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324 Nutrition Mngmt of Broodmares

324 Nutrition Mngmt of Broodmares - Nutrition and Feeding...

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Unformatted text preview: Nutrition and Feeding Management of Broodmares Pete G. Gibbs‘ and Gary D. Potter2 Horse producers should be concerned about their mares' reproductive performance and ability to mother strong, healthy foals. Economic survival often hinges on mares foaling early in the year. rebreeding quickly and nursing a growing foal that develops soundly. While achieving these goals in a herd of brood mares is dependent upon many factors. nutritional well- being is an important part of an effective brood mare operation. Brood mares have specific nutritional requirements that differ from other classes of horses. There are differences both in the amount of feed mares need and in the nutrient concentration needed in that feed. Therefore. the brood mare fits into a class of her own. Along the neck Along the withers Body Condition Affects Reproductive Performance Mare managers should monitor body condition on a regular basis. Historically. there were varying opinions as to the body condition most desirable for pregnant and milking mares. There is no longer any reason for debate nor controversy. Research results offer valuable management information relative to the effect of nutrition on reproductive performance in mares. It has been clearly shown that mares should be kept in good condition the year round. and especially as breeding season approaches. By checking the apparent fat cover in mares at the areas shown in Figure l, managers can assign a Crease down back Tailhead Inner buttocks Figure 1. Areas emphasized in the condition score. “‘ Adapted from Henneke et a1. ( I983) ‘ Professor and Extension Horse Specialist. Department ofAnimal Science. Texas A&M University 1 Professor and Equine Science Section Leader. Department ofAnimal Science, Texas A&M University The Condition Score System3 Description Poor. The horse is emaciated. The spinous processes (backbone), ribs, tailhead and hooks and pins all project prominently. The bone structures of the withers. shoulders and neck are easily noticeable, and no fat can be felt anywhere. Very Thin. The spinous processes are prominent. The ribs, tailhead and pelvic bones stand out. and bone structures of the withers. neck and shoulders are faintly discemable. Thin. The spinous processes stand out. but fat covers them to midpoint. Very slight fat cover can be felt over the ribs, but the spinous processes and ribs are easily discemable. The tailhead is prominent, but individual vertebrae cannot be seen. Hook bones are visible but appear rounded. Pin bones cannot be seen. The withers, shoulders and neck are accentuated. Moderately Thin. The horse has a negative crease along its back and the outline of the ribs can just be seen. Fat can be felt around the tailhead. The hook bones cannot be seen and the withers, neck and shoulders do not look obviously thin. Moderate-The Threshold Level of Body Condition. The back is level. Ribs cannot be seen but can be easily felt. Fat around the tailhead feels slightly spongy. The withers look rounded and the shoulder and neck blend smoothly into the body. Moderate to Fleshy. There may be a slight crease down the back. Fat around the tailhead feels soft and fat over the ribs feels spongy. There are small deposits along the sides of the withers. behind the shoulders and along the sides oftbe neck. Fleshy. There may be a crease down the back. Individual ribs can be felt. but there is noticeable fat between the ribs. Fat around the tailhead is soft. Fat is noticeable in the withers. the neck and behind the shoulders. Fat. The horse has a crease down the back. Spaces between ribs are so filled with fat that the ribs are difficult to feel. The area along the withers is filled with fat, and fat around the tailhead feels very soft. The space behind the shoulders is filled in flush and some fat is deposited along the inner buttocks. Extremely Fat. The crease down the back is very obvious. Fat appears in patches over the ribs and there is bulging fat around the tailhead. withers. shoulders and neck. Fat along the inner buttocks may cause buttocks to rub together. and the flank is filled in flush. “ Adapted from Henneke et a]. ( l983) numerical condition score to mares. This is Research has demonstrated that mares important because both mare owners/managers with condition scores of less than 5 do not breed and stallion managers need to be "on the same as well as mares with scores greater than 5. page" regarding the condition of mares to be bred. Mares that are moderately fleshy or even fat mares can be expected to a) cycle earlier Horsemen should use this scoring in the year. b) have fewer cycles per conception. system as a basic management tool for c) have a higher pregnancy rate and d) maintain determining whether or not mares are in pregnancy more easily than thin mares. optimum condition for breeding