Horses with straight legs, travel with the laterals on separate tracks. They don't interfere.
Horses with crooked legs, tend to travel on one track (often called rope walking), they tend to wing, and have a tendency to interfere. The supporting leg, when moving, tends to be at an angle rather than straight down.
What is happening in this picture (below)? Look at the right rear and the left front. These two limbs should be traveling on separate tracks. In this image, they are overlapping on a single track, generally called "rope walking". This can cause interference.
This horse (below) has straighter flight of the limbs, on two separate tracks.
Teaching a Horse to Talk - Listen very carefully to hear the horses "talking". As they learn, they will get louder; this is just the start.
8 years ago