No one ever said mothering was easy. As your broodmare gets closer and closer to her due date, you've been noting, with some satisfaction, her bulging belly, her increasingly matronly attitude, and the look of lazy contentment in her eyes. But while she might look relaxed on the outside, inside, her growing foal is making ever-increasing demands on her body. Those demands won't stop when she gives birth, either. As any mother will tell you, that's when the real work begins!
The early stages of pregnancy, when the fetus is the size of a walnut, aren't particularly strenuous for the average equine, but that situation begins to change radically as the mare enters her final 110 days of gestation. It's in the last trimester that the unborn foal's growth accelerates at a surprising rate--and with it, the mare's nutritional requirements. Over the course of a healthy pregnancy, a mare's weight should increase by an amount equal to the weight of the foal at birth plus the weight of the placenta and the uterine fluids--generally 9-12% of the mare's original weight. An 1,100 pound mare, for example, should gain between 100 and 130 pounds (or 45-60 kg) during the course of her gestation, with some two-thirds of that total weight gain coming in the final three months (averaging about three-fourths of a pound to one pound of weight gain per day in that time period).
In the last 110 days of her pregnancy, your broodmare's energy needs progressively will increase by 10-20%. She'll need almost twice the amount of calcium and phosphorus in her diet that she normally would require. Her need for protein also will inch up to about 1.3 times its usual level. All of these nutrients are important for the construction of a strong, healthy foal. In order to satisfy those needs, her appetite will increase.
Once she has given birth, the nutritional demands don't decrease. In fact, lactation (the process of producing milk for her offspring) will accelerate the challenges to your mare's system. Her energy needs will shoot up by a full 80%, her protein needs will more than double, and her requirement for calcium and phosphorus (both important minerals essential for the foal's correct growth) will almost triple. Nursing her foal for the first eight weeks is as strenuous an activity as your mare ever will undertake, and that time will have a lasting impact on how well her foal develops and matures. Knowing this, it's a sure bet you'll want to provide your mare with an optimum diet and all the nutritional support she needs, throughout her pregnancy and during the time she is nursing her baby, right up until weaning.
Nutrition For Moms-To-Be
Although in the early stages of pregnancy a mare should be fed like any other mature horse, according to her workload, it's important to keep her supplied with enough good-quality feed to enable her to store a little extra body fat. As long as enough food is available, mares will store these fat reserves early on, so they'll be available later for the strenuous demands of lactation. It's important, however, not to let her get obese; contrary to assumptions made based on other species, obesity doesn't seem to affect a mare's ease of foaling or the duration of her pregnancy, but it can decrease her milk production, resulting in a slower growth rate for her foal.
If your mare lives outside and has access to lots of good-quality grazing, that might satisfy all of her nutritional requirements for the first eight months of her pregnancy. Indeed, a great many broodmares receive no grain, protein, or mineral supplements through most of their "in foal" time and do very well. If, however, your pasture is of less-than-wonderful quality, if her turnout is limited, or if she's carrying one foal while nursing another, you will have to supplement her diet. She first needs lots of high-quality legume or early-cut grass hay, and second needs the possible addition of a concentrate (grains). Don't forget her salt/calcium/phosphorus mineral lick.
In the Northern Hemisphere, the last three months of a mare's pregnancy generally coincide with winter, and the worst availability of fresh pasture. Even if pasture is available, it usually is too low in phosphorus at that time of year. If it's a grass, rather than a legume, it probably won't supply enough calcium, either. That means for the foal's optimum growth, you'll have to begin supplementing your broodmare's diet.
As always, good-quality hay, fed free-choice (in other words, as much as she can eat) is your starting point. This is one situation, however, where an alfalfa or clover hay might be a better choice than a grass hay. Mature grass hays generally are lower in protein, calcium, phosphorus, and dietary energy than legume hays, and while that's a good thing for most mature horses, in the case of the broodmare, it means she'll suffer dietary deficits as her pregnancy progresses. Have your hay analyzed to find out its crude protein, calcium, phosphorus, and dietary energy values, and consider supplementing her diet with these nutrients if the hay comes up short.
