Those who have worked with different breeds of horses almost always have their opinion as to basic temperament and behavioral characteristics of certain breeds. Few would not agree that in general the warmblooded breeds, such as Thoroughbreds and Arabians, are generally more reactive than the more stoic, cold-blooded (draft) or pony breeds. Also, horse breeders have long recognized the heritability of certain basic temperaments in lines of horses and select for those characteristics when breeding. So there is no doubt that genetics plays a big role in basic temperament and behavioral characteristics of horses. While many good behavioral characteristics and problem behavioral characteristics are heritable, they are probably not highly heritable. For example, a stallion with a tendency to savage people is probably more likely to have some male offspring born with that tendency than a stallion which does not savage people. But the savage stallion is also likely to have many male offspring which do not have the tendency. The same is true of the tendency for positive traits; there are no guarantees.
Probably the broadest generalizations concerning basic equine temperament and behavior involve comparisons of mares, stallions, and geldings. Stallions, of course, are intact males. The majority of equestrians would not consider keeping or using a stallion for other than breeding. A stallion is typically very strong physically, and strong willed. If not trained when and where to breed, a stallion will instinctively respond sexually whenever the occasion arises. In most equine athletic disciplines, those who prefer to work with stallions usually appreciate the strength and competitive drive of an intact male horse. For such experienced handlers or trainers, the sexual and aggressive behavior of a stallion is remarkably well controlled with simple behavior modification. The key to success with stallions appears to be firm, consis