Abstract: Energy is an essential nutrient for all horses, and it is especially important in performance horses, pregnant and lactating mares, and young growing horses. A negative energy balance in horses such as these may result in unsatisfactory performance, decreased fertility, or slow growth. Therefore, ensuring adequate energy intake is an important aspect of the nutritional management of the equine. This study was undertaken to investigate the effects of feeding large, carbohydrate-rich, concentrate meals on the satiety-inducing hormone, leptin. Three groups of yearling horses were rotated through 3 feeding schedules in a replicated 3x3 Latin square design. Horses were fed 2, 3, or 4 times per day (2x, 3x, and 4xfeeding schedules, respectively), each for a period of 11 d, with the total amount of daily feed held constant. Horses were weighed and BCS was determined on the first day of each period. Blood samples were collected before the morning meal on d 1, 4, and 7 of each period. Additionally, blood was sampled for the last 24 h of the 2xand 4xdietary periods. Neither weight nor BCS changed during the study (P = 0.99 and P = 0.28, respectively). Both mean and peak plasma glucose were greatest in 2xhorses (P < 0.05), as were mean areas under the curve. Serum leptin concentration increased in 2xhorses (P < 0.05), but not in horses fed 3 or 4 times daily. Leptin was elevated in horses with greater BCS (P < 0.05) and increased steadily throughout the study (P < 0.05). Data from the 24-h collection indicated that 2xhorses had fluctuations in leptin production throughout the day (P < 0.05), whereas horses fed 4 times daily did not. Overall, this study indicates that feeding horses 2 large concentrate meals daily can increase mean serum leptin concentrations and may cause fluctuations in leptin production over a 24-h period. This departure from baseline leptin concentration has the potential to affect appetite, along with numerous other physiological processes.

Abstract: Discriminative learning abilities were studied in 12 mature, malnourished horses. All horses initially received a condition score (CS) between 2 and 4 on a scale of 1 (poor) to 9 (extremely fat). Then horses were assigned to one of 3 treatments based on their eventual, rehabilitated CS during discrimination testing: thin, CS 1-3; moderate, CS 4-6; and fat, CS 7-9. The discrimination learning task was performed for 14 days with a maximum of 20 trials per day. Daily criterion was set at eight consecutively correct trails. Total trials to first criteria and total errors during testing were recorded. Analysis of variance showed that treatments did not differ (P>0.05) in total trials to first criterion, however horses on the fat treatment did have higher total error scores (P<0.05) than horses on the thin or moderate treatments. This difference was probably owing to lack of motivation in the fat treatment horses, rather than to true learning ability differences. The sex of the horse did not significantly affect either learning score.

Abstract: Forty weanling Quarter Horses, from the Pitchfork Ranch, Dickens, Texas, were randomly assigned to one of five groups based on the amount of handling they would receive. The five groups were: (1) limited handling; (2) 1 week of handling; (3) 2 weeks of handling; (4) 3 weeks of handling; (5) continuous handling for 18 months. As 2-year-olds, the horses were tested in a simple place-learning T-maze after being preconditioned. A maximum of 30 daily trials were conducted for 20 consecutive days, with feed location alternating between sides on successive days. If a horse met the criterion of 11 out of 12 correct responses with 8 correct responses being consecutive, it was retired without completing the 30 trials. Group 1 made fewer correct responses during the 20 days than any other group except Group 3. All groups achieved learning by Day 10, but the most-handled group reached a consistently higher percentage of correct responses earlier than the less-handled groups. Group 5, the group receiving the most handling, was the least emotional, as determined by the animals' reactivity to a novel stimulus, and received the highest scores for trainability after being ridden. Preconditioning trainability scores, or estimates of the horses' ability to learn prior to conditioning and testing, tended to predict maze-learning ability. These scores were also significantly correlated with post-maze training scores.

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.