and as a communication tool between mare managers. Research also indicates that a condition stallion managers and veterinarians. score of 5 or less in milking mares means they do not have enough stored fat to support efficient reproductive performance. Those mares in marginal or poor body condition (5 or less) are more likely to skip a breeding season, and their bodies use dietary nutrients primarily for milk production rather than reproduction. When mares receive inadequate nutrition the incidence of embryo loss also increases (see table 1). So. it is important to get mares in suitable body condition and keep them that way year round. Reproductive performance often can be improved in thin mares when they are fed to gain weight. However. putting weight on an extremely thin mare is costly. and can be dangerous as well because some digestive disorders are associated with high levels of feed intake. It can also be difficult to achieve weight gain with milking mares during the breeding season (see table I). especially those in marginal condition While no foaling difficulties or rebreeding problems have been found in mares that are obese. there are no reproductive advantages to keeping mares in a condition of8 or 9. This can also be economically prohibitive. Therefore. scores of 5.5 to 7.5 represent the economic optimum, because mares in this condition normally spend fewer days at the breeding farm and less time open (see table 2). Management of body condition should be supported by careful selection of feedstuffs and accurate ration formulation, because this is an important step in promoting normal foal growth. The Importance of Roughage Brood mares normally require good quality. long~stem roughage as part ofthe daily diet. Whether it is provided in the form of high quality grazing or as hay. this is usually the starting point for the development of an effective brood mare feeding program. Roughage plays an important role in minimizing digestive problems such as colic or founder. and discourages undesirable vices such as cribbing. wood chewing and tail chewing. Good roughage serves as a major source of nutrients for the mare. Some types of grazing and hay can be potential health hazards for brood mares. Certain hybrid sorghum/sudan grasses have been reported to cause Cystitis Syndrome and/or Prussic Acid Poisoning. which can cause death. Pregrazing grow1h of these forages must be monitored and horses must be removed from grazing for several days when weather changes occur. Therefore. alternative roughage sources should be available if at all possible. Horsemen who feed alfalfa hay as roughage should beware of the potential for blister beetle poisoning. Blister beetles contain the compound cantharidin, which is extremely toxic to all horses. Alfalfa from early. first cuttings is less likely to contain beetles than hay put up in the mid-summer months. Hay that is not crimped or conditioned may be less likely to contain blister beetles. but there are no guarantees. Horsemen should take time to visit with hay producers. consider the harvest date and method of cutting, and check alfalfa hay regularly for the presence ofblister beetles. Fescue can be a good roughage for horses in general. but it is harmful to mares if it contains endophyte fungus. Problems such as the total absence of milk production (agalactia) and early foal death have been associated with fescue fungus. Fescue can be tested to determine whether or not it contains fungus, and endophyte-free seed is available for reseeding. To be on the safe side. pregnant mares should be removed from questionable fescue at least 90 days prior to foaling. Kleingt'ass is not a suitable forage for horses because it is very unpalatable and may associated with liver damage in horses. Hay selected on the basis of l) lealiness, 2) cleanliness, 3) aroma and 4) color will provide a safe and effective foundation for the brood mare feeding program. A high leaf:stem ratio. combined with cleanliness and a fresh smell. indicate quality from a nutrient standpoint. Hay that contains foreign material and is excessively weedy should be avoided. as should hay that looks or smells even the least bit moldy. lfround bales are used. care must be taken to maintain hay quality. It is often necessary to remove the weathered outer layer of a round bale. allowing mares to reach the high quality hay farther inside. There can be considerable wastage as mares forage from large round bales in the pasture or dry lot. It is important to provide liberal amounts of round bale hay to allow mares to select and cull undesirable portions of the hay. Mares kept in stalls or dry lots should receive at least 1 percent of their body weight in long roughage daily (1 pound hay/ IOO pounds body weight). Hay cubes can be fed as a roughage source. although some long-stem roughage may sometimes be needed to minimize possible problems such as wood chewing. Mares with access to top quality grazing will often consume more roughage than 1 percent of their body weight daily. Once the