Phytase supplementation effects on amino acid digestibility depend on the protein source in the diet but are not related to InsP6 degradation in broiler chickens

Feeding sunflower meal with pullets and laying hens even at a 30% inclusion rate does not impair the ileal digestibility of most amino acids

The use of locally available protein sources in poultry nutrition is challenging for feed manufacturers and farmers. Sunflower meal (SFM) is available in high quantities in several European countries and could be used as a poultry feedstuff at higher inclusion rates. However, its maximum inclusion rate in the diets of different poultry species and age categories is unknown. Pullets and laying hens can probably tolerate higher amounts of SFM, but only limited information is available on these poultry groups. Therefore, a digestibility trial was carried out with 8-week-old layer type pullets and 50-week-old laying hens. Beside a basal diet, SFM was fed at 10, 20 and 30% inclusion rates. Feeding SFM significantly improved the digestibility of essential amino acids (AA) of threonine, valine, lysine, tyrosine, glycine, aspartic acid, and arginine in the pullet diets. No such improvement was found in laying hens. Only the absorption of the two branch-chain AAs, leucin (pullets) and isoleucine (hens), declined due to SFM. The AA digestibility of the SFM itself was also calculated by linear regression. The coefficients were, in all cases, higher in hens than in pullets. Comparing the measured digestibility coefficients of SFM with table values, it can be concluded that high variance exists because of the differences in the methodology and the test animals in the digestibility trials. From the present trial, it can be concluded that SFM can entirely replace extracted soybean meal in pullet and layer diets, without negative effects on the protein digestion of birds.

Interactions of zinc with phytate and phytase in the digestive tract of poultry and pigs: a review

Phytase supplementation is gaining importance in animal nutrition because of its effect on phosphorus (P) digestibility and the increasing relevance of P for sustainable production. The potential inhibitors of phytase efficacy and phytate degradation, such as calcium (Ca) and zinc (Zn), have been a subject of intense research. This review focuses on the interactions of Zn with phytate and phytase in the digestive tract of poultry and pigs, with an emphasis on the effects of Zn supplementation on phytase efficacy and P digestibility. In vitro studies have shown the inhibitory effect of Zn on phytase efficacy. However, relevant in vivo studies are scarce and do not show consistent results for poultry and pigs. The results could be influenced by different factors, such as diet composition, amount of Zn supplement, mineral concentrations, and phytase supplementation, which limit the comparability of studies. The chosen response criteria to measure phytase efficacy, which is mainly tibia ash, could also influence the results. Compared to poultry, the literature findings are somewhat more conclusive in pigs, where pharmacological Zn doses (≥ 1000 mg kg-1 Zn) appear to reduce P digestibility. To appropriately evaluate the effects of non-pharmacological Zn doses, further studies are needed that provide comprehensive information on their experimental setup and include measurements of gastrointestinal phytate degradation to better understand the mechanisms associated with Zn and phytase supplements. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of dietary calcium concentration and exogenous phytase on inositol phosphate degradation, mineral digestibility, and gut microbiota in growing pigs

Variations in the dietary Ca concentration may affect inositol phosphate (InsP) degradation, and thereby, P digestibility in pigs. This study assessed the effects of dietary Ca concentration and exogenous phytase on InsP degradation, nutrient digestion and retention, blood metabolites, and microbiota composition in growing pigs with ileal cannulation. In a completely randomized row-column design with four periods, eight ileal-cannulated barrows (initial body weight 27 kg) were fed four corn-soybean- and rapeseed meal-based diets containing 5.5 or 8.5 g Ca/kg dry matter (DM), with or without 1,500 FTU of an exogenous hybrid-6-phytase/kg diet. No mineral P was added and the P concentration in the feed was 4.8 g P/kg DM. Prececal InsP6 disappearance in pigs fed diets containing exogenous phytase was lower (P = 0.022) with additional Ca than without. Concentrations of InsP2-4 isomers and myo-inositol in the distal ileal digesta and prececal P digestibility were greater (P < 0.001) with exogenous phytase than without exogenous phytase. In feces, InsP6 disappearance was lower (P < 0.002) and concentration of InsP5 and InsP4 isomers was higher (P ≤ 0.031) with additional Ca compared to without additional Ca. The prececal amino acid digestibility, energy digestibility, and hindgut disappearance of energy did not differ. The Shannon diversity index of the microbiota in the distal ileal digesta and feces was similar among the diets but was lower in the distal ileal digesta than in the feces (P < 0.001). Permutation analysis of variance revealed no dietary differences between the bacterial groups within the ileal digesta and fecal samples (P > 0.05). In conclusion, additional Ca reduced the effect of exogenous phytase on prececal InsP6 degradation. Endogenous InsP degradation was impaired by additional Ca only in the hindgut but the abundance of bacterial genera in feces was not affected.

