Horse feed manufacturer Blue Chip has launched the UK’s first dedicated feed balancer for hormonal mares as part of its established range of super-concentrated balancers. While there are many supplements targeted specifically at “moody mares”, this is the first feed balancer of its kind.

The Happy Mare balancer is formulated specifically to support the nutritional needs of mares, helping them maintain a normal oestrus cycle as undesirable behaviour is often attributed to hormonal fluctuations that affect the mare’s physical comfort and way of going.

The balancer combines targeted botanical ingredients, including chaste tree berry, raspberry leaf and dandelion, with complete daily nutrition to support hormonal balance, digestive health, and overall wellbeing. The ingredients have been chosen to help mares maintain an even temperament and steady energy levels, while supporting muscle tone and topline for good-doers.

The new balancer provides mare owners a practical and easy feeding solution that offers an alternative to adding a supplement to their existing daily feed ration. As a small daily serving, the balancer can also be fed by hand, which makes it ideal for fussy eaters.

Blue Chip describes the formulation as being underpinned by a strong focus on digestive health, recognising its critical role in hormone function, adding that when the gut is out of balance, hormones can be, too. By combining targeted ingredients with the right balance of essential vitamins, minerals, amino acids, and advanced digestive support, Happy Mare balancer is formulated to help mares feel more consistent, settled and comfortable.

This balancer is not recommended for pregnant mares or broodmares because of its chaste tree berry content.

Blue Chip Happy Mare balancer

The Blue Chip Happy Mare balancer is available in a 3kg recyclable pouch with an RRP of £31.75. This bag will last a 500kg horse one month.

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You might also like to read:

Best feed balancers for all horses: what’s on the market?

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11 supplements formulated to help hormonal mares

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Everyone knows a “moody mare” – whether their hormones are causing them to be difficult to handle, ride or train, or are interfering with a broodmare’s natural breeding cycle, it can present a real challenge. But this is something that the best supplements for moody mares can often help with.

The length of a mare’s natural breeding season varies, but it typically starts around March/April each year, so early spring is a great time to begin supplementing to encourage regularity, reduce unpredictability and support more consistent behaviour, which will in turn lead to improved performance and a happier horse.

Supplements for moody mares: what are your options?

Here is a selection of the best supplements for moody mares that are currently available, including the manufacturers’ descriptions of their products…

NB: Cost per day has been calculated using the maintenance measure for a 500kg horse in light work (where there was variation) and the RRP of the smallest available tub. Some products require you to feed more in certain situations or a loading dose, which will increase the cost per daily measure, while buying a larger tub will likely decrease it – these costs per day are a guide only.

Dodson & Horrell Stroppy Mare

Form: Powder

Sizes: 1kg

RRP: £18.78 for 1kg

Daily measure: 30g

Cost per day: £0.56

A comforting blend for a hormonal mare that includes herbs that support hormonal function and the reproductive system, as well as having calming properties.

NAF Five Star Oestress

Form: Liquid

Sizes: 1l, 2l, 5l

RRP: £39.99 for 1l

Daily measure: 25–50ml

Cost per day: £1.00–2.00

This supplement compliments the natural oestrus cycle by encouraging regularity and supporting hormone balance. Also available as a powder.

Equine America No More Moods

Form: Liquid

Sizes: 1l

RRP: £25.99

Daily measure: 15–30ml

Cost per day: From £0.39

This supplement contains micronutrients that help to balance hormones, contribute to relieving muscle tension and support a calm mare.

Premier Performance Sassy Mare Plus

Form: Powder

Sizes: 480g, 960g, 1.3kg, 1.92kg, 3.84kg, 9.6kg

RRP: £26.25 for 480g

Daily measure: 16–32g

Cost per day: £0.85–1.75

Formulated with a specific blend of herbs, minerals, vitamins and amino acids to support hormonal balance, wellbeing and overall calmness.

Equine Products UK Mood Balancer

Form: Liquid

Sizes: 1l

RRP: £28

Daily measure: 30ml

Cost per day: £0.84

Designed to maintain normal behaviour and temperament so that performance doesn’t suffer.

Global Herbs FriskyMare Plus

Form: Powder

Sizes: 1kg, 5kg

RRP: £43.50 for 1kg

Daily measure: 25g

Cost per day: £1.09

A mix of traditional calming herbs that help manage the behaviours and comfort of cycling mares, reducing unpredictability and aggression caused by hormone levels.

EquiNutritive Moody Madam

Form: Powder

Sizes: 1kg, 3kg

RRP: £45.99 for 1kg

Daily measure: 30g

Cost per day: £1.38

This natural mare supplement is a carefully cultivated mix of seven dried herbs combined to maintain hormone balance and support your mare through her season.

Science Supplements HormonAid

Form: Powder

Sizes: 1.55kg

RRP: £44.99

Daily measure: 51g

Cost per day: £1.19

Designed to work alongside the natural cycle of the mare, this supplement helps to relieve tension and support a more amenable demeanour. It contains vitex agnus-castus extract, which helps to ease transitions through the oestrus cycle, selected herbs that encourage a stable mood, vitamins that promote a good mental attitude and magnesium, which helps to ease hormone associated muscle cramps or tenderness.

Hilton Herbs Easy Mare

Form: Liquid

Sizes: 1l, 3l, 5l

RRP: £32.95 for 1l

Daily measure: 25ml

Cost per day: £0.82

This supplement contains medical grade herbs selected to help support a balanced hormonal system and offer mares comfort during their seasons.

Cavalor Venus

Form: Liquid

Sizes: 500ml, 2l

RRP: £42 for 500ml

Daily measure: 20ml

Cost per day: £1.68

A herbal extract that supports the hormonal balance in sensitive and moody mares by helping to regulate the hormonal cycle.

Omega Agnus Castus

Form: Powder

Sizes: 1kg, 3kg

RRP: £14.99 for 1kg

Daily measure: 30g

Cost per day: £0.45

Agnus castus is linked to supporting a healthy pituitary gland and endocrine system. This allows horses to healthily self-regulate their metabolism, growth, reproductive system and response to stress. It’s also a powerful antioxidant that contains compounds that ease stress and low mood.

How to choose the best supplement for moody mares

Most hormonal supplements for mares are made of a combination of a range of herbs that are known for their regulating and calming properties. They are available in both liquid and powder form. Your horse may have a preference to one over another, you need to make sure your horse is receiving the recommended dose or they won’t receive the benefit.

We’ve calculated the daily cost of all the supplements featured in this guide to help you compare them easily. To make it as comparable as possible, we’ve used the smallest tubs available, but if you’re better off buying a larger volume of supplement if you can as the daily cost can become significantly lower.

If you compete with your horse then it is important you make sure any supplements you use do not contain any prohibited substances.

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A website has renamed the product “Slut Mix” after a complaint to the Advertising Standards Agency (ASA) was upheld — but the same product and description remain on other sites.

The product description stated that “Slut Mix does attract a fair bit of attention, not least because of the name! However, it’s a serious product that… really can work. If your mare is constantly in and out of season, aggressive and temperamental then this product has proved to be highly successful in easing the problem”.

The complainant who, the ASA said, “believed the ad, especially the name of the product, was sexist and perpetuated negative stereotypes of women, challenged whether it was offensive”.

LeMieux Ltd said it was a third-party stockist of the product, which was named by its manufacturer. The company told the ASA it did not advertise the product beyond its listing on the website, and asked the manufacturer to comment on the complaint.

“The manufacturer said ‘slut’ was a term commonly used by horse trainers to refer to a problem filly,” the ASA ruling states. “They said that the product was exclusively for horses and they did not intend to cause offence to people. They said that the product had been on sale since 2000 and was sold in 15 countries.”

In upholding the complaint, the ASA noted that customers would know the product was for horses.

“However, the term ‘slut’ was a well-known negative stereotype of women and was commonly used to refer to women who had or were perceived to have many sexual partners, in a derogatory way that passed judgment on those behaviours,” the ASA stated. “We considered that, even in the context of an ad for horse supplements, consumers were likely to consider the word ‘slut’ to be highly offensive, derogatory towards women and sexist. For those reasons, we concluded that the ad, which included an offensive gender stereotype, was likely to cause serious offence.”

The ASA ruled that the ad must not appear again in its current form, adding: “We told LeMieux Ltd to ensure that their future ads did not contain anything that was likely to cause serious or widespread offence, including the use of offensive gender stereotypes.”

A LeMieux spokesman told H&H: “We are a third-party stockist of this product and have renamed it on our website to Mare Mix in recognition of the negative connotations associated with the original product name.”

The product is still on sale elsewhere, still named Slut Mix and with the original description. Manufacturer Herbal Wise declined to comment when approached by H&H.

The ASA told H&H it will be in touch with other sites on which the product is still named Slut Mix, with the original description, to let them know they must change the wording in accordance with the ruling. As the product is made in Ireland, it would be up to the ASA for Ireland to decide whether it breaches rules there.

“We encourage anyone with concerns about any ads they’ve seen to get in touch,” the spokesman said.

You might also be interested in:

Mareish behaviour: In season, unsound or something else?

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Subscribe to Horse & Hound magazine today – and enjoy unlimited website access all year round

Horse & Hound magazine, out every Thursday, is packed with all the latest news and reports, as well as interviews, specials, nostalgia, vet and training advice. Find how you can enjoy the magazine delivered to your door every week, plus options to upgrade your subscription to access our online service that brings you breaking news and reports as well as other benefits.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Is your mare suffering from a hormone imbalance or is there something else causing that unwanted behaviour? Charlotte Thomas MRCVS investigates

Oestrus, or in-season behaviour, is easy to recognise in some mares. Signs can include frequent urination, squatting, everting the vulval lips to expose the clitoris (known as winking) and unpredictable behaviour that can be difficult to manage. Oestrus behaviour is a normal manifestation of the mare’s cycling breeding hormone levels throughout the year.

In non-domesticated herds, this behaviour is important to indicate to the stallion when the mare is receptive to covering and when she is at the point most likely to conceive within her cycle. Likewise, in a stud farm scenario, the mare’s responsiveness to a “teaser” (a stallion that is used to test if a mare is ready to be served) is used alongside ultrasound imaging to determine when is the best time to natural cover or artificially inseminate.

In equestrian situations not related to breeding, although this behaviour is not abnormal, it can be unwelcome. Problems can manifest in a subtle loss of performance to a mare that is unrideable when in season.

But are changes in behaviour related to a mare’s seasons? Before embarking on treatment to address unsavoury in-season behaviour, it must be ascertained if the mare’s reproductive system is actually the root of the problem. If the difficult attitude is shown all the way through the mare’s cycle during spring – as well as through the winter when most mares don’t cycle – it is unlikely that her reproductive hormones are the source of the problem. Lameness, back, teeth, gastric ulcers and training issues must be considered alongside hormonal causes.

A complex network of hormones

The signs of oestrus are caused by a complex network of hormones made in different organs of the mare’s body, including her ovaries. The main oestrus hormone is oestrogen and the main dioestrus (out of season) hormone is progesterone.

Most mares have a cycle of about 21 days. The mare will be in season for five or six of these days and then out of season for the remaining 15 or 16. At the end of the period of dioestrus, if a pregnancy has not been conceived, then hormone signals will be sent to expel the corpus luteum, which is the progesterone secreting structure in the ovary.

Oestrogen and progesterone are important in bringing about the physical changes in the body required for releasing an egg from the ovaries and supporting a pregnancy. They also promote or inhibit the action of different neurotransmitters in the brain, and therefore have a strong influence on behaviour.

Hormone changes

Some mares are more susceptible to hormone changes or show exaggerated signs of being in season. There can be an underlying cause, such as an ovarian tumour or urinary tract pain.

This means that a full veterinary examination, including an ultrasound and blood tests, is important. Once we have ruled out these problems we can look to diagnose a hormone imbalance.

Resting levels of the main oestrus hormones are likely to be the same in problem mares as they are in mares who do not show difficult oestrus behaviour. However, research has shown that when the adrenal glands are stimulated by a naturally occurring hormone called adrenocorticotropic hormone (ACTH), levels of progesterone, cortisol and testosterone are affected to a different degree in problem mares compared to normal mares. This suggests that it is not just the ovaries involved in the mare’s hormonal balance, and that the underlying physiology of difficult mares is different and therefore the problem is not all in the mind.

Undesirable behaviour

It would seem logical that, in the case of a mare exhibiting undesirable behaviour associated with being in season, removal of the ovaries (ovariectomy) would solve the problem. However, the manifestation of oestrus signs is due to low progesterone levels rather than high oestrogen levels. Therefore, removing the ovaries would remove the source of progesterone and may lead to more frequent and long-lasting oestrus signs.

Studies have shown that around 35% of mares continue to show signs of oestrus after surgical removal of both ovaries, making it a poor course of action for most mares. An exception to this would be when the ovaries were affected by a hormone secreting tumour known as a granulosa cell tumour (GCT).

These tumours account for 2.5% of all equine tumours and can cause three distinct behavioural patterns depending on the hormones they secrete. They can cause anoestrus (a lack of hormonal cycles), which often goes unnoticed by the owner unless they are actively trying to breed from the mare. They can also cause masculinisation if the main hormone involved is testosterone, leading the mare to show dominant behaviour and even try to cover the other mares in the field. Lastly, they can cause persistent in-season signs that can be a headache for the humans involved in their care. GCTs are diagnosed by ultrasound and the measurement of the blood hormone levels.

A frequent owner complaint is that their mare seems to undergo a “mega-season” in the spring when her regular cycles are replaced by a long period of oestrus of several weeks. This can often be explained by the mare going through the transitional period. Mares are seasonal breeders and therefore their ovaries and reproductive tracts are usually quiescent or in anoestrus over the winter period.

In the transition period between winter and the first cycle of the year, there may be several waves of the hormones involved in ovulation before the first egg is finally released from the ovary. This can keep the mare in season for a long period but will likely settle down as the hours of daylight increase as the year goes on. As the season goes on, some follicles become anovulatory or get stuck at the point of ovulation and instead of bursting to release an egg, continue to produce oestrogen, leading to a long period of being in season.

 A softening follicle

It is known that some women get ovarian pain associated with ovulation and it may be the case that this is true for mares also. Any vet familiar with performing an ultrasound examination of the ovaries will have noticed that a softening follicle in the ovary will become more tender as the mare approaches ovulation.

Some mares have a persistent endometritis, which is an irritation of the uterus lining. This can be following a covering or spontaneous in older mares, often associated with poor vulval conformation, a tight cervix and decreased uterine defence mechanisms such as lymphatic drainage. This inflammation causes the release of prostaglandins from the uterus lining, leading to the mare coming back into season.

In conclusion, your mare’s vet can help investigate whether her difficult behaviour is linked to her seasons, and determine whether there are exaggerated oestrus signs or a physical problem such an ovarian tumour and therefore make a treatment plan.

The most common method

Treatment options include the removal of an ovary with a tumour, flushing the uterus if endometritis is present or the suppression of oestrus. The most common method to suppress oestrus is the use of synthetic oral progesterone, sold under the name of Regumate in the UK.

Another method gaining popularity is the use of a gonadotrophin-releasing hormone (GnRH) vaccine, which prevents the mare coming into season. However, the vaccine must be imported from Australia through a special licence.

There is an off-licence vaccine available in the UK, but the disadvantages can include muscle soreness at the injection site and potentially permanent infertility. It is cheaper and more convenient than daily progesterone.

Some vets have used plant oils infused into the uterus as a treatment option, as early research suggested this method could be effective. Later studies failed to show the effectiveness of this treatment and showed the method could result in uterine inflammation.

An older technique is the placement of a large glass marble inside the mare’s uterus to mimic a pregnancy and stop the mare coming into season. The results of this technique are variable and the marble can occasionally degrade, causing endometritis and threatening future fertility.

A new type of intrauterine device, called a Upod, is being developed. It is made of shatterproof magnetic beads that self-assemble into a ring in the uterus. It can be inserted at any time during the mare’s cycle and doesn’t cause endometritis. The owner can check the device is still present by using a metal detector.

There are various nutraceutical supplements for mares that have an anecdotal calming effect for the mare who seems to be at the mercy of her own hormones. Some of these may contain substances prohibited for competition horses, so it’s a good idea to check the ingredients with the help of your vet. In any case, thorough consultation with your vet to determine the best course of action is advisable.

Ref Horse & Hound; 16 April 2020

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If your grumpy mare could speak or indeed write with her hooves, we all know her Christmas wish list would make your heart sink faster than your trailer in a muddy field. Forget ‘nightmare before Christmas’, if Santa listens to your horse, it’s going to be a ’mare all year around as Ploy Radford describes…

1. To be allowed within biting distance of that poncey thoroughbred three doors down

Because she’s fed up of seeing him get secretly fed extra carrots by all his doting fans and can’t wait to sink her teeth into his glossy behind.

2. A brand new expensive rug

So she can see your tears of frustration when you find out that she has somehow ripped the gorgeous new rug that cost you an arm and a leg within 24 hours. She’ll happily nip your remaining arm and leg though to say sorry.

3. For the vet to let his guard down

And be swiftly reminded with her hooves why needles are not welcome within a 100m radius of her gorgeous physique. Same goes for anyone trying to bring clippers within said same radius.

4. An equine photoshoot

Because she thinks it would be a loss to the world if the sight of her bucking you off were not immortalised in art.

5. A new saddle

Let’s face it, she’s eaten a lot of hay and stolen goodies all year and it would be selfish and cruel of you to not spend an eye-watering amount of money on a new saddle for her.

6. That awful Shetland to move yards

While every other pony and horse on the yard cowers in fear when your mare approaches, hilariously that tiny Shetland is the only thing you have witnessed chasing her around.

7. To return to the competition circuit

Because there’s nothing more fun than discovering new humans to kick out at, new hay nets and food stands to steal from and to find more creative ways to get you eliminated in front of a huge crowd. She has no idea why you’ve been so reluctant to take her out competing since that time you “let” her have a little paddle in the water jump.

8. Death to all bins

Those horrid black things are clearly allies of the Shetland and eat horses. All must be destroyed or she’s never willingly leaving the yard again.

Continued below…

11 confessions of a moody mare

If your mare could speak, her ‘confessions’ would probably go something like this…

9. Never to be put into fancy dress again

Looking adorable really damages her stable cred, don’t you know? And she’ll just sulk and refuse to move out of her loose-box to prevent being seen by anyone (especially that awful Shetland or the handsome thoroughbred), so just stop with the tinsel and reindeer antlers would you?

10. A kiss under the mistletoe

Because it’s the season for love and forgiveness, blah blah blah, so just smother her velvety nose with kisses, which she secretly actually really enjoys. She promises she won’t sneeze all over you and step on your foot when you do it this time.

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Moody, tricky, stubborn — mares have to put up with a lot of bad press. But before we start feeling too sorry for them, Andrea Oakes meets the mares living up to their stereotype wholeheartedly

‘She just says NOPE!’

“I’ve owned my eventing mare for six years now. Normally she’s a complete cross-country machine, but when she’s feeling extra-mareish she sometimes just says ‘NOPE!’ In our last event of 2016 she refused the ditch part of a combination and then got in such a tizzy that she refused another couple jumps. This resulted in us getting eliminated for the first time ever. Embarrassing!” Mirelle Radley

‘Honey won’t take any rubbish’

“My 18-year-old mare, Honey, is an angel with people but won’t take any rubbish from any horse in her field. Her fieldmate Chloe started this by raising a leg, but Honey proceeded to handstand about six times in a row.”

Bianca Tella

‘The epitome of the comedian mareish mare’

“While everyone else had lovely show day photos of their horses at the Appaloosa Nationals, my mare Lavender decided to get down and roll on the rubber and sand surface. Lavender, also known as ‘Cowbag’ and ‘Spotbag’ by everyone who has met her, is the epitome of the comedian mareish mare – a tart to end all tarts and happy to get her own way, by hook or by crook. You can tell I love her to bits…” Jude Robinson

‘She would totally explode’

“My little palomino, Hope, is now backed, ridden away and going really well, but she would totally explode every time she had a roller on. She has actually turned out to be a very quiet ride, surprisingly.” Abby Barker

Like this? You might also enjoy reading these:

11 confessions of a moody mare

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‘She makes life a little more interesting’

“Misty, my very own moody mare, has the attitude of Attila the Hun with the disposition of a coiled cobra. Loving and sweet, if you like chewing lightbulbs, but she sure makes life a little more interesting…” Bettina Snowdon

‘I just laugh at her general sassiness’

“When Indie is feeling aggrieved, she kicks over her water, picks up the bucket and throws it over the door. She then picks up the tyre it sits in and throws that against the wall. I’ve learned that if you argue with her she’s only going to be the winner, so now I just laugh at her general sassiness. She once bit my iPhone from my hand as I was talking on it, but I wouldn’t trade her for the world.” Vanessa Murnaghan

Don’t miss our mares special issue, out today (2 February 2017), where we look at ways to help manage your mares and whether you have the right temperament to ride one

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

If you’ve got a mare, you may suspect that she spends at least some of her time plotting evil. And you’d be right. If she could speak, her ‘confessions’ would probably go something like this…

1. Mucking out

“I’m in a generous mood and I know how much you hate mucking out, so I’ve saved you the trouble by hiding all my poo in the shavings banks. There’s loads of it in there. You’re welcome.”

2. Spatial awareness

“Yes, I did stand on your foot. No, I’m not sorry. I meant it.”

3. Face-off

“I’m going to rub my face vigorously on your arm. Don’t be fooled into thinking this is a gesture of affection. I’ve got a horsefly on my cheek and I’m hoping it decides to bite you instead.”

4. Feeling soppy

“I’m in season, and feeling unusually affectionate, so you may cuddle me. But if you accidentally touch any of my sensitive bits in the process, I will kick you. Consider yourself warned.”

5. The perfect revenge

“It was me that bit that gelding in the field next to mine. I know everybody thought it couldn’t be me, because the electric fencing was on, but it was. I just picked my moment carefully. That gelding was really annoying me, by breathing and moving about. He totally deserved it.”

6. Fashion policing

“It was also me that tore my field-mate’s rug. I don’t want to be a bitch, but she looks awful in turquoise blue. It’s just not her colour. I was doing her a favour by trying to get it off her. Any true friend would have done the same so don’t judge me.”

7. Setting standards

“If you don’t ride like Charlotte Dujardin in this lesson, I’m going to buck you off. Just saying.”

8. Staying safe

“Don’t try telling me that’s a ‘fence’. It’s a couple of horse-eating monsters lightly snacking on a pole – clearly the taster for the main course of a moody mare kebab. If you insist on making me go near it again, I’ll dump you so you can kill it for me, then we’ll continue with this jumping malarkey. OK?”

9. House proud

“I’ve pooed in my water bucket. And in my window grille – and have you any idea how high I had to reach my bum in order to do that? Once again, I’ve worked hard to keep my stable clean for you. I hope you’re suitably grateful.”

Continued below…

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10. Hair care tips

“You know how you carefully plaited me up for that show? Well, I rubbed half my tail off in the trailer. You really should buy one of those tail guard things, you know. You have only yourself to blame.”

11. Keeping things interesting

“You know how I hate my field mates, the gelding next to me, and most of the time, you? Well, if you put me in that field on my own, I’m going to gallop round neighing so wildly and loudly that you’ll think I’m having a panic attack. I know, there’s no logic to it. Keeps you on your toes though, doesn’t it?”

Stay in touch with all the news in the run-up to and throughout the major shows and events during 2026 and beyond with a Horse & Hound subscription. Subscribe today for all you need to know ahead of these major events, plus online reports on the action as it happens from our expert team of reporters and in-depth analysis in our special commemorative magazines. Have a subscription already? Set up your unlimited website access now

Laura Kraut’s top showjumping mare Nouvelle (pictured below) was on good form on the international circuit last September when problems set in.

“She’s always been a little flighty and inconsistent, but she jumped brilliantly in Los Angeles,” says Laura, who has owned Nouvelle for four years, since the KWPN mare was seven.

“After a short break we took her to compete in Stuttgart, where she broke out in such a sweat that she was covered in white lather within minutes. She didn’t jump well, but when the vet examined her and could find nothing wrong we thought perhaps she had been upset by the atmosphere at the show.

“Two weeks later we went to Paris. The moment I got on her she started to sweat and after jumping one small round I knew something was wrong.”

Nouvelle returned to the US, where scans revealed she was suffering from ovarian cysts. She underwent surgery in January to have both ovaries removed.

“One ovary was misshapen and not at all healthy,” says Laura, who brought Nouvelle back to fitness in spring and scored a big win with the mare at Windsor in June.

“It has taken a bit of time for her to regain confidence, as she was anticipating pain, but she’s now so much more relaxed and has none of the nervousness and tension that has been present throughout her career.

“I think the cysts had been bothering her for a long time. You can see in her eyes that she’s happier.”

A common problem

Nouvelle’s condition is rare, but highlights the fact that ovary problems can produce a range of physical and behavioural issues.

Emma Houghton MRCVS explains that enlarged ovaries are seen frequently within equine practice, for a number of reasons.

“Enlargement may be due to tumours, or very occasionally ovarian cysts. More commonly they are found as a result of a problem with the release of an egg from the ovary. They may also be a normal finding during pregnancy,” she says.

According to Emma, the most common ovarian tumour is the granulosa cell tumour, or GCT (pictured below).

“GCTs account for 2.5% of all tumours seen in horses,” she explains. “They are slow growing, benign and usually unilateral — that is, affecting just one ovary. They can occur at all ages, although the average age is 10.

“These tumours cause an increase in various hormone levels. The resulting hormonal imbalance can profoundly affect the mare’s reproductive behaviour and personality.”

Signs that a GCT may be present include:

• Persistent, irregular or absent oestrus (the mare’s season).

• Aggressive, stallion-like behaviour. Affected mares may strike out or attempt to mount other mares in the field, and in long-term cases may develop excessive muscle and a cresty neck.

• Occasionally colic, if the tumour is especially large and causes tension on the ligaments attaching the ovary to the abdominal wall.

• Low-grade lameness in the performance horse, or other vague signs of discomfort such as irritability when being ridden.

Reaching a diagnosis

“Granulosa cell tumours can be identified by an ultrasound scan during a rectal examination,” says Emma. “They typically appear as an enlarged, multi-cystic, honeycomb-like structure and can reach up to 40cm in diameter. The other ovary is often small and inactive.”

Emma points out that there is significant variation in the appearance of granulosa cell tumours, so vets will usually recommend a blood test to differentiate the tumour from other possible diagnoses.

“The blood test is now very accurate,” she says. “We usually request the measurement of a panel of hormones within the blood, comprising the anti-müllerian hormone along with inhibin, testosterone and progesterone.

“Other ovarian tumours include cystadenomas and teratomas, although these are not normally hormonally active and therefore behaviour is not usually affected.”

Treatment involves surgical removal of the affected ovary, a procedure associated with a good prognosis.

“Surgical removal is recommended, especially in mares that are showing abnormal behavioural signs,” says Emma. “The procedure can normally be performed by flank laparoscopy [minimally invasive keyhole surgery], under standing sedation, allowing for a quick recovery time.

“Mares typically return to their normal cycling hormone patterns between six and 12 months after surgery,” adds Emma. “They can be bred from the following year, and studies show that 77% of mares can continue to produce live foals.”

Could they be cysts?

Less common ovarian abnormalities include the ovarian cysts that Nouvelle developed.

“These cysts arise from the developmental tissue of the ovary or surrounding structures,” says Emma. “They may be identified as a solitary cyst or as a cluster of multiple small cysts around or within the ovary.

“Cysts can be diagnosed by palpation of the ovary via the rectum, and are often described as a freely movable structure a short distance from the ovary. They do not typically have a detrimental effect on fertility, but larger cysts may interfere with early pregnancy transport into the uterus.

“The larger cysts may also cause signs of colic or low-grade lameness, as they can place pressure on the ligaments that suspend the ovary in the abdominal cavity.”

