Stepwise Reduction of Dietary Phosphorus in Diets for Piglets and Fattening Pigs of Different Genetic Origin Housed under Various Station Environments-A Ringtest.

The reduction of emissions of nutrients from livestock is one of the main topics in areas with intensive animal husbandry. In order to minimize the loss of nutrients into the environment, it is common practice to feed animals as close as possible to metabolic demands. For phosphorus (P), there are various studies for swine and poultry, which showed that a reduction of dietary P levels is possible, if a sufficient level of phytase is added to the diet. The supplementation of a sufficient dosage of phytase to plant-based diets leads to an increase in digestible phosphorus (dP) upon the hydrolisation of phytate (InsP6) to P and lower inositol-phosphates. However, most of these studies were conducted under standardized experimental conditions. In terms of transfer to practical conditions with varying housing, management and genetics, there are concerns that have led to speculation by farmers and veterinarians whether the reduction of dietary P could negatively affect bone health and therefore animal welfare. In order to test whether a reduction of dietary P according to the recommendations for dP of the German Society of Nutrition Physiology (GfE) affects bone mineralization and growth performance, a ringtest was conducted where piglets and fattening pigs were fed at four experimental stations with three centrally produced diets from the same batches. The diets contained three different levels of P and were designed to reflect practical diets. The P level decreased from diet one to three, respectively. Diets one and two were calculated to contain P levels, which are typically fed under practical conditions in Germany. The third diet was optimized to fulfill the requirements of dP by the GfE. The animals were fed in two phases as post-weaning piglets (8-15 kg and 15-28 kg BW) followed by a three-phase fattening regime (28-60 kg, 60-90 kg and 90-120 kg BW). Individual body weight and feed consumption (pen basis or individually, depending on the experimental station) were recorded for every feeding phase. At the end of the experiment, animals were slaughtered. At one experimental station, additional blood serum, metatarsi of the left leg and kidney tissue were sampled to analyze serum P concentration, expression of P transporters in the kidney and bone traits. In two experimental stations, femur and vertebra were sampled, and bone ash was determined. Overall, animal performance and all other traits analyzed did not differ between the treatment with the highest and the treatment with the lowest dietary P concentration. The results demonstrate that it is possible to decrease dietary P according to the recommendations for dP of the GfE, without impairing the animals' performance or mineral homeostasis and health. A reduction of total P by reducing mineral P to the levels of the present study require the supplementation of phytase to achieve sufficient concentrations of dP.

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.

The dietary calcium concentration can influence the release of phosphorus from phytate in growing pigs. This study assessed the effects of dietary calcium and exogenous phytase on inositol phosphate (InsP) degradation and nutrient digestibility in ileal-cannulated, growing pigs. The phosphorus, calcium, and myo-inositol concentrations in the blood, microbiota composition in the ileal digesta and feces, and volatile fatty acid concentrations in the feces were also evaluated. Additional dietary calcium decreased prececal inositol hexakisphosphate (InsP6) disappearance, but only with exogenous phytase. Concentrations of InsP2-4 isomers and myo-inositol in the ileal digesta and prececal phosphorus digestibility were greater with exogenous phytase, but not affected by dietary calcium concentration. In contrast, fecal InsP6 disappearance was lower and the concentration of InsP4-5 isomers in feces was greater with additional dietary calcium. Regarding microbiota, the Shannon diversity index was lower in ileal digesta than in feces but was unaffected by dietary calcium concentration or exogenous phytase. In conclusion, dietary calcium concentration is relevant for phytate disappearance in feces, but not in the ileal digesta. However, when exogenous phytase is used, the dietary calcium concentration is important because prececal phytate degradation is changed.

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.

Relative phytase efficacy values as affected by response traits, including ileal microbiota composition.

The objective of this study was to compare the effects of graded inclusions of 2 phytase products and a mineral P source in broiler chickens using different response traits, including ileum microbiota composition. Eleven experimental diets were used. These were a low-P basal diet and diets supplemented with increasing levels of dicalcium phosphate (DCP), Natuphos E 5000 G (NE), or Natuphos 5000 G (N). The performance traits, prececal P digestibility, and tibia and foot ash results were subjected to regression analysis and slope ratios were used to compare the supplements based on the measured evaluation traits. In the microbiota analysis, total nucleic acids were extracted and the 16S rRNA gene was targeted for use in the amplicon sequencing process. Phylogenetic analysis was performed using Mothur, followed by a multivariate statistical analysis. The various response traits caused different estimates of relative efficacy. The mean results of all the response traits showed that a 1.75-fold increase in the activity of N was needed to achieve the same response as NE and the variability among the detected traits ranged from 1.59 (prececally digestible P intake) to 1.91 (amount of tibia ash). The mean slope ratio between DCP and NE was 311 and varied between 208 (ADG) and 349 (foot ash concentration). The mean slope ratio for phytase N with DCP was 552 and varied from 357 (ADG) to 640 (tibia ash concentration). The ileum microbiota composition was not different among the diets. A similar composition was driven in the abundance of Lactobacillus crispatus, Lactobacillus salivarius, and Lactobacillus gallinarum. The results suggest that different response traits cause markedly different estimates of relative phytase efficacy.