Comparison of mucosal phosphatase activity, phytate degradation, and nutrient digestibility in 3-week-old turkeys and broilers at different dietary levels of phosphorus and phytase

A comparison between 3-wk-old female turkeys (B.U.T. 6) and broilers (Ross 308) was performed to study the effects of species, dietary P, Ca, and phytase levels on gut mucosal phosphatase activity, myo-inositol hexakisphosphate (InsP₆) degradation along the digestive tract, digestibility of P, Ca, and amino acids, and concentrations of myo-inositol in the digesta and blood. The experimental diets were corn-soybean meal-based and identical for both species. Two dietary P and Ca concentrations (CaP-: 4.1 g P/kg, 5.5 g Ca/kg and CaP+: 9.0 g P/kg, 12.0 g Ca/kg) and 2 levels of phytase supplementation (0 and 1,500 FTU/kg) were used in a 2 × 2 factorial design and fed to the animals for 7 d in their third week of age. Each diet was randomly assigned to 6 broiler and 6 turkey pens, with 10 birds each. After slaughter, blood, digesta from the crop, gizzard, duodenum, lower ileum, and mucosa from the jejunum were collected. When fed CaP- without phytase supplementation, there were no differences between species in gut mucosal phosphatase activity, prececal InsP₆ disappearance, and P and Ca digestibility, indicating a similar intrinsic capacity for phytate degradation in both species. When fed CaP+ without phytase supplementation, turkeys showed higher prececal InsP₆ disappearance than broilers. Phytase supplementation increased prececal InsP₆ disappearance and digestibility of P and Ca in both species. However, the phytase-induced increase in prececal InsP₆ disappearance was more pronounced in broilers than in turkeys, possibly due to more adequate conditions for phytase activity in the broiler crop. In broilers, phytase supplementation increased amino acid digestibility overall, whereas, in turkeys, it increased with CaP+ and decreased with CaP-. In addition, the relationship between myo-inositol concentration in the ileum and blood differed between species, indicating differences in myo-inositol metabolism. It was concluded that 3-week-old turkeys and broilers differ in nutrient digestibility and InsP degradation in some segments of the digestive tract but have similar endogenous InsP₆ degradation when fed low P and Ca diets.

Phytase Supplementation of Four Non-Conventional Ingredients Instead of Corn Enhances Phosphorus Utilization in Yellow-Feathered Broilers

The present study was conducted to evaluate the effects of unconventional feedstuff such as wheat, broken rice, distillers dried grains with soluble (DDGS), and wheat bran, replacing 15% of the corn in the basal diet and the supplementation of bacterial phytase on nutrition digestibility. A total of 500 yellow-feathered broilers with similar body weights of 1.65 ± 0.15 kg were divided into 10 dietary treatments with 5 replicates per treatment (5 male and 5 females per cage). The AME and AIDE were significantly higher when supplied with phytase (p < 0.01) in the DDGS group. The ileal and total tract digestibility of calcium and phosphorus were significantly increased in the phytase-supplied group (p < 0.001). Additionally, the ileal digestibility of CP was increased when phytase was supplemented (p < 0.001). The results infer that the wheat, broken rice, DDGS, and wheat bran had no negative effect when replacing 15% corn. Supplementing 0.02% phytase in their diets can effectively optimize nutrient digestibility in yellow broilers.

