According to a team of British researchers*, the more dominant the horse, the more likely it is to have a higher body condition score or struggle with obesity. This finding was established after observing 203 domesticated horses in a feed test. The horses were divided among 42 herds in the UK and lived outdoors. The feed test consisted of offering individual portions of hay or concentrates, spaced one horse-length apart. The feed was given in the paddocks at the same time and it was then measured how often the horses moved between the feeding points. Ranking was then determined by those movements (the number of times an individual was moved from the feed vs. the number of times the individual moved another horse from the feed). Ages, height and body condition score (BCS) were measured for each horse. 

The main findings of the study were as follows: 

• The mean body condition score of the horses in this study was 5.53 on a scale from 1 to 9 
• 17.24% of the horses were overweight (BCS of 7 or higher) 
• A strong relationship was found between dominance and BCS, which means that as soon as the ranking went up, the BCS also rose. In fact, the rank was 11 times higher in overweight horses than in non-overweight horses 
• Smaller horses (ponies) were more likely to be overweight 
• Middle-aged horses were more likely to be dominant than young or old horses 
• Height (at the withers) did not affect dominance 

“This study found a lot of obesity in the horses that live outdoors, as well as a higher rank in overweight horses. When you take into account the negative relationship between obesity and health and the increased risk of nutrition-related problems, it is important to understand more about the social and behavioural factors that influence body condition.” Says Peter Huntington, B.V.Sc., M.A.C.V.Sc. director of nutrition, Kentucky Equine Research (Australia). 

This research is interesting for a number of reasons. First, this research shows that the BCS influences dominance more than other factors such as height. Second, the researchers indicated that dominance in horses is very context-specific, meaning that a horse can be dominant in a nutrition-related situation, but may not be dominant when it comes to other situations such as finding shelter. Third, this study found that herds that had less variation in age and height had more interactions (such as kicking, biting, moving). Putting horses of comparable age and height together is often common practise. This research suggests that when horses of different ages and breeds are kept together, they are more likely to engage in friendly social interactions. 

* Giles, S.L., C.J. Nicol, P.A. Harris, et al. 2015 Dominance rank is associated with body condition in outdoor-living domestic horses (Equus caballus). Applied Animal Behavior Science 166: 71–79. 

Source: http://www.equinews.com/article/obese-horses-likely-be-more-dominant