Spring is trying to make it’s come back here on the West Coast. California really likes to make the seasons work for it, almost as much as mares like to make stallions work for it. Have you ever heard the saying “love is in the air”? What about “twitterpated”? The latter is lesser known, I know it from Bambi. Spring is the season of being twitterpated, infatuated, in love, in…the “mood”. You knew this post was coming.

Let’s start with a fun fact. Have you ever seen a horse or cow/bull curl their upper lip, it’s cute right? This is called the Flehmen response, and it’s believed that it is used to help males identify mating opportunities, or females to identify young or other females in heat. So next time you are near an animal displaying this move maybe, take a step back. 😉 Nah! I’m kidding horses aren’t like dolphins, if you catch my drift. Let me explain what this response is doing and maybe it will make a little more sense.

Under the nasal cavity there is a very small duct called the Nasopalatine duct that opens up into the Vomeronasal organ. When the upper lip is curled is restricts airflow to the nasal passage and creates subatmospheric (lower than that of the atmosphere) pressure in the nasopalatine duct. This allows fluids to be aspirated through the duct and into the vomeronasal organ sensory surfaces. The vomeronasal organ is an accessory “smelling” organ that consists of two blind ducts and is believed to be associated with identifying volatile and non-volatile materials. Pheromones are a volatile substance, meaning they are easily evaporated in normal temperatures. Examples of a non-volatile substances would be a placental fluids, pee, etc.. For stallions this means they can pick up on certain mares that are ready to mate by the pheromones they put off. For mares this means they can pick up on other mares coming into heat, differentiating between their own foal verses anothers, or just identifying their own foal post birth.

These pheromones can cause behavioral and physiological changes in both males and females. Meaning, it can prep stallions for breeding, mares to be receptive to breeding, and among other things it can attract females to males. This area of science really hasn’t been studied much in horses, that’s why I say “believed to” instead of “it does”. When I was still in college and debating whether I wanted to tack onto my student debt, I was really considering doing my Master’s work on reproduction with a focus on mate selection and the major histocompatibility complex (MHC). It was an area that seriously fascinated me and we only covered it in the last couple of weeks of my final quarter. Typical.

The MHC has been studied in humans and it is actually fascinating. Before I get to that I’ll give you your weekly dose of nerdom. What is the MHC? The Major Histocompatibility Complex is a bunch of molecules that function in intracellular pathogen defense. In the human genome, on the short arm of chromosome six there is a region that is the MHC, it contains many genes that encode cell surface molecules that are involved in immune recognition of certain pathogens. Short put, its the region in your genes that codes for your innate behaviors of immunity to certain pathogens so, how your body attacks viruses. Why this is important and what it has to do with mate selection is as follows. Over time evolution has caused diversity of the loci (or ends) of the MHC molecules, meaning they allow for negative assortment (random mating). This observance in humans has lead to some controversy and therefore not a lot of concrete evidence, but the studies have still sparked a lot of interest. In real people speak, the MHC is thought to cause females to choose males with a dissimilar MHC therefore improving the diversity of the ends of the MHC in their offspring (making offspring with strong immune systems). “Must find strong man to make strong babies.” You know, that jazz.

In humans they did a t-shirt study where they had a random group of men wear t-shirts and get them sweaty. They then chose women with dissimilar MHC to the men and had them smell the t-shirts. They found that women perferred the t-shirts from MHC-dissimilar men. Sweat is a volatile substance, meaning it evaporates easily at normal temperatures. So the smell of the t-shirts triggered an innate response in the women to choose a male who’s MHC was different than their own. This is evolutions way of “ensuring” their children would have a new diverse MHC and therefore would have strong immune systems.  The controversy comes from a world study with real couples where a certain gene was studied and there were mixed results. They found some couples had similar MHCs and some had dissimilar, throwing a wrench in the theory that all couple have dissimilar MHCs. What we studied in school were some of the things that may cause this to happen. Studies have shown that oral contraceptives can suppress the immune system. Women on birth control may react different to pheromones, making them less receptive and therefore likely to choose a mate with a similar MHC. Not to say that since a woman is on a contraceptive that she would choose the “wrong” guy. No, this is only saying that contraceptives can alter the way your brain receives pheromones. Don’t worry your babies will be beautiful and strong.

I can’t be the only one that thinks this is fascinating! Genes influencing how we select mates… science!

Ok enough “big-word” speak. Funny stories from the past couple weeks: Our mini-teaser stud tried to run me down, apparently he doesn’t like getting shots all that much. It’s only slightly embarrassing that a mini pony ran me up a fence. Yes we have a mini pony, and yes he is a stallion and yes, it’s as funny as you think he is. He is all that is “man”, or he likes to think so. We use him to check our mares to sees if they are in heat. It’s safer and a tad easier to handle than a life-size stallion. My cat knocked the tv off of the table, it’s only funny because the tv still works and she, now, won’t go anywhere near it. I put salt in my tea the other morning instead of sugar (that was fun) and just goes to show the lack of REM cycles I’ve had. The power went out one evening which meant checking the mares every twenty minutes to make sure no one tried to pull the wool over my eyes and have their baby incognito.

Actually that’s a pretty funny story. The power goes out, I’m at home in the shower, I call the power company they say it won’t be back on for about four to five hours. I immediately go check mares, the Foalert system works even when the power is out but the call box doesn’t. So the alarm will sound but I need to be in the barn to hear it. I start to set up to have a little station in the barn to chill until the power comes back on. This requires warmer clothing and a flashlight, and maybe a snack. I run home, the power comes back on. Sweet! I go back to the barn to make sure the call box is working (it was, we all got “the call”), so I visually check the mares on last time and everyone looks calm and cool. I head back home to attempt a shower for the second time. I kid-you-not, I get in the shower and my Foalert ringtone goes off. I blow out of the shower, jump into some clothes and run to the barn. It’s not a test, there’s a baby coming! This was about ten minutes after I got home from testing the system and checking the mares. Everything went smooth, momma and baby were happy and healthy. I attempted and succeed in my third shower later that night, incase you were worried.

That foal put the boys in the lead, 3-2. Nemo and Dori are our “twins” this year, their mother double ovulated last year and we were able to get two embryos out of her. Though biologically they are twins, they were born out of two different recipient mothers about 24 hours apart. We can’t get over their cuteness!!

We are in the beginnings of a pretty good storm up here, I’m thinking someone has to want to foal out during this crappy weather because.. WHY NOT?!

Thank you all for the continued support with my little experiment blog. So far I’ve gotten a bunch of good feedback, I love hearing from you all!

–The Equine Midwife