The nutritional needs of broodmares change dramatically as they progress through their pregnancyAn average of 340 days elapses between conception and foaling. The way the genetic dice fall is a major determinant of the foal's future during those 11-plus months. The mare's health and nutritional status are other factors.

The typical mare gains between 150-to-200 pounds over the course of her pregnancy. Fluids, placental tissue, and the fetus itself account for most of that weight. The mare also needs reasonable fat reserves to draw upon when she begins producing milk. A mare's dietary needs change throughout her pregnancy and while nursing a foal. Giving that foal the best start in life sometimes means putting aside some misconceptions rooted in tradition.



The first four months

A mare without a foal at side only needs to be fed to maintain her weight during the first trimester of pregnancy. At this stage, the fetus weighs less than five pounds and makes few demands on her body. In fact, overfeeding the mare with a fortified grain mix, the best alfalfa, and three or four vitamin-mineral supplements at this point may actually harm the foal's development. Instead, give the mare a total ration (grain plus hay) approximately 1 1/2%-to-2% of her body weight. That is about 18-to-24 pounds for a 1,200-pound mare, and most of that should consist of good quality hay. Two to three pounds of a 10% crude protein grain with minerals balanced to complement the hay will suffice with no additional supplements necessary.

If overweight is a concern, wait until at least two months into the pregnancy before putting the mare on a diet, or she may react to the energy reduction by reabsorbing the fetus. Cut calories up to 20%, but do not cut protein, vitamin, or mineral levels along with calories. (While fat reduction might be healthier for the mare, fetal cells are differentiating at a rapid rate and this is no time to malnourish her.) This can be accomplished by removing the grain totally, by reducing the grain and hay by 20%, or by lowering grazing time allotment.



The second trimester

Recent research indicates that there is more maternal weight gain in the second trimester than previously thought. This seems to vary from breed to breed and from one line to another within a breed, but many Thoroughbred mares appear to follow this pattern.

This means that the 100- to 150-pound weight surge that many farm managers expect and feed for during the third trimester may actually occur sooner or over a longer period of time. The mare's crude protein, vitamin, and mineral intake needs to increase about midway through the second trimester in order to sustain fetal tissue growth and help the mare deposit the fat reserves she will need to draw upon when she begins nursing.

At this stage, feed the mare approximately 2.00%-to-2.25% of her own body weight daily. That translates into 24-to-27 pounds of feed daily for a 1,200-pound mare. Give her 22-to-25 pounds of good grass hay supplemented with 2-to-5 pounds of a grain mix fortified with vitamins and minerals. If she gets alfalfa hay, she can get by with less grain, but her diet must be balanced for calcium and phosphorous. Her total ration should include about 10% crude protein and at least 0.4% calcium and 0.3% phosphorous. This is the time to evaluate trace mineral levels in the diet. Pay close attention to copper, zinc, manganese, and selenium.



Late pregnancy

The mare in late pregnancy should be fed at about the same rate as a working horse or a stallion during the breeding season. She needs more protein now and a grain mix fortified with ample calcium, phosphorous, and trace minerals. Give the late pregnancy mare a total ration equal to 2.25%-to-2.5% of her body weight with 5-to-7 pounds of that supplied by a grain mix formulated to meet the calcium, phosphorous, and trace mineral needs of pregnant mares.

There is less concern now among scientists than in the past regarding excessive weight gain in mares during this period. Recent research indicates that putting on excess weight is unnecessary but not necessarily harmful to the mare or her foal. Excess fat does not appear to affect rebreeding or fetal weight, but common sense dictates that this is not the time to stress the mare's cardiovascular system, ligaments, and joints with too much surplus fat.

Bringing a mare into late pregnancy in thin condition is more serious. This mare has no energy reserves for herself or the process of birth. Her milk production will be scanty. She may have lower resistance to infection and fewer antibodies to pass on to her foal. Not only are conception rates lower for thin mares at rebreeding, but they also have a higher incidence of embryonic death and lower foal birth rates.



Lactation

If many mares are overfed in their last trimester, far more are underfed while nursing their foals. This is the point of highest nutritional demand on the mare throughout the reproductive cycle.

A lactating mare burns more energy daily than a hard-working performance horse. Compared to a performance horse whose energy needs gradually increase through a cycle of training and conditioning, the lactating mare's energy needs change rapidly in the space of just 24 hours. That nutritional stress can translate into rapid weight loss. Hip bones and ribs sometimes seem to appear overnight. When a lactating mare's ribs begin to show, she is starting to break down her own body reserves to produce milk. This not only hurts the mare, but can also jeopardize any new fetus she may be carrying.

