Unlocking Phytate with Phytase: A Meta-Analytic View of Meat-Type Chicken Muscle Growth and Bone Mineralization Potential

The inclusion of exogenous phytase in P- and Ca-deficient diets of broilers to address the growing concern about excessive P excretion into the environment over the years has been remarkably documented. However, responses among these studies have been inconsistent because of the several factors affecting P utilization. For this reason, a systematic review with a meta-analysis of results from forty-one studies published from 2000 to February 2024 was evaluated to achieve the following: (1) quantitatively summarize the size of phytase effect on growth performance, bone strength and mineralization in broilers fed diets deficient in P and Ca and (2) estimate and explore the heterogeneity in the effect size of outcomes using subgroup and meta-regression analyses. The quality of the included studies was assessed using the Cochrane Collaboration's SYRCLE risk of bias checklists for animal studies. Applying the random effects models, Hedges' g effect size of supplemented phytase was calculated using the R software (version 4.3.3, Angel Food Cake) to determine the standardized mean difference (SMD) at a 95% confidence interval. Subgroup analysis and meta-regression were used to further explore the effect size heterogeneity (PSMD ≤ 0.05, I2 > 50%, n ≥ 10). The meta-analysis showed that supplemental phytase increases ADFI and BWG and improves FCR at each time point of growth (p < 0.0001). Additionally, phytase supplementation consistently increased tibia ash, P and Ca, and bone strength (p < 0.0001) of broilers fed P- and Ca-deficient diets. The results of the subgroup and meta-regression analyses showed that the age and strain of broiler, dietary P source, and the duration of phytase exposure significantly influence the effect size of phytase on growth and bone parameters. In conclusion, phytase can attenuate the effect of reducing dietary-available phosphorus and calcium and improve ADFI, BWG, and FCR, especially when added to starter diets. It further enhances bone ash, bone mineralization, and the bone-breaking strength of broilers, even though the effects of bone ash and strength can be maximized in the starter phase of growth. However, the effect sizes of phytase were related to the age and strain of the broiler, dietary P source, and the duration of phytase exposure rather than the dosage.

Effect of dietary zinc source, zinc concentration, and exogenous phytase on intestinal phytate degradation products, bone mineralization, and zinc status of broiler chickens

This study aimed to determine the effect of Zn source and dietary level on intestinal myo-inositol hexakisphosphate (InsP6) disappearance, intestinal accumulation of lower InsP and myo-inositol (MI), prececal mineral digestibility, bone mineralization, and Zn status of broilers without and with exogenous phytase in the feed. Male Ross 308 broilers were allocated in groups of 10 to 8 treatments with 8 pens each. Experimental diets were fed from d 7 to d 28 and contained 33 mg/kg dry matter plant-intrinsic Zn. Experimental factors were phytase supplementation (0 or 750 FTU/kg) and Zn source (none [0 mg/kg Zn], Zn-sulfate [30 mg/kg Zn], Zn-oxide [30 mg/kg Zn]). Additional treatments with 90 mg/kg Zn as Zn-sulfate or Zn-oxide and phytase were included to test the effect of Zn level. No Zn source or Zn level effects were observed for ADG, feed conversion ratio, prececal P digestibility, intestinal InsP6 disappearance, and bone ash concentration. However, those measurements were increased by exogenous phytase (P < 0.001), except the feed conversion ratio, which was decreased (P < 0.001). Ileal MI concentrations were affected by phytase × Zn source interaction (P < 0.030). Birds receiving exogenous phytase and Zn supplementation had the highest MI concentrations regardless of exogenous Zn source, whereas MI concentrations were intermediate for birds receiving exogenous phytase only. Exogenous phytase and exogenous Zn source increased the Zn concentration in bone and blood of broilers (P < 0.001). In conclusion, measures of exogenous phytase efficacy were not affected by phytase × Zn source interaction. Further studies are needed to rule out an effect from Zn sources other than those tested in this study and to investigate the effect of Zn supplementation on endogenous phosphatases. The missing effect of increasing Zn supplementation from 30 to 90 mg/kg in phytase-supplemented diets gives reason to reconsider the Zn supplementation level used by the industry.

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.

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.

