Overfeeding for optimal studbook showing: a comparison of subjective and objective techniques to monitor the effect of condition on the status of the locomotor apparatus in Shetland ponies.

Abstract

Background and aims: Traditionally, Shetland ponies are overfed for optimal studbook showing, simultaneously increasing their laminitis risk. Thus, this study aimed to prove that obese ponies being on a double diet would be suffering from a subclinical lameness of both front feet. The administration of hoof percussion would increase and that of a local block would decrease the sensitivity of the hooves, illustrated from both subjectively scored and objectively measured parameters.

Materials and methods: A group of n=10 adult Shetland mares (Mean±SD 5.0±2.1 years; 102.8±3.8 cm) had been randomly (n=5) assigned to two different diets for 8 months resulting in a normal (100% ratio: 189±15 kg), and an obese (200% ratio: 247±42 kg) group. A n=18 infrared (IR) camera Optical Motion Capture (OMC) system (Qhorse®; 200Hz) and n=3 reflective markers at Head, Withers, and Pelvis were used to objectively assess their kinematics before and after a diagnostic nerve block of their forefeet at similar speeds (before: 2.71 m/s, after: 2.67 m/s).

Results: In the obese group diverging hoof rings and dorsal hoof wall percussion scores were clearly higher. The heartrates in the control group did increase after locomotion measurements (before: 29,8 hb/m, after 40,9 hb/min), while the heartrate in the obese group stayed the same (before 47,2 hb/min, after: 50,3 hb/min). After blocking the Stride Duration (before: 0.51s, after: 0.55s) in the obese group significantly increased (P<0.05), in contrast to the normal group (before: 0.52s, after: 0.52s). The stride frequency decreased in the obese group after blocking (before: 1,94 strides/s, after 1,85 strides/s) while the average speed stayed the same (before 2,65 (m/s), after 2,60 (m/s).

Conclusions and clinical relevance: Using objective gait analysis equipment, we found locomotor parameters for monitoring subclinical foot pain. Apparently, but not surprisingly, traditional doubled feeding has put the obese group at risk for painful feet; their extra positive blocking response possibly illustrates that these obese animals -when pain free- would more optimally perform at studbook showing because of a higher stride duration and decrease of stride frequency compared to control ponies.