Overnight stabling of horses who spent their days on pasture appeared to have a positive effect on chronic stress levels, researchers in Italy report.
Scientists with the University of Milan have reported on the results of a study of 47 leisure horses whose levels of the stress hormone cortisol were monitored in their hair during a year-long study.
Silvia Michela Mazzola and her fellow researchers, writing in the journal Animals, noted the growing priority placed on meeting the behavioral needs of horses.
“There is growing awareness that stabled horses may be deprived of opportunities both for social contacts and the possibility to perform natural behaviors, limited by stable designs and insufficient box dimensions,” they said.
The researchers described an experiment centered on three stables in the Lake Garda region of northern Italy, based on three different horse management strategies as chosen by horse owners.
In Stables 1 and 2, horse owners could choose whether to allow their horse to spend most of the day at pasture in social groups of about 10 individuals. Each evening, the horses were taken back to their individual boxes, where they received their ration of hay and feed and spent the night. The authors referred to these horses as the mixed management group.
Alternatively, the horse owners could opt to permanently leave their horse in the paddocks, including overnight. In other respects, these horses were cared for the same way as the mixed management group. They received hay and feed, and similar veterinary care. These horses formed the paddock group.
The third group was inspired by the principles of natural management. The horses lived in a herd on six hectares of land, wood, and olive groves. Two natural ponds allowed horses to access water. There were three sheds, open on one side, which offered shelter to the animals, and four hay racks were distributed well apart to encourage the horses to move. Subjects that required additional concentrate feed wore a computer chip around their pastern that was read by the automatic oat dispenser to deliver the appropriate amount of food daily. These horses formed the natural management group.
The horses across all three groups were similar in terms of sex and age.
In the experiment, hair samples were collected on the same day from all the horses four times during a year, once for each season.
Hair cortisol concentrations, considered a reliable marker of long-term (chronic) stress, were analyzed.
The researchers found that the highest hair cortisol values were detected in the autumn and summer, regardless of the horse management strategy used, and levels were also significantly higher in individuals older than 15 years. The hair cortisol concentration was not influenced by horses’ sex or coat color.
However, the comparison of the different management strategies showed that, in the summer, autumn, and winter, the hair cortisol levels were significantly lower in horses who spent the night in stables.
“Spending the night in the stables would seem to impact the well-being of the horses positively, and this could be related, at least in part, to the sleep quality,” the study team said.
“Sleep is an essential facilitator of physical well-being and optimal mental functioning, especially when we consider that horses, being large prey animals, sleep for an average of only three hours a day.
“Our results demonstrated that, for horses that spent the day grazing, with social interaction and free to move, stabling could represent a nocturnal environment that promotes sleep.”
Multiple factors could negatively influence the well-being of the horses spending the night in the paddock. These include the weather, ambient temperature, insects, or interactions with other horses.
They suggested that the lack of differences seen in the spring could be related to the mild climate of this season in this particular area of Italy.
The authors noted that some of the mixed management horses wore a blanket continuously during the coldest months.
“Although the number of subjects was limited, the statistical analysis revealed that those without blankets had statistically significant lower hair cortisol levels.”
It is possible that, not being exposed to particularly demanding thermoregulatory challenges, horses experienced the blanket more as a limitation in movement than a thermal benefit, they said.
The researchers said the higher cortisol concentrations found in horses aged over 15 could be related to the lower ability of elderly subjects to cope with stressors, which is why older horses should be even more carefully managed.
In conclusion, the authors said the growing awareness that leisure horses’ welfare is related to the satisfaction of their behavioral needs makes it increasingly necessary to investigate the question from a scientific perspective.
“At present, due to the lack of scientific literature about the effect of management on horses’ welfare, breeders, stable managers, and owners can only rely on experience and common sense.
“This is the first study that has shed light on the relevance that some management variables, so far scarcely considered, could have on horses’ homeostasis using the hair cortisol concentration, a reliable and noninvasive indicator of chronic stress in the species.”
The findings, if confirmed by further studies, may be useful to enhance horse welfare and assist in management choice decision-making, they said.
The study team comprised Mazzola, Carla Colombani, Giulia Pizzamiglio, Simona Cannas, Clara Palestrini, Emanuela Dalla Costa, Alessia Libera Gazzonis, Arianna Bionda and Paola Crepaldi.
Mazzola, S.M.; Colombani, C.; Pizzamiglio, G.; Cannas, S.; Palestrini, C.; Costa, E.D.; Gazzonis, A.L.; Bionda, A.; Crepaldi, P. Do You Think I Am Living Well? A Four-Season Hair Cortisol Analysis on Leisure Horses in Different Housing and Management Conditions. Animals 2021, 11, 2141. https://doi.org/10.3390/ani11072141