However, ovarian enlargement is not always related to or caused by disease, and may be discovered during routine ultrasonography of the reproductive tract.

“Persistent anovulatory follicles can occur when a mare fails to ovulate during her cycle,” says Emma, explaining that an ovulation abnormality can result in an egg remaining trapped in the follicular cavity. “Ovarian haematomas are another common reason for enlargement, developing from an ovulation where the collapsed follicle fills with blood.

“Pregnancy also causes bilateral [affecting both ovaries] enlargement due to the normal waves of follicular growth that occur during gestation.”

Although there may be no obvious outward signs, ovarian problems could be the cause of behaviour changes or loss of performance.

“Writing a diary for your mare to identify behavioural patterns can help your vet identify if something is wrong,” adds Emma.

Ref: Horse & Hound; 16 July 2015

Top riders share their tips for beating the effects of hormones in competition mares

• Lucinda Fredericks has eight eventing mares in her yard, four of which are on Regumate.

She says: “Neither of my top mares, Brit [Headley Britannia] nor Prada, are on any form of medication — in fact, the year Brit won Badminton [2008], she was in season.

“Every mare is an individual; some are mareish, some aren’t, but, for those who are, I would always try them on Regumate.

“It doesn’t work in every case, but most of the time it gives them a little bit of help.”

• Richard Davison’s Olympic dressage partner Ballaseyr Royale was on Regumate when she competed in Athens 2004.

He explains: “When a mare comes into season she can be at a definite disadvantage, so it’s only fair that she should be able to be given medication to help put her on a level playing field competitively with the geldings.

“As far as the future is concerned, I would welcome any kind of scientific development that benefits a competition mare long-term, but it must not compromise their welfare — either now or later on in their career.”

• Helen Tredwell has never used any form of medication to manage oestrus in her top showjumping mares.

She says: “I have never found them a problem when they are in season. Neither Opportunity B nor Naomi V has ever been affected by their hormones.

“But if they were, I certainly wouldn’t have any hesitation putting them on a supplement.”

For the full article on managing competition mares, see the current issue of Horse & Hound (1 July, ’10)

Which hormone management techniques allow mares to be at their competitive best? H&H investigates

Regumate

Regumate is a synthetic progesterone-containing medicine that suppresses the behavioural signs of oestrus. It is administered orally on a daily basis.

Pros

• Proven to be the most effective hormone suppressant

• Now allowed under FEI rules (although paperwork must be completed with the FEI vet prior to competition)

• Should not compromise long-term fertility

Cons

• Costly — in the region of £30-£40 for a two-week course

• Must be given daily

• High risk of cross-contamination

• Must handle with care

Mare-bles

Mare-bles are glass marbles placed in the uterus to manage behavioural problems. It is thought that the marbles mimic pregnancy in the mare.

Pros

• Does not rely on medication

• When it does work, it is effective and does not appear to cause discomfort to the mare

• No risk of the cross-contamination you could get with some medication

Cons

• Not widely available in the UK

• Not always effective

• Undetectable from the outside, so could cause problems when horses change ownership

• Risk of uterine inflammation

Natural/herbal/homeopathic supplements

Various alternative remedies which are usually in the form of dried herbs or liquid added to feed.

Pros

• Cheap compared with Regumate

• Should not compromise long-term fertility

• A wide variety of products to choose from

Cons

• No ‘hard’ science to prove they work

• Risk of some of them containing banned substances

• Their effectiveness can vary greatly from mare to mare

For the full article on managing competition mares, see the current issue of Horse & Hound (1 July, ’10)

Mares frequently come to the vet with a history of behaving badly or being difficult to train or manage when they are in season (oestrus). Occasionally, mares may show stallion-like or nymphomaniac behaviour.

Some mares experience pain and/or colic during oestrus around ovulation. In these animals, medicines to alter their cycle can help, such as treatments to encourage the follicle to ovulate.

Hormonal products

Vets may be asked to supply a hormonal product to help. The only hormone that can effectively suppress the behavioural signs of heat is progesterone. In this country, only the synthetic progesterone–like drug Equine Regumate, which is an oil solution for oral use, is approved for use in horses.

To suppress signs of heat effectively, Regumate needs to be either given in the feed or syringed into the mare’s mouth every day. It may take several days to work and the oily solution can be tricky to administer, so owners must wear gloves whenever handling the product. Although it is the most commonly used method to suppress oestrus, behavioural problems may well recur following cessation of treatment.

Although Regumate has a product licence for use in horses, it is important to remember that it is regarded as a “prohibited substance” by the governing bodies of organisations such as the Jockey Club. This means that any horse must be off the medication for at least eight days before racing. Other organisations, such as the FEI, do permit mares to compete on Regumate.

Surgery

Surgical removal of the ovaries of badly behaving mares is recommended in some cases. Their reproductive cycle will, of course, cease but in several cases oestrous behaviour persists. The mare is permanently prevented from breeding and the surgery is expensive and not without risk. This drastic approach should be considered only after careful thought.

Vaccination

In Australia a vaccine is marketed to immunise the mare against the hormones responsible for the bad behaviour. This vaccine is called Equity and is used successfully to prevent bad behaviour.

A single injection will be effective for anywhere from six to 24 months. As far as is known, the vaccine is safe, although since it has been used for only a few years there is not enough information on any long-term detrimental effects on breeding.

Marbles

Placing a sterile 35mm glass ball into the mare’s uterus to suppress oestrous behaviour was first described Dr Gary Nie and his colleagues from North America in 2001.

There appears to be no discomfort, nor, from Dr Nie’s studies, any detrimental effects on future breeding prospects. Results so far indicate that around half of the mares were kept out of heat following placement of a marble.

The technique is not widely used in Britain at the moment, and Dr Nie has no figures on how wide its use is in the United States, but he believes that marbles are being used in many breeds and in many areas of the horse industry.

