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

Evaluating the nutritional impact of co-expressed phytase genes from Escherichia coli and Aspergillus niger in Pichia pastoris on broiler chickens

Two phytase genes originating from Escherichia coli (6-phytase) and Aspergillus niger (3-phytase) (appA and phyA) were co-expressed in Pichia pastoris as the expression host. In vivo and in vitro tests were employed to assess the biological properties of the recombinant phytase. The recombinant protein had a phytase activity equal to 160.97 U/ml and was tested in the feed of 180 broilers to measure Crude Protein, Dry Matter, Fat, Phosphorus, Calcium, Iron, Magnesium, Zinc and p-phytate digestibility. The experimental chickens were subjected to six dietary treatments in six replicates (5 birds per replicate). The treatments included one control group (basal diet), and three feed treatments with 500, 1000, and 1500 FTU phyA + appA. The basal diet contained 500 FTU/kg Hostazym® P, and the basal diet contained native Pichia pastoris. Total tract apparent disappearance of phytate-P and nutrient retention were assessed at 19-21 days of age. Broilers fed with phytases had greater retention of P, Ca, Mg, Fe and p-phytate, and the digestibility of CP and DM (P < 0.05) was greater than the control group. Fat digestibility and Zn retention were not significantly different. As a result, the recombinant phytase used in this study could be used as a feed supplement in poultry farming to enhance mineral digestibility.

Dietary non-phytate phosphorus and phytase interaction affects growth performance, mineral transportation and metabolism in broiler chickens

The interaction effects of dietary non-phytate phosphorus (NPP) and phytase on growth performance, mineral metabolism, and gene expressions of mineral transporters in broilers duodenum and kidney (0-3 weeks) were studied. The levels of NPP (0.45 %, 0.35 %, or 0.25 %) and phytase (0 or 2,500 FTU/kg) in the diets were applied in a 3 × 2 factorial arrangement to carry out rearing feeding strategies. Broilers received the diet containing 0.25 % NPP showed lower (P < 0.05) body weight gain (BWG), feed intake (FI), plasma calcium (Ca) and phosphorus (P) levels, bone attributes, and higher (P < 0.05) mortality rate than those of broilers fed diets containing 0.45 % NPP alone or in combination of phytase, 0.35 % NPP or 0.25 % NPP in combination of phytase. Significant interactions (P < 0.05) of phytase and NPP were found in BWG, FI, bone attributes, plasma Ca and P levels, and mortality rate of broiler. Broilers received the diet containing 0.25 % NPP had higher (P < 0.05) mRNA expressions of nuclear vitamin D receptors (nVDR), Calbindin-D28k (CaBP-D28k) and Plasma membrane Ca ATPase 1b (PMCA1b) in duodenum, mRNA expressions of CaBP-D28k and sodium-dependent phosphate cotransporters type IIa (NaPi-IIa) in kidney, and liver 25-hydroxylase mRNA expression than those of broilers fed diets containing 0.45 % NPP alone or in combination of phytase, 0.35 % NPP or 0.25 % NPP in combination of phytase. The interaction of NPP and phytase significantly affected (P < 0.05) the mRNA expressions of nVDR, CaBP-D28k and PMCA1b in duodenum, the mRNA expressions of CaBP-D28k and NaPi-IIa in kidney, and liver 25-hydroxylase mRNA expression. Dietary phytase supplementation improved growth performance, bone attributes, and absorption of Ca and P even if dietary NPP level dropped to 0.25 %.

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.

Efficacy and Equivalency of Phytase for Available Phosphorus in Broilers Fed an Available Phosphorus-Deficient Diet

This study was conducted to assess the effectiveness of phytase on the performance, carcass traits, nutrient digestibility, tibia characteristics, and inositol phosphorus (IP) degradation in broiler chickens. Additionally, the available phosphorus (AP) equivalency of phytase in AP-deficient diets was estimated for 35 days after hatching. A total of 336 one-day-old Ross 308 broiler chicks were allocated to one of seven dietary treatments with six replications with eight birds per cage. The dietary treatments were as follows: (1) positive control containing 0.45% AP of the starter and 0.42% AP of the grower diet (PC), (2) 0.10% AP deficiency from the PC (NC-1), (3) 0.15% AP deficiency from the PC (NC-2), (4) 0.20% AP deficiency from the PC (NC-3), (5) NC-3 +phytase (500 FTU/kg; NC-3-500), (6) NC-3 + phytase (1000 FTU/kg; NC-3-1000), and (7) NC-3 + phytase (1500 FTU/kg; NC-3-1500). On d 35, the NC-3 diet exhibited lower tibia weight compared to the other treatments (p < 0.001). The NC-3-1500 group had higher calcium and phosphorus contents in the tibia than the other treatments on d 35 (p < 0.01). Phytase supplementation led to a reduced IP6 concentration and increased IP3 concentrations in different sections of the gastrointestinal tract on d 21 and 35 compared to the control diet (p < 0.05). In conclusion, based on the tibia phosphorus content, this study determined that 500 FTU/kg phytase was equivalent to 0.377% and 0.383% AP in the diet on d 21, and 0.317% and 0.307% AP in the diet on d 35, respectively. Likewise, 1000 FTU/kg was determined to be equivalent to 0.476% and 0.448% AP on d 21, and 0.437% and 0.403% AP on d 35, respectively. Furthermore, 1500 FTU/kg was determined to be equivalent to 0.574% and 0.504% AP on d 21, and 0.557% and 0.500 AP on d 35, respectively.