Palomino Genetics

I was chatting to some old friends (not old old; we just go back a long way) and we were discussing chestnuts and their sensitivity, and then started to discuss how palominos can be equally quirky. We could remember that there was a genetic link between the two colours, but after that it all became a bit vague.

I needed to lay my mind to rest, so thought I would share my research with you.

This is genetics at their very basic level, so apologies to any readers who are more versed in it.

All horses start out genetically as either a chestnut, or a black horse. A chestnut horse does not have an extensor gene (so is referred to as ee), whilst a black horse does (so is either referred to as EE or Ee). What the extensor gene does, I’m not sure, but this is after all very basic!

From here, the Agouti gene modifier works on the black horse to create the bay colour. Bay, along with chestnut and black, forms the three basic colours from which all other equine coat colours are derived, with the help of additional genes.

A palomino horse, which is my main focus of this blog, is a chestnut colour (lacking the extensor gene) with one cream dilution gene. This gene causes the red coat to lighten to a yellow colour (anywhere from very light creamy colour, to golden, to an almost chocolatey colour) and for the mane and tail to be white.

Have you heard of the colour “chestnut with a flaxen mane and tail”? This colouring is different from palomino, although they can look similar to the bystander. There is a flaxen gene, which only works on chestnut horses, and lightens their mane and tail so that it is lighter than their body. The coat of the horse is still red, as opposed to the yellowy colour of a palomino.

Equine coat genetics are complicated. I’d like to know more, but even just visually categorising coloured horses into tobiano, overo, tovero gets me in a muddle. I do find it interesting that palomino and chestnut horses have such similar colour genetics, and I’m sure these genes are linked to other genes which contribute to other areas of their personality, giving chestnut mares particularly, a bad name. Perhaps it is that the chestnut coat genes are linked with thinner, more sensitive skin, which can cause problems with ill fitting tack and rugs, or rough handling or riding, which gives the chestnuts the bad name. Perhaps the gene which gives chestnuts thinner skin (don’t ask me where I read that article, but I did whilst researching the chestnut mare myth) is also prevalent in palominos, which could explain why some palominos have that feisty reputation.

Or perhaps it’s just down to the way they’ve been brought up and managed…

Maybe I’ll see if I can find an equine genetics book for dummies to read.

Chestnut Mares – Fact or Fiction?

Everyone groans when you mention chestnut mares. I saw someone I hadn’t seen for a couple of years today and we were updating each other on our equines. When I mentioned that Phoenix was a mare, she groaned. And when I mentioned that she was chestnut, she groaned again.

It really does seem like chestnut mares are all tarnished with the same brush, and widely regarded as melodramatic, emotional, high maintenance sociopaths.

So tonight, I thought I’d look into it.

Firstly, I guess is the fact that mares are considered harder to handle than geldings. You know the saying …

Tell a gelding. Ask a stallion. Discuss it with a mare.

Geldings are usually the most docile to handle because they have the least hormones affecting their mood. Mares have their ovulation cycle which causes a fluctuation in hormone levels, which can cause them to become more emotional and affect their behaviour. Exactly the same as with humans females! And just like with humans, some mares are more affected by their oestrus cycle than others.

So mares can be more sensitive and delicate to handle than geldings, but this applies to all shades of mare, but to what extent depends on the individual and their hormone levels.

Next up, is the chestnut aspect. I did have to look this up. One gene, the extension locus, determines whether a horse is chestnut, black or bay by altering the production of black versus red pigment. The gene has no influence on temperament at all.

There are a number of other coat colours that are a modified version of chestnut which we don’t associate with quirkiness – strawberry roan, palomino, cremello, skewbalds. These colours are all identical at a genetic level, at the extension locus to chestnut horses. And the extension locus is the only thing which makes a solid chestnut horse different to a black or bay in the first place.

This means that there is no genetic reason for a chestnut horse to be more sensitive than other colours. I read a saying in my research, which seemed very apt.

A good horse has no colour,

Perhaps it is our prejudice of redheads being volatile that is projected onto chestnut horse, which causes us to behave differently towards them and to expect then to be more flighty?

Then I remembered an article I read a couple of years ago about skin colour and sensitivity. It is said, although I can’t find any scientific research, that chestnut horses have thinner skin so are more prone to tack sores and more affected by flies and skin problems, such as rain scald. I’d like to see more convincing evidence rather than just observations before making a conclusion.

In my experience with Phoenix, the chestnut mare adage doesn’t hold true. She doesn’t seem to suffer mood fluctuations due to her hormones, nor do I feel that I have to negotiate work with her any more than other horses. I don’t think she’d like to be told what to do like a gelding, but that’s not really the approach I take to riding anyway. I would say that she does seem to have sensitive skin, much preferring the soft body brush rather than a dandy brush, even on her woolly hindquarters. Her summer coat is far thinner and finer than Otis’s, which could be colour-related genetics, or just her individuality. Either way, I don’t think she, or any chestnut mare, deserves the reputation that equestrians give them. Prejudiced handlers have a set of expectations from chestnut mares which can cause them to be put in situations where they will behave unfavourably, and shape their behaviour to meet their expectations which creates a self fulfilling prophecy. Unfortunately I think it is a case of a couple of hormonal, temperamental mares, perhaps with very sensitive skin which causes tension or pain, who just happened to be chestnut, creating a bad name of chestnut mares everywhere. So yes, buy a chestnut mare, but remember to have your eyes open to their sensibilities,