Foal Heat & Re-breeding

Foal Heat and Re-breeding
By Tina Lewis, MyEquineNetwork.com Contributing Writer

Most breeders today breed their mares every year so they can get a bigger return on their investment and so the mares can effectively "earn their keep". In the show world, having foals born early in the year means bigger weanlings and yearlings for showing and winning. Most horses are “officially” a year old on January 1 after their birth date and must continue to use that date as their official birth date. As a result, it is optimal to have a foal born on January 1st, making it a bigger yearling. But, by the same token, it would be highly detrimental if it happens to be born on December 31st, as it is considered a yearling the very next day and would be very small in the show ring. 

If a mare, for one reason or another, is due to foal late in the Spring or early Summer, some breeders will elect to skip breeding her when she foals and put her under lights to induce estrus early in the Spring so she can be bred for a January baby the next year. This, in reality, only loses a few months but gains the advantage in the show ring. Some breeders elect to skip a year and give the mare a break or to keep down the herd, as it is sometimes not cost effective to have too many mouths to feed. It also gives them time to break and sell the ones already on the ground, especially in a slow market.

Most good broodmares will breed, take, and carry foals until they die. Choosing the time of year you want to have a foal hit the ground for your area is important when deciding when to breed your mare. If you have severe weather you will not want a January baby unless you have an enclosed barn to keep it warm until the weather is better. If you are trying to gain a few days or weeks each year and get your mare foaling earlier in the season you will need to either skip a year, put her under lights and start early. Another option is to simply be diligent in breeding on the foal heat each year to gain anywhere from 10 days to 2 weeks per year (easier said than done).

It is common practice to breed a mare on her foal heat as long as there had been no foaling problems or injuries during the previous birth, she kept her weight well, and she is healthy. Some breeders believe that keeping that reproductive tract active helps to keep it in good working order. The foal heat is a bit tricky though. Unlike the regular heat of 5-7 days, the foal heat generally lasts about 3 days, beginning approximately 9-12 days after she foals. Effectively getting a mare in foal on her foal heat drops to about a 50% success rate for several reasons. 

Once the mare foals, the ovaries begin to start cycling. They start from a stage that is similar to being about half way through a normal heat cycle so it is only about 10 days until ovulation, and this can vary from 5-16 days. Getting a mare to even tease to a stallion, much less breed on her foal heat is quite a task, and understandably. It has only been 10 days since she delivered a 150 pound foal, placental tissue, and the fluids that surrounded the foal. The uterus is contracting the muscle in the walls, and is frantically trying to evacuate itself so it can clean up any residual left behind from the birth. These contractions are strong and cause considerable discomfort. Often times a mare will pass the tenth day and not have shown any signs of heat at all by normal teasing but have a normal follicle after an ultrasonography exam. She will be physiologically in heat, but not psychologically receptive to the stallion due to the new foal and a mother's concern for its safety – especially in the presence of a vocal and excited stallion.

If the mare does not show any signs of heat but you can determine she is in standing heat via ultrasonography exam and has a healthy follicle, artificial insemination would best be used in this case. If the mare is receptive to the stallion, the foal can be put into a safe foal pen near the mare while she is being bred via live cover. For shipped semen, it would be best to have a culture done, skip the foal heat and short cycle her with Prostaglandin and catch her when she comes into heat a few days later. You will still gain a few days but lessen the chances of having to ship again and lose more valuable time and money.

Most breeders start teasing or checking their mares about day 6 after the foal is born so as not to miss that short, 3 day heat. Once it's gone the only recourse is to short cycle her and bring her back into heat. This heat should be a normal 5-7 day heat but she still may not show any signs with regular teasing methods due to her motherly instincts and the foal at her side. This is another reason some breeders breed their mares every other year.

Until ultrasonography there was no way to tell when these mares were in heat, as they wouldn't allow the stallion to breed. Some breeders actually guessed and inseminated or restrained a mare for live cover breeding at days 9 and 11 and called it good, crossing their fingers. Today we have ultrasound, phantoms/dummy mares, Artificial Vaginas and Artificial Insemination to help us overcome some of the obstacles that caused much stress over the years. We can now deal with the fears of a new mother with her young foal, never having to have her and her foal in the company of the stallion. I believe this makes for a happier, less stressed mare as well - possibly improving her conception during the foal heat.