Modeling improvements in ileal digestible amino acids by a novel consensus bacterial 6-phytase variant in broilers

Data from 13 datasets from 4 trials on the effect of a novel consensus bacterial 6-phytase variant (PhyG) on the apparent ileal digestibility (AID) of amino acids (AA) in broilers were used to model AID AA responses. The datasets were obtained from 3 trial locations (New Zealand, Australia and United States) and collectively incorporated variations in diet composition (feedstuff composition, phytate-P (PP) level, limestone solubility), feed form (mash or pellet), bird genetics (strain), and age at sampling (11-35 d of age). In total, 384 observations were analyzed. First, the relationships between AID of AA (as coefficients) and increasing phytase dose level from 0 to 4,000 FTU/kg were evaluated across all datasets using exponential curve fitting. Second, the percentage unit change in AID of AA at each phytase dose level from baseline (basal diet [BD] without phytase) was calculated separately for each dataset and the data then modeled together using exponential curve fitting. The model-predicted mean coefficient of AID of total AA in basal diets was 0.76 (range 0.56 [Cys] to 0.83 [Glu]), which was increased by PhyG to 0.80 and 0.81 at 2,000 and 4,000 FTU/kg, respectively. Exponential increases in the percentage unit improvement in AID of 18 individual and of total AA with increasing phytase dose level were evident (P < 0.05). Improvements (vs. BD) at 2,000 FTU/kg and 4,000 FTU/kg, respectively, were greatest for Cys (+9.2 and +11.0% units), Met (after deduction of synthetic Met, +8.4 and +9.0% units), and Thr (after deduction of synthetic Thr, +6.2 and +7.3% units). The data demonstrated consistent improvements in the AID of AA by the phytase. The modeling results generated from data gathered from birds sampled at different ages and from different dietary settings with correction of synthetic AA for Lys, Met, Thr, and Trp, enabled a more accurate prediction of the digestible AA contribution from the diet by this novel phytase. This will allow diet-specific AA matrix recommendations to be made in commercial feed formulations.

Effects of a novel consensus bacterial 6-phytase variant on the apparent ileal digestibility of amino acids, total tract phosphorus retention and tibia ash in young broilers

The effect of a novel consensus bacterial 6-phytase variant (PhyG) on apparent ileal digestibility (AID) of amino acids (AA) and phosphorus (P) utilization in young broilers when added to diets with high phytate-P (PP) content without added inorganic phosphate (Pi) and deficient in digestible (dig) AA and metabolizable energy (ME) was investigated. A total of 256 Ross 308 male broilers were assigned to 4 treatments (8 birds/cage, 8 cages/treatment) in a completely randomized design. Treatments comprised a positive control (PC, 2,975 kcal/kg ME, 3.7 g/kg dig P, 2.83 g/kg PP, 8.4 g/kg Ca, 10.6 g/kg dig lysine), a negative control (NC) without added Pi (ME −68 kcal/kg, crude protein −10 g/kg, dig AA −0.1 to −0.4 g/kg, Ca −2.0 g/kg, dig P −2.2 g/kg, Na −0.4 g/kg vs. PC), and NC plus 500 or 1,000 FTU/kg of PhyG. Test diets were corn/soy/rapeseed-meal/rice-bran-based and fed from 5 to 15 d of age. Ileal digesta and tibias were collected on day 15. Excreta was collected during days 12 to 15 to determine P retention. The NC (vs. PC) reduced (P < 0.05) P retention (−10.4% units), tibia ash (−14.3% units), weight gain (−109 g), feed intake (−82 g) and increased FCR (from 1.199 to 1.504), confirming that the NC was extremely deficient in nutrients and energy. Phytase addition to the NC linearly (P < 0.001) improved performance, but did not fully recover it to the level of the PC due to the severe nutrients/energy reduction in NC. Phytase linearly increased P retention (P < 0.001), tibia ash (P < 0.001), AID of dry matter (P < 0.05), nitrogen (P < 0.01), gross energy (P < 0.05), and all 17 individual AA (P < 0.01). At 1,000 FTU/kg, phytase increased (P < 0.05) P retention vs. PC and NC (+14.5 and +24.9% units, respectively) and increased tibia ash vs. NC (+13.8% units), equivalent to PC. The NC decreased AID of Cys, Gly, Thr, and Met vs. PC (P < 0.05). At 1,000 FTU/kg, phytase increased AID of all 17 AA vs. NC (P < 0.01), equivalent to PC. At 1,000 FTU/kg, AID AA responses (above NC) ranged from +4.5% (Met) to +15.0% (Cys), being maximal for essential Thr (+10.4%) and Val (+8.2%) and non-essential Cys (+15.0%) and Gly (+10.4%). The results highlight the efficacy of PhyG at a dose level of 500 to 1,000 FTU/kg in young broilers for improving the ileal digestibility of nitrogen, AA, and energy alongside P retention and tibia ash. The performance data emphasize the need to consider digestible nutrient intake as a response variable in exogenous enzyme studies.

