Effect of mares’ dominance rank on suckling behaviour in the loose housed domestic horses

Suckling is a main part of maternal investment in equids. The suckling period is crucial for adequate physical as well as psychical development of the foal. The rank of the mother and her aggressiveness could be factors responsible for later reproductive or social success of the foal. We hypothesised that under conditions characterized by balanced diet adjusted to the needs of lactating mares, but limited space, that the dominance relationships and agonistic interactions among mares are responsible for differences in suckling behaviour which cannot be explained by the foal's age. The studied animals were eight groups of loose-housed lactating mares with foals of Kladruby horse. In total, 79 foals (32 males, 47 females) were born to 59 individual mares within two seasons. Not frequency, but suckling bout duration was correlated to the dominance rank of the mare (P < 0.01). In addition to lower direct intervention by subordinate herdmates the longer suckling bouts in higher ranked mares reflected higher amount of maternal care the mare provides to her foal. In our study, mares which were more frequently targets of interventions by their dominant herdmates during suckling were also the younger ones (P < 0.05). This further supports the role of dominance relationships in alteration of suckling behaviour. Nevertheless, from the practical point of view, the mares’ aggressiveness towards other adult herdmates was low and not severe. As such, according to the horse management, it seemed to have only limited practical impact on suckling behaviour in the herd. From this point of view loose housing could be recommended as appropriate housing, even for lactating mares with foals.