects of microbial phytase on mucin synthesis, gastric protein hydrolysis, and degradation of phytate along the gastrointestinal tract of growing pigs

An experiment was conducted to test the hypothesis that pigs fed diets supplemented with exogenous phytase reduce mucin synthesis in the small intestine, increase protein hydrolysis in the stomach, increase breakdown of phytate along the gastrointestinal tract, and increase mineral and AA digestibility. A diet based on corn, soybean meal, and canola meal was formulated to meet requirements for growing pigs except for Ca and P, which were lower than requirements. Three additional diets were formulated by adding 750, 1,500, or 3,000 units of phytase (FTU) per kilogram to the basal diet. Eight growing barrows (38.45 ± 3.06 kg) were prepared with a T-cannula in the duodenum and another T-cannula in the distal ileum. Pigs were housed individually and allotted to a replicated 4 × 4 Latin square design with four pigs and four periods in each square. Each period lasted 14 d with the initial 7 d being the adaptation period to the diets. Pigs were fed twice daily in combined amounts equal to 3.2 times the estimated requirement for maintenance energy. Results indicated that the apparent ileal digestibility (AID) and the apparent total tract digestibility (ATTD) of Ca and P increased (linear and quadratic, P ≤ 0.05) as phytase inclusion increased. However, values for AID of Ca and P were not different from values for ATTD of Ca and P, indicating that there is no net absorption of Ca and P in the hindgut. The apparent duodenal digestibility (ADD) of Ca and P was ~30% and 10% to 20%, respectively, indicating some digestion in the stomach of both Ca and P. A quadratic increase (P < 0.05) of the AID of GE was observed with the breakpoint around 1,500 FTU, but there was a negative linear (P ≤ 0.001) effect of dietary phytase on the ATTD of GE. Phytase did not affect mucin synthesis in the small intestine, protein hydrolysis in the stomach, or ileal digestibility of dispensable and indispensable AA. However, degradation of higher phytate esters (IP6 and IP5) into lower phytate esters (IP4 and IP3) and inositol increased as dietary phytase increased, indicating that it is possible to completely degrade dietary phytate if microbial phytase is included by at least 3,000 FTU in the diet. In conclusion, supplementing diets with phytase resulted in increased degradation of phytate and phytate esters and improved digestibility of Ca and P, but phytase did not change intestinal mucin synthesis, gastric protein hydrolysis, or the AID of AA.

Improving efficiency in meat production

Selective breeding and improved nutritional management over the past 20–30 years has resulted in dramatic improvements in growth efficiency for pigs and poultry, particularly lean tissue growth. However, this has been achieved using high-quality feed ingredients, such as wheat and soya that are also used for human consumption and more recently biofuels production. Ruminants on the other hand are less efficient, but are normally fed poorer quality ingredients that cannot be digested by human subjects, such as grass or silage. The challenges therefore are to: (i) maintain the current efficiency of growth of pigs and poultry, but using more ingredients not needed to feed the increasing human population or for the production of biofuels; (ii) improve the efficiency of growth in ruminants; (iii) at the same time produce animal products (meat, milk and eggs) of equal or improved quality. This review will describe the use of: (a) enzyme additives for animal feeds, to improve feed digestibility; (b) known growth promoting agents, such as growth hormone, β-agonists and anabolic steroids, currently banned in the European Union but used in other parts of the world; (c) recent transcriptomic studies into molecular mechanisms for improved growth efficiency via low residual feed intake. In doing so, the use of genetic manipulation in animals will also be discussed.

Contribution of intestinal- and cereal-derived phytase activity on phytate degradation in young broilers

