Horses and Mules

by WILLIAM JACKSON

IN 1947 Americans owned 8 million horses, the smallest number in 75 years. Nevertheless, those of us who believe there will always be a place for horses in the rural scene have gone ahead with tests and experiments to breed better horses and to learn more about them. Institutions that have taken the leadership are the agricultural experiment stations in California, Michigan, Mississippi, Missouri, Indiana, Montana, Tennessee, Wisconsin, Utah, Kentucky, and Minnesota; the Army Remount Service; and the Department of Agriculture, chiefly at the United States Morgan Horse Farm at Middlebury, Vt., and its Range Livestock Experiment Station at Miles City, Mont.

Interesting experiments have been started at the Michigan station to produce a handy-size farm horse for comparison with heavy draft horses in adaptability to general farm work, market demand, and size. Mares of draft breeding, mainly Percheron and Belgian, are being bred to Arabian, Thoroughbred, and Morgan stallions. The fillies from these crosses will be bred back to stallions of the same light breeds, respectively, and later mated with draft stallions.

Another aim of the work in Michigan is to find cheaper ways to produce horses by using pastures as much as possible and eliminating feeding of grain, chore labor, and housing. Results indicate that both draft and light-type colts can be raised satisfactorily by keeping them out-of-doors on pasture in summer, and on uncut meadows and stacked hay in winter. Such colts reach full mature weights, and have better legs and feet than similar colts housed in stalls. When sold as yearlings or 2-year-olds, they are in somewhat rougher condition than stall-fed colts, and consequently tend to sell at slightly lower prices, but bring a higher net profit because of their lower cost to produce. Four fillies raised outdoors have produced 12 colts in the 3 years since they were first bred as 3-year-olds, thus giving 100-percent colt crops for three successive seasons—an achievement in any stud.

Attention also has been given to developing practical means of measuring equine performance and utility. A series of preliminary tests with light horses at the Morgan Horse Farm developed a useful background of experience for such measurements, which Ralph W. Phillips, G. W. Brier, and W. V. Lambert have summarized in this way: The tests of speed and length of stride demonstrated significant differences between horses; horses tend to increase the length of stride during a test, indicating that records must be taken under similar conditions if individuals are to be compared; normal respiration and heart rates are difficult to obtain. A slight disturbance resulted in an increase. If normal rates at rest are to be obtained, they will probably have to be taken in the stall, at complete rest, and by someone with whom the horse is familiar. The extent to which respiration and heart rates rise during exercise and the rate of return to normal vary with the amount of exercise and also with the individual horse.

Tests at Middlebury

Based upon these observations, a series of tests has been devised through which all progeny of the Department's Morgan stud are measured in harness and under saddle at 3 years of age. Speed of walking and trotting and length of stride are recorded over a measured mile when the animal is pulling 60 percent of its body weight under harness and hitched to a two-wheel training cart, and again under saddle carrying 20 percent of its body weight. Endurance is measured by a trot over a 5-mile course, the horse being hitched to the cart, and, on another day, over an 11.5-mile cross-country ride under saddle, during which each animal covers measured and marked portions of the ride at three different gaits, which add up to 4.7 miles at a walk, 5.7 miles at a trot, and 1.1 miles at a canter. For the 5-mile test, respiration and heart rates are taken before removing animals from their stalls, at the end of the test, and 5, 10, and 15 minutes thereafter. After these endurance tests, the animals are scored for signs of fatigue, ease of gaits from the standpoint of the rider, and other factors.

These tests should help us discover some correlation between characteristics like temperament and conformation, on the one hand, and speed, endurance, and other important performance qualities on the other; and help us to use the geneticist's tools of inbreeding and rigid selection to produce animals that can perform as we want them to.

The tractive dynamometer, an electrical instrument in which the pointer is deflected as a result of a force exerted between fixed and moving coils, is still the most practical instrument for measuring performance in draft animals. It was first developed at Iowa State College. Its use has shown that the weight of a team is the most important factor in determining how much it can pull. But no reliable specific correlation has been found between body type and the animal's pulling ability.

After 9 years of observing pulling contests in Utah and southern Idaho, Milton A. Madsen, Harry H. Smith, and Ralph W. Phillips reported that the average body weight of all teams performing in nearly 2,500 entries was 2,872 pounds, and their average tractive pull was 2,385 pounds. These workers also summarized data from various sources on the amounts of tractive pull required to do different jobs on the farm, and discussed the relationship of results of the study to the ability of the horse to do farm work. Since dynamometer contests are almost all conducted for teams, to measure maximum pull rather than ability to work day after day, and are participated in by relatively few highly trained teams, these men concluded that the results now available are of little use in guiding breeding operations. They suggested that tests should measure walking speed, length of stride, and increase in heart and respiration rates of horses while doing definite amounts of work.

At the Missouri station, H. H. Kibler and Samuel Brody, working in cooperation with the Department, are attempting to establish indices for obtaining those measures. They are based on the assumption that heart and lung capacity are important factors, that temperament and will to work make a big difference, and that on a given day—temperature, humidity, air movement, feeding, and handling vitally influence the animal's ability to work. The men at Missouri, using mules for experimental animals, have constructed an ergometer with a weight and pulley system mounted on a trailer. It measures the amount and speed of work done and eliminates the variables of grade and irregularities of surface on which the animal performs. Within the automobile pulling this trailer is mounted an open-circuit respiration apparatus that enables the animal being tested to breathe normal outdoor air and at the same time to be measured with respect to significant physiological responses.