mares' roughage requirements are met. then supplemental energy, protein. minerals and vitamins can be provided in a concentrate mix to meet the remainder of their nutrient requirements. Concentrate Feeds Horsemen have some flexibility in terms of choosing feedstuffs for a horse ration. Commercially prepared feeds are practical for feeding a small number of horses. Many ofthese feeds from reputable companies are balanced for protein. calcium, phosphorus. trace minerals and salt. and are fortified with vitamins. Horse owners should not hesitate to consult the feed company for additional information that may not be listed on the feed tag. Owners with a large number ofbrood mares may find it more economical and practical to custom mix a ration or order formulated feed that can be delivered in bulk loads. Those owners choosing to mix rations on the farm should take time to balance for protein, minerals and vitamins. If individual grains are purchased for mixing. only the highest quality should be used. Inferior corn grain. for example. can contain the mycotoxin Fusarium moniliforme. which causes leucoencephalomalacia or moldy corn poisoning in horses. Horse owners should not use grain feeds that contain corn screenings. Recent interest has developed in feeding fat to brood mares, and research has shown that feed-grade. rendered fat can be utilized by mares to good advantage. Some commercial companies also add fat to feed concentrates. These fat-added feeds have varying energy densities and their daily feeding recommendations are normally listed on the tag or sack. Some of these feeds contain stabilized forms of fat. which allows them to be stored for longer periods of time. Fat-added diets are discussed further in the sections on late pregnancy and lactation. There has been little research on the use of complete feeds, or those designed to be the only source of both concentrate and roughage. These feeds are normally very high in fiber and. therefore, contain less digestible energy than other concentrates. In some cases, the way in which these high fiber feeds are processed causes mares to consume them more slowly, thus making it possible to feed mares on a free choice basis. Consequently, some complete feeds may be practical. depending on the overall management system being used and the facilities available for feeding brood mares. Cattle feeds sometimes can be utilized to good benefit. Some companies sell [0 percent and I4 percent crude protein cattle feeds and all- natural range feeds. often at a lower price than horse feeds. Contrary to popular opinion. horses can tolerate about the same level of urea in the diet as can cattle. However. urea is not useful other than in helping meet maintenance requirements. and is best left out of mare diets. Mare owners should make sure that any cattle feeds fed to horses contain absolutely no mold or additives such as rumensin or bovatec and that pelleted feeds are of good quality, not soft and crumbly. Total Feed Intake The expected feed consumption by mares in various stages of pregnancy and lactation is shown in Table 3. Total daily feed intake by mares (hay + concentrate) normally ranges from 1.5 percent to 3.0 percent of body weight, with 2 percent serving as an average. Daily feed intake depends on the type of hay or grazing available and varies according to the crude fiber level and energy density of the concentrate. Furthermore, mares are somewhat individualistic and daily feed intake often varies from horse to horse. Feed intake may have to be increased for hard keepers or heavy milkers. and decreased for other mares in the herd who are easier keepers. Table 1. Body condition score changes. pregnancy rate and loss in mares ofdifferent breeding status. 80er Condition Initial 5.1 4.6 4.3 " from Gibbs and Davison (1992) Pregnancy Pregnancy Rate 1%1 89 Loss {0/01 Table 2. Reproductive performance of mares in varying body condition.a Body Condition Adapted from Henneke et al. (1984) Table 3. Expected feed consumption by mares (percent body weight).‘ Mare Status Concentrate Forage 'l‘otal Early pregnancy Late pregnancy Early lactation Late lactation “ adapted from NRC (1989) Early and Mid—gestation A bred mare that is dry (not nursing a foal) and in the first 8 months of gestation has nutrient requirements very similar to those of any other mature. idle horse (Table 4). The unborn foal grows very slowly during this time (.2 pound/day) and it is usually considered sufficient simply to meet the mare's nutrient requirements for maintenance. Brood mare owners may want to take advantage of available grassland grazing to maintain mares during this early to mid-gestation Cycles per Conception 2.8 1.4 1.4 Conception Rate (5) 71 time. Horses allowed free choice grazing will consume as much as 3 percent of their body weight in long roughage daily. which normally meets their needs for protein, energy, calcium and phosphorus. Poor quality pasture will not be adequate. however. and will lower the body condition of mares. High quality hays, either grass