Last week I brought Phoenix in after her fortnight of running feral. She was good overall, but I noticed that she was in season. She trotted over to me in the field and was a bit possessive when the other mares wandered over. Then on the yard and to lunge she just got a bit distracted by any gelding that passed – turning and pricking her ears at them. Nothing bad when you consider how hormones can affect some mares, but today (now we’re out of season) I realised that I know very little about a mare’s oestrus cycle and I’ve never blogged about it.

Of course I learnt about breeding at college – we had a lovely male lecturer who was quite effeminate (he’d call out whilst teaching us “*our name* angel, darling, petal, poppet. Will you NOT do that?” Which elicited lots of giggles from us teenage girls and vows to not repeat said behaviour) who taught us about breeding. It was so memorable because there were lots of squeals, shudders and yucky faces made at the technical terms – and for my BHS Stage IV.

Mares come into season every 19-22 days from early spring until autumn. The longer daylight hours triggers the first season and the shorter days cause their seasons to cease. In winter, they don’t have seasons (although it’s been known in mild winters for mares to have a random season), which is called an anoestrus period. This is to stop a mare foaling the following winter – the gestation period of a horse is 11 months – when it’s coldest and hardest to survive.

However, in competitive circles horses are aged from the 1st of January (1st August in the Southern Hemisphere). This means that a horse’s passport may have their birth date as 12th May 2016. But from the 1st January 2018 they will be considered a two year old. Consequently, breeders often put mares under lights to trick their bodies into thinking that the days have gotten longer so they come into season earlier in the year, which will give their offspring a competitive edge because they are born closer to the official birth date so are physically more mature than foals conceived naturally and born in May.

Fillies are sexually mature by the age of two, but they shouldn’t be bred from until the age of five or six when they are physically mature. Mares can produce foals annually until they’re in their twenties, providing that they’re healthy and well cared for, but most breeders leave them barren every few years.

Some people continue to keep pregnant mares in work, particularly in the early stages, and into the latter stages when new owners don’t realise their mare is pregnant. From my own experience, I’d have thought a mare would cope better with pregnancy if they are of a healthy weight initially and have an active life. So often brood mares, particularly natives, are overweight and I suspect that reduces fertility, which means fewer foals and more time, effort and money invested into covering the mare. However, I think it can be difficult to strike the balance between lightly exercising a pregnant mare and overworking her, especially when you consider that they are carrying the extra weight of a foal as well as the tack and rider. In my humble opinion I’d have thought light hacking in the initial couple of months if they are used to that work load before a combination of long reining, lunging and ground work to keep the pregnant mare fit. I’d also ensure they are on good grazing, but over extensive land, perhaps with an incline, which will help maintain their general fitness and prevent sudden and rapid weight gain when there’s a flush of rich grass.

So how do seasons affect the behaviour of mares? It depends entirely on the mare themselves – just like some women suffer more from PMT than others. But often a mare can become cranky – sensitive when grooming, or reluctant when being exercised. Sometimes they just have more sass. Like Phoenix tossing her head and cantering on the lunge when I sent her away from me instead of her usual walk. They tend to notice geldings more, but some will just sniff or snort at them in passing whilst others will reverse up to some poor unsuspecting gelding and lift their tail flirtatiously.

Some people use herbal supplements or hormone drugs to minimise the hormone fluctuations and seasonal behaviour. I’ve had friends who favour mares over geldings because when they’re on form their performance is superior to that of the non-hormone driven geldings. I like to know what I’m getting each day so like the even keel of geldings and the less mareish mares. I’m also of the belief that ensuring your mare knows where she stands in the human-horse relationship is important in managing her hormones as she will be less likely to behave badly with you, which makes her safer to handle. This comes from consistent expectations, routine and training.

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