Effect of diets containing enzyme supplements and microwave-treated or untreated wheat on inositol phosphates in the small intestine of broilers

Phytate degradation and phosphorus utilisation by broiler chickens fed diets containing wheat with increased phytase activity

1. The objective of this study was to investigate wheat genotypes bred for increased intrinsic phytase activity for InsP₆ disappearance and the formation of lower inositol phosphates in such wheat-fed broiler chickens. The influence of monocalcium phosphate (MCP) supplementation on these characteristics and the utilisation of P and Ca were also determined. A three-step in vitro assay and a broiler trial were performed.2. In the 63 wheat genotypes tested in vitro, phytase activity varied from 1900 FTU/kg to 5200 FTU/kg, and InsP₆ disappearance increased with higher phytase activity of wheat in a linear manner. The addition of MCP significantly reduced in vitro InsP₆ disappearance by one-third, independent of the inclusion level of wheat in the feed. When exogenous phytase was added to wheat, in vitro InsP₆ disappearance increased independently of the phytase activity of the wheat used.3. In the broiler trial, four wheat genotypes with phytase activities between 2400 and 3700 FTU/kg were included at 400 g/kg in diets with and without MCP. The diets were not pelleted. Separately, wheat 1, without MCP, was tested with the addition of exogenous phytase. Unsexed Ross 308 broiler chickens were allocated to 72 metabolic units of 10 birds each and assigned one of the nine diets. Mineral utilisation was measured based on excreta collection from 20 to 23 d of age. Digesta from the crop and terminal ileum were collected on d 24.4. In the crop and ileum, InsP₆ disappearance was not affected by the wheat genotypes, but the addition of MCP significantly decreased InsP₆ disappearance. Precaecal P disappearance was significantly reduced by the addition of MCP, with wheat genotypes exerting an effect. Wheat genotypes and the addition of exogenous phytase significantly affected P utilisation. Exogenous phytase had no effect on InsP₆ disappearance in the crop but did up to the terminal ileum, the precaecal InsP₆ and P disappearance increased with the addition of exogenous phytase.5. Although the intrinsic wheat phytase activity exerted distinct effects on in vitro InsP₆ disappearance, no such effect was found in the broiler trial. The addition of MCP significantly inhibited InsP₆ degradation in vitro and in vivo.

Effect of supplemental phytase and xylanase in wheat-based diets on prececal phosphorus digestibility and phytate degradation in young turkeys

This study aimed to investigate the effect of phytase and a combination of phytase and xylanase on the prececal phosphorus digestibility (pcdP) of wheat-based diets in turkeys. A low-P basal diet (BD) based on cornstarch and soybean meal, and 2 diets containing 43% of different wheat genotypes (genotype diets GD₆ or GD₇) were fed to turkeys from 20 to 27 d of age. Diets were fed either without enzyme supplementation or supplemented with phytase (500 FTU/kg) or a combination of phytase and xylanase (16,000 BXU/kg). At 27 d of age, digesta were sampled from the lower ileum of animals to determine pcdP and pc myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP₆) disappearance, and to analyze the concentrations of lower inositol phosphate isomers. Similar pcdP was observed in non-supplemented BD and GD (∼36%). Phytase alone increased the pcdP in all diets by 8 to 12%, but a beneficial effect of xylanase was found only for BD. Similar results were found for pc InsP₆ disappearance, although xylanase addition compared to phytase alone decreased pc InsP₆ disappearance in GD₇ compared to phytase alone. Animals fed GD₇ performed better than those fed GD₆; however, these differences could not be linked to the pcdP. The pattern of lower inositol phosphates in digesta also changed with enzyme supplementation, resulting in lower proportions of InsP₅ and higher proportions of InsP₄. Phytase alone decreased Ins(1,2,3,4,6)P₅ but increased D-Ins(1,2,3,4,5)P₅ and D-Ins(1,2,5,6)P₄ concentrations. An additional increase in D-Ins(1,2,3,4,5)P₅ and D-Ins(1,2,5,6)P₄ concentrations was achieved with xylanase, although for the former isomer, this was observed only with GD. These results indicate that enzyme supplementation alters the pc degradation of InsP₆, and that combining both enzymes had a minor additional effect on the pcdP from wheat-based diets when compared to phytase alone.

Influence of dietary carbohydrases, individually or in combination with phytase or an acidifier, on performance, gut morphology and microbial population in broiler chickens fed a wheat-based diet

