Horse-Breeding Tip: Pregnant Mare Care in Hot Weather

Courtesy of America’s Horse Daily

Guard your mare in late summer against heat, bugs and sparse pasture.

Being pregnantin the summer is no day at the beach for mares. Add a suckling foal at her side and you can understand why she pins her ears as sweat drips down her body and flies nip at her teats. For a mare whose body is already stressed by nurturing a foal – on the ground, in utero or both – coping with heat, bugs and slim pickings in the pasture can put all of them in danger.

Like the dead of winter, the dog days of summer also are a time when mare owners need to pay special attention to nutritional needs, deworming, vaccinations and comfort.


Marilyn Mowry Bowling, owner of Oasis Ranchin Purcell, Oklahoma, has cared for hundreds of broodmares over the years at her full-service breeding facility that has been in existence since the 1970s.

“The No. 1 thing is to make sure the mare is properly fed. If she is lactating, you need to make sure she is producing enough milk,” Marilyn says. “Here, our mares are out on pasture, and we don’t really need to supplement them with a lot. We just make sure they have a salt block and plenty of water. If we feed them inside, we mainly feed alfalfa.” Marilyn says each mare is on a highly individualized diet according to her age and condition. She typically feeds alfalfa because she says it is the best feed for the dollar in her area. “But sometimes the calcium content is so high that we have to supplement the mare’s diet with phosphorus to assure a 2:1 phosphorus-to-calcium ratio.”

Mares that cannot sustain foals because they have inadequatemilkor dried-up udders do not alarm Marilyn. She recently brought a mare home from colic surgery who was unable to nurse her foal.

“Actually, a mare that dries up has some sort of other problem, like this one, and you have to deal with that first,” she said. Although Marilyn is savvy about nutrition, she has no formal science background. However, she has read every notable book on nutritionthat is available. Her primary reference book is “Feeding and Care of the Horse” by nutritionist Lon Lewis.

“If there is a book about nutrition that is logical, I probably own it. The National Research Council’s Nutrient Requirements of Horses is being constantly revised, so you have to keep on top of things,” she says. “Any of the major name-brand feeds will supply plenty of nutrition for the mare. It is the last trimester of pregnancy in most horses when you have to worry about providing the developing foalwith adequate nutrition. Where some people get in trouble is when they have a mare on just grass hay during this time. She might drop 200 pounds in one month before they realize she needs more than that.”


“A good deworming program is right up there with good nutrition,” Marilyn says. She stresses that, even if you feed the best diet possible, your broodmare might still have a difficult time maintaining good body conditionif your deworming program fails. Horses can be affected by six major groups of parasites – large strongyles, small strongyles, ascarids, pinworms, bots and tapeworms.

Deworming schedulesusually rotate two classes of drugs. However, tapeworms are not eradicated by a typical deworming program and might be the problem if you are unable to keep your mare in good flesh. Tapeworms most commonly cause damage to the area where the small intestine joins the large intestine and can cause colic. If tapeworm damage causes the colon to prolapse, surgery is required. Tapeworm infestation in horses cannot be detected by a fecal test, but administering a double-dose of pyrantel will take care of the problem. Although a double-dose of pyrantel is safe for most pregnant mares, if your horse is within two weeks of foaling, it is best to delay double dosing until after she foals. Check with your veterinarian before deworming your pregnant mare.