There is little consensus as to the capability of poultry to utilize dietary phytate without supplemental phytase. Therefore, an experiment was conducted to examine the extent to which endogenous phytase of intestinal and cereal origin contributes to phytate degradation in birds aged 0 to 14 d posthatch. Ross 308 broilers (n = 720) were fed one of 4 experimental diets with differing dietary ingredient combinations and approximate total phytate levels of 10 g/kg, dietary phytase activity analyzed at 460 U/kg, dietary calcium (Ca) levels of 11 g/kg, and nonphytate-phosphorus (P) levels of 4 g/kg. Broiler performance, gizzard, duodenum, jejunum and ileum pH, Ca and P digestibility and solubility, amount of dietary phytate hydrolyzed in the gizzard, jejunum, and ileal digesta phytase activity were analyzed at d 4, 6, 8, 10, 12, and 14 posthatch. Intestinal endogenous phytase activity increased significantly (P < 0.001) between d 4 and 6, resulting in increased phytate hydrolysis in the gizzard (P = 0.003), jejunum (P < 0.001), and ileum (P < 0.001). Phytase activity and phytate hydrolysis continued to increase with age, with a greater phytase activity and associated increase in phytate hydrolysis and mineral utilization between d 10 and 12. Gizzard and jejunum Ca and P solubility and ileal Ca and P digestibility increased significantly (P < 0.001), and gastrointestinal pH decreased significantly (P < 0.001) between d 4 and 6. By d 14, phytase activity recovered in the ileum was approximately 45 U/kg. There were strong correlations between phytase activity measured in the ileum and phytate hydrolyzed in the gizzard (r = 0.905, P < 0.001), jejunum (r = 0.901, P = 0.023), and ileum (r = 0.938, P = 0.042). This study shows intestinal- and dietary-derived endogenous phytase activity is responsible for phytate-P hydrolysis in broilers.

Effect of high-dose phytase supplementation in broilers from 22 to 42 days post-hatch given diets severely limited in available phosphorus

1. Two trials were conducted from 22 to 42 d post-hatch to evaluate the effectiveness of high concentrations of supplemental phytase in maize-soya bean meal-based diets severely limited in available phosphorus (P). Growth performance, plasma P and tibia ash (TA) were measured. 2. Each trial used 220 21-d-old male broilers in 20 pens with 11 birds per pen. Dietary treatments included a positive control [PC, 4.3 g/kg nonphytate P (NPP)], negative control [NC, 2.3 g/kg NPP (Trial 1) or 1.4 g/kg NPP (Trial 2)] and NC plus 1000, 2000 or 4000 phytase U/kg of the diet. 3. Birds fed on the PC diet had higher average daily gain (ADG), gain to feed ratio (G:F), plasma P (Trials 1 and 2) and TA (Trial 2) than those fed on the NC. 4. In Trial 1, ADG and G:F values of the NC plus 1000, 2000 or 4000 phytase U/kg reached those of the PC. Plasma P values of the NC plus 2000 or 4000 phytase U/kg reached that of the PC. Although TA values of the NC, NC + 1000 or NC + 2000 reached that of the PC, TA of the NC + 4000 was more than that of the PC. 5. In Trial 2, ADG and G:F values of the NC plus 4000 phytase U/kg reached those of the PC; nevertheless, plasma P values of the NC diets did not come up to that of the PC. While TA values of the NC, NC + 1000 or NC + 2000 did not reach that of the PC, TA of the NC + 4000 was greater than that of the PC. 6. Results of this study showed that, in the diets with 2.3 and 1.4 g/kg NPP, respectively, 1000 and 4000 phytase U/kg can be sufficient to obtain a comparable performance in broilers to those given diets adequate in available P.

Effect of high phytase inclusion rates on performance of broilers fed diets not severely limited in available phosphorus

Phytate is not only an unavailable source of phosphorus (P) for broilers but it also acts as an anti-nutrient, reducing protein and mineral absorption, increasing endogenous losses and reducing broiler performance. The objective of this study was to investigate the anti-nutritional effects of phytate by including high levels of phytase in diets not severely limited in available P. A total of 768 male Arbor Acres broilers were distributed in six treatments of eight replicate pens of 16 birds each consisting of a positive control diet (PC), positive control with 500 FTU/kg phytase, negative control (NC) diet with lower available P and calcium (Ca) levels and the same NC diet with 500, 1,000 or 1,500 FTU/kg phytase. Body weight gain (BWG), feed intake (FI), feed conversion ratio (FCR) and mortality were determined at 21 and 35 d of age while foot ash was determined in four birds per pen at 21 d of age. FI, FCR and foot ash where not affected by the lower mineral diets at 21 d of age nor by the enzyme inclusion but broilers fed lower Ca and available P diets had lower BWG. At 35 d of age no difference was observed between broilers fed the positive or NC diets but broilers fed 500, 1,000 and 1,500 FTU/kg on top of the NC diet had better FCR than broilers fed the positive control diet. When compared to birds fed a diet adequate in P, birds fed the same diet included with 500, 1,000 and 1,500 FTU/kg of phytase in marginally deficient available P and Ca diets had an improvement of performance. These results support the concept that hydrolysing phytate and reducing the anti-nutritional effects of phytate improves bird performance on marginally deficient diets that were not covering the P requirement of birds.