Microbial phytase is widely used in commercial broiler diets to improve digestion of phosphorus (P) and reduce its excretion into the environment. Phytase improves the digestion of phosphorus and other nutrients including amino acids (AA). This study evaluated the effect of a novel consensus bacterial 6-phytase variant (PhyG) added to a nutrient-reduced diet without any added inorganic P on the digestibility of nutrients including P and AA in the ileum of young broilers. Effects on P retention and bone mineralization were also assessed. Compared to an unsupplemented negative control diet, PhyG improved growth performance, P retention, bone mineralization (tibia ash), digestibility of dry matter, nitrogen, gross energy, and all 17 individual AA during 5 to 15 d post-hatch, in a dose-dependent manner (dose range 0 to 1,000 phytase units [FTU] per kilogram of feed). For some AA, the increases in digestibility with PhyG at 1,000 FTU/kg were substantial (cysteine: +15.0%, threonine:+10.4%), and for all AA were equivalent to the responses produced by a nutritionally adequate positive control (unsupplemented) diet. The results demonstrate the efficacy of PhyG to improve AA digestibility alongside growth performance, P retention, and bone mineralization in young broilers.

Amino acid digestibility and metabolisable energy of spring and winter faba beans grown on two sites and effects of dehulling in caecectomised laying hens

BACKGROUND

The variation in amino acid (AA) digestibility and metabolisable energy (ME_N ) in four spring and four winter faba bean genotypes differing in vicine/convicine (V/C) concentrations grown on two sites was investigated in caecectomised LSL-Classic laying hens. Effects of dehulling one faba bean genotype were also examined. Diets containing one out of 17 faba bean variants each and a basal diet were fed to ten caecectomised laying hens in a row-column design to achieve five replicates per diet.

RESULTS

Ranges and levels of digestibility of the hulled variants differed widely among AA with the lowest and highest range determined for Arg (90-93%) and Cys (-12-65%), respectively. ME_N ranged between 10.3 and 12.3 MJ kg^-1 dry matter. Lower ME_N and digestibility of Cys, Glx, Phe, Pro, Tyr, and Val (P < 0.050) was determined for the winter genotypes grown in Nimtitz compared to the other variants. Digestibility of Ser was lower for the spring than for the winter genotypes (P < 0.050). Negative correlations with AA digestibility were determined for phytate, but not for tannin and V/C concentrations (P < 0.050). Negative correlations between tannin fractions and ME_N were weak (P = 0.082-0.099). Dehulling increased ME_N by 1.8 MJ kg^-1 dry matter and raised the digestibility of Pro, His, and Glx (P < 0.050).

CONCLUSIONS

The results indicated that the digestible AA and ME_N supply of laying hens was increased by using low phytate faba beans while breeding for low V/C genotypes did not affect AA digestibility or ME_N . Dehulling increased ME_N and the digestibility of some AA. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Low-calcium diets increase duodenal mRNA expression of calcium and phosphorus transporters and claudins but compromise growth performance irrespective of microbial phytase inclusion in broilers

