Adaptation strategies to seasonal changes in environmental conditions of a domesticated horse breed, the Shetland pony (Equus ferus caballus).
Abstract: Recent results suggest that the wild ancestor of the horse, the Przewalski horse, exhibits signs of a hypometabolism. However, there are speculations that domestic animals lost the ability to reduce energy expenditure during food shortage and adverse environmental conditions. Therefore, we investigated physiological and behavioural strategies employed by a robust domesticated horse breed, the Shetland pony, over the course of a year under temperate conditions by measuring ambient temperature (T(a)), subcutaneous temperature (T(s)), locomotor activity (LA), lying time, resting heart rate, body mass and body condition score. Ten animals were kept on pasture in summer and in open stables in winter; further, in winter the animals were allocated into one control and one feed-restricted group of five animals each to simulate natural seasonal food shortage. The annual course of the mean daily T(s) of all horses showed distinct fluctuations from a mean of 35.6±0.5°C, with higher variations in summer than in winter. Diurnal amplitudes in T(s) were highest (P<0.001) in April (12.6°C) and lowest in January (4.0°C), with a nadir around dawn and a peak around mid-day. The feed-restricted group had a significantly lower daily T(s) compared with the control group on cold winter days, with T(a) values below 0°C. Mean annual heart rate and LA followed T(a) closely. Heart rate of the feed-restricted animals significantly decreased from a mean of 52.8±8.1 beats min(-1) in summer to 29±3.9 beats min(-1) in winter and differed from the control group (P<0.001). Mean daily LA was lowest at the end of winter (7000 activity impulses day(-1)) and highest in summer (25,000 activity impulses day(-1)). Our results show that Shetland ponies exhibit signs of a winter hypometabolism indicated by reduced heart rate and T(s). Thus, domesticated horses seem to have maintained the capacity for seasonal adaptation to environmental conditions by seasonal fluctuations in their metabolic rate.
Publication Date: 2012-03-09 PubMed ID: 22399650DOI: 10.1242/jeb.064832Google Scholar: Lookup
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- Journal Article
Summary
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The research investigates how the Shetland pony, a breed of domesticated horse, adapts to seasonal changes in the environment. The study presents evidence that, contrary to previous beliefs, these domesticated horses retain the ability to modify their metabolism according to the seasons, much like their wild ancestors, the Przewalski horses.
Research Methodology
- Ten Shetland ponies were observed for a year under varying environmental conditions. Their physiological parameters such as ambient temperature, subcutaneous temperature, locomotor activity, lying time, resting heart rate, body mass, and body condition score were measured.
- The animals were kept in two different environments – on pastures in summer and in open stables in winter.
- A subset of the ponies was subjected to a restricted-food regimen in winters to imitate natural seasonal food shortage.
Observations and Findings
- There were apparent changes in the daily mean subcutaneous temperature (Ts) with notable differences in fluctuations between winter and summer.
- The Ts depicting the highest amplitude in April and the lowest in January, with a low around dawn and a peak around mid-day.
- The ponies in the food-restricted group showed a significantly lower daily Ts on chilly winter days when the ambient temperature was below 0°C.
- Both the annual average heart rate and locomotor activity in all ponies closely followed the pattern of changes in ambient temperature.
- In the food-deprived group, the heart rate significantly fell from a summer average of around 52.8 beats per minute to approximately 29 beats per minute in winter
- The locomotor activity was observed to be the least towards the end of winter, and highest during summer
Conclusions
- The brainchild of these observations, the hypothesis that Shetland ponies display signs of winter hypometabolism (low metabolic rate during winters), was validated. This is marked by a reduced heart rate and Ts during winters.
- The research concluded that, against initial speculations, domesticated horses like the Shetland pony have preserved the ability to make seasonal adjustments to their metabolic rates in response to changes in environmental conditions. This feature is akin to the horses’ wild ancestors.
Cite This Article
APA
Brinkmann L, Gerken M, Riek A.
(2012).
Adaptation strategies to seasonal changes in environmental conditions of a domesticated horse breed, the Shetland pony (Equus ferus caballus).
J Exp Biol, 215(Pt 7), 1061-1068.
https://doi.org/10.1242/jeb.064832 Publication
Researcher Affiliations
- Department of Animal Sciences, University of Göttingen, Göttingen, Germany.
MeSH Terms
- Adaptation, Physiological
- Animals
- Animals, Domestic / physiology
- Behavior, Animal / physiology
- Body Temperature / physiology
- Body Weight / physiology
- Breeding
- Circadian Rhythm / physiology
- Heart Rate / physiology
- Horses / physiology
- Locomotion
- Rain
- Rest / physiology
- Seasons
- Temperature
Citations
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