Not only must the proper amount be fed, the horse must also eat the proper amount. If the horse refuses a feed, both the feed and the horse should be closely examined. If no disease, injury, oral or dental problems, or cause of pain, discomfort, or distraction for the horse are found or suspected, the feed may be at fault, particularly if it is refused or eaten poorly by more than one horse and/or if there has been a recent feed change. The feed should be examined, smelled, and tasted. However, many feed-related poisonings and palatability problems require extensive laboratory and/or feeding tests to determine their cause, as described in Chapter 19. A different feed should be tried. If that feed is eaten normally, this is a strong indication that there is a problem with the refused feed. If it isn’t eaten normally, it suggests the problem is with the horse, particularly if it is the only horse affected.

TABLE 10–2 Grain Needed for Physical Activity^a

If there has been extensive sweating, inappetence may be due to water and electrolyte deficits, particularly potassium, chloride, and sodium. If this could be the case, give the horse 3 oz (85 g) of a mixture of equal parts common salt (sodium chloride) and “lite” salt (a mixture of equal parts sodium chloride and potassium chloride, available at most grocery stores), 2 to 3 times daily for 2 to 3 days. The salt mixture should be added to a sweet feed or a dampened grain mix to prevent it from sifting out. The most common cause of a decrease in appetite in the hardworking horse, or the horse in training or use, however, is overwork. In this case, work must be decreased sufficiently until appetite returns.

Whether due to inappetence, disease, injury, or any other reason, as a general rule, if there is a break in work or training, the amount of grain fed should be reduced by one-half, beginning ideally with the evening feeding before the break. If the break is for more than 2 to 3 days, don’t feed any, or only a minimal amount of, grain during the break. When the break is over, increase the amount of grain fed at a rate of not more than 0.5 lbs (0.2 to 0.3 kg) daily to a maximum of no more than 0.5 lb/100 lbs body wt (0.5 kg/100 kgs) per feeding and to not more than a total of an amount equal to one-half of the total weight of the diet.

More grain than necessary may be fed because it is easier or less expensive to feed grain than hay, or to decrease gastrointestinal fill and, therefore, the weight carried during physical activity. The horse’s gastrointestinal tract can hold up to 25 to 30 lbs/100 lbs body weight (25 to 30 kgs/ 100 kgs) and it takes 50 hours for undigested fiber, which is highest in forages, to pass through the gastrointestinal tract and be excreted. Thus, decreasing gastrointestinal fill can substantially reduce the amount of weight the horse carries. This reduction may be beneficial for short-duration exertion, but appears to be detrimental for long-duration activity. Forage intake increases the amount of water, electrolytes, and energy-supplying nutrients in the gastrointestinal tract and thus their availability to replace those needed for physical activity and loss due to sweating.

The amount of forage consumed should never be less than 0.5 lb/100 lb body weight/day (0.5 kg/100 kgs), and it is safer if it constitutes at least one-half of the total weight of feed eaten. For the horse being used for prolonged physical activity, forage intake should be at least 1 to 1.5 lbs/ 100 lbs body weight/day (1 to 1.5 kgs/100 kgs) and grain fed as needed for weight maintenance.

COLD WEATHER CARE OF HORSES

Even in cold weather, horses frequently prefer and are better off outdoors. Closed and heated stables are often poorly ventilated. Respiratory diseases are higher in horses kept in poorly ventilated stables than in those kept outdoors, even during cold weather. Horses acclimate to cold temperatures without much difficulty if given the opportunity. The thermal neutral or comfort zone for the horse is usually quite different from that for people. Don’t evaluate the horse’s environment based on your comfort. The horse, particularly when cold acclimated, is comfortable at temperatures quite chilling to you. However, during cold weather the horse should have access to shelter from wind, sleet, and storms, and during the summer it should have shade available from the hot sun. Trees, brush, or free access to a stable or open-sided shed work well for all seasons.

Horses in severe cold group closely together to provide mutual shelter and body heat. They may all take a run to increase body heat production, then come back together and stand in a close group to share the resulting increased warmth. In the absence of wind and moisture, horses tolerate temperatures down to near 0°F (− 18°C) or, with shelter, to even − 40°F (− 40°C), but are more comfortable at temperatures above 18 to 59°F (-8 to 15°C), depending on their hair coat (Table 10–3). In severe, stormy weather horses stop grazing and will stand with their rear end to the wind. The tail is held close to the dock, allowing it to be blown between the legs and thus shield the hairless area of the perineum, the groin and the inner thighs. The density of the hair coat and the direction in which the hair lies, especially over the hindquarters and back, act as a weather shield so efficient that ice may form on the horse without chilling the skin.