Effects of calcium level and source, formic acid, and phytase on phytate degradation and the microbiota in the digestive tract of broiler chickens.

BACKGROUND: Diet acidification, dietary calcium (Ca) level, and phytase supplementation are known influences on the microbial community in the digestive tract and on phosphorus (P) utilization of broiler chickens. Effects of dietary factors and microbiota on P utilization may be linked because microorganisms produce enzymes that release P from phytate (InsP6), the main source of P in plant feedstuffs. This study aimed to detect linkages between microbiota and InsP6 degradation by acidifying diets (i.e., replacing Ca carbonate (CaCO3) by Ca formate or adding formic acid to CaCO3-containing diets), varying Ca levels, and supplementing phytase in a three-factorial design. We investigated i) the microbial community and pH in the digestive tract, ii) prececal (pc) P and Ca digestibility, and iii) InsP6 degradation. RESULTS: All factors under investigation influenced digesta pH and the microbiota composition. Predicted functionality and relative abundance of microorganisms indicated that diets influenced the potential contribution of the microbiota on InsP degradation. Values of InsP6 degradation and relative abundance of the strains Lactobacillus johnsonii and Lactobacillus reuteri were correlated. Phytase supplementation increased pc InsP6 disappearance, with differences between Ca levels, and influenced concentrations of lower inositol phosphate isomers in the digestive tract. Formic acid supplementation increased pc InsP6 degradation to myo-inositol. Replacing CaCO3 by Ca-formate and the high level of these Ca sources reduced pc InsP6 disappearance, except when the combination of CaCO3 + formic acid was used. Supplementing phytase to CaCO3 + formic acid led to the highest InsP6 disappearance (52%) in the crop and increased myo-inositol concentration in the ileum digesta. Supplementing phytase leveled the effect of high Ca content on pc InsP6 disappearance. CONCLUSIONS: The results point towards a contribution of changing microbial community on InsP6 degradation in the crop and up to the terminal ileum. This is indicated by relationships between InsP6 degradation and relative abundance of phosphatase-producing strains. Functional predictions supported influences of microbiota on InsP6 degradation. The extent of such effects remains to be clarified. InsP6 degradation may also be influenced by variation of pH caused by dietary concentration and solubility of the Ca in the feed.

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.

The objective was to determine phytase effects on prececal amino acid (AA) digestibility and phytate (InsP6) breakdown when different oilseed meals were used in broiler chicken diets. The study included 14 diets: a corn-soybean meal (SBM) basal diet and 6 diets that contained SBM, rapeseed meal (RSM), and sunflower meal (SFM) with 2 inclusion levels at the expense of corn starch (150 and 300 g/kg SBM or SFM, or 100 and 200 g/kg RSM). Each diet was mixed with or without a phytase supplement of 1,500 FTU/kg. Diets were provided to broilers for 5 D. Digesta from the posterior half of the ileum were collected on day 21. The average essential AA digestibility, calculated by a regression approach, without and with phytase was 84 and 85% (SBM), 74 and 77% (SFM), and 66 and 73% (RSM), respectively. In the diets, phytase effects on AA digestibility were lower owing to other protein sources also present in the diet, but significant. Prececal InsP6 disappearance was significantly affected by interactions between oilseed meal, inclusion level, and phytase supplementation. Overall, prececal InsP6 disappearance was higher in SBM diets (52%) than in SFM diets (38%) and intermediate in RSM diets (43%). Across diets, phytase supplementation effects on prececal InsP6 degradation linearly increased with the InsP6 concentration of the diet up to 12 g/kg DM. The only exception from linearity was the diet with the high inclusion of SFM, which contained 15.9 g InsP6/kg DM. In the ileal content, the concentration of myo-inositol was significantly increased by phytase supplementation, and this effect was highest in the diets that contained SBM as the only oilseed meal. Concentrations of lower inositol phosphates were increased by phytase supplementation, and this effect was most remarkable for Ins(1,2,3,4)P4 and inositol tetrakisphosphates. The study showed that phytase effects on AA digestibility varied among the 3 tested oilseed meals, but these differences were not detectable in the diets containing these meals. Although phytase effects on ileal content of InsP6 and its degradation products were substantial, they were not related to the effects on AA digestibility.