Effect of Phytase Level and Form on Broiler Performance, Tibia Characteristics, and Residual Fecal Phytate Phosphorus in Broilers from 1 to 21 Days of Age

The present study evaluated the individual and combined effects of coated and uncoated phytase on broiler performance, tibia characteristics, and residual phytate phosphorus (P) in manure. Two repeated studies were conducted using 240-day-old Cobb 500 by-product male broilers per trial. For each trial, birds were assigned to four treatments with four replicate battery cages per treatment (60 birds/trt) and grown for 21 days. Treatments included: (1) negative control (NC), (2) NC + 1000 phytase units (FTU) coated phytase (C), (3) NC + 1000 FTU uncoated phytase (U), and (4) NC + 500 FTU coated + 500 FTU uncoated phytase (CU). Data were analyzed with a one-way ANOVA and means were separated using Tukey’s HSD. In the pooled data for both trials, all treatments with dietary phytase had a higher body weight (BW) and feed consumption (FC) than the NC on day 21 (p < 0.05). Similarly, a six-point reduction was observed for day 1 to 21 feed conversion (FCR) for U and CU (p < 0.05). All treatments with phytase inclusion differed from the NC in every evaluated parameter for bone mineralization (p < 0.05) and had significantly lower fecal phytate P concentrations compared to the NC (p < 0.05). Overall, bird performance was essentially unaffected by phytase form, indicating that combining phytase forms does not appear to offer any advantage to the evaluated parameters from day 1 to 21.

Progress on Gut Health Maintenance and Antibiotic Alternatives in Broiler Chicken Production

The perturbation of gut health is a common yet unresolved problem in broiler chicken production. Antibiotics used as growth promoters have remarkably improved the broiler production industry with high feed conversion efficiency and reduced intestinal problems. However, the misuse of antibiotics has also led to the increase in the development of antibiotic resistance and antibiotic residues in the meat. Many countries have enacted laws prohibiting the use of antibiotics in livestock production because of the increasing concerns from the consumers and the public. Consequently, one of the most significant discussions in the poultry industry is currently antibiotic-free livestock production. However, the biggest challenge in animal husbandry globally is the complete removal of antibiotics. The necessity to venture into antibiotic-free production has led researchers to look for alternatives to antibiotics in broiler chicken production. Many strategies can be used to replace the use of antibiotics in broiler farming. In recent years, many studies have been conducted to identify functional feed additives with similar beneficial effects as antibiotic growth promoters. Attention has been focused on prebiotics, probiotics, organic acids, emulsifiers, enzymes, essential oils, tributyrin, and medium-chain fatty acids. In this review, we focused on recent discoveries on gut health maintenance through the use of these functional feed additives as alternatives to antibiotics in the past 10 years to provide novel insights into the design of antibiotic-free feeds.

Effect of sodium sources and exogenous phytase supplementation on growth performance, nutrient digestibility, and digesta pH of 21-day-old broilers

The effect of sodium chloride (NaCl) and NaCl+sodium hydrogen carbonate (NaHCO3) and supplemental phytase (0, 500, 1,000, and 2,000 FTU/kg) on performance, nutrient digestibility and utilization, and digesta pH of male broiler chickens were investigated in a 2 × 4+1 factorial arrangement of treatments in a completely randomized design with 6 replicate cages of 8 birds per replicate. Data were analyzed as a 2 × 4 factorial with contrast between the positive control and the diets containing 0 FTU phytase. Phytase supplementation linearly improved (P < 0.05) average body weigh gain (BWG) and feed intake (d 0-14 and 0-21). Apparent jejunal dry matter (DM) digestibility and digestible energy in birds fed diets containing only NaCl increased (linear and quadratic; P < 0.05) with phytase supplementation whereas quadratic (P < 0.05) effect was observed in birds fed diets containing a combination of NaCl and NaHCO3. Phytase supplementation improved (linear and quadratic; P < 0.05) apparent ileal nitrogen and P digestibility. Apparent utilization of DM, nitrogen, energy, and metabolizable energy increased (linear; P < 0.05) with increasing level of phytase supplementation. Apparent P utilization increased (linear and quadratic; P < 0.05) for both sodium sources but calcium utilization only increased (linear; P < 0.05) with the combination of NaCl and NaHCO3. Bone breaking strength (linear and quadratic) and bone ash (linear) increased (P < 0.05) with phytase supplementation. The combination of NaCl and NaHCO3 resulted in lower (P < 0.05) pH of digesta in the proximal ileum whereas the pH of the digesta in the distal ileum (linear) and the average pH of ileal contents (linear and quadratic) increased (P < 0.05) with phytase supplementation. Results from this study showed that birds' performance and utilization of nutrients and energy by broilers in the presence of phytase was, in general, not influenced by the source of sodium in the diet. Data from this study showed that NaHCO3 can replace a portion of NaCl in the diet of broilers supplemented with phytase without any significant negative effect on performance and that the 2,000 FTU phytase level resulted in better BWG and feed intake as well nutrient and energy utilization.

