Responses to climatic variables of horses housed outdoors under Nordic winter conditions

Abstract

The aim of this study was to investigate the responses to cold winter weather of Icelandic horses kept permanently outdoors. The horses were kept in a 0.8-ha enclosure, with free access to grass silage and a shelter. Behaviours were recorded during 23 d using direct observation scan sampling at 20-min intervals between 1600 and 0000, embracing air temperatures down to -31°C. Body condition score, coat length and serum thyroid hormone (T 4 ) level were recorded. Horses spent most of their time outdoors under all weather conditions, and the average incidence of being outdoors was 70%. The horses made more use of the shelter at low ambient temperatures (P < 0.01). There was also a strong tendency for increased use of the shelter in response to rain and wind (P < 0.07). Precipitation as snow had no effect. Shivering was observed once in a single horse, on a rainy day at +5°C. Average maximum neck coat length was 4.6 ± 0.9 cm. Body condition score remained within satisfactory limits during winter. Serum T 4 showed no correlation with ambient temperature (P = 0.70). It is concluded that a cold climate with temperatures down to -31°C does not challenge the thermoregulation of cold-acclimated Icelandic horses, provided that there is sufficient quality feed and access to a shelter. Key words: Horse, winter climate, shelter, behaviour, welfare, thyroid hormone