It is possible that there may be long-term effects on fertility, and owners must be aware of this before choosing the technique.

Other methods

Another approach would be to put the mare in-foal. However, a few pregnant mares will display behavioural signs of oestrus. After giving birth, the behavioural problems may reappear, and there may also be some loss of conformation following foaling.

Another potentially controversial technique was presented at the British Equine Veterinary Association annual congress. A number of mares were inseminated and scanned 18 days later. If an early pregnancy was detected, it was gently squeezed to rupture and destroy it. The corpus luteum (the part of the ovary that produces progesterone) persisted in all the mares and they remained out of heat for an average of three months.

This technique involves repeated examination of the mare prior to insemination and the need for a source of semen, presumably at some financial expense. Some owners may also not agree with the idea of aborting an early pregnancy for behavioural reasons.

This veterinary feature was first published in Horse & Hound (7 July, ’05)

It is easy to forget that mares are ‘entire’ animals and, as such, may be prone to hormonal imbalances. This can result in what is commonly known as ‘marish’ behaviour, which can sometimes make life difficult for owners and riders, particularly within the competitive sphere.

Around 10 per cent of mature mares suffer symptoms affecting their performance around the time of oestrus. Despite this, the syndrome is not well understood and there is little comparative research to enable owners and vets to choose the best treatment.

The symptoms

• Oestrus-related problems range from symptoms of pain, aggression and reduced willingness to work to signs of sexual receptiveness that are out of place in the competition ring.
• Affected mares may suffer from colic, or resent grooming or tacking up – they may also urinate repeatedly.
• Symptoms may be most marked during the first season of the year, or occur at every oestrus, but are normally absent in the winter, when most mares won’t come into season.

It is impossible to know for sure what mares feel as they ovulate, and much evidence relating to ‘marish’ behaviour is anecdotal. However, a proportion of women experience pain linked to ovulation and some mares suffer otherwise unexplained colic at this time, suggesting that ovulation may be painful for them, too.

Another potential source of pain during oestrus is traction on the ovarian ligament, caused by a 4-5cm diameter follicle (egg) hanging into the abdomen. This is usually seen in older mares, as they have heavier ovaries and longer ovarian ligaments.

The hormones associated with oestrus may also cause some of the symptoms. Increased oestrogen acts on the behavioural centres of the brain to induce sexually responsive behaviour, and may be linked to greater sensitivity or aggression. This may reflect the fact that the mare’s biological drive during oestrus is to mate, overriding her training and her willingness to perform.

Supplementation as treatment

The most common treatments for marish behaviour are herbal or food supplements. Most contain a mixture of herbs, including some that have a mildly sedative effect and others thought to act on the hormonal system. For example, the chaste tree berry (a common ingredient) is thought to act on the pituitary gland to suppress seasonal activity.

The problem with herbal supplements is that it is difficult to know which mares will respond to which product – it can be worth trying several over time to see which works best for your horse.

Bear in mind that some products contain substances banned under FEI or Jockey Club rules, so they should not be used in competing mares unless the manufacturer can guarantee that they comply with regulations.

The most effective treatment is to prevent seasons, thus avoiding both the hormonal and physical effects. There are a number of possible methods, with more being developed. Most either suppress oestrus behaviour altogether or mimic pregnancy, which in turn suppresses symptoms.

The ‘equine pill’ option

Regumate Equine is an oral, hormonal treatment that mimics progesterone (which is released during pregnancy) and acts to prevent oestrus.

A recent ruling stated that it may be used in horses competing under FEI regulations, and as a result its popularity is set to continue. However, withdrawal of this medication results in the resumption of normal cycles, so prolonged daily treatment is needed for ongoing oestrus prevention.

A recent development in the USA – likely to appear soon in the UK – is a long-acting injectable progestagen (a substance that mimics progesterone), which achieves the same results as Regumate, but requires just one injection every two weeks, reducing costs as a result.

Ongoing research has resulted in the development of an anti-GNRH (a hormone linked to reproduction) vaccine that aims to prevent oestrus. Although still at the experimental stage, this treatment may offer hope to affected mares in the future.

Some owners find that using a low dose of phenylbutazone (bute) around the time of oestrus can reduce pain and inflammation, although this cannot be used in mares competing under FEI or Jockey Club rules.

Long-term management

As the symptoms of ovarian pain tend to become more marked with age, and are generally not associated with any underlying problem or disease process that needs to be cured, affected mares often need ongoing treatment to allow them to continue to work.

Finding the appropriate medical and management methods that regulate the symptoms for your particular mare is the key to long-term management. Rest around the time of oestrus is also an option – after all, wouldn’t you rather stay in bed?

