Foaling and Due Dates

We had a foal on Monday. The humans went all gaga over it. I was more like, “Hey, can a cat get some attention over here?” I guess she’s cute. There is some debate over what color she is. Even odds right now on buckskin vs. bay. What’s really exciting about this foal is that she’s finally here. May, the mom,  went 378 days from ovulation to foaling. That’s way over the normal gestation of 340 days, but mares are mares and will do what they please, including ignoring due dates. And on that note, let’s talk about why it was okay that May went 378 days, and why that’s often better than foaling too soon.

Let’s talk placentas

Horses have what’s known as diffuse placentation. When you look at a horse placenta, it looks almost like velvet (red, gooey velvet, but velvety nonetheless). That velvet forms a connection at a microscopic level with mom’s blood vessels. Humans do sort of the same thing, but only in one spot on the placenta. Cows make these connections in a bunch of big knots called cotyledons. This matters because horses need every bit of the placental connection they’ve got to grow that big ol’ foal in there. It’s why twins in horses are usually a bad idea. Where the twins touch, there’s no connection to mom, which means not enough nutrition to grow into a healthy, happy foal.

When placentas go bad

It goes without saying (but I’m going to say it anyway) that bacteria in the uterus with a baby is bad. The cervix does its part to keep the outside out, and the immune system works hard to keep things from the blood stream out of the placenta. However, life being what it is, sometimes stuff happens. In this case that thing is called placentitis. Placentitis occurs when bacteria get into a pregnant uterus and start attacking the placenta. The most common place for this to happen is at the cervix. In some ways, that’s a good thing.

My Docs recommend ultrasound exams throughout those long 11 months (or sometimes 12 months +) of pregnancy. One of the things they are evaluating is the placenta at the cervix. They know it should normally measure less than 1cm and should be tight against the cervix. If they see anything even a little bit off they can start treatment right away. My Docs ultrasounded May at 5, 7, and 9 months gestation and everything was good, so placentitis was unlikely. To be fair, May got ultrasounded a few more times when she started going past her due date, but that’s because the Docs wanted to be doubly and triply sure. And who doesn’t get a little antsy waiting 378 days for a foal???

Uh Oh! There’s an udder!

To be honest though, the Docs weren’t worried about May because her udder wasn’t growing. The udder is an excellent way to tell how the foal/uterus/placenta are doing. Udders should start developing around Day 330 of gestation. If the udder is growing any sooner than that, Call My Docs IMMEDIATELY. Was I clear enough there? Milk coming in before day 330 is not good!!!

May’s udder showed absolutely no changes until about 10 days ago. It then grew at glacial speeds, despite twice daily checks from the techs, Docs, and everyone else around here. (Glacial means really, really slow, for all you native Floridians who avoid all things cold-weather related.)

Antibiotics to the rescue

It’s 290 days of gestation for your mare, every check-up until now has been normal, but suddenly this morning she has a huge udder and you can express milk. My Docs ultrasound her and find some separation of the placenta at the cervix. What now? Antibiotics! And Regumate, and Banamine. But mostly antibiotics. The good news about placentitis is we can generally get it treated with SMZ antibiotics. A little Regumate is added in to quiet the uterus down, and Banamine reduces inflammation. The sooner placentitis is caught, the better the chances things will go well.

May’s placenta was normal, her cervix was tight, and she had no udder. That means no placentitis. My Docs did a couple extra things to make sure everything was OK in there. They did a serum amyloid A test. This looks for inflammation from infection. May’s was normal. They also used the ultrasound from outside that enormous belly to be sure the foal was moving. She was. That left my impatient humans with sitting and waiting. Which they did very, very reluctantly. Lo and behold, we had milk early on Monday morning with a pH of 6.2 (read here about why that’s important), and later in the morning we had a bouncing baby girl!

Can’t you induce like they do in humans?

NO!! is the definitive, emphatic answer. Foals develop their lungs in the last 36 hours of gestation. We don’t have a way to know when that is. Take May as an example: if she had been induced at day 340 of gestation (her technical due date), her baby would have still needed 36 days more for her lungs to mature. I may be a cat, but I’m guessing no lungs doesn’t go well with the outside world.

As I said earlier, mares are mares and they will do as they please. It’s a philosophy I can really get behind. Got questions about your mare or due dates? Want to breed? Go check out my blog page for tons of wisdom. Want the wisdom every week? Scroll down a little farther and subscribe to my blog. So easy, even a human can do it!

Until next week,

~ Tony

Tuesdays with Tony is the official blog of Tony the Office Cat at Springhill Equine Veterinary Clinic in Newberry, Florida. For more information, please call us at (352) 472-1620, visit our website at SpringhillEquine.com, or follow us on Facebook!