The hypothesis that dietary inclusion of microbial phytase improves apparent calcium (Ca) digestibility thereby allowing a lower dietary Ca inclusion without compromising growth performance was tested. One-day-old male Ross 308 broilers (25 birds/pen, 9 pens/treatment) were assigned to 8 experimental diets containing one of 4 dietary Ca to retainable P (rP) ratios (1.3, 1.8, 2.3, and 2.8) with (1,000 FTU/kg) or without microbial phytase. On d 21 to 23, digesta from different intestinal segments of 8 birds per pen were collected to determine apparent Ca and P digestibility. Mid duodenal mucosa was collected for expression of Ca (CaBP-D28k, PMCA1) and P (NaPi-IIb, PiT-1, PiT-2, and XPR1) transporters by RT-qPCR. Dietary phytase inclusion in low Ca/rP diets increased Ca digestibility in the distal ileum (P_interaction = 0.023) but not the proximal or distal jejunum. Broilers receiving the lowest Ca/rP displayed the lowest body weight gain, highest feed conversion ratio (P < 0.001), and lowest tibia strength, irrespective of dietary phytase inclusion. Incremental dietary Ca/rP linearly reduced P digestibility to a greater extent in the absence of phytase in the distal jejunum and ileum (P_interaction = 0.021 and 0.001, respectively). Incremental dietary Ca/rP linearly reduced serum P more in phytase-free diets (P_interaction < 0.001), and lowered duodenal expression of P transporters NaPi-IIb, PiT-2, and XPR1 (P = 0.052, 0.071 and 0.028, respectively). Incremental dietary Ca/rP linearly increased (P < 0.001) serum Ca irrespective of phytase inclusion, accompanied by a lower (P < 0.001) duodenal expression of Ca transporters CaSR, CaBP-D28k and PMCA1 and Ca-pore forming claudins CLDN-2 and CLDN-12. Dietary phytase increased (P = 0.026) NaPi-IIb but reduced (P = 0.029) CLDN-2 expression. Incremental Ca/rP reduced Ca and P digestibility, increased serum Ca, lowered serum P and inhibited mRNA levels of Ca and P-related transporters, indicating that these transporters and CLDN contribute to the observed effect of dietary Ca and phytase on Ca and P absorption. Despite the improvement in Ca digestibility, dietary phytase did not restore the compromised growth performance and tibia strength of broilers fed a Ca-deficient diet, leading to rejection of the hypothesis.

Phytase Supplementation Effects on Amino Acid Digestibility in Broiler Chickens are Influenced by Dietary Calcium Concentrations but not by Acid-Binding Capacity

BACKGROUND

Responses to dietary calcium (Ca) and supplemented phytase on prececal amino acid digestibility (pcAAD) in broiler chickens vary among studies. The variation may arise from the dietary acid-binding capacity (ABC) that influences the activity of enzymes in the digestive tract and from microbial activity.

OBJECTIVE

This study aimed to investigate whether the ABC influences phytase effects on pcAAD and whether microbial activity contributes to this.

METHODS

Male Ross 308 broiler chickens were provided 1 of 12 diets in 72 pens (15/pen) from day 16 of age until the end of the experiment on days 21 or 22. In a 3 × 2 × 2-factorial arrangement, the ABC was varied by replacing calcium carbonate (CaCO3) with Ca-formate or by adding formic acid to CaCO3-containing diets, and contained 5.6 or 8.2 g Ca/kg and 0 or 1500 phytase units/kg. The ileum content was collected for pcAAD measurement and microbial community composition was used to investigate whether changes in pcAAD are related to the microbiota.

RESULTS

Three-factor ANOVA showed that reducing the ABC increased pcAAD (average 1.1 percentage points) and no significant interaction of the ABC with Ca concentration and phytase supplementation including 3-way interactions. Without phytase, increasing dietary Ca concentration decreased pcAAD (average 3.1 percentage points). Phytase supplementation increased pcAAD (average 2.1 and 5.0 percentage points at low and high Ca concentrations, respectively), to reach the same level for both Ca concentrations. Microbial functional predictions pointed towards an influence of the microbiota in the crop and ileum content on amino acid concentrations, as indicated by different relative abundances of predicted genes related to amino acid biosynthesis, degradation, and metabolism.

CONCLUSIONS

Dietary Ca concentrations but not the ABC modulates the effect of supplemented phytase on pcAAD in broiler chickens. The microbiota might contribute to differences in pcAAD by changing the amino acid composition of the digesta. The extent of this effect is still unknown.