Extra energy is best supplied by carbohydrates (grains) and/or fats (vegetable oils). There are many good commercial grain mixes available that are formulated specifically for pregnant and lactating mares. A high-fat diet (containing 5-10% overall crude fat) is a particularly good choice, as it supplies concentrated energy without much bulk. It also is easily stored by the body to support lactation while maintaining the mare's good condition.
Your mare's crude protein requirements will increase in the last 110 days of gestation from about 8% to 11%, at the rate of about 1% a month. If your hay has a crude protein level less than 11%, you might begin adding a commercial broodmare grain mix to her diet, or feed a good-quality 25-30% protein supplement such as soybean cake or meal to the tune of about two pounds (one kilogram) a day for an average 1,000-pound mare. (Soybean has one of the best amino acid profiles of any plant-source protein supplement, and it is a better choice for the broodmare than a poorer-quality protein supplement such as linseed or cottonseed meal.) There also are a number of very palatable commercial protein supplements, such as Calf Manna, available. Ask at your feed store for recommendations.
If you're feeding straight grains rather than a commercial mix for broodmares, or if your hay is less-than-terrific or is more than a few months old, it also would be a good idea to add a general vitamin/mineral supplement to your broodmare's diet in the final three months of her pregnancy. Mares grazing on green grass receive plenty of vitamins A and D in their diet, but come winter, they receive far less of these two essential nutrients. A vitamin A deficiency, in particular, can result in a deficiency in the foal since it is not passed along to him in the colostrum. Vitamin A deficiency in foals has been implicated in compromised immune function and a greater likelihood of contracting infectious diseases, especially respiratory or diarrheal conditions. Some veterinarians recommend that broodmares receive beta-carotene (the precursor to vitamin A) injections on a regular basis when they are pregnant and not grazing on fresh pasture. Consult your veterinarian for specific recommendations.
Vitamin E, which is closely tied to reproductive function in mares, is another nutrient which could benefit your broodmare during her pregnancy. Ordinarily, she would glean plenty of vitamin E from grazing on fresh grass, but in winter, her intake will be substantially less. If your mare has a vitamin E or selenium deficiency while she's nursing, chances are her foal also will have a deficiency, usually before one month of age. However, it's important to point out that vitamin E deficiencies have not been shown to have any impact on a mare's reproductive ability (i.e., her ability to "catch" when bred) as they have in other species. Thus far, there is no evidence that giving large doses of vitamin E will help a mare become pregnant or carry a foal. So there's no need for heroic measures. Any general vitamin/mineral supplement that contains vitamin E will be perfectly appropriate for your mare. (Unless your location is selenium deficient and you know your feed contains no added selenium. It's best not to supplement this mineral along with the vitamin E; as pointed out in previous columns, selenium has an extremely low toxicity level and too much could be more damaging than too little.)
In the last four months of your mare's pregnancy, you should expect to increase the amount of total feed she receives daily by about 5% a month. Of course, it goes without saying that you should choose the highest-quality feeds you can get. Feeds contaminated with molds or fungus might be enough to stimulate an abortion. (See the sidebar on fescue toxicosis on page 100.) Be careful not to let her get too thin; underweight mares generally have smaller foals, produce less milk, and are less likely to cycle normally after delivery.
Once your fuzzy foal is born, he'll almost immediately begin to make nutritional demands on his mother. For the first few weeks of his life, she'll be his only source of food--and perhaps because we don't really selectively breed horses for superior milk production (as we do for cattle and goats), the amount, and quality, of milk that a mare produces can vary widely. So, too, does the impact nursing will have on her. Some mares are copious milkers and seem to have no trouble maintaining their own butterball condition while nursing Junior, but we've all seen mares which become virtual bone-racks.
The likelihood of that is increased if the mare is stressed during lactation, as she might be if she is shipped for rebreeding, for example, or moved to new or strange surroundings. While a thin mare initially will draw on her body's fat and nutrient reserves and sacrifice her own condition to make sure the quality of her milk stays high, she cannot sustain that trend forever. Eventually, the milk production of an underweight mare will decrease (and if she is thin at foaling time, she also might produce less colostrum, thus compromising the foal's early immunity). There's a direct correlation between decreased milk production and decreased growth of the foal. Therefore, for the sake of both mother and baby, it's important to ensure that the mare maintains a moderately fleshy condition throughout lactation. This is particularly true in the first eight weeks, when the foal nurses the most and when milk production is at its peak.