Evaluation of the responses of broiler chickens to varying concentrations of phytate phosphorus and phytase. Ⅰ. Starter phase (day 1-11 post hatching)

Growth performance, tibia ash, apparent ileal digestibility (AID), and total tract retention (TTR) of nutrients responses of broiler chickens fed diets containing varying concentrations of phytate P (PP) and a novel consensus bacterial 6-phytase variant (PhyG) from d 1 to 11 post hatching were evaluated with 1,152 broiler chicks. Diets were a nutrient-adequate positive control diet (PC) with 2.8 g PP/kg or one of 15 nutrient-reduced negative control (NC: PC minus 88 kcal/kg ME, 0.8 g/kg dig. Lys, 2.0 g/kg available P, 1.8 g/kg Ca and 0.5 g/kg Na) diets with 3 PP (g/kg) levels, mainly from rice bran, at 2.3 (NC1), 2.8 (NC2), or 3.3 (NC3) and 5 PhyG supplementation at 0, 500, 1,000, 2,000, or 4,000 FTU/kg in a 1 + 3 × 5 factorial. All treatments had 6 replicate cages with 12 birds per cage. Despite comparable PP levels, birds fed the PC diet had greater (P ≤ 0.01) body weight (BW), feed intake (FI), tibia ash, AID of energy, AA, P, and Ca as compared with birds fed the NC2 without phytase. There was no interaction between PP and phytase for all responses. Increasing PP concentrations linearly decreased (P < 0.01) BW, FI, AID, and TTR of P and Ca. With phytase supplementation, there was a quadratic response (P < 0.05) in BW, FI, tibia ash, and a linear increase (P < 0.05) in the AID of energy, nitrogen, and all the measured AA. Increasing phytase dose from 0 to 4,000 FTU/kg increased (P < 0.01) AID of P and Ca by 88 and 18%, respectively. There was also a quadratic response (P ≤ 0.05) on TTR of P and Ca with increasing phytase dose. In conclusion, increasing levels of PP reduced growth performance and most nutrient utilization responses of broiler chickens while phytase supplementation positively impacted the responses of broiler chickens during d 1 to 11 post hatching.

Evaluation of a novel hybrid 6-phytase using an updated phosphorus deficiency model in broiler chickens

One-day-old broiler chicks were used to investigate the optimal age to start feeding phosphorus (P)-deficient (PD) diets with two non-phytate P (nPP) concentrations in experiment 1, and 7-d-old broiler chicks were used to determine P equivalency of a hybrid 6-phytase to inorganic P in monocalcium phosphate (MCP) in experiment 2. In experiment 1, six treatments were prepared with 5, 6, or 7-d-old birds to start feeding PD diets with 1.3 or 1.5 g·kg−1 nPP. Age of birds to start feeding P-deficient diets tended to decrease (P = 0.052) mortality of birds during 14 d of feeding P-deficient diets. In experiment 2, twelve treatments including one basal diet, five diets supplied with 0.5, 0.9, 1.3, 1.7, or 2.1 g·kg−1 inorganic P, and six diets supplied with 250, 500, 750, 1000, 1500, or 2000 FTU·kg−1 phytase were fed to chickens from days 7 to 21 post hatching. Increasing phytase activity quadratically increased (P < 0.01) body weight gain, feed intake, and tibia ash of birds and apparent ileal digestibility and total tract retention of P. In conclusion, age of birds to start feeding PD diet affected their performance, and hybrid 6-phytase may partly replace MCP in a PD diet for broiler chickens.

Additivity of apparent and standardized ileal digestibility of phosphorus in mixed diets containing corn and soybean meal fed to broiler chickens

Phosphorus (P) is an integral part of diet formulation for broiler chickens as P is required for various biochemical processes essential to life. A study was designed to examine the additivity of apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of P in mixed diets containing corn and soybean meal (SBM) with or without phytase supplementation. Birds were fed a commercial starter diet from day 0 to 21 after hatching and then allotted to 7 dietary treatments in a randomized complete block design with the BW as a blocking factor. Four semipurified diets were prepared to contain corn or SBM as the sole source of P with or without the addition of phytase at 1,000 phytase units/kg of diet. Two mixed diets were also prepared to contain corn and SBM with or without the addition of phytase at 1,000 phytase units/kg diet. A P-free diet (PFD) was formulated to determine the basal ileal endogenous loss of P. There were 16 replicate cages of the PFD and 8 replicate cages of the 6 experimental diets, with 8 birds per replicate cage for a total of 512 birds. Diets were fed for 3 d. The ileal digesta of birds were collected from the distal two-thirds of the ileum on day 24 after hatching. The SID of P in corn and SBM were 52.2 and 65.4%, respectively (SEM = 1.37). The addition of phytase improved (P < 0.05) both the AID and SID of P in the corn, SBM, and mixed diets. The determined AID or SID in the corn and SBM with or without phytase was used to predict the AID or SID in the mixed diets. There were no differences between the predicted and determined digestibility values in the mixed diets for either AID or SID of P and thus additive. Phytase supplementation of the mixed diet did not influence the additivity of AID or SID. In conclusion, the AID or SID of P in the corn and SBM was additive in the mixed diets containing corn and SBM with or without the addition of phytase.

