Three common hitches exist in the trailer industry: the weight-carrying hitch; the weight-distributing or load-equalizer hitch; and the fifth-wheel hitch, also called the gooseneck.
Weight-carrying hitches are often affixed directly to bumpers and carry all of the trailer's tongue weight. These are intended for light loads such as those in utility trailers; they seldom suffice for hauling horses.
A load-equalizer hitch includes a receiver (a square, female tube) and detachable hitch plate and trailer ball. The hitch frame is attached to the tow vehicle's frame in such a way as to distribute tongue weight among all tow-vehicle and trailer axles. Typically, these hitches are used on SUVs and trucks to balance moderate to heavy loads over multiple axles, and are safe for two-, three-, and sometimes four-horse trailers, if the total tow-load weight doesn't exceed the towing capacity of the vehicle.
Fifth-wheel hitches are mounted in the middle of a truck bed, approximately over the rear axle, and are used for gooseneck-type trailers. These hitch systems add hundreds of pounds to the trailer, but make the rig comparatively more stable and less susceptible to road sway and high winds. Many people also find fifth-wheel trailers easier to park, although the trailer can actually damage the truck bed if pinched too tightly while backing.
For four-horse and larger trailers, most horsemen prefer the gooseneck trainer/hitch option coupled with a 3/4-ton or larger tow vehicle, such as the Ford? F250? Super Duty or the Dodge? and Chevrolet? 2500 or 3500 series pickups.
For more great trailering advice, read "Safe Trailering" in the August 2010 issue of Horse & Rider.