The lactating mare needs a total ration equal to about 3% of her body weight daily. Since she can only consume so much hay daily, the way to increase her energy level is to double her grain intake. Again, use a grain mix fortified especially for broodmares to supply her protein, vitamin, and mineral needs. This is also the time to splurge on the best quality grass hay or alfalfa you can find so that the mare gets maximum nutrition from her forage. To avoid colic, begin switching to post-foaling grain levels about 7-to-10 days before the mare's expected foaling date, adding from one-half pound to one pound of grain daily until reaching her new feeding level.

While it is very difficult to influence the composition of a mare's milk through her diet, the quantity of milk a mare produces can be influenced by her feeding level. More grain (increased calories) produces more milk. Mares are not selected for milk production and horses have smaller udders than many other species. The size of a mare's bag is a poor indicator of her overall milk production, but if the mare has a very small udder and the foal is nursing constantly, it is probably hungry. For the first four months, foals gain an average of 3-to-5 pounds daily, so they need a great deal of nourishment from their dam.

A 1,200-pound lactating mare on a grass hay diet would need about 24-to-30 pounds of hay, plus 5-to-10 pounds of grain mix with at least 0.6% of calcium and 0.5% of phosphorous, plus trace minerals lacking in grass hay. Fed high quality alfalfa hay, the mare will need about 35 pounds of forage daily, plus about 2-to-3 pounds of a grain mix with at least 0.5% phosphorous to balance the calcium in the alfalfa, plus added trace minerals such as copper, zinc, and magnesium.

The lactating mare on grass pasture needs to harvest about 100 pounds of grass daily to meet her nutritional needs, since pasture grass is 80%-to-90% water. She will need minimal grain, but it should be well fortified with calcium (at least 0.6%), phosphorous (a minimum of 0.5%), and trace minerals.

Because of grass's high water content, the pastured lactating mare can supply much of her increased water needs through grazing. Milk is 98% water and, at peak lactation, a mare produces about four gallons of milk daily. So a lactating mare needs about three times the water a non-lactating mare requires. A five-gallon bucket filled twice a day will not serve her needs. This reduced water may lead to impaction or lowered milk production and a slow-growing foal. A small oversight can have catastrophic consequences.



Weaning

Start the weaning process by cutting back the mare's rations to reduce her milk production. About a week prior to weaning, cut the mare's total ration 20% by halving her grain. Three days before weaning, cut the total ration 20% again, usually by removing all grain. Lowering calories will cut the mare's milk production with two benefits. First, this gradually begins the drying-up process for the mare, which translates into fewer problems with swollen udders or mastitis at actual weaning time. Secondly, less milk means a hungrier foal who will more readily investigate outside sources of food and water.

Keep the mare off grain for about three more days after weaning to help her continue the drying-up process. Keep her off grain no more than a week, however, or there is a risk of compromising her nutrition or that of any fetus she is carrying. Add grain back into her diet one-half pound daily until she reaches her maintenance level again and the cycle of feeding during gestation and nursing begins again.



Feeding guidelines

(Approximations, based on a 1,200-pound mare in good health and of average weight for her size.)



First trimester

• Total daily ration: 1 1/2-to-2% of body weight (18-to-24 pounds of feed)
  
  
• Ration should consist primarily of good quality hay, and
  
  
• 2-to-3 pounds of 10% crude protein grain
  
  
• No additional supplements necessary
  
  

• Total daily ration: 2.00-to-2.25% of body weight (24-to-27 pounds of feed)
  
  
• From 22-to-25 pounds of good quality hay, supplemented with
  
  
• 2-to-5 pounds of grain mix fortified with vitamins and minerals
  
  
• Daily ration should be comprised of 10% crude protein, 0.4% calcium, and 0.3% phosphorous.
  
  
• Also needed: copper, zinc, manganese, and selenium

• Total daily ration: 2.25-to-2.5% of body weight (27-to-30 pounds of feed)
  
  
• Good quality hay, supplemented with
  
  
• 5-to-7 pounds of fortified grain mix, with calcium, phosphorous, and trace minerals to meet the needs of pregnancy
  
  

• Total daily ration: 3% of body weight (36 pounds of feed)
  
  
• From 24-to-30 pounds of the best quality grass hay, plus
  
  
• 5-to-10 pounds of grain mix with at least 0.6% calcium and 0.5% phosphorous, plus trace minerals. Or,
  
  
• Mares fed quality alfalfa hay will require 35 pounds daily, plus
  
  
• 2-to-3 pounds of grain mix with at least 0.5% phosphorous to balance calcium in alfalfa, plus trace minerals
  
  

• A week prior, cut total ration 20% by reducing mare's grain by half
  
  
• Three days prior, remove all grain
  
  
• Reintroduce grain within a week, so as not to compromise the nutrition of mare or fetus she is carrying