Effects of protease, phytase and a Bacillus sp. direct-fed microbial on nutrient and energy digestibility, ileal brush border digestive enzyme activity and cecal short-chain fatty acid concentration in broiler chickens

Two experiments were conducted to determine the effects of protease and phytase (PP) and a Bacillus sp. direct-fed microbial (DFM) on dietary energy and nutrient utilization in broiler chickens. In the first experiment, Ross 308 broiler chicks were fed diets supplemented with PP and DFM in a 2×2 factorial arrangement. The 4 diets (control (CON), CON + PP, CON + DFM, and CON + PP + DFM) were fed from 15–21 days of age. In Experiment 1, significant interaction (P≤0.01) between PP and DFM on the apparent ileal digestibility coefficient for starch, crude protein, and amino acid indicated that both additives increased the digestibility. Both additives increased the nitrogen retention coefficient with a significant interaction (P≤0.01). Although no interaction was observed, significant main effects (P≤0.01) for nitrogen-corrected apparent ME (AMEn) for PP or DFM indicated an additive response. In a follow-up experiment, Ross 308 broiler chicks were fed the same experimental diets from 1–21 days of age. Activities of ileal brush border maltase, sucrase, and L-alanine aminopeptidase were increased (P≤0.01) by PP addition, while a trend (P = 0.07) for increased sucrase activity was observed in chickens fed DFM, in Experiment 2. The proportion of cecal butyrate was increased (P≤0.01) by DFM addition. Increased nutrient utilization and nitrogen retention appear to involve separate but complementary mechanisms for PP and DFM, however AMEn responses appear to have separate and additive mechanisms.

Separate feeding of calcium improves performance and ileal nutrient digestibility in broiler chicks

A total of 144 Cobb 500 broilers were used to investigate if modern commercial broilers could regulate their calcium (Ca) intake using choice feeding and whether separating the delivery of a portion of the Ca from the mixed ration would be advantageous for performance and nutrient recovery. Birds were fed corn+soy-based diets formulated to contain 2.5, 5.0, 7.5 or 10.0 g/kg total Ca and all groups had access to a separate Ca source (CaCO3). The trial was conducted from Day 1 to Day 21 and birds had ad libitum access to both the experimental diets and a separate Ca source throughout. Total feed and separate Ca intake were monitored daily, weight gain and feed intake weekly and on Day 21, the apparent ileal digestibility of DM, nitrogen, selected minerals and amino acids were determined. Consumption of the separate Ca source increased (P < 0.05) with decreasing total Ca concentration of the mixed ration. No differences (P > 0.05) in toe ash were found. Increasing dietary Ca concentration negatively influenced the apparent ileal digestibility of DM, nitrogen, minerals and amino acids. It can be concluded that broilers can select and consume Ca from a separate source to broadly maintain their requirement. Feeding a separate source of Ca in combination with reduced dietary Ca in the mixed ration had beneficial effects on nutrient digestibility, phosphorus excretion and performance.

