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Journal of animal physiology and animal nutrition2025; doi: 10.1111/jpn.14127

Starch Allowance and Muscle Enzyme Activity in Healthy Standardbred Trotters Trained by Professional Trainers.

Abstract: It is generally accepted that plasma muscle enzyme activity of creatine kinase (CK) and aspartate aminotransferase (AST) may increase in racehorses after exercise and racing, indicating muscle fibre damