Maybe I'm biased because I own two of them, but I do love a good mare. Like many riders, I believe a mare who loves her job will try her heart out for you. Some have their quirks, but deciphering them is half the fun, right? I also love mares' personalities--sassy, inquisitive, yet sweet. Why would anyone not want a mare as a sport horse? Because of the hormones, duh.

Hannah's estrus behavior includes squealing, making ugly faces, and screaming for other horses.

Photo: Erica Larson

Lily and Hannah have been hormone supplement-free until last month when both started developing less-than-desirable estrus behavior. Coincidence that they decided to show their true colors nearly simultaneously? Probably not. Longer days and rising temperatures naturally trigger mares' bodies to begin secreting hormones that affect the ovaries. Some breeding farms even intentionally "synch" all their mares' estrus cycles.

Lily's initial marish signs were subtle--things I chalked up to freshness, discomfort, or training challenges. In the arena she felt like a freight train when pointed toward her female pasturemates' field. Any other direction she remained nice and quiet. She also developed a sudden affinity for ponies. If a pony happened to be in the ring while we were riding, all focus was lost; Lily had eyes only for him. Then the signs became more obvious: pinning her ears at other horses (and people!), particularly when jogging or hacking at horse shows, and acting increasingly herdbound.

During spring vaccinations I asked my vet about starting Lily on some sort of supplemental progesterone, a naturally occurring hormone that shuts down the estrus-stimulating hormones. She agreed we should give a monthly slow-release, long-acting injectable altrenogest (a synthetic progestin marketed as Regu-Mate) a try--or, as one of Hagyard Equine Medical Institute's repro vets, Dr. Karen Wolfsdorf, calls it: "happy juice." My veterinarian did, however, conduct a full exam first to rule out any other body issues that might be causing her crankiness. Dr. Wolfsdorf says she always urges doing this before trying to modify a mare's mood using progesterone. She likens it to humans: You can't always blame a woman's attitude on her ovaries!

Hannah's estrus behavior was primarily limited to the ground: kicking out and squealing when I groomed her flanks; making nasty faces and postures in her stall; and screaming to her friends. But having just started Lily on monthly hormone injections, I was more keyed into this behavior being estrus-related. Time to start Hannah on happy juice as well! (Again, only after my vet had checked her over for any other issues.)

Thus far I've definitely seen an improvement in Lily's focus and demeanor. And with a horse show coming up next week, I'll find out if that improvement transfers to the show ring. With Hannah it might be too soon to tell, as the injections take about 7-10 days to kick in, but I'm eager to see how she too behaves at this upcoming show.

Have you dealt with performance mares and hormone-related issues? What solutions did you find?