Extra-phosphoric effects of superdoses of a novel microbial phytase

An experiment was conducted to evaluate the influence of a novel microbial phytase on broiler performance from d 0 to 42 and tibia ash at d 21. Male Cobb 500 broilers (n = 2,016) were fed 1 of 7 experimental diets: positive control (PC) formulated to meet or exceed nutrient recommendations; PC plus dicalcium phosphate (PC+DCP) formulated to provide Ca and P at 0.10% above the PC; PC plus 500 U/kg of microbial phytase (PC+500); negative control (NC) with Ca and P reduced from the PC by 0.16 and 0.15%, respectively; and NC plus 500 (NC+500), 1,000 (NC+1,000), or 1,500 (NC+1,500) U/kg of microbial phytase. Diets were fed in 3 phases from d 0 to 21, d 22 to 42, and d 43 to 49 to 32 birds/pen and 9 replicate pens/diet. From d 0 to 21, broilers fed the NC diet had decreased (P ≤ 0.05) BW gain and tibia ash compared with broilers fed all other diets, except tibia ash in birds fed PC+500. Phytase supplementation at 500, 1,000, or 1,500 U/kg to the NC improved (P ≤ 0.05) BW gain and tibia ash comparable with the PC. Feed conversion ratio (FCR) was improved (P ≤ 0.05) in broilers fed NC+1,500 compared with broilers fed all other diets. From d 0 to 49, growth performance was not influenced (P > 0.05) by diet. However, FCR was improved (P ≤ 0.05) in broilers fed 1,500 U/kg of microbial phytase compared with broilers fed the PC, PC+DCP, and NC. There were no differences in performance or tibia ash between broilers fed the PC or PC+DCP, which would indicate the PC diet was sufficient in Ca and P. Therefore, the improvements in FCR in the NC+1500 may be associated with mitigation of the antinutrient effects of phytate rather than improved P utilization.

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.

Performance and total tract nutrient digestibility of growing pigs fed hulless low phytate barley

Woyengo, T. A., Akinremi, O. O., Rossnagel, B. G. and Nyachoti, C. M. 2012. Performance and total tract nutrient digestibility of growing pigs fed hulless low phytate barley. Can. J. Anim. Sci. 92: 505–511. An experiment was conducted to determine the performance and nutrient digestibility of growing pigs fed hulless low phytate (HLP) barley without or with phytase for 28 d. Twenty-four growing pigs (average initial body weight=25.3 kg) were fed three diets in a completely randomised design. The diets included a regular-hulled barley-based diet, and a HLP barley-based diet without or with phytase at 500 phytase units kg−1. Pigs fed the HLP barley-based diet without phytase had greater (P<0.05) average daily gain (0.911 vs. 0.717 kg), and apparent total tract digestibility of dry matter, energy, P, Mg, and Na were higher (P<0.05) than the regular barley-based diet. Supplementation of phytase to the HLP barley-based diet resulted in improved (P<0.05) feed conversion efficiency (0.506 vs. 0.547 kg kg−1), and apparent total tract digestibility of N, P and K. In conclusion, pigs fed the HLP barley-based diet had higher growth performance and nutrient digestibility than those fed the regular-hulled barley-based diet, indicating that the HLP barley is a better source of nutrients for pigs than regular barley. Phytase supplementation to the HLP barley-based diet can result in a further increase in nutrient utilisation by pigs.

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.

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 dietary sodium phytate and microbial phytase on the lipase activity and lipid metabolism of broiler chickens

The objective of the present study was to investigate the effect of dietary phytate and microbial phytase on the lipase activity, lipid metabolism and mRNA expressions of fatty acid synthase (FASN) and leptin in broiler chickens. The study was conducted as a 2 x 3 factorial arrangement of treatments with phytate phosphorus at 0.20 and 0.40 % (added as the sodium phytate) and supplemental microbial phytase at 0, 500, or 1000 phytase units/kg. The results showed that phytase improved (P < 0.05) the growth performance and ileal digestibility of nutrients of broilers, but phytate had no effect (P>0.05) on these parameters, except the decrease (P < 0.01) in the digestibility of Ca. Phytate decreased (P < 0.05) the lipase activity, serum total cholesterol (T-CHO) and hepatic TAG, and elevated (P < 0.01) serum NEFA and HDL cholesterol. Phytase decreased (P < 0.05) serum NEFA, but increased (P < 0.01) serum T-CHO and hepatic TAG. Phytate and phytase also influenced (P < 0.01) the mRNA expressions of leptin in the liver. There were significant (P < 0.05) interactions of phytate and phytase on the concentrations of serum TAG and LDL cholesterol, hepatic NEFA and T-CHO, and the mRNA expressions of FASN. The results suggest that phytate and phytase can affect lipase activity and lipid metabolism of broiler chickens.