Additivity of apparent and standardised ileal digestibility of phosphorus in corn and canola meal mixed diets; basal endogenous loss of phosphorus responses to phytase and age in broiler chickens

1. The additivity of apparent ileal digestibility (AID) and standardised ileal digestibility (SID) of phosphorus (P) in mixed diets containing corn and canola meal (CCM) with or without phytase supplementation and the impact of age on the basal ileal endogenous loss (BEL) of P were investigated in broiler chickens.2. Treatments were arranged as a 2 × 3 × 2 factorial with two ages (13 d or 21 d post hatching), three diets (corn, canola meal, or CCM), and two phytase levels (0 or 1,000 FYT/kg diet) in a randomised complete block design. There were eight or six birds per cage at 13 d and 21 d of age, respectively, and six replicate cages per treatment, with a total of 588 birds. A P-free diet (PFD) treatment was included at each age to determine the basal endogenous loss (BEL) of P.3. Birds were fed a commercial starter diet from d 1 to d 10 or d 18 and then fed the experimental diets for 3 d until d 13 or d 21, respectively. Predicted digestibility values calculated from the individual feed ingredients were used to test additivity in the mixed diets. Chromium oxide was included in diets as an indigestible marker.4. The ileal digesta, collected from birds at d 13 or d 21, was used to determine nutrient digestibility.5. The AID and SID of P at d 13 was higher (P < 0.01) when compared with older birds at d 21, regardless of dietary phytase supplementation. Regardless of age or phytase supplementation, AID and SID of P were additive, as there were no differences between predicted and determined values in the mixed diets. The BEL of P (g/kg DM intake) in birds at d 13 was higher (P < 0.05) than birds at d 21 (0.197 vs. 0.159).6. In conclusion, age had an impact on the BEL of P and the utilisation of minerals in the diets. The apparent and standardised ileal digestibility of P in the mixed diet containing corn and canola meal were additive, regardless of age or phytase supplementation.

Response of broiler chickens in the starter and finisher phases to 3 sources of microbial phytase

A broiler chicken study was conducted for 42 D to evaluate their responses to 3 commercially available microbial phytases. Growth performance, nutrient digestibility, and bone mineralization at days 21 and 42 posthatching were used as parameters of evaluation. The study was a randomized complete block design with 12 treatments, 8 replicate pens, and 25 birds per pen. Treatments included a positive control (PC), a negative control (NC) with crude protein (CP), nonphytate phosphorus (P), and calcium (Ca) reduced by 18, 1.5, and 1.8 g/kg, respectively; the NC + 4 levels of phytase A (250, 500, 750, 1,000 FTU/kg), 3 levels of phytase B (250, 500, 750 FTU/kg), and 3 levels of phytase C (500, 750, 1,000 FTU/kg). Broilers fed the NC diet had reduced (P < 0.05) performance and digestibility measures at days 21 and 42 relative to the PC. All phytase enzymes improved (P < 0.05) BW, gain, feed efficiency, and tibia ash weight and percent. Inclusion of phytase at the highest levels improved (P < 0.05) tibia ash weight by an average of 18.5 and 22% at days 21 and 42, respectively, over the NC. Phytase A linearly improved (P < 0.05) the apparent ileal digestibility (AID) of DM, Ca, P, copper, and sodium at day 21, and the AID of energy, nitrogen, and all amino acid (AA) digestibility at day 42 posthatching. Phytase B linearly (P < 0.05) improved BW gain and feed efficiency of birds at day 21 and quadratically improved (P < 0.05) the AID of nitrogen and all AA in birds at day 42. Supplementation of birds fed the NC with phytase C linearly improved (P < 0.05) the BW gain, feed intake, feed efficiency, and AID of DM, energy, nitrogen, all AA, and all minerals except manganese at day 42. In conclusion, all 3 phytase products improved the growth performance, nutrient and mineral digestibility, and bone mineralization of birds fed diets deficient in nitrogen, Ca, and P similar to or more than birds fed diet adequate in P and CP.

