Abstract: Abstract
In response to a request published in Equus, a magazine for those interested in horses, 85 owners of older geldings exhibiting sexual behavior completed history forms. The mean age of geldings was 16 f 5 years. Only 39 of the owners had had the gelding for at least a year before the behavior was noted. These cases could be used to determine the true age of onset of the problem. When log survivorship was used to determine whether there were one or two different populations, a break or change in the slope at age 16 indicated that there are two populations. One population shows the behavior from the time of castration and the other first exhibits the behavior in old age, possibly in response to an ACTH secreting pituitary adenoma. A total of 40% of the horses were Quarterhorses, the most numerous breed in the US; 78% of the horses were purebreds. Fewer than half the owners knew the age at which their horse had been castrated because they did not own the horse at the time.
The mean age at castration, when known, was 3.3 f 2.5 years. The reason for contacting us was sexual behavior (70%), aggression (24%). or some other problem ( 1 o/o). Whether or not aggression was the presenting problem, most of the horses showed aggression (95%), particularly towards other geldings (88%)) but also towards people (3 1%). Copulatory behavior (mounting) was shown by 69% of the geldings and half of those were able to intromit. These findings indicate that the sexual behavior of geldings is a problem for owners and that aggression usually accompanies sexual behavior.
The owners were encouraged to send serum samples taken before and after human chorionic gonadotropin (HCG) administration for testosterone and estrone sulfate analysis to determine whether residual testicular tissue was responsible for the horse’s behavior. Of the 14 horses tested, only one had elevated levels of testosterone indicating that there was residual testicular tissue. A total of six of the owners agreed to treat their horses with cyproheptadine at a dose of 8 mg day- ’ gradually increased to 88 mg day- ’ per horse. A total of three of the horses showed a decline in sexual and aggressive behavior, one got worse and two had side effects and treatment was withdrawn.

Abstract: Mares quickly form a bond with their foals, probably within the first hour. They lick the foal usually beginning at the tail end, then the head and later the body of the foal. Licking behavior disappears within the first hours in most mares. Once the bond is formed the mare will let no other foal nurse and stays within a meter of the foal most of the time during the first week. The foal follows her when awake, but when he sleeps she stands over him. As the foal matures the distance the mare maintains from the foals get longer and she may graze as he sleeps. The bond of the mother to the foal gradually weakens as revealed by her response to separation from the foal. Weaning usually takes place shortly before the birth of the next foal. Some mares will attempt to steal foals and this can lead to injury of either the mares or the foal. Because of the strong and exclusive bond of most mares to their foal, foal rejection is especially abnormal. It occurs in some breeds more frequently than others, indicating a heritable component. Arabian mares reject 5% of their foals and other breeds reject less than 2%. There are three types of foal rejection- simple fear of the foal that can be quickly solved by holding the mare so the foal can suckle. The mare learns that nursing is pleasurable. This process usually takes only a few hours of holding the mare because foals suckle so frequently- about four times an hours. The second form of foal rejection is avoidance of tactile stimulation of the inguinal fold. When the foal attempts to suckle he usually strikes that skin fold and causes the mare to cow kick and move away. Desensitization to stimulation of the inguinal fold can solve this problem in a few hours. Treatment is more complex and longer for mares that are aggressive to the foal even when it does not touch them. This type of foal rejection can be treated with drugs that inhibit dopamine such as acepromazine-not the alpha adrenergic agent xylazine. Dopamine inhibits the pituitary hormone prolactin, a putative maternal hormone, which increases milk production. Blocking dopamine will increase prolactin. The mare should always have visual contact with the foal, but be restrained so she can not bite or kick the foal. A pole across the stall confining the mare against a wall is best. Maternal behavior can be induced in non-pregnant mares using injections of estrogen, progesterone, and the dopamine inhibitor sulpiride. Once lactation begins cervical stimulation can be used to elicit maternal behavior toward the next foal the mare sees.

Abstract: Reasons for performing study: Crib-biting is an equine stereotypy that may result in diseases such as colic. Certain breeds and management factors have been associated.
Objectives: To determine: breed prevalence of crib-biting in US horses; the likelihood that one horse learns to crib-bite from another; and owner perceptions of causal factors.
Methods: An initial postal survey queried the number and breed of crib-biting horses and if a horse began after being exposed to a horse with this habit. In a follow-up survey, a volunteer subset of owners was asked the number of affected and nonaffected horses of each breed and the extent of conspecific contact. The likelihood of crib-biting given breed and extent of contact was quantified using odds ratio (OR) and significance of the association was assessed using the Chi-squared test.
Results: Overall prevalence was 4.4%. Thoroughbreds were the breed most affected (13.3%). Approximately half of owners believed environmental factors predominantly cause the condition (54.4%) and crib-biting is learned by observation (48.8%). However, only 1.0% of horses became affected after being exposed to a crib-biter. The majority (86%) of horses was turned out in the same pasture with other horses and extent of contact with conspecifics was not statistically related to risk.
Conclusion: This is the first study to report breed prevalence for crib-biting in US horses. Thoroughbreds were the breed more likely to be affected. More owners believed either environmental conditions were a predominant cause or a combination of genetic and environmental factors contributes to the behaviour. Only a small number of horses reportedly began to crib-bite after being exposed to an affected individual, but approximately half of owners considered it to be a learned behaviour; most owners did not isolate affected horses.
Potential relevance: Genetic predisposition, not just intensive management conditions and surroundings, may be a factor in the high crib-biting prevalence in some breeds, and warrants further investigation. Little evidence exists to suggest horses learn the behaviour from other horses, and isolation may cause unnecessary stress.