A long, thick hair coat is an excellent insulator and provides the first line of defense against the cold. Its insulating value is lost, however, if it gets wet, which is why it is important to keep horses dry and sheltered from the wind in cold weather. A combination of cold and wind, especially in wet weather, is particularly stressful. Nothing is so chilling to the horse as wind with cold rain, sleet, or snow. The quantity and quality of hair in the mane and forelock are quite important in protecting the horse’s ears and eyes from severe cold. A full mane, with natural length and density, can act as a waterproof screen for the head, throat, and neck.

As shown in Table 10–3, beef cattle, and therefore possibly horses, with a dry, heavy winter hair coat are comfortable at effective ambient temperatures down to 18°F (− 8°C), and energy needs for maintenance increase only 0.7% for each degree Fahrenheit (0.4/°C) of cold below this temperature. In contrast, the animal with a wet, or a summer, hair coat is comfortable only down to a temperature of 59°F (15°C), and energy needs increase 2.0%/°F (1.1%/°C). Thus, for example, the 1000-lb (454-kg) horse with a dry, heavy winter coat would need only about 16.5 lbs of good-quality hay (allowing 10% for wastage or loss) at effective ambient, or wind chill, temperatures above 18°F (−8°C). But if the wind chill temperature was 0°F (−18°C), 18.6 lbs (8.4 kgs) (i.e., [16.5 lbs × (18°F × 0.007/°F)] + 16.5 lbs = 18.6 lbs) would be needed; 22.4 lbs (10.2 kg) (i.e., [16.5 lbs × (18°F × 0.020/°F)] + 16.5 lbs = 22.4 lbs) would be needed at this wind-chill temperature if the horse had a summer, or a wet, hair coat instead of a dry winter hair coat.

TABLE 10–3 Effect of Hair Coat on Comfort and Dietary Energy Needs in Cold Weather^a

^aFor beef cattle and, therefore, probably similar for horses. However, growing horses’ digestible energy intake has been found to increase by only about one-half this amount with decreasing temperature below freezing, i.e., by 0.36%/°F below 32°F (0.2VC below 0°C).

^bTemperature minus the value given in Table 10–5 times wind speed; e.g., at 54°F and a wind speed of 24 mph, the wind chill temperature would be 54 − (1.5 × 24) = 54 − 36 = 18°F (Table 10–5).

Blanketing the horse is beneficial when the effective, or wind-chill, temperature is less than comfortable (Table 10–3). Above this temperature, however, blanketing is not beneficial—it does not provide increased comfort for the horse. It decreases hair-coat adaptation to the cold and is uncomfortable for the horse during warm periods of the day, particularly sunny ones. Although blanketing the horse does induce shedding earlier in the spring, frequent grooming and an adequate diet may be preferable, as discussed in Chapter 9 (see section on “Skin and Hair-Coat Care”).

After the hair coat, the next line of defense against cold is fat; a layer of fat under the skin provides additional insulation against cold. In cold climates, the horse ideally should be moderately fleshy to fleshy (Table 1–4) when cold weather begins. In cold weather, more dietary energy is needed for maintenance of thin than moderately fleshy animals.

Sufficient cold increases energy needs both to maintain body temperature and, at least in cattle, because feed digestibility decreases with decreasing environmental temperature below the comfort temperature. As shown in Table 10–4, energy needs for maintenance are 23 and 47% higher for beef cattle at 30 and at 10°F (− 1 and − 12°C), respectively, than at 68°F (20°C), and at 10°F (−12°C), these needs are increased an additional 19% by a wind of 10 mph (16 kph).

The more wind speed increases, the more it decreases the effective ambient, or wind-chill, temperature (Table 10–5). For example, a wind speed of 15 mph would decrease the effective ambient temperature 15°F (l°F/mph of wind speed, as given in Table 10–5), but an additional 15 mph increase in wind speed would decrease the effective temperature twice as much, or an additional 30°F (1.5°F/ mph, as given in Table 10–5, times 30 mph = 45°F decrease). These effects of cold on dietary energy needs and, as a result, feed intake during the winter were well demonstrated in the study shown in Table 10–6.

TABLE 10–4 Cold Temperature Effect on Metabolizable Energy Needs^a

TABLE 10–5 Wind Effect on Effective Ambient (Wind Chill) Temperature^a

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