The impact of age and feeding length on phytase efficacy during the starter phase of broiler chickens

Phytase is of importance to the poultry industry because of its ability to hydrolyze phytate and release phosphorus (P) for use by poultry. However, the effect of age on phytase efficacy is not fully understood. A total of 864 day-old broiler chicks were used to investigate the effect of age and feeding length on phytase efficacy using growth performance, mineral utilization, and tibia ash as response criteria of evaluation. The experiment was arranged as a 3 × 2 × 2 factorial in a randomized complete block design with 3 diets including; a positive control (PC; 0.4% non-phytate P (nPP)), a negative control (NC; 0.2% nPP) and a NC diet supplemented with phytase at 2,000 FYT/kg; 2 ages (i.e., days 14 and 22); and 2 feeding lengths (i.e., 2 and 5 D) with 8 replicates each. Birds fed the NC had decreased (P < 0.01) body weight gain and feed efficiency compared with birds fed the PC regardless of age or feeding length. Similarly, birds fed the phytase-supplemented diet had improved (P < 0.01) performance as compared to birds fed the NC regardless of age. There were no significant differences in P utilization between birds fed for 2 to 14 D or 22 D and birds fed for 5 D to both ages. However, phytase was more efficacious at day 14 than day 22 when mineral utilization was considered because the super dose of phytase elicited greater response in birds fed the phytase supplemented diet for 2 D until day 14. In contrast, percentage tibia ash improved (P < 0.01) in birds fed phytase supplemented diet for 5 D at both ages as compared with birds fed for 2 D. In conclusion, testing phytase products, even at high doses, for 2 D during the second week in the life cycle of broiler chicks, can be recommended from the results of this study.

Effects of available phosphorus source and concentration on performance and expression of sodium phosphate type IIb cotransporter, vitamin D-1α-hydroxylase, and vitamin D-24-hydroxylase mRNA in broiler chicks

This experiment was conducted to examine the effect of 2 phosphorus (P) sources on broiler performance to day 14. The P bioavailability was estimated using bird performance and tibia ash measurements, whereas P digestibility, intestinal P transporter, kidney vitamin D-1α-hydroxylase, and vitamin D-24-hydroxylase mRNA abundances were also determined. Slope regression analysis was used to determine the bioavailability of dicalcium phosphate (Dical P) and nanocalcium phosphate (Nano P) with dietary available P (AvP) set to 0.20% P (control) using AvP from the major ingredients and Dical P. The experimental treatments were achieved by supplementation with either Dical P or Nano P to generate 0.24, 0.28, 0.32, and 0.36% AvP. A total of 648-day-old unsexed broiler chicks were divided into 72 birds per treatment (8 replicate cages of 9 birds). Slope regression analysis showed positive linear relationships between BW, feed intake (FI), tibia ash weight (TAW), and tibia ash percentage (TAP) with dietary Dical P and Nano P levels. Comparisons between regression slopes for Dical P and Nano P fed birds were not significantly different for BW, feed intake, tibia ash weight, and tibia ash percentage, indicating similar P bioavailability from Dical P and Nano P. There were interactions between P source and AvP for feed efficiency (FE) and apparent ileal P digestibility (AIPD). Dicalcium phosphate had greater FE than Nano P at 0.28% AvP and greater AIPD than Nano P at 0.24% AvP. The addition of AvP from Dical P and Nano P resulted in reduced sodium phosphate cotransporter mRNA abundance in the duodenum in a dose–dependent response. In the kidney, vitamin D-1α-hydroxylase mRNA abundance was greater at 0.36% Nano P compared with control, but there was no difference with Dical P. There was no difference in vitamin D-24-hydroxylase mRNA abundance between control and supplementation with Nano P or Dical P. In conclusion, Nano P and Dical P had the same bioavailability but had different effects on gene expression.

Influence of age and duration of feeding low-phosphorus diet on phytase efficacy in broiler chickens during the starter phase

A total of 1,408 male broiler chickens were used to evaluate the impact of age and duration of feeding low-phosphorus (P) diet on the efficacy of phytase using growth performance, nutrient utilization, tibia ash, and plasma indices. Diets were formulated with 2 non-phytate P (nPP) concentrations (i.e., 0.20 and 0.40%) and 2 phytase concentrations (i.e., 1,000 and 2,000 FTU/kg) added to the 0.20% nPP diet. Four dietary treatments with 8 replicate cages each were fed to broiler chicks at different ages and for different duration. Specifically, these were days 6 to 8 (12 birds per replicate), 12 to 14, 9 to 14, 20 to 22, or 6 to 22 (8 birds per replicate). Parameters were measured on the last day of each period. Duration of feeding effect was examined by comparing responses of birds fed for 2 or 5 D at day 14 and for 2 or 16 D at day 22; age effect was determined by comparing responses of birds fed for 2 D at age 8, 14 and 22 D post-hatching. Body weight gain and gain-to-feed ratio were increased (P < 0.01) in birds fed diets supplemented with phytase; however, an increase in duration of feeding improved (P < 0.01) feed efficiency with birds fed for 16 D performing better than birds fed for 2 D at day 22. In addition, phytase supplementation improved (P < 0.01) apparent P and calcium digestibility and retention, but the age effect on phytase efficacy was more apparent at day 14 and the duration of feeding effect was evident in birds fed for 2 D due to the increased levels of mineral utilization at that age/duration of feeding as compared with the other groups. The results of this study show that phytase efficacy was at optimum in birds fed low-P diet for 2 D at day 14. This period can be recommended for further bioefficacy studies of phytase.

