Forsøksdyr: Physiological adaptations for ultra-endurance in long-distance sled dogs

Godkjenningsdato 27.04.2022

Godkjenningsperiode 27.04.2022-27.04.2024

Long-distance sled dogs are among nature's elite endurance athletes. How can sled dogs run so fast and for so long without fatigue? The answer may be found in their genetics evolved through selective breeding, affecting physiological and phenotypical traits for running and influencing speed, endurance, attitude and the ability to handle Arctic weather conditions. Sinding et al (2020, Science 368:1495-1499) showed that the first Arctic sled dogs emerged in East Siberia already 9,500 years ago. Their adaptation to physical labour in the cold at the genetic level indicates a selection over time for a special (sled-pulling) function. The genome of these ancient dogs is surprisingly similar to that of modern sled dogs. Today's Alaskan huskies can maintain high average speeds (16 km/h) during long-distance races under harsh climatic conditions, while Siberian huskies competing in the same races are often outrun by the Alaskans. Skeletal muscles need energy (ATP) for mechanical work (contractions and hence running), produced by mitochondria inside the cells. Previous data indicate that Alaskan huskies maintain a high mitochondrial protein turnover facilitating rapid adaptation to environmental extremes and energetic challenges (Miller et al, 2017, PLOS ONE 12:e0174874). The present project aims to determine and compare muscle mitochondrial respiratory capacity during racing season and off-season in Alaskan and Siberian huskies, to gain new knowledge on the adaptive potential of skeletal muscle mitochondrial function in sled dogs.

A micro-biopsy (approximately 50mg) will be taken from the biceps muscle of the thigh of 6 Siberian and 4 Alaskan huskies, once in May 2022, once in August/September 2022 and again in May 2023. The total strain of the procedure on the animals is considered minimally invasive ('lett belastende'), without expected long-lasting effects. A light sedation and appropriate analgesia will be applied to ensure animal welfare. The dogs are well socialized and used to being handled, so minimal stress is expected.

Long distance sled dogs provide a unique model to examine the variability in mammalian aerobic exercise performance. The overall aim of this study is to increase our knowledge on physiological adaptations in sled dogs, studying the effects of endurance training on aerobic capacity in ultra endurance long distance sled-dogs. This study explores differences in physiological adaptations in the respiratory capacity of skeletal muscles arising from selective breeding and training intensity in huskies.

8 dogs (Canis lupus familiaris): 4 Alaskan huskies, 6 Siberian huskies.

Replacement: There are no suitable in vitro or model approaches that can recapitulate the mitochondrial phenotype and yield information on respiratory capacity of skeletal muscle in sled-dogs.
Reduction: Each sample will be used for several parallel experiments to ensure high quality data, and to minimize the total number of biopsies and individuals needed.
Refinement: The biopsy procedure to be employed is considered to be minimally invasive. Anti-inflammatory NSAIDs will be used as analgesic to ensure good animal welfare.