The normal oestrus cycle

• The normal mare cycles regularly every 18-24 days between April and October, with longer periods of oestrus at either end of this timespan.
• The follicular phase lasts around four to six days: the hormone GNRH is released from the brain, stimulating the ovaries and causing the development of ovarian follicles (eggs).
• The oestrus period lasts around three to five days in mares: one or two follicles dominate and develop until they measure around 4-5cm in diameter. A surge of oestrogen from the ovaries prompts ovulation, as well as inducing sexually receptive behaviour in the mare. The egg then travels to the fallopian tube and awaits fertilisation.
• The luteal phase lasts around two weeks: a corpus luteum (progesterone-secreting mass of cells) forms from the remnants of the ovarian follicle after the release of a mature egg. The release of progesterone delays return to the follicular phase of the cycle. In the absence of conception, the corpus luteum regresses after around two weeks and a new follicular phase begins.
• If conception occurs, the one- to two-week-old embryo induces hormones
  to increase the longevity of the corpus luteum, maintaining pregnancy and preventing oestrus.Controversial techniques
  Roberta says: “An alternative method for controlling marish behaviour is now available that involves creating an unwanted pregnancy in the affected mare (usually by artificial insemination), then preventing development of the embryo from about 16-17 days of pregnancy by ‘nipping’ it during a rectal examination.“This method suppresses seasons for three to four months and can be repeated to prolong the effect. It works because in the second week after conception, the developing embryo induces the mare to produce hormones that maintain the false pregnancy for the first trimester, even if the embryo does not survive beyond this time.“In the USA a few years ago, an attempt was made to mimic a three- to four-month false pregnancy by inserting a marble into a mare’s uterus. The theory was that it could induce hormones that maintain pregnancy, like an early embryo. However, it carries the risk of infection and of creating adhesions in the uterus. Also, the marble may be difficult to recover, so the treatment is not recommended.”Steps to take if you think your horse suffers from ‘marishness’
• Call the vet and get a full health check and rectal examination of your mare’s reproductive system.
• Follow that up with an ultrasound scan of her ovaries.
• Discuss blood tests to detect hormonal levels with your vet.

Begin appropriate treatment based on the type and severity of your mare’s symptoms and her intended level of performance.

Q: I own a six-year-old 15.1hh Thoroughbred mare who is good-natured until I try to groom her. She becomes irritable and fidgets when I brush her, often trying to bite me, and has occasionally lifted her back leg and threatened to kick me. How should I deal with this problem and how can I encourage her to relax and enjoy being groomed?

Liz Clemence replies: Maybe rough grooming in the past has caused your horse’s apparent dislike of this activity, or she may have a physical reason causing her discomfort. It might simply be that, like many well-bred or fine-coated horses, she has sensitive skin and finds the brushes irritate her.

Sensitive handling should help to build her trust. Do not groom your horse for any longer than necessary. Remain calm and be sympathetic but firm when you are handling her. She must be made to realise that kicking and biting is not an option.

Avoid sudden movements and talk to her soothingly if she becomes agitated. For best results, groom your horse after exercise when she is warm and her pores are open.

She is also less likely to fidget once she has been worked.Tie her up in a suitable place, away from draughts and on a fairly short lead, so she can’t bite you. Put a rug over her quarters to keep her warm.

Groom her using a natural bristle body brush. Avoid hard or plastic-bristled brushes and take care brushing bony or sensitive areas.

A goat hair body brush is soft and ideal for use around her face and sensitive areas.

Alternatively, wash the worst of the sweat from dirty areas, using a sponge and warm water, then brush when dry.

Giving her a small haynet to eat while you are grooming may help.

Read more horsecare advice:

• Q and A: Getting to grips with grooming
• Q and A: Improving a messy mane
• Q&A: Perfect pulled tails

Q: I have owned my New Forest mare for nearly a year. Over the winter, when she is just ridden at weekends as opposed to every day in the sumer, she becomes extremely stroppy and moody.

She tries to bite me when I do up her rug or girth and when I go into her stable. I have tried tapping her muzzle or neck and saying “no” to her, but this just seems to makes her angry. What can you suggest that I do?

Equine psychic Gaynor Davenport replies: Firstly, I’d get your mare’s teeth checked and ask your vet to examine her to rule out any medical causes.

I have found in my work that mares often suffer from SAD (Seasonal Affective Disorder), ie depression in the winter months caused through a lack of light.

Your mare could be suffering from this problem since she only developed behavioural problems in the winter months. Watch her closely and see if she improves in the spring and summer.

Massaging can be extremely useful, especially combined with essential oils. Try massaging gently from her girth towards her heart in small circles. Use lavender oil, which has a calming effect, in a carrier oil such as sesame seed (preferably organic). Dab a little of the lavender each side of her withers and under the saddle area.

It’s worth remembering that if you cut back on her workload, you should alter her feeding programme accordingly. Ask for advice from a feed company .

If you try the above and she doesn’t improve, talk to an equine behaviour expert.

Chaste berry is a plant which grows naturally in an area from the Mediterranean to Western Asia, however in the 16th century it was widely grown in England because of its potency.

Chaste berry (or agnus castus) is part of the vervain family of plants and is an aromatic shrub with long spires of pale lilac flowers and small grey/brown hard fruits (which look similar to black peppercorns).

This plant can be found growing next to water, particularly fast flowing streams, but also grows indry rocky areas on the Greek and Italian coastlines.

Chaste berry has been used for medicinal purposes since approximately 400BC. The Greeks and Romans used the plant for women¨s hormone imbalance and around 900AD this herb was widely used in the Middle East, especially in Persia and Egypt.

In the 15th century, as herbalism gathered pace, many references to chaste berry can be found throughout Europe.

Gerard, one of the great herbalists of that time, encouraged the use of agnus-castus asa “female herb” and stated that “the seeds are good against pain and inflammation of the uterus”.

More recently a great deal of research has been carried out in Germany. According to Dr Rudolf Fritz Weiss, chaste berry acts on the hypothalamus andpituitary. The pituitary gland regulates the other glands of the body, including the sexual hormones.

It is known that agnus-castus can decrease the oestrogen balance in the body.

Using chaste berry on horses

It has been known for some time that mares suffer from PMS prior to and during their “seasons”.

This can cause irritability, aggression and general unpleasantness in the mare and makes riding during this time difficult.

Agnus-castus given just before themare¨s season commences, and continued through each season can have a dramatic effect on the mare.

While there is no guarantee that it will work in all cases, there is evidence to suggest that where unsociable and aggressive behaviour is brought about through PMS and hormone imbalance, chaste berry can help.

Information supplied by Equine Health & Herbal, manufacturers of Hormonise. For further information contact Equine Health & Herbal on (tel: 01787 476400) or visit www.equinehealthandherbal,co.uk