The frog allows the hoof to expand upon landing. It also plays a major role in the hoof’s ability to absorb shock.
A healthy frog is smooth and wide. It’s even on both sides. It makes some ground contact at the heels, sloping downwards towards its tip. The ridge running through the middle (the central sulcus) is shallow and clear. This helps the heels expand.
You can assess the health of a hoof’s frog after trimming the walls, heels and dead sole within the collateral grooves. Lay your rasp across the heel-landing platform. Check that the frog is level 1/3 of the way down, making contact. Then lay your rasp across the hoof walls at the tip of the frog. This area should not be weight bearing.
If necessary, trim the frog level with the heels, using your farrier knife. Next, make sure it follows a slope downwards towards its tip. Clear the central sulcus of dirt and debris.
If you’ve cleared the collateral grooves the frog should be able to expand properly. If it bulges over these, trim the sides carefully to bring it back into place.
A horse that’s just come out of shoes may have a shrivelled frog. Confined to the shoe, it hasn’t been able to expand naturally. The result is contracted heels, poor shock absorbance and a deep central sulcus. This can be a breeding ground for thrush.
But the frog is a softer tissue, and will grow relatively fast. Keep it clean, in the correct position, and give your horse regular exercise. In time it will expand.