Phosphorus absorption and gene expression levels of related transporters in the small intestine of broilers

To investigate the P absorption and gene expression levels of related co-transporters, type IIb sodium-dependent phosphate co-transporter (NaPi-IIb), inorganic phosphate transporter 1 (PiT-1) and inorganic phosphate transporter 2 (PiT-2) in the small intestine of broilers, 450 1-d-old Arbor Acres male broilers were randomly allocated to one of three treatments with ten replicate cages of fifteen birds per cage for each treatment in a completely randomised design. Chickens were fed a diet with no added inorganic P (containing 0·06 % non-phytate P (NPP)) or with either 0·21 or 0·44 % NPP for 21 d. Plasma P concentration in the hepatic portal vein, mRNA and protein expression levels of NaPi-IIb, PiT-1 and PiT-2 were determined at 7, 14 and 21 d of age. The results showed that the concentration of P in plasma in the hepatic portal vein increased as dietary NPP increased (P<0·0001). At 14 and 21 d of age, the increase in dietary NPP inhibited (P<0·003) NaPi-IIb mRNA expression level in the duodenum, as well as PiT-1 mRNA and protein expression levels in the ileum, but promoted NaPi-IIb protein expression level (P<0·002) and PiT-2 mRNA and protein expression levels (P<0·04) in the duodenum. These results suggest that NaPi-IIb, PiT-1 and PiT-2 might be important P transporters in the small intestine of broilers. Higher intestinal P absorption may be achieved by up-regulating the protein expression levels of NaPi-IIb and PiT-2 and down-regulating the protein expression of PiT-1.

Graded levels of phytase on performance, bone mineralization and carcass traits of broiler fed reduced dicalcium phosphate

Objective

This study was conducted to assess increasing doses of phytase added to broiler diets formulated with different levels of available phosphorus (avP), calcium (Ca), and sodium (Na), and the respective effects on performance parameters, quantitative carcass characteristics, ash and phosphorus deposition in tibia and weight of organs.

Methods

Three different matrices were assumed for phytase with the following nutritional values: matrix A (MT A): 0.165% Ca, 0.150% avP, and 0.035% Na; matrix B (MT B): 0.215% Ca, 0.195% avP, and 0.045% Na; matrix C (MT C): 0.245% Ca, 0.225% avP, and 0.053% Na. There were six different diets: No phytase (formulated to meet the nutritional requirements); phytase 500 FTU/kg+MT A; phytase 1,000 FTU/kg+MT A; phytase 1,500 FTU/kg+MT A; phytase 1,000 FTU/kg+MT B and phytase 1,500 FTU/kg+MT C.

Results

There was no significant phytase influence on performance, quantitative carcass characteristics, ash and phosphorus deposition in tibia and weight of the organ throughout the study period, however, it was possible to observe a tendency of improvement in body weight corrected feed conversion for broilers fed the phytase 1,500+MT C diet, where potentially these birds were more efficient on utilize phytic phosphorus and other nutrients bounded to phytate molecule, translating into improvement in performance, and there was also a non significant numerical improvement in body weight corrected feed conversion of broilers fed this diet.

Conclusion

Broilers fed with diets formulated with different levels of avP, Ca, and Na and increasing doses of phytase have shown no change on performance, quantitative carcass characteristics, ash and phosphorus deposition in tibia and weight of organs.

The efficacy of dietary xylanase and phytase in broiler chickens fed expeller-extracted camelina meal

