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Fat horses rule

A study by UK scientists has revealed a strong correlation between dominance and body condition in horses kept in groups at pasture.

The experiment involved more than 200 horses of mixed breeds, sizes and sexes in over 40 social groups, but no stallions. Every herd or group was living out full-time in winter.

During the study, all horses in the group were simultaneously given a bowl of food or pile of hay. Each feed station was far enough away from other horses to avoid problems with kicking. The groups were filmed and video footage analysed.

As expected, certain individuals finished their rations quickly and then moved on to approaching other horses that were still eating. By recording signs of dominance — such as ears back, head outstretched and bared teeth — and also signs of submission, such as moving away from the food as a more dominant horse approached, the scientists were able to rank horses for dominance.

They then analysed every horse or pony for age, sex, height, colour, breed, body condition and other factors. The strongest indicator of dominance was body condition. Animals that were in good condition or obese tended to be most dominant, irrespective of anything else.

Other, weaker correlations were observed. Middle-aged horses were generally more dominant, and there was less squabbling over food in groups where all the horses were about the same size. Overall, however, fatness was the best indicator of bossiness.

Are fat horses more dominant because their temperament always gets them the best grub? Or perhaps thinner horses perceive that fatter ones are more successful and just give in to them?

Could it be true?

Vets from Connecticut investigated whether the position and type of hair whorl on a horse’s forehead of a horse could be linked to his personality.

Experienced trainers assessed 12 horses and recorded their personality traits. Each horse was assessed by more than one trainer.

When the horses’ frontal whorls were analysed there was statistical evidence that whorl type and position either was, or was likely to be, an indicator of temperament. The study was very small and results were not absolutely conclusive, so more is being done to look into this. If it turns out to be correct, it’s an extraordinary finding.

Does Cushing’s disease predisposed to infection?

Horses with Cushing’s disease (pictured) the pituitary dysfunction now called PPID, tend to be more prone to infection than healthy ones.

For some reason horses affected by this hormonal condition have lower or less efficient levels of immunity against bacteria and viruses. We have not properly understood the reason for this link – why should an endocrine, metabolic disease make them more prone to developing a respiratory, skin or gut infection?

Certainly, PPID occurs more frequently in older animals and in ponies rather than horses, but generally ponies are more robust and less likely to get infections. There is no reason to think that middle age itself is a risk factor for infection.

Scientists in Oklahoma took blood samples from horses and ponies with PPID and extracted their white blood cells in the laboratory. White blood cells are an essential line of defence against infection; to engulf and gobble up invading bacteria and viruses they have to be able to find and to stick to the foreign invaders and to produce substances that kill the pathogens.

Horses with PPID do not have fewer white blood cells, but the scientists were able to show that these cells from affected horses had depressed abilities. In particular, their adhesion to foreign material was lower and their ability to produce a burst of zapping chemicals was impaired.

It looks as though some of the abnormally high levels of pituitary hormones circulating in horses with PPID are reducing the efficiency of their white blood cells and allowing infections to become established.

Ref: Horse & Hound; 9 July 2015