Here come the girls!

Spring, and what that means for mares, by Kate Hore. RNutr (Animal). R.Anim.Technol (Cert)., head nutritionist at NAF.

Spring is in the air, and for those of us lucky enough to own mares that means a reawakening of their monthly oestrus cycles.

Mares are described as seasonally polyestrous, meaning she has multiple heat cycles at certain times of the year – for horses, that is spring through to early autumn. Most mares will have entered a non-breeding period over winter, known as anoestrus or anovulatory, but will now be entering the spring transition period where her cycling restarts.

It is wise to be prepared for this change, as often the earliest cycles during this period can be particularly erratic and extreme - you could say her hormones literally ‘kick-start’ at this time of year!

Whether advising owners of ridden mares wanting to manage those fluctuations, or owners of broodmares wanting to use her reproductive health, it is important to have a basic knowledge of mare health and how to support her cycles.

Hormonal Cycle

Once her cycles settle into a seasonal routine they should follow a roughly twenty-one day cycle, split into two different clear sections. Oestrus lasts four or five days and is the time that she is sexually receptive. Mares may flirt more with the geldings during this time, and certainly if there are stallions or colts on the yard, we should advise owners not to allow unplanned contact between them.

Oestrus is followed by around sixteen days of Dioestrus, when naturally mares would reject the stallion, and behaviour may be more dominant or pushy during this time. Though it is worth noting that signs of seasonal cycling differ with the individual, and are split into two clear groups.

To be confident it is her hormones that are the issue, owners should look for mare specific behaviour. These signs are most typically seen in hormonal mares, giving you a very good indication that the behaviour is hormone related. Non-mare specific signs may also be seen, but could also relate to many other triggers. If owners are only seeing the non-specific signs, it is important to get tack fit and teeth checked, and a check from their vet to rule out other causes.

Condition Scoring for Mares

Maintaining a healthy body condition score is important in all horses and ponies for health and welfare; but in mares excess weight brings its own challenges.

Research shows that, in a herd environment, overweight horses are more likely to be dominant. Whilst it might seem obvious to assume the dominance leads to more access to feed and, therefore, weight gain, that isn’t proven. In fact, if we extrapolate from evidence across species, it seems very likely the opposite is true, and the excess weight causes the dominance.

Research also shows that overweight mares are more likely to extend the breeding season for longer, into the anovulatory winter season. So whichever way we look at it, ensuring she stays in fit not fat condition is important.

One word of caution with this is the potential broodmare. Again, it is important that she is not overweight, which can definitely impair reproductive success. However, being underweight will also lower fertility rates; so particularly if taking a lean, fit mare from competition to stud, then allow her some time to relax and aim for a body condition score around 5-6 on the 1-9 scale.

Dietary Support

A high fibre, low concentrate diet, balanced for trace elements will suit all mares, whether continuing their ridden career, or heading to stud. However, targeted supplementary support can be advised to provide the nutritional tools she requires for support and fine tuning of the diet.

Ridden Mares

The therapeutic use of herbal blends goes back for hundreds of years and are often a great choice for providing natural effective support. There are a number of different herbs which may support the ridden mare. The primary targets of those are helping her stay focused on the job in hand, and, just as importantly, to maintain comfort through her cycles.

Did you know that the traditional name of herbs often tells you its action? Nowhere is this truer than for chasteberry. Scientific name Vitex agnus castus, the traditional name of ‘chasteberry’ or ‘chastetree’ refers to being ‘pure and chaste’, due to its action as a libido suppressor.

However, it is important to remember that seasonal stress in mares is multifactorial. If we only concentrate on her behaviour we miss the root of much of the issue, and that is hormonal discomfort. Therefore, we advise feeding a blend which targets both behaviour but support for comfort with, for example, herbs like peony or nutrients including magnesium. Here too we see appropriately named herbs, like crampbark (Viburnum opulus), named for its traditional role easing premenstrual cramps in indigenous tribes in its native North America.

We are often asked whether a mare supplement is only needed at those times of her cycle when she is displaying those signs. However, to see the beneficial effects, we advise feeding daily through the breeding season to support all stages of her cycle.

Broodmares

Experienced broodmares often find it relatively easy to conceive and maintain the pregnancy, but this is certainly not true for maiden mares, particularly if older.

If a mare owner decides that, having had success with her as a ridden partner, they now want to breed from their mare, targeted supplementary support for oestrus and reproduction would be advised. Look for a blend fortified with high rates of vitamins A and D, together with vitamin E, selenium and zinc.

Recent research shows feeding a targeted blend for a minimum of four weeks prior to covering is the recommended approach to optimize her chance of reproductive success.

Girl power!

Mares, like stallions, are ‘entires’ and do bring that edge, which can be a real benefit. Mares are brave, quick thinking and once you’ve got that relationship, she will really look after you.

Rather than seeing mare ownership for its challenges, let’s see its opportunities. As advisors, we have a responsibility to help owners with their mares’ comfort and focus, but once we have done that, there is no stopping her!