Let me tell you something – for a cat, Easter is heaven. There are all the usual joys of holiday snacking – cookies, delicious cakes, and other goodies flowing in from our wonderful clients. However, instead of having a cold winter day, surrounded by snowmen and the scary horned beasts in nativities, just think about Easter. Small, squeaky chicks, ducks and rabbits on a warm spring day, with many flowers to sniff and soft grass to roll in. And, of course, the always-popular Peeps in the microwave trick. I think it may be my favorite holiday.In celebration of spring (known to us in the Animal Kingdom as the season of the dreaded twitter-painting), I decided to begin a series on breeding your horse. It is a very complicated subject, and very different from what you know about people (or dogs or cats for that matter). In every discussion about equine reproduction, it is important to remember that all individuals are different, and so there can be (and usually are) exceptions to nearly every rule.Every species is unique when it comes to reproduction, and so I’ve learned that we classify many things about it – such if the species is ‘seasonal,’ or only breeds during one part of the year (horses are, cats and people aren’t!). If it is seasonal, when? Horses are considered seasonal breeders, and breed during the time of the year when the days are longest – eg. spring and summer. This is the opposite of say, sheep, who are seasonal but in the fall.  Funnily enough, both end up having babies in the spring (as sheep are pregnant for about 5 months and horses are closer to 11). In Florida, we enjoy a prolonged breeding season due to our ample sunlight, so fall breedings and foalings are not uncommon.

Let’s talk more about seasonality. In winter, the mare generally is considered ‘seasonally anestrus.’ ‘Estrus’ (while many definitions exist) is the term scientists use to describe heat, or the period that the female is receptive to the male. In the horse, it is usually 3-7 days long, with an average of five days. ‘Anestrus’ is the term for when an animal does not experience heat cyclicity. This brings us to another classification for the horse – ‘polyestrus,’ or having multiple heat cycles in one season. All together, the horse is considered seasonally polyestrus (long-day breeder) with a period of winter anestrus. That was your check point – if you don’t understand that statement, please go back to the top of the blog.

Now let’s talk about the transition periods. Horses experience vernal (spring) and autumnal transitions – progressing from the anestrus period to the cyclic period, and back again. Spring transition is a matter of key concern for many people, most notably, the Thoroughbred racing industry. A Universal birth date of January 1st is assumed for all Thoroughbred racehorses, and so the first baby born in the New Year is the oldest and the strongest in the pack. During these periods, the ovary is slowly adjusting to the new patterns. We will discuss more about ovarian activity and the corresponding changes in the uterus during our next blog, as we will about the specific changes that occur during the transitional periods. As always, thanks for reading! May your litter box ever be clean, and your food bowl full!

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