Horses appear to prefer the great outdoors during cold and dry conditions, but significantly increased their use of available man-made shelters in wet and windy conditions, a Norwegian study has shown.
Grete Jorgensen and her colleagues said horses may adapt to a wide range of temperatures and weather conditions, but owners often interfered with this natural thermoregulation ability by clipping and the use of blankets.
Some horse owners provide shelters in the paddock in the expectation horses will use them in bad weather. Interestingly, free-ranging horses monitored in other research sought shelter mainly from insects and the sun on hot days. Domestic horses used man-made shelters in a similar way, but also during heavy rain and low temperatures.
The study team set out to investigate the effects of different winter weather conditions on the shelter-seeking behaviour of horses and their preference for additional heat. They conducted their experiment in the northern part of Norway, not far south of the Arctic Circle.
During the experimental period in 2013 the average air temperature was 0.5 degrees Celsius, with a range -8.7 to +11°C. During the 2014 experimental period, the average temperature was 2.9°C.
Twenty-two privately owned mature horses and ponies of different breeds and sex were used in the study. The horses were categorised into five breed categories according to the presence of Warmblood and Coldblood characteristics, as well as their height, weight and body condition score.
Hair coat samples were also collected from a 3cm by 3cm area above the gluteal muscle. The samples were dried and weighed, and each was assigned as being either low weight (less than a gram), medium (1–2g) or high (over 2g).
The uncovered horses were given a free-choice test between staying outdoors, going into a heated shelter compartment, or into a non-heated shelter compartment.
The two compartments were 11 metres by 11 metres and made of wood and corrugated iron. Both had lights, and a 1.4 kilowatt infrared heater was installed in both, but was only turned on in one of the compartments at a time, and randomly changed to prevent horses from choosing them based on preferred position, rather than the presence of additional heat.
Each horse’s preferences were observed once a day for an hour during the study period. Weather factors were continuously recorded by a local weather station.
Weather conditions influenced time spent outdoors, ranging from 52% of all observations on days with mild temperatures, wind and rain to 88% on days when it was both dry and the temperature was below 0°C.
Shivering was observed only during mild temperatures and rain or sleet.
Small Warmblood horses were observed to select outdoors less (34% of all observations) than small Coldblood horses (80%).
The researchers found significant correlations between hair coat sample weight and the number of observations outdoors.
“Horses selected shelters the most on days with precipitation and horses changed from a non-heated compartment to a heated compartment as weather changed from calm and dry to wet and windy,” the study team reported in the Equine Veterinary Journal.
“Horse breed category affected the use of shelter and body condition score and hair coat weight were associated with voluntary shelter selection.”
Discussing their findings, they said that, for most of their observations, horses chose to stay outdoors, and individual horses used the shelter to different degrees regardless of weather.
“Significantly more horses were observed outdoors during cold and dry weather compared to days with mild temperatures, precipitation and wind.
“This corresponds with other studies on horse use of shelters.
“By dividing weather factors into ‘dry’ and ‘wet’ weather, we also found that horses were located outdoors significantly more often in dry weather than on days with rain or snow.”
The average proportion of time spent in the heated compartment was 50.7% and it was 49.3% in the unheated compartment, indicating no specific preference for the heated compartment.
“During rain, the preference for the heated compartment was most marked,” they reported. They found that small Coldblood horses spent more time outdoors than small Warmblood horses, and small Warmblood horses were observed in the heated compartment significantly more often compared to small Coldblood horses.
“This is not surprising, as heat loss is dependent on breed-related properties such as subcutaneous fat deposits and hair coat thickness.
“Looking at the extremes within the weather factors, we observed that large Warmblood and large Coldblood horses shifted from using non-heated compartments in calm and dry weather to heated compartments in severe winter weather with precipitation and wind.
“Both precipitation and wind will reduce the animals’ cover insulation. Water may also cause the hairs to mat together and hence reduce the cover depth and replace the still air close to the skin with water.”
Horses with heavy hair coat sample weights spent more time outdoors, they noted.
“The hair coat provides protection against the elements and its insulative value increases with weight density.
“Clipping this hair coat renders the horse without its basic protection and blankets are, at best, a poor replacement.
“Providing a shelter in outdoor enclosures might therefore be a better management solution than extensive use of blankets, allowing horses with intact hair coats to self-adjust their heat loss to the environment, as weather changes rapidly during the course of the day.”
Behaviours indicating possible discomfort, such as standing tensely and shivering, were rarely observed.
The study was funded by Stiftelsen Hästforskning, a joint Swedish and Norwegian horse research fund, administered through the Norwegian Research Council.
The researchers were variously affiliated with the Norwegian Institute of Bioeconomy Research in Tjøtta, the Norwegian Veterinary Institute in Oslo, and the Norwegian University of Life Sciences in Ås.
Jørgensen, G. H. M., Aanensen, L., Mejdell, C. M. and Bøe, K. E. (2015), Preference for shelter and additional heat in horses exposed to Nordic winter conditions. Equine Veterinary Journal. doi: 10.1111/evj.12522
The full study can be read here.