A study was conducted to investigate the effects of dietary phytase (PHY) and xylanase (XYL) on growth performance, nutrient utilization, and intestinal characteristics in broilers fed corn-soybean meal-based diets with added expeller-extracted camelina meal (CM). The corn-soybean meal-based diets without or with CM was formulated to contain 2.9 or 2.7 g/kg non phytate phosphorus, respectively. A total of 384 male Ross 708 broilers were allocated to 8 dietary treatments in a randomized complete block design with 6 replicates per treatment, from 7 to 21 d post hatching. The experiment consisted of a 2 × 2 × 2 factorial arrangement of treatments with 2 dietary CM levels (zero or 100 g/kg), 2 dietary levels of XYL (zero or 800 unit/kg), and 2 dietary levels of PHY (zero or 4,000 unit/kg). Chromic oxide was included in the diets as an indigestible marker. Growth was measured throughout the experiment and excreta were collected on d 18 to 21 post hatching for measurement of nutrient and energy retention. On d 21 post hatching, broilers were euthanized by CO2 asphyxiation, ileal digesta was collected for nutrient and energy digestibility measurements, and the left tibia was removed for bone ash measurement. Furthermore, duodenal digesta was collected and a segment of the mid jejunum was excised for viscosity and morphology measurement, respectively. Broilers fed 100 g/kg CM diets showed lower (P < 0.001) BW gain and G:F than those fed zero g/kg CM diets for 7 to 14 d and 7 to 21 d post hatching periods, respectively. Phytase supplementation improved (P < 0.05) all the growth parameters measured regardless of CM addition. Phytase supplementation resulted in an increase (P < 0.05) in jejunum villus height but there was no impact of CM or XYL. Additionally, duodenal digesta viscosity increased (P < 0.001) with added CM. Tibia ash and weight increased (P < 0.001) with PHY supplementation. There was a CM × PHY interaction (P < 0.05) on percentage tibia ash, with greater PHY effect in zero g/kg CM diets compared with 100 g/kg CM diets. Phytase supplementation increased (P < 0.05) ileal DM, N, energy, P, and neutral detergent fiber (NDF) digestibility. In diets with 100 g/kg CM, addition of PHY had a greater effect (CM × PHY; P < 0.05) on ileal P digestibility compared with diet without CM. There was a CM × PHY interaction (P < 0.05) for ileal digestible energy (IDE) in which PHY increased the IDE in birds fed CM supplemented diets. Both ileal digestibility and retentions of DM, N, energy, and IDE, AME, and AMEn were decreased (P < 0.05) by CM supplementation. Retention of ether extract and NDF decreased (P < 0.05) with CM supplementation. Nitrogen retention, AME, and AMEn decreased (CM × XYL; P < 0.05) with XYL supplementation in zero g/kg CM diets. There were CM × XYL interactions (P < 0.01) for P and Ca retentions in which XYL increased retentions in 100 g/kg CM diets. In conclusion, PHY was efficacious at improving P digestibility and retention of birds fed low P corn-soy based diets without or with CM. However, regardless of CM addition, XYL did not improve nutrient utilization and growth performance of broiler chickens. The present data also show that the mechanism underlying the detrimental effects of CM inclusion on nutrient utilization is not mediated through gut morphology and goblet cell density. The data also show that the villus height increase occurring with PHY addition might be a contributor to the improvements in ileal DM, N, and energy digestibility obtained with PHY supplementation.

Modulation of small intestinal phosphate transporter by dietary supplements of mineral phosphorus and phytase in broilers

Dietary phosphorus (P) is known as a main modulator of phosphate (Pi) transporter expression. The effect of supplemented mineral P with or without phytase on protein expression of two sodium-dependent Pi (NaPi) transporters and a calcium channel was studied in the small intestine of broilers. Thirty-six broilers were randomly assigned to six different diets at 15 days of age. Two levels of total P (tP, adjusted by monocalcium phosphate (MCP) supplementation), 0.39% (BD-) and 0.47% (BD+) were fed until day 25; and at each tP level, three levels of phytase were used with 0, 500, and 12,500 FTU/kg of an E. coli phytase. Mucosa samples from jejunum and ileum were taken and apical membranes were isolated by MgCl2 precipitation. Protein expression of NaPi IIb, NaPi type III (PiT1) and the calcium channel TRPV6 were semiquantitatively measured by Western blotting and jejunal mucosal phytase activity by measurement of Pi release. The jejunal NaPi IIb transporter was expressed with two distinct bands, which were modulated differently by diet. NaPi IIb Band1 increased (P < 0.05) and Band2 decreased (P < 0.05) with phytase supplementation but was not affected by MCP supplementation. This inverse modulation of Band1 and Band2 was significantly related to the amount of net absorbed P with higher expression of Band1 at higher amounts of net absorbed P. In addition, a second Pi transporter, PiT1, was detected in which ileal expression decreased (P < 0.05) in response to higher phytase supplementation. The expression of the calcium channel TRPV6 was increased in BD+ groups. A trend for an interaction between MCP and phytase supplementation on mucosal phytase activity was observed (P = 0.079) with a decrease in activity when BD+ with 12,500 FTU/kg phytase was fed. Chicken intestinal epithelial cells responded to dietary supplemented phytase and MCP by changing the Pi transporter expression in apical membranes. In conclusion, availability of Pi is most likely the key modulator of transporter protein expression. However, a contribution of lower inositol phosphates generated by phytases and other phosphatases may also be relevant.