The objective of this study was to examine the effects of dietary carbohydrases (xylanase and β-glucanase; XG), individually or in combination with phytase or acidifier on the growth performance, carcass attributes, intestinal microbial counts and morphology in broiler chickens fed a wheat-based diet. A total of 240 one-day-old male broiler chicks were randomly allocated into 4 treatment groups with 6 replicates of 10 birds each. The dietary treatments included a basal diet, the basal diet with an enzyme complex containing XG, XG plus a microbial phytase (XG + P) and XG plus acidifier (XG + A). The results indicated that feed conversion ratio (FCR) was improved in broiler chickens which received XG + A during the entire production period (1 to 35 d) of the trial (P < 0.05). The broiler chickens fed XG + P had lower feed intake compared with the control group at 29 to 35 d of age. The experimental treatments had no effect on the body weight gain of broiler chickens. In carcass traits, except for spleen (P < 0.05), the dietary treatments had no effects on the carcass characteristics of broiler chickens. The birds which received diets supplemented with XG and XG + A had a lower weight of the spleen compare with the control. Addition of XG in combination with phytase (XG + P) resulted in a decrease in ileal enumeration of Escherichia coli at 35 d of age (P < 0.05). However, dietary treatments did not alter the population of ileal Lactobacilli in broiler chickens. Supplementing carbohydrases with phytase and acidifier (XG + P and XG + A) significantly increased the intestinal villus length at 35 d of age (P < 0.05). In conclusion, the present study demonstrated that supplementation of the wheat-based diet with a combination with carbohydrases and acidifier (XG + A) improves FCR in broiler chickens. Furthermore, combinations of carbohydrases with phytase (XG + P) and with acidifier (XG + A) decrease the E. coli counts and increase the villus length in broiler chickens.

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

BACKGROUND

An in vitro assay was modified to study the disappearance of inositol hexakisphosphate (InsP₆ ) and the formation of lower inositol phosphate (InsP) isomers in the poultry digestive tract, and three experiments investigated the influence of diets with different ingredients and additives. Using the poultry diet as a matrix, the assay simulated the conditions (e.g. pH, temperature, proteolytic enzymes, water content, and retention time) of the crop, stomach, and small intestine, and extraction and analysis of InsP isomers were immediately conducted.

RESULTS

The assay produced highly reproducible results with coefficients of variation ≤10% for an InsP isomer concentration ≥0.4 µmol g^-1 DM (n = 3), and it was sensitive to the factors that varied in the three experiments.

CONCLUSION

The described assay is a suitable tool that can be used to screen feed enzymes and to investigate the effects of supplements in the absence of endogenous phytases. The ease of handling and high reproducibility of the assay indicated that the assay is a rapid and feasible method that can be used to examine the degradation pathway of phytate in feed under gastrointestinal conditions. © 2017 Society of Chemical Industry.

Results of an international phosphorus digestibility ring test with broiler chickens

The objective of this ring test was to investigate the prececal phosphorus (P) digestibility of soybean meal (SBM) in broiler chickens using the trial protocol proposed by the World's Poultry Science Association. It was hypothesized that prececal P digestibility of SBM determined in the collaborating stations is similar. Three diets with different inclusion levels of SBM were mixed in a feed mill specialized in experimental diets and transported to 17 collaborating stations. Broiler chicks were raised on commercial starter diets according to station-specific management routine. Then they were fed the experimental diets for a minimum of 5 d before content of the posterior half of the ileum was collected. A minimum of 6 experimental replicates per diet was used in each station. All diets and digesta samples were analyzed in the same laboratory. Diet, station, and their interaction significantly affected (P < 0.05) the prececal digestibility values of P and calcium of the diets. The prececal P digestibility of SBM was determined by linear regression and varied among stations from 19 to 51%, with significant differences among stations. In a subset of 4 stations, the prececal disappearance of myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate)-P; InsP6-P) also was studied. The prececal InsP6-P disappearance correlated well with the prececal P digestibility. We hypothesized that factors influencing InsP6 hydrolysis were main contributors to the variation in prececal P digestibility among stations. These factors were probably related to the feeding and housing conditions (floor pens or cages) of the birds in the pre-experimental phase. Therefore, we suggest that the World's Poultry Science Association protocol for the determination of digestible P be should extended to the standardization of the pre-experimental period. We also suggest that comparisons of P digestibility measurements among studies are made only with great caution until the protocol is more refined.

Recent findings regarding calcium and phytase in poultry nutrition

Calcium (Ca) is an essential element for poultry and even a mild deficiency can lead to significant welfare and performance issues. As a result, it is often fed at levels in excess of requirement, partly as an insurance policy and, to some degree, because of its relatively low cost compared with other feed ingredients. However, when diets meet but do not exceed the phosphorus (P) requirements of the bird, a marginal Ca excess can interfere with P digestibility. This problem is exacerbated when phytases are used to provide some of the required P because Ca decreases the efficiency of phytate (IP6) hydrolysis in a dose-dependent manner. More recently, phytases have been used at very high doses (1500 FyTase units (FTU); ‘superdosing’) in commercial diets, to improve bird performance by removing as much of the dietary IP6 and lower esters of phytate (IP5, IP4, IP3 and IP2) as possible, all of which are considered anti-nutrients, and concomitantly producing as much inositol, a nutrient, as possible. In such a regimen, the ability of the phytase to degrade the lower phytate esters, namely IP4, IP3 and IP2, takes on greater importance than does simply releasing phytate P. Calcium has recently been shown to reduce the efficacy of hydrolysis of the lower phytate esters to a greater degree than the extent to which it decreases IP6 hydrolysis. As a result, Ca concentrations in the diet should be monitored frequently if the maximum value of a phytase is to be realised.