Homestead Veterinary Hospital

November 2007

Four researchers associated with the Animal Health Foundation gave presentations at the Fourth International Equine Conference on Laminitis and Diseases of the Foot in November in West Palm Beach, Fla.

The three-day forum was attended by more than 350 veterinarians, veterinary students, farriers, horse breeders, trainers and owners from all over the world.

The AHF researchers were:
— Dr. Donald M. Walsh of Homestead Veterinary Hospital;
— Dr. Chris Pollitt of the University of Queensland;
— Dr. Philip Johnson of the University of Missouri;
— Kathryn Watts, a plant scientist from Center, Colo.

Dr. Pollitt also served as assistant director of the conference. He began his opening remarks by talking about the Animal Health Foundation, saying the AHF benefit held Oct. 20, 2007, in St. Louis had raised more money for his laminitis research than the Australian government had in all of 2006, and he openly thanked St. Louisans for their generosity.

The conference was started jointly in 2001 by Mr. and Mrs. John Castle of West Palm Beach and New Bolton Center in Pennsylvania in memory of the Castles' horse, Spot, who struggled for years with laminitis. New Bolton Center treated the horse.

The meeting brings together the world's leading researchers to review work and spark new projects and partnerships.

Dr. Pollitt reviewed two major theories, repeating what he had presented at the AHF benefit two weeks earlier:

His first was that the hoof wall of a horse who's had severe acute laminitis may grow in an abnormal direction, anteriorly (or forward) rather than downward, due to the descent of the coffin bone below the circumflex vein, as seen on a venogram.

Cells in the hoof wall proliferate in two places, in the coronary corium (coronary band) and the terminal laminar/sole complex (the white line area). When the coffin bone drops, it changes the alignment of these germinal cells. As the proliferative tissue in the two areas pushes forward against the intact hoof horn, the tissue has nowhere to go, so it expands posteriorly (to the rear), causing the venus blood supply in the coronary plexus (venus blood supply at the coronary band) to be shut down, again as seen on a venogram, and causing the tip of the coffin bone, or third phalanx, to be pushed posteriorly, making it appear that the deep flexor tendon is pulling P3 in that direction.

This wedge of tissue pushing up against P3 often will leave a notch in P3 all the way abound the base.

The strongest argument to support this theory is Dr. Pollitt's question to those who argue the pull of the deep flexor tendon causes P3 to rotate posteriorly: Why doesn't the rotation occur at the onset of laminitis when the most damage has been done to the laminae and they are at their weakest? Rather, it occurs weeks after the onset of laminitis, which is when the proliferative response would begin to press against the bone, resulting in the commonly seen ski tip portion of P3 and the loss of bone density just proximal to the tip.

If a venogram shows the coffin bone has dropped below the circumflex vein, this valuable information should tell a practitioner it's time to act to prevent the rotation of the coffin bone by thinning the hoof wall over the distal end of the third phalanx (approximately 1/2 to 3/4 inch from the ground surface) to allow the normal proliferation growth to proceed in the new anterior direction, reducing the pressure on the coffin bone.

Dr. Pollitt's second major topic was a review of the work of Kate Asplin and Catherine McGowan at the University of Queensland showing that hyperinsulinaemia produced laminitis in a group of ponies. This new finding raises the possiblity that controlling a horse's insulin with diet and exercise can prevent laminitis. In fact, Dr. Walsh presented data proving such a correlation in a study he conducted from 2005 through 2007 with 24 laminitic horses in his practice. There was a strong correlation in the study between insulin level and lameness: The lower the insulin, the better each horse did.

For more on Dr. Pollitt's work, go to laminitisresearch.org.

Dr. Johnson talked about the long history of laminitis research at the University of Missouri and the current direction of his own work. He has been examining how tensile (or tension-related) forces affect specific cells by mimicking the mechanics of an equine foot during movement; he also has developed methods to study laminitis without working on live horses. He said Mizzou has a vast tissue collection that the school would be willing to share with other researchers and he looked forward to future collaboration. In his second talk, he summarized interesting results from a survey of veterinarians on laminitis and the pregnant mare.

Kathryn Watts gave a conference-high five presentations, all on grass- and hay-related issues. She has summarized much of her work at safergrass.org.