Just to give you some perspective on how draining lactation can be is the following example: If provided with an adequate diet, the average mare will produce 3-4% of her body weight in milk every day for the first eight weeks of the foal's life. After that initial two months, her baby will start to show more and more interest in solid food, and her milk production gradually will decrease. At five months after birth, she'll be milking at the rate of about 2% of her body weight per day. The nutrient content of her milk will decrease steadily throughout lactation, too.
Expect your mare to need lots of nutritional support right up until weaning time, but especially in the first eight to 12 weeks after foaling. This is the time when it's most valuable to provide her with free-choice amounts of straight legume hay (or a mixed hay that's heavy on the alfalfa) plus a commercial broodmare feed designed to meet the needs of lactation. Most researchers agree a lactating mare should receive about 13% crude protein in her daily diet, along with at least 0.5% calcium and 0.35% phosphorus, and almost twice as much dietary energy as she would otherwise need. It's particularly important to maintain her body condition if you plan to breed her again while she is nursing a foal.
All in all, you should expect your mare to go through an astonishing amount of feed during the time she's nursing, but don't begrudge her the nutrient support she needs for lactation. It's a good idea to keep her on a general vitamin/mineral supplement, too, at least for the first eight weeks. Remember that the quality of her milk will have a direct impact on the growth of her foal.
Not all nutrients are passed along in mare's milk. Interestingly, many of the trace minerals your mare needs don't show up in any significant concentration in her milk. A mare's intake of iodine and selenium directly will correlate to the concentration of these minerals in her milk, but there seems to be no such relationship for potassium, copper, zinc, magnesium, or iron. These minerals, all of which are required in only minute amounts, are best supplied to the foal in the form of a creep feed as he begins to mature and eat solid food.
As your foal approaches the three-month mark, you can help him make the transition to solids by gradually decreasing your mare's daily grain ration by about half (thus helping decrease her milk production). Some breeders also feel it's helpful to eliminate all grain from your mare's diet one to two weeks before you plan to wean her foal, and keep her off concentrates for at least two weeks afterward. The resulting decrease in dietary energy should assist her in drying up.
Your mare's nutritional condition will have a significant impact on her fertility, something to keep in mind if you expect to send her back to a stallion while she has a foal at foot. Studies have demonstrated, for example, that a mare has the best chance of conception if she is in "moderate" body condition (neither too fat nor too thin) and is gaining weight in the final few weeks before she is bred. This sometimes can be a challenge if your mare is not a particularly good milker and is being nursed into ribbiness by a ravenous foal! Many veterinarians recommend that you consider beta-carotene injections in the six weeks prior to breeding, as well as feeding at least 50 IU (international units) of supplemental vitamin E.
On the other hand, an obese mare doesn't seem to have any particular problem conceiving, but obviously is in less-than-the-healthiest shape for other reasons. If you put her on a weight-loss program, however, avoid doing anything drastic immediately before you send her for breeding, or in the first 90 days of her pregnancy. A "cold turkey" diet might decrease her reproductive efficiency, making it more difficult for her to conceive, or putting her at risk for "slipping" the foal (early abortion).
Inadequate levels of protein or dietary energy in your broodmare's diet can be one cause of delayed or failed ovulation, and also can contribute to early embryonic death if the mare does manage to conceive. Energy and/or protein deficiencies usually are associated with thin mares, which might have trouble maintaining their pregnancies and could have delayed foal heats afterward.
Hyperlipemia, a condition in which large amounts of fats are dumped into the bloodstream to help meet energy needs, can occur when mares are in late pregnancy or nursing and have high energy needs that for some reason aren't being met. The classic scenario is the fat pony mare which is put on a crash diet or is unusually stressed by shipping or other situations while she is pregnant or has a young foal at foot.
