Tuesdays with Tony

Can you believe it’s the time of year where we talk about breeding again? It’s like I woke up from my nap this weekend and it’s already mid-November and we’ve got to start preparing the mares.  Well, I don’t. But, if you intend to breed your mare in 2021, it’s time to start planning now. Believe it or not, there’s a significant amount of preparation, planning, and follow-up when it comes to breeding.  It’s not a one-and-done kind of thing. Sometimes I wish it were, and I know my docs do as well. Did you know that during breeding season, my docs disturb me multiple times a day, even on the weekends, just to check on mares. Rude!

 Preparing Your Mare

Yes, I realize it is not even Thanksgiving yet, and oh, how I long for leftover Turkey! My address for sending leftovers is 2283……. ugh, never mind. My minions have said I am not allowed leftovers, apparently diet is important when you have diabetes. Anyway, if you are breeding your mare next year, now is the time that she needs to be put under lights. 

 What exactly does that mean and why do we do it? It means exactly what it sounds like. In “winter” it gets dark early. We need to keep the mares exposed to light for more hours a day to encourage early ovulation.  When the days get shorter, most mares stop ovulating. They are what my docs refer to as “long day ovulaters”. Meaning, they do not cycle and ovulate year around.  If left to nature, most mares do not start to cycle until late April, early May.  By this time of year, it is already well into what most people consider the normal breeding season. In order to comply with what society has deemed the normal breeding season, we have to alter our horse’s normal cycle. We do this by exposing them to light for longer periods of time.

 Broodmares who will be bred early in 2021 should be brought into their stalls early evening where they can be exposed to additional hours of light. The goal for these mares is to have them under light for a total of 16 hours and allow them around 8 hours of darkness.  The type of light doesn’t matter and it’s not necessary to make a gradual increases in duration of light exposure. You know I love topics that have been researched. Well, it has been studied and shown that if a mare is housed under 10 or more foot-candles of light, follicular growth will be stimulated. A 200-watt incandescent light bulb is enough to provide 10-12 foot-candles of light in a typical 12ft x 12ft stall. 

 If your mare’s stall is attached to a run, you will need to lock her into her stall so she can’t go out into the darkness unless the run-out area is lit as well.  If you choose to encourage follicular growth by using artificial light, it is highly recommended that you keep your mare housed this way until she has been confirmed in foal.  Research has shown that if a mare is allowed to resume her normal daily activities and light exposure is reduced, she may regress and return to an anestrus state where she will not have any follicular growth and will not ovulate.  Bad news if you are trying to make a baby!

Springhill Equine Veterinary Clinic


You have your mare set up under lights so that hopefully she will start to cycle early next year, great job! You might think that you are all done for a while now, but you would be wrong. The next step is to bring your mare into my docs for a checkup.  A full health check should be performed on your mare by the first part of January. This is the time to talk to my docs about your mare’s over all wellbeing. They will perform a full physical examination on your mare. They will listen to her heart and lungs, they will evaluate her for any lameness, and any other abnormalities that could prevent your mare from conceiving or carrying a foal to term.

 Your mare’s body condition and conformation will also be evaluated. A mare that is too fat or too skinny will undoubtedly have trouble conceiving and most certainly will have trouble foaling out. Some mare’s conformation sets them up to be passing manure right over their vulva. If your mare has this kind of conformation, she may be more prone to uterine infections and may require a procedure where part of the vulva is sewn shut (called a caslicks). Don’t fret, your mare will still be able to urinate normally, this procedure just prevents fecal material and bacteria from entering your mare’s vagina, and subsequently, her uterus. 

 During this examination they will also perform a full evaluation of your mare’s reproductive system.  A rectal ultrasound of your mare’s uterus and ovaries will be evaluated for any abnormalities. It will also give my docs an idea of where your mare may be in her cycle. Any abnormalities will be noted and explained. A speculum examination will be performed to assess your mare’s cervix for any scarring, discharge, or other abnormalities. A uterine culture may be recommended, and many stallion owners require a negative culture prior to shipping semen for the mare.  More reasons to get this examination performed earlier rather than later!

 If a culture comes back positive, this leaves my docs time to treat it before breeding season is in full swing. For completeness, it is also a good plan to have my docs obtain a uterine biopsy.  Your mare’s uterus is given a score, which tells my docs how easy it will be to get your mare pregnant, how easy it will be to keep her pregnant and if she will be able to carry a foal to term.  The full physical examination and reproductive system evaluation are crucial to a successful breeding season. 


Let’s say you’ve done all the right things. You put your mare under lights, you brought her in for a pre-breeding evaluation, and my docs were able to get her in foal quickly.  Awesome for you! Breeding is rarely that easy in real life.  It can often take up to 3 or 4 cycles to get a mare confirmed in foal, which is why you want to start breeding early in the year.  But let’s pretend it was quick and easy for you. 

 You bring your mare back for her 14-day pregnancy check and everyone gets to see that little black dot in the middle of the ultrasound screen, yay, right? One little black dot is great, but what if my docs see 2 little black dots? Twins are bad news. We never, ever want to see twins. If my docs see twins at your 14-day check, they are going to insist your mare stay with them for several days. They have to perform a procedure where they reduce one of the twins. Mares should never be allowed to carry 2 foals to term.

 Hopefully you only saw one dot. You might be thinking, surely Tony, I’m done now, right? Nope, you get to bring her back in another 14 days.  The 28-day check is when my docs will confirm that your mare’s fetus has a heartbeat.  Once a heartbeat is confirmed, the next check is the 60-day pregnancy check, followed by the 90-day pregnancy check.  During these exams, my docs are ensuring that the fetus is developing properly and checking for potential early embryonic loss.

 Next you get to bring your horse in at 5, 7, and 9 months.  These visits are usually fairly quick, particularly the 5- and 9-month checks.  During these visits, your horse will get her pneumavbort vaccines. At her 7-month visit an ultrasound will be performed to assess for the development of placentitis. Then, finally, your mare is due. Whew, that was a lot to get to this point! But wait, there’s more.

 Now you get to determine where your mare will foal out. Will you have her in her pasture, will she be in her stall, or will you bring her to the Clinic?  No matter where she foals out, she needs to be monitored very closely and my docs highly recommend that someone who has foaled out mares before be present during the birth.  Within 24 hours after the foal is born, my docs need to see it. They will assess the mare and foal for any post-foaling complications and will check that the foal has nursed well to ensure that he received adequate colostrum from the mare. Colostrum provides the foal with antibodies to fight off any illness/infection in his early months.

 As you can tell, breeding is not for the faint of heart. It requires impeccable timing, planning, and follow-up on your part. Many vet visits are required and it’s not all sunshine and rainbows all the time.  It can be heartbreaking, but it is also beautiful.  If you think you might want to breed your mare, give my docs a call and get your mare on their schedule soon.

 Until next week,


 P.S. My docs have done several podcasts on the topic of breeding and foaling. You can listen to them free on my website, or you can subscribe to Straight from the Horse Doctor’s Mouth wherever you get your podcasts. If you’re breeding, you’ll need all the information you can get, trust me!

Tuesdays with Tony is the official blog of Tony the Clinic Cat at Springhill Equine Veterinary Clinic in Newberry, Florida. If you liked this blog, please subscribe below, and share it with your friends on social media! For more information, please call us at (352) 472-1620, visit our website at SpringhillEquine.com, or follow us on Facebook!

[jetpack_subscription_form title="Subscribe to Whinny's Wisdoms"]

More Adventures of the Horse Doctor's Husband