Project 2.1
Myo-inositol and low-P supply effects on intestinal processes of InsP6 degradation and P utilisation in two contrasting high-yielding laying hen strains
Markus Rodehutscord / Korinna Huber
The results obtained in the first funding period indicated distinct differences between two laying hen strains in gastrointestinal degradation of InsP6 from the feed, mucosal phosphatase activities, and myo-inositol concentrations in blood and eggs. The objective in the renewal period is to gain a deeper insight into myo-inositol and phosphate metabolism of laying hens. The disappearance of InsP6 and the appearance of lower inositol phosphate isomers and myo-inositol in the ileum will be studied and related to measurements of myo-inositol in blood and eggs. This is complemented by myo-inositol and phosphate transporter expression studies in the brush border membrane vesicles of the small intestine and kidney. Mucosal phosphatases are characterised by enzyme activity determination and detection of hydrolysis end products in a modified in vitro assay. The overall efficiency of phosphorus utilisation of the hens will be determined based on quantitative intake and excretion data. Multiple linkages with the objectives and methods of other projects exist, primarily in relation to renal metabolism, intestinal microbiota and tissue functioning, and genetic studies.
The specific hypotheses of this project in the renewal period are:
1. Myo-inositol provided with the feed at moderate and high amounts enters the blood stream and is partially transferred to the egg with differences in the transfer efficiency between hen strains.
2. Complete removal of mineral P supplements from the feed leads to increased InsP6 degradation, MI release, and InsP6 utilisation by laying hens. Those effects are related to differences in endogenous phosphatases activities resulting in variations of intestinal phosphate and MI supply between hen strains and at onset of egg production.
3. Variation of intestinal supply of MI and phosphate related to feed composition competitively modulates its absorption and re-absorption in the jejunum and kidney by modulation of MI and Pi transporter protein expressions.
4. The biological potential of P utilisation efficiency is affected by the genetic background of the hens.
