The effect of high (1000–3000 phytase units (FYT)/kg) doses of microbial phytase on performance, nutrient digestibility and plasma inositol concentrations in young Ross broiler chicks was investigated in two separate experiments. In both experiments pelleted corn/soy-based diets were used and experimental duration was from Days 8 to 21 and Days 15 to 28 in Experiments 1 and 2, respectively. Treatments in Experiment 1 were arranged as a 2 × 4 + 1 factorial with two concentrations of calcium and available phosphorus and four concentrations of phytase (0, 1000, 2000 or 3000 FYT/kg), with a reference diet containing additional phosphorus and calcium from inorganic sources. In Experiment 2 only four dietary treatments were used, being a nutritionally adequate positive control, a negative control formulated to be insufficient in calcium and available phosphorus and the negative control supplemented with either 1000 or 2000 FYT/kg exogenous phytase. In both experiments, phytase improved performance relative to the appropriate control diet and increased the retention of calcium and phosphorus (P < 0.001). Tibia strength and ash content were increased (P < 0.001) by phytase addition. Plasma inositol concentrations were substantially increased (P < 0.001) by phytase addition to the diet. As inositol has been found to be an insulin mimetic in a range of animal species, these results suggest that part of the beneficial effect of high doses of phytase in broiler production may be conferred via insulin-like mechanisms. The effect of phytase on the expression of insulin-sensitive glucose transport systems, gluconeogenesis and nitrogen cycling is an area for future research. It can be concluded that phytase is effective in improving performance of broiler chicks fed diets that are sufficient and insufficient in calcium and phosphorus. Furthermore, phytase addition results in increased plasma inositol concentrations that may be beneficial in nutrient transport and protein deposition.

The effect of phytase on phosphorus retention, broiler (Gallus gallus) performance and bone mineralization in diets with reduced inorganic phosphate concentration is well documented. Furthermore, so-called 'extra-phosphoric' effects of phytase have been described in the literature that may be associated with changes in mineral and amino acid partitioning and requirements per se. In particular, the role of myo-inositol in phytase responses is implied but not well elucidated. It was the purpose of the experiment reported herein to explore the effect of phytase on broiler growth, nutrient digestibility, blood biochemistry and gene expression. A 5-week broiler floor pen trial was conducted to evaluate the effect of supplementation of a moderately phosphorus-deficient diet with 1000 U/kg of a 6-microbial phytase. Parameters measured were growth performance, phosphorus (P), calcium (Ca) and myo-inositol plasma concentrations, apparent ileal P digestibility, bone mineralization, breast meat weight and Pectoralis major muscle transcriptome. Supplementation of the diet with phytase improved weight gain during the starter period (18%) and the whole period (24%) compared with animals that received the control diet (p < 0.05). Improved feed conversion ratio, increased myo-inositol plasma concentration, tibia ash contents and breast meat weight were also observed in animals fed phytase. The transcriptomic analysis revealed that some differentially expressed genes (DEG) in broilers, receiving phytase in comparison with animals fed reduced phosphorus diet without phytase, were part of pathways involved in muscle development, via calmodulin/calcineurin and insulin-like growth factor. Microarray data confirmation was performed on six genes by quantitative PCR (qPCR): PI3K regulatory and catalytic subunit, Phospholipase C beta, Myocyte Enhancer Factors 2A and 2C, and calcineurin A. The results suggested that dietary supplementation with this phytase could generate low molecular weight phytate esters and indirectly myo-inositol, and could help us to understand how muscle metabolism may be affected at a gene level.

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The efficacy and safety of a novel microbial 6-phytase expressed via the use of synthetic genes in Aspergillus oryzae was investigated from d 8 to 22 of age using 480 Ross PM3 broiler chickens. Five treatments were tested. A diet containing 5.6 g/kg of Phosphorus (P) was fed to the control treatment. Another diet containing 4.1 g/kg P was fed to another treatment as negative control. This diet was fed in 3 other treatments with the addition of phytase (500, 1000, or 2000 U/kg). Feed intake, body weight, tibia ash (%) and strength (N) and P and Ca utilization (% of intake) and excretion (g/kg DM) were measured. Enzyme safety was determined by genotoxicity and sub-chronic oral toxicity studies. Lower feed intake and higher weight gain was obtained with the treatment containing 2000 U/kg phytase compared to the two control treatments and the treatment containing 500 U/kg phytase, leading to a significant improvement in FCR with the 2000 U/kg phytase. Tibia strength and ash were improved with the latter and were dose-dependent described by an exponential function. Safety test using a concentrated preparation of the novel 6-phytase enzyme did not reveal any toxicological significant findings. The enzyme did not induce mutagenic activity in the Ames test and did not increase the frequency of micronucleated binucleated cells in the micronucleus assay. In conclusion, this novel microbial 6-phytase improved broiler performance and reduces the need for phosphate fortification of feed. In addition, it can be Generally Recognized as Safe (GRAS) feed ingredient according to the safety test carried out.

The purpose of the study that is presented herein was to develop near-infrared reflectance spectroscopy (NIRS) calibrations to predict total phosphorus (P), phytate-P, and protein concentrations of feed ingredients commonly used in monogastric feed formulation. Samples representing 14 vegetable ingredients (cereals, cereal by-products, and oilseed meals) were collected worldwide throughout 2013. The samples were assayed by standard wet chemical techniques for total P, phytate-P, and protein content. There was substantial variability in protein, phytate-P, and total P within and between ingredients used in the calibration set. Protein content varied from 76 to 487 g/kg. Total P ranged from 2.09 and 22.5 g/kg and phytate-P ranged from 0.99 and 13.8 g/kg. Within these broad ranges, NIRS values were highly correlated for determination of protein, total P, and phytate-P with a standard error of prediction equal to 9.06 g/kg, 0.80 g/kg, and 0.66 g/kg, respectively. The wide diversity and heterogeneity of the mix of feed ingredients allowed the development of NIRS calibrations of sufficient accuracy to help nutritionists control the nutritional composition of their feed.