I stand corrected, it was Dr. Strasser who had written about the reduced blood flow. Here's an exerpt that I found from the study I had read, but I have also seen this hotly debated on other forums, so I guess it must be taken with a grain of salt:
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"With horses whose hooves have been contracted (or shod) for a long time, altered liver and kidney function values are noticeable in blood tests.
[SIZE=12pt]"The kidneys and liver of a horse with contracted hooves are overstressed as a result of having to deal with the excess metabolic waste protein in the blood stream. Their function is disrupted and, especially with liver function disrupted, frequent bouts of colic and other problems can result.[/SIZE]
[SIZE=12pt]"This is why it is important, before beginning with the rehabilitation of a horse with badly damaged and long-term contracted hooves, to establish the values for kidney and liver function via a blood test. The results can also aid in clarifying for the owner and any veterinarian treating the horse the reality and seriousness of the damage in the horse as a result of impaired hoof functions, as well as provide concrete records showing the effectiveness of this rehabilitation method.[/SIZE]
[SIZE=12pt]"If the kidneys and liver are working only poorly, the long-term, slow poisoning of the entire organism (especially the heart) can be so severe that, after reactivation of hoof mechanism and the removal of dead corium regions (which burdens the kidney and liver even more), the overall toxicity can lead to metabolic organ or heart failure--in other words, the sudden death of the animal." (VII-35)[/SIZE]
[SIZE=12pt]"Blood contains a high amount of protein, and a large part of this protein must be excreted, such as via the hooves in the form of horn, or via the skin as hair. When the blood flow in the hoof corium is restricted (such as through shoeing, contraction, lack of movement), less waste protein is excreted here, and too much remains in the bloodstream and the organism. This excess protein must then be excreted, along with the regular metabolic waste, by the kidneys and skin. For the kidneys, this extra work is a strain which adversely affects their normal functions. As a result, regular metabolic waste which should have been excreted by the kidneys remains in the organism, putting stress on other organs. The liver, as a metabolic organ, is one of these, and is then no longer able to function properly.[/SIZE]
[SIZE=12pt]"This is why blood tests for horses that have been shod or have had contracted hooves for some time show abnormal values for liver and kidney functions. The reduced corium circulation in horses with long-term shoeing and contracted hooves thus also sets the stage for laminitis, which can then be triggered by even a slight change in blood composition, or metabolism--such as results from a small amount of excess grain, grass, or a vaccination (none of which are the cause of laminitis, only the trigger." (X-25-26)[/SIZE]
[SIZE=12pt](Above excerpts from: The Hoofcare Specialist’s Handbook: Hoof Orthopedics and Holistic Lameness Rehabilitation[/SIZE], [SIZE=12pt]by Hiltrud Strasser, DVM & Sabine Kells; published 2001 in Canada by Sabine Kells.)[/SIZE]