Oxygen transport during exercise in large mammals. I. Adaptive variation in oxygen demand.
Abstract: This study investigated mechanisms used by horses and steers to increase O2 uptake and delivery (VO2) from resting to maximal rates and identified the mechanisms that enable horses to achieve higher maximal rates of O2 consumption (VO2max) than steers. VO2 and circulatory variables were measured while Standardbred trotting horses and steers (450-kg body mass) stood quietly and ran on a treadmill at speeds up to those eliciting VO2max. As VO2 increased in both species, heart rate and circulating hemoglobin (Hb) concentration increased, thereby increasing O2 delivery by the circulation, while cardiac stroke volume remained unchanged. At VO2max arterial PCO2 increased from its resting value in horses but was unchanged in steers, and arterial PO2 decreased in both species. Although the horses hypoventilated and were hypoxemic at VO2max, no significant decrease in arterial Hb saturation occurred. VO2max of the horses was 2.6 times higher than that of the steers and was associated with a 100% larger cardiac output, 100% larger stroke volume, and 40% higher Hb concentration, whereas heart rates at VO2max were identical in the two species. The higher cardiac output of the horses at VO2max resulted from a 1.2-fold higher mean arterial pressure and 1.6-fold lower peripheral tissue resistance (associated with a larger skeletal muscle capillary bed). Both the magnitude of the difference in VO2max between horses and steers and the mechanisms used to achieve it are the same as observed in smaller pairs of mammalian species with large variation in aerobic capacity.
Publication Date: 1989-08-01 PubMed ID: 2793686DOI: 10.1152/jappl.1989.67.2.862Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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The research article discusses the oxygen intake and delivery (VO2) methods utilized by horses and cows during exercise, observing adaptive variations in oxygen demand and identifying mechanisms through which horses achieve higher maximal rates of O2 consumption (VO2max) than cows.
Research Methodology
- The research measured VO2 and circulatory variables in Standardbred trotting horses and steers while they stood in place and ran on treadmills at increasing speeds until the point of VO2max was reached.
- Changes in heart rate and circulating hemoglobin (Hb) concentration were tracked for both species as VO2 increased. Cardiac stroke volume, arterial PCO2, and arterial PO2 were also measured at resting and VO2max values.
Key Findings
- As VO2 increased in both species, heart rate and circulating Hb concentration also increased, boosting oxygen delivery, while cardiac stroke volume remained constant.
- In horses at VO2max, arterial PCO2 increased from the resting level, whereas it remained unchanged in steers. Arterial PO2 decreased in both species at VO2max.
- Despite horses showing signs of hypoventilation and hypoxemia at VO2max, there was no significant decrease in arterial Hb saturation.
- The horses’ VO2max was 2.6 times greater than that of the steers and was linked to a 100% greater cardiac output, 100% larger stroke volume, and 40% higher Hb concentration. Heart rates at VO2max were the same for both species.
- The horses’ higher cardiac output at VO2max resulted from a 1.2-fold increased mean arterial pressure and a 1.6-fold decreased peripheral tissue resistance, which was associated with a larger capillary bed in the skeletal muscles.
- The differences in VO2max between horses and steers and the mechanisms used to achieve these differences correspond with those observed in smaller pairs of mammalian species with large variations in aerobic capacity.
Implications of Findings
- The research reveals key insights into the adaptation variations in O2 intake and delivery during exercise between equine and bovine species.
- These findings could provide valuable insights into large animal veterinary medicine, species-appropriate training programs, and comparative physiological studies.
Cite This Article
APA
Jones JH, Longworth KE, Lindholm A, Conley KE, Karas RH, Kayar SR, Taylor CR.
(1989).
Oxygen transport during exercise in large mammals. I. Adaptive variation in oxygen demand.
J Appl Physiol (1985), 67(2), 862-870.
https://doi.org/10.1152/jappl.1989.67.2.862 Publication
Researcher Affiliations
- Department of Medicine I, College of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala.
MeSH Terms
- Adaptation, Physiological
- Animals
- Cardiac Output
- Cardiac Volume
- Cattle / physiology
- Exercise Test
- Heart Rate
- Hemoglobins / analysis
- Horses / physiology
- Oxygen Consumption
- Physical Conditioning, Animal
- Physical Exertion
- Respiratory Physiological Phenomena
Citations
This article has been cited 27 times.- Ebisuda Y, Mukai K, Takahashi Y, Yoshida T, Kawano A, Matsuhashi T, Miyata H, Kuwahara M, Ohmura H. Acute exercise in a hot environment increases heat shock protein 70 and peroxisome proliferator-activated receptor γ coactivator 1α mRNA in Thoroughbred horse skeletal muscle. Front Vet Sci 2023;10:1230212.
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