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Chapter 12
BREEDING STALLION FEEDING AND CARE
FEEDING BREEDING STALLIONS
The same feeding programs given in Chapter 10 for idle and working horses apply to breeding stallions. Breeding does not require an increase in any nutrient except those needed for energy. The increased energy needed for the act of breeding itself is small. However, the increased physical activity that may be associated with breeding, such as pacing and nervousness, increases dietary energy needs by an average of one fourth to one third above that needed by the idle horse for maintenance (Appendix Table 4). The amount of increase is variable among individuals, but varies little with the number of mares bred. The proper amount to feed is that necessary to maintain a moderate body condition (Table 1-4).
During breeding season, some stallions’ appetite may be reduced, and weight loss may occur. Feeding a diet high in quality, palatability, and energy density, and if possible turning the stallion out on green grass pasture for at least a few hours daily, will help prevent this. Up to a maximum of 0.75 lbs/100 lbs body wt (0.75 kg/100 kg) daily of a grain mix containing molasses, high-energy-dense grains such as corn, and even to 10 to 20% added fat or oil if necessary may be fed. However, the amount of grain mix fed and/or its energy density should be reduced if the stallion becomes too high-spirited to handle, or if its body condition increases above moderate. More often, most stallions’ body weight decreases a few percent during breeding season.
The breeding stallion should be fed a diet similar in nutrient content to that of the exercised or working horse (Appendix Tables 1, 2, and 3). Vitamin C and E supplements are occasionally used to enhance the stallion’s reproductive performance or ability. However, numerous studies have shown that giving vitamins C or E, even in large doses, is of no benefit for this purpose, as described in sections on these vitamins in Chapters 2 and 3. If feeding a vitamin supplement is desired, or if one wishes to ensure that the stallion’s diet contains a sufficient amount of all vitamins for optimum health and reproductive ability, giving a balanced vitamin supplement providing additional quantities of all vitamins without excessive amounts of any, such as described in Table 3-5, is best. Giving a vitamin supplement of this type may be beneficial in some situations, as described in Chapter 3, and even if not needed will not be harmful.
EXERCISE FOR BREEDING STALLIONS
Most have considered exercise helpful in maintaining the breeding stallion’s appetite and libido. Although exercise increases feed consumption, even moderate, nonfatiguing exercise has been shown to decrease the stallion’s libido. The exercised stallion, however, is easier to handle and displays less excessive energy when taken from its stall.
Decreasing or eliminating exercise is unlikely to transform a stallion with poor libido into one with excellent libido. However, less sexually aggressive stallions’ libido may gradually increase over a period of time by decreasing or eliminating regular exercise, and by increasing their dietary energy intake, providing these procedures don’t result in excess body weight or condition. Conversely, hard-to-handle stallions may become easier to control if placed on a regular exercise program and if their dietary energy intake is decreased.
BREEDING EVALUATION OF STALLIONS
The breeding stallion should be evaluated for breeding soundness: (1) before purchase, (2) before each breeding season, (3) to estimate the number of breedings or inseminations that can be made during a season, (4) anytime lowered fertility is suspected, (5) anytime it would be desirable to increase the number of mares to be bred, (6) when abnormal sexual behavior is observed, and (7) when the stallion is suspected of harboring a potential disease-producing organism. In addition, the stallion’s reproductive performance should be monitored continuously with respect to the percentage of pregnancies per service, number of breedings or inseminations per pregnancy, and pregnancy rate (%) by month and by cycle.
At least two ejaculates of semen collected with an artificial vagina 1 hour apart should be evaluated for semen quality; or, to determine daily sperm output, an ejaculate obtained once daily for 7 to 8 days should be evaluated. After 3 to 7 days, spermatozoa reserves are depleted and sperm output becomes stable at the quantity that stallion is capable of producing. Sperm output is normally about 50% lower in the second than in the first ejaculate taken 1 hour apart; it is also lower in semen obtained during the winter than in that obtained during late spring and summer. The number of spermatozoa produced is helpful in predicting the number of mares that can be booked to that stallion if artificial insemination is being used. In contrast to what many stud managers believe, the volume of ejaculate doesn’t affect fertility; it is instead the number of sperm in that ejaculate, which is unrelated to semen volume. Also in contrast to common belief, a stallion’s sexual behavior, or speed and vigor of mounting and copulation, is not indicative of his fertility.
In addition to semen evaluation, total scrotal width should be measured and testicular tone evaluated. The number of spermatozoa that a stallion is capable of producing is directly related to the size of the testes. The average total scrotal width of normal stallions of light horse breeds of all ages, taken early in the spring, is 85 to 130 mm (3¼ to 5 inches). If the scrotal width is less than 80 mm (3⅛ inches), it is recommended that the stallion not be used even though its seminal characteristics are normal. Stallions with small testes are potentially poor producers of spermatozoa, and testicular size is probably highly heritable, as it is in other species. Breeding a stallion that has one testicle not in the scrotum also is not recommended, as this characteristic may be heritable. Stallions with both testicles retained are not fertile. Those with a retained testicle sooner or later often exhibit abnormal sexual behavior.
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