The interplay of dietary nutrient specification and varying calcium to total phosphorus ratio on efficacy of a bacterial phytase: 1. Growth performance and tibia mineralization

A 14-d experiment was conducted to study the effects of 2 dietary variables on efficacy of a 6-phytase from Citrobacter braakii on broiler growth performance and tibia mineralization. Diets were formulated with or without nutrient matrix values for phytase as negative or positive control (NC or PC, respectively) and with 2 Ca:total P (tP; 2:1 or 2.5:1). The diets were supplemented with 0, 1,000, or 2,000 phytase units (FYT)/kg, thus producing a 2 × 2 × 3 factorial arrangement. Birds and feed were weighed on d 7 and 21, and tibia bones were collected from all the birds on d 21. The main effects of nutrient matrix, Ca:tP, and phytase supplementation were significant (P < 0.05) for all the growth performance responses (except for G:F for which there was no effect of matrix). The Ca:tP × phytase and matrix × phytase interactions were significant (P < 0.05) for weight gain. In the PC diets, phytase increased weight gain (P < 0.05) relative to the control only in diets with 2,000 FYT/kg, whereas in NC diets weight gain increased (P < 0.01) only from 0 to 1,000 FYT/kg levels. Broilers consuming diets with 2.5:1 Ca:tP had lower (P < 0.05) tibia ash, whereas phytase increased (P < 0.01) tibia ash, Ca, P, and Zn but decreased (P < 0.01) tibia K. Phytase supplementation of diets with 2:1 Ca:tP increased (P < 0.05) tibia P in birds receiving 1,000 FYT/kg relative to the control with no further increase at 2,000 FYT/kg, whereas each level of phytase supplementation increased (P < 0.05) tibia P in the diets with 2.5:1 Ca:tP. It was concluded that the best response to lower phytase supplementation (1,000 FYT/kg) was in NC diets with narrow Ca:tP, whereas the best response to higher level of phytase supplementation (2,000 FYT/kg) was achieved in diets in PC diets with wide Ca:tP.

The interplay of dietary nutrient level and varying calcium to phosphorus ratios on efficacy of a bacterial phytase: 2. Ileal and total tract nutrient utilization

A 14-d broiler experiment was conducted to assess the effects of 2 dietary variables on efficacy of a bacterial 6-phytase from Citobacter braakii on nutrient and phytate P (PP) utilization. Diets were formulated with or without nutrient matrix values (matrix) for phytase as negative control (NC) or positive control (PC), respectively, and with 2 Ca:total P (tP) levels (2:1 or 2.5:1). The diets were supplemented with 0, 1,000, or 2,000 phytase units (FYT)/kg of diet, thus producing a 2 × 2 × 3 factorial arrangement. Excreta were collected on d 19 to 21 and ileal digesta on d 21. There was no 3-way interaction on digestibility of any nutrient. There was matrix × phytase (P < 0.01) interaction for Ca and DM digestibility and Ca:tP × phytase interaction (P < 0.05) for acid hydrolyzed fat and Ca and P digestibility. Prececal flow of Mn, Zn, and Na was greater (P < 0.05) in NC diets, whereas phytase increased (P < 0.05) prececal flow of Mg, Fe, Mn, and Zn but decreased (P < 0.05) prececal Na flow. Total tract PP disappearance and total tract Ca retention increased (P < 0.05) with phytase supplementation in diets with 2:1 Ca:tP, whereas there was no effect of phytase supplementation on PP disappearance or Ca retention in diets with 2.5:1 Ca:tP. Total P and Ca retention were reduced (P < 0.05) in PC and NC diets when Ca:tP increased to 2.5:1, but the depression was more pronounced in the NC diet. In addition, PP disappearance decreased (P < 0.05) with increasing Ca:tP in the PC diets, but there was no effect of widening Ca:tP on PP disappearance in NC diets. It was concluded from the current study that the effect of phytase supplementation on P utilization is reduced when diets contain adequate P as exemplified in the PC diets and that the negative impact of wide Ca:tP is more pronounced in diets with phytase matrix allowance as exemplified in the NC diets.

Why is it important to understand substrates if we are to optimize exogenous enzyme efficacy?

The use of exogenous enzymes in feeds for poultry has increased dramatically between 1990 and 2013. Today, the use of enzymes is broad, going beyond phytases and β-glucanases and xylanases to include other carbohydrases and proteases as well as lipases. The number of scientific articles and publications related to enzymes in feed clearly shows that this has been an area of intense and broad interest for scientists and nutritionists. However, knowledge of the different substrates available in the feed and how these substrates change depending on feed ingredient selection has not received the same level of attention. Understanding substrates is key to better developing and implementing exogenous enzymes. Of importance today is to potentiate endogenous digestive capabilities and use exogenous enzymes to optimize nutrient digestion and use. Our aim with this symposium was to call attention to the importance of having a more in-depth knowledge about substrates and to fill the large gaps in our current understanding of the digestive processes in poultry.