How to organise and manage groups of horses ?

To be successful when managing groups of horses, it is important to take into account a horse’s behaviour in a natural free-roaming environment.

A family in a free-roaming environment is composed of an adult stallion, from one to three mares from different families and of their prepubescent younsters. It is therefore a rich social environment, which surrounds the youngster during his development. Horses who are not socialised when very young, have not acquired any social competences.

Dominance relationships between youngsters are not very clear. The presence of adults in a group of younsters is important, as the lower the ratio of adults to younsters, the stronger the agressive behaviour between younsters, thus demonstrating the moderating role of adults.

Family stability is based on the links created by the mares, and the constant rounding up of his  mares by the stallion. Relationships between females are mainly characterised by maintaining their hierarchical rank during slightly agonistic (=aggressive) interactions and through mutual grooming. Within a group, horses generally have one to three favorite partners, with whom they are most often observed, or with whom they carry out mutual grooming.

Provide sufficient space for the size of the group

• Modification in the relative proportion of types of behaviour observed ;
• Disappearance of some types of behaviour.

This can be seen as a deterioration of the horse’s well-being. In addition, social relationships are disrupted, with an increase in aggressive behaviour or in avoidance techniques, while reducing positive social behaviour (= affiliative).

Thus, in a group of mares kept on high density paddocks (44 mares, with 50m² per mare) and where fodder is not constantly available, some behavioural traits like lying down, rolling and mutual grooming are hardly ever observed. The most observed behaviour is movement, which then represents : 27 % of the horse’s time, 18 % being active movement, which is high compared to herds in free-roaming conditions. On the other hand, the time spent eating is much lower : 26 % (54 % to 69 % in free-roaming conditions). With regard to social relationships, only negative social reactions remain (2,5 per mare per hour) with no positive interactions.

When the size of the enclosure is increased (85m² per mare), a few positive social interactions appear, particularly mutual grooming (less than once per mare per hour), but the number of agonistic interactions remains high.

When using even larger fields, over 300 m² per mare, aggressions tend to disappear completely.

The size of the shelter should also be adapted to the number of horses, so that they can all lie down, including the most dominated horse.  The minimum size is different depending on whether it follows statutory rules (e.g 7m2 per horse of 1m65 in the Swiss ruling) or recommendations  based on research (11m2 to 16m2  for a horse of the same size).

Provide resources in sufficient quantity

The best solution is for horses to have constant access to fodder : grass or hay. Limiting resources can, in fact, lead to an increase in agonistic interactions, inversely proportional to the time when fodder is available. Aggressivity also increases depending on how fodder is distributed, and appears to be higher when it is distributed on the ground than when in hay nets or racks.

It is also important to make sure that the horses with the lower ranks in the hierarchy also have access to a resource, otherwise thay may not be able to feed properly, take this into account and allow more feeding space per animal.

Organising the composition of a group

Again it is best to try to keep close to natural conditions, where cohesion is established by the family structure, and where aggressivity is lower in permanent harems. Yet, as a general rule, on stud farms groups are made up of mares with foals, younsters, stallions are isolated, mares and geldings are seperated to avoid any semblance of sexual behaviour.

It is therefore recommended to integrate adult horses into the groups of youngsters to promote social learning situations and recognition of hierarchy. This enriches the behavioural repertoire, promotes positive social interaction, and reduces negative behaviour.

Raising a foal alone with his dam is not ideal, as she will be naturally more tolerant with him. For the organisation of a riding school or a livery yard, it can be a good idea for the daily running of the structure, to put horses who work together out together.

Adapt the size of the groups

Whether domesticated or free-roaming, the aggressivity rate and amount of movement are higher when the size of the group increases : for domestic horses , 8 horses versus 11 versus 23, for Przewalski horses 4 versus 13. Moderate size groups of between 4 to 6 horses are recommended by some authors.

Ensure group stability

In a stable group, aggressivity levels, approaching, withdrawing, and total number of interactions are constant throughout the year. On the other hand, when the groups are often changed, even with horses who know each other, there is far more agonistic threatening behaviour, even if there are few resulting injuries. Over the weeks, if changes keep on occuring, the horses cannot get accustomed.

First contacts between unfamiliar horses often lead to aggression, as it disturbs the group structure, with horses trying to find their place, or defending their old position in a hierarchy.

The different advice found in different reference books all seem to converge : it should be done gradually. When it is to put two horses together, it is suggested that they be placed in two loose boxes next to each other, where they can establish contacts, then in two adjacent paddocks before turning them loose together. When it is integrating a new horse into a previously formed group, several different organisations have been tested :

(1) Place the new horse and one of the horses from the previously formed group together in a paddock adjacent to the rest of the herd for 1 to 7 days, before putting both horses into the herd ;

(2) Introduce the new horse immediately ;

(3) Introduce the horse after he has spent 1 to 7 days alone in an adjacent paddock.

The first suggestion induces the lowest aggression rate. The social rank is very quickly determined after the introduction, and remains stable.

The experiment of putting stallions in a group was conducted by the Agroscope team from the Swiss national stud in Avenches. The Franche Montagne stallions aged between 8 and 19, were firstly stabled next to each other for two weeks, where they could interact thanks to open partitions. They were then unshod, and put together in groups of four to five, in a large 4 ha field. The number of aggressive interactions decreased over the 21 day observation period from 20 per stallion per hour to almost 0. At the same time, the number of affiliative interactions (mutual grooming and play) increased from 0,2 to 0,4 per stallion per hour. The authors insist however on a number of necessary precautions : the stallions should be isolated from the mares, with solid fencing, and should be unshod.

Another experiment consisted in introducing a stallion to a group of 7 mares. The stallion was first placed in the mares field alone for a month, then the 7 mares were reintroduced, one by one, over a two month period. The order in which the mares were reintroduced was chosen with regard to their temperament, to their position in the hierarchy, to their centrality (number of other mares they are connected to) and their aggressivity. The first mare was the one with the following criteria : most centrality, less herd instinct, less aggressivity, and less dominance.

This is a stressful moment for the horse. This was brought to light by measuring the rhythm of cortisol on mares who had been previously backed, and who were observed for 4 days before and 5 days after their transfer from their social group to an individual stable. The morning of the transfer, cortisol rates were multiplied by three, and the rhythm remains dirupted for the 5 following days, even though it gradually goes back down.

A recent experiment showed that isolating a young horse from his social group was less stressful (measured from heart rate) when carried out with another horse from the group. It therefore appears to be advisable not to associate stabling with isolation, but to stable two horses from a same group in adjacent loose boxes.