Effects of the composition of the basal diet on the evaluation of mineral phosphorus sources and interactions with phytate hydrolysis in broilers

Abstract

The objectives of this study were to determine the availability of P from mineral phosphate sources by using different basal diets and measurement of P retention and prececal (pc) P digestibility as well as pc myo-inositol phosphate (InsP) degradation in broilers. Semi-synthetic and corn-soybean meal-based basal diets were used in experiment 1, and corn-based and wheat-based basal diets were used in experiment 2. Anhydrous monosodium phosphate (MSPa) or monocalcium phosphate monohydrate (MCPh) was supplemented to increment the P concentration by 0.05, 0.10, and 0.15% or by 0.075 and 0.150% in experiments 1 and 2, respectively. Titanium dioxide was used as an indigestible marker. Diets were pelleted through a 3-mm screen. In experiment 1, retention was measured based on total excreta collection from 20 to 24 d of age using 7 replicated birds per diet. In experiment 2, digesta from the terminal ileum was collected from 22-d-old broilers penned in groups of 19 with 5 replicated pens per diet. The P retention response to supplemented MSPa did not differ between the 2 basal diets in experiment 1. The response in pc P digestibility to MCPh supplements also did not differ between the 2 basal diets in experiment 2, as calculated by linear regression analysis. Hydrolysis of InsP6 measured on both the excreta and pc levels was high in the basal diets without a mineral P supplement. Mineral P supplementation significantly decreased (P < 0.05) InsP6 hydrolysis from the InsP-containing diets in both experiments. Thus, the choice of the basal diet did not affect the evaluation of the supplemented mineral P source. However, calculated values for mineral P sources need to be adjusted for the decline in hydrolysis of InsP contained in the basal diet that results from the P supplement.

Dietary effects on inositol phosphate breakdown in the crop of broilers

“…In contrast, crop InsP 6 hydrolysis in the present study was high (59%) when a wheat-based diet with intrinsic phytase activity (623 U/kg) was fed to birds in Experiment 1. Several recent studies found no relation between dietary intrinsic phytase activity and InsP 6 hydrolysis in the ileum of broilers (Leytem et al 2008;Shastak et al 2014). This pH is likely to support the activity of wheat phytases, which under in vitro conditions were shown to exhibit maximal activity at pH 6.0 (phytase 1) and pH 5.5 (phytase 2) in a study by Nakano et al (1999).…”

“…The pH measured in the digesta from the crop in Experiment 1 averaged 5.3 (SD 0.42) (treatment means did not differ significantly (data not shown)). However, InsP 6 hydrolysis by microbiota-and mucosa- associated phytases in the small intestine might compensate for the lack of crop hydrolysis in the absence of intrinsic plant phytase and likely explains why the degree of InsP 6 hydrolysis measured in the terminal ileum of broilers was not lower when a wheat-based diet was fed compared to a maize-based diet (Shastak et al 2014). Comparatively, the far lower InsP 6 hydrolysis in birds fed BD TW (26%) compared to birds fed BD UTW was most likely the consequence of the lower activities of intrinsic wheat phytase and other enzymes following microwave treatment.…”

“…Added microbial phytase, mineral P and factors affecting the accessibility or solubility of phytate have been described as influencing factors (Tamim and Angel 2003;Woyengo et al 2010;Shastak et al 2014;Zeller, Schollenberger, Witzig et al 2015). In the digestive tract, P is primarily absorbed as orthophosphate.…”

Modification and application of an in vitro assay to examine inositol phosphate degradation in the digestive tract of poultry

“…In this context, an understanding of the inhibitory effects of several factors on InsP 6 disappearance in the digestive tract is important. Previous studies have found negative effects of P and calcium (Ca) additions to poultry diets on InsP 6 disappearance in the gastrointestinal tract (GIT) . In contrast, the addition of microbial phytases ( myo ‐inositol hexaphosphate phosphohydrolases) to feed results in increased availability of P from plant ingredients, and complexes between phytate and other minerals might be diminished .…”

Effect of suboptimal levels of non-phytate phosphorus and exogenous phytase on precaecal digestibility of phosphorus and calcium in laying hens

“…Gao et al (2013) used an even lower NPP level (1.0 g/kg, total phosphorus 3.4 g/kg) than in this study, and they also reported a higher coefficient of apparent ileal digestibility of phosphorus from this diet (0.506) compared with phosphorus digestibility from diet with total phosphorus 5.7 g/kg and 3.2 NPP g/kg (0.474). Thus, it can be inferred that the digestibility of phytate phosphorus in Zeller et al (2015) and Shastak et al (2014) who published that mineral phosphorus supplementation reduces the degradation of myoinositol phosphates. On the other hand, Hafeez et al (2016) also published very similar coefficients of apparent ileal phosphorus digestibility in layer diets (from 0.311 to 0.409).…”