Hyperlipemia can occur in any mare, and it can be quite dangerous. A hyperlipemic mare will be feverish, depressed or drowsy, reluctant to eat or drink, and might suffer muscle twitching, colic, incoordination, diarrhea, edema along her belly-line, and sometimes even a rapid loss of condition, coma, and death. If blood is drawn, her plasma will be characteristically milky looking, due to the large amounts of body fat that are being mobilized faster than she can use it. It's also common for a mare with hyperlipemia to suffer impaired liver and kidney function; sometimes these or-gans fail altogether.
Hyperlipemia is difficult to treat and has a high fatality rate. The best approach is to feed a high-energy, low-fat diet for a period of one to three weeks. Because these mares often have little appetite, you might have to get your veterinarian to tube-feed them.
Prevention of the syndrome is far better than attempting a cure. Simply provide adequate intake of good-quality feed, especially in the last 110 days of gestation and throughout the time the mare is nursing. This goes double for fat ponies, even if your instincts say "put her on a diet." Preventing mares from becoming obese in the first place is a much better approach.
BEWARE OF FESCUE
Most broodmare owners have heard of the dangers of tall fescue (Festuca arundinacea), a hardy pasture grass that grows in many parts of the United States. Although fescue has many admirable qualities (it's easily established, tolerates close grazing well, stands up to heavy traffic, is resistant to insect damage, and survives drought conditions that would wither most other grasses), it has one significant problem--it's prone to infection by an endophyte fungus, which lives among the plant cells (making it practically invisible) and produces, or causes the grass to produce, an alkaloid toxin. The endophyte is seed-borne and cannot be spread any other way, and most tall fescue pastures can be assumed to be infested with it. Cutting the grass for hay doesn't destroy the endophyte, or reduce the effect of the toxin. (See article on Pastures on page 80.)
Although relatively harmless to most adult horses (with some reports of slow hoof growth and rough hair coats), the fescue fungus, when ingested by a mare in the last trimester of her pregnancy, can cause an abnormally thickened placenta, decreased or failed milk production (agalactia), prolonged gestation (often 30 to 40 days longer than normal) resulting in a difficult birth, retained placenta after birth (resulting in uterine infections, founder, and difficulty conceiving again), and sometimes late abortion or stillbirth due to premature separation of the placenta. Endophyte-infested fescue also has been implicated in some cases of reduced growth in weanlings and yearlings, so some researchers recommend keeping young growing stock off fescue pasture.
The good news is that there is a reliable method of testing your fescue pasture for presence of the endophyte, and there also is "certified endophyte-free" fescue seed that can be planted in any pasture in which you expect to keep broodmares. Consult your local agriculture agent or feed store for recommendations on how best to get rid of infected fescue pasture on your property, and how to replace it (generally with endophyte-free fescue, orchard grass, or Kentucky bluegrass).
If you have any fescue on your property, the best approach is to remove your broodmares from the pasture (and any fescue hay) 90 days before foaling. Keeping detailed records of your mare's foaling patterns can help you determine whether she is exhibiting any signs of toxicosis (keep in mind that maiden mares tend to gestate longer, produce less milk, and have more difficult births than experienced mares, and that mares carrying colts tend to have longer gestations than those carrying fillies). If you think there is any chance your mare has ingested endophyte-infected fescue during the final trimester of her pregnancy, consult your veterinarian about administering domperidone, a dopamine agonist drug that can be given in a paste form before labor begins to help guard against toxicosis. (A recent study suggests that this paste, given daily in the 25 to 30 days before foaling, could safeguard mares without having to remove them from fescue pasture.)
Because an affected mare might not produce any colostrum, it's also a good idea to have some frozen colostrum on hand for the newborn foal, and to have your veterinarian test the foal for failure of passive transfer (see article on Colostrum on page 91).
There are a few other types of grass to watch out for if you have a broodmare. Sorghum, Sudan grass, Johnson grass, and hybrids of these all contain a chemical that can be converted, in the horse's system, to cyanide. If this chemical builds up in sufficient quantity, it can cause incoordination and bladder problems in horses, and it has been implicated in abortion in mares and in the birth of foals with fused joints.
About the Author
Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.
POLL: University Equine Hospitals