or legume. are also excellent for maintaining dry. pregnant mares in the first stages of pregnancy. As an average. most mares will require from 1.5 to 1.75 percent oftheir body weight in high quality roughage daily to satisfy nutrient requirements. Whether on good pasture or hay or both, dry mares in early pregnancy need only to be provided good water and access to a balanced mineral supplement and salt. Grazing and/or hay will usually maintain a mare that is already in acceptable body condition. but often will not put sufficient weight on mares that are in marginal condition. Table 4. Daily nutrient requirements (1,100-pound mare)“ Nutrients required Crude protein (pounds) Digestible energy (megacalories) Calcium (grams) Phosphorus (grams) Copper (milligrams) Zinc (milligrams) Vitamin A (1.000 lU's) Vitamin [3 (1,000 IU's) “ Adapted from NRC (I989) Whether on good pasture or hay or both, dry mares in early pregnancy need only to be provided good water and access to a balanced mineral supplement and salt. Grazing and/or hay will usually maintain a mare that is already in acceptable body condition. but often will not put sufficient weight on mares that are in marginal condition. When high quality hay or grazing is not available in adequate amounts (as well as when weather is inclement), mares will need supplemental feed to maintain body weight and condition. Individual mares respond differently, but in most cases a concentrate with at least 10 percent crude protein fed at .5 to .75 percent of body weight daily will keep mares in good shape. Late Pregnancy As a mare enters the last few months of pregnancy. nutrient requirements increase because the unborn foal is growing more rapidly. averaging l pound/day (Figure 2). During this time. a mare in good condition will require only a little more total feed daily. but the concentration of protein. energy. calcium. phosphorus. trace minerals and Vitamin A in the feed must increase (Table 4). Nutrient balance is of major importance, since most fetal growth occurs during the last 4 months of gestation. It is during the tenth month that the largest amount of mineral retention occurs in the unborn foal. Therefore. adequate nutrition ofthe mare is Early to mid-gestation Late gestation Lactating mare critical for normal fetal development. In late gestation the mare should receive about 1.5 to 2.0 percent of her body weight in total feed daily. If top quality (minimum [8 percent crude protein) alfalfa hay or legume grazing is the source of roughage. the concentrate being fed should usually contain about 10 percent crude protein, as shown in Table 5. Mares receiving typical quality (7.5 percent crude protein) grass hay or grazing, or average quality alfalfa ( 15 percent crude protein), will usually require a higher protein concentrate such as the 14 percent mix shown in Table 6, Careful attention to the pretein balance ofthe diet at this stage can help prevent problems with foal growth. Brood mares that were previously maintained solely on hay or grazing should be introduced to grain feeds slowly. Likewise. mares being switched from grass to legumes should be changed over gradually so as to minimize digestive upset. Where concentrate intake is less than .5 percent of body weight (6 pounds of grain/l . l00-pound mare). this amount usually can be provided in one daily feeding. Larger amounts should be provided in two feedings at 12-hour intervals. 120 100' 80 60* 40 Conceptus weight (lbs.) 20* O 1 2 3 4 a Gestation (months) Parturition fl-> Last Trimester 6 7 8 9101112 Figure 2. Growth of equine conceptus in early/mid/late gestation. Some brood tnare operations may use small grain pastures for mares in late pregnancy. in which case mares will normally receive tnost ot'their requirements from oats. ryegrass or wheat pastures. However, some supplemental feeding (10 percent crude protein) usually is needed to maintain body condition. As mentioned previously. feed grade rendered fat can be incorporated into the concentrate to increase the energy content of the grain feed rather significantly. Table 7 shows an example ofa brood mare ration that contains 5 percent added fat. Compared to the grain mix shown in Table 6, this mixture provides almost 10 percent more energy per pound of feed. When such a ration is prepared with animal fat or vegetable oil. the owner should not mix large amounts of feed that will require lengthy storage. These fat-added rations can become rancid and cause mares to go "offfeed." Research has shown that fat supplemented diets can put weight on mares that are in unsatisfacrory body condition. The advantage of feeding fat in late pregnancy is that body condition can be improved without having to feed excessive amounts of concentrate on a daily basis. With a 5 percent added fat ration such as that shown in Table 7, a mare usually can be maintained in the same body condition with 7 to 15 percent less feed (by weight) titan would be needed with the ration shown in Table...
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