Whether for weight gain or loss, speed or shine, nearly everything we offer our horses is given to bring about a desired effect. Stacie Appleton, PhD, and Mike Jerina, BS, presented a demonstration on "Measuring the Physiologic Response to Nutrition" to show how the lab goes about measuring the effect of their feeds, at the Purina Equine Veterinary Conference in St. Louis, Mo., Oct 17-19, 2008.

Every horse at the Purina Mills Equine Research Facility is involved in one of three categories of research: palatability studies, growth and development studies, or exercise physiology.

Current growth and development research at Purina monitors 12 foals to measure skeletal growth, spontaneous activity levels, and body condition scores. Most of the foals are Quarter Horses from similar working cow horse genetic lines. Each foal receives full radiographic studies within three days of birth, with radiographs repeated every six weeks for two years. Scientists place GPS units on each foal to monitor when they move around, are most active, and when they rest. This is used to evaluate how diet affects behavior and activity level. Rump fat thickness is measured with ultrasound to determine a body condition score. Other parameters include weight, skeletal development, insulin and glucose sensitivity, and various blood parameters.

For mature horses, Jerina described an exercise physiology study on unfit, obese horses (body condition score of 8) and response to a weight loss dietary formulation. Each of three groups had eight horses: one group of controls, another was on a diet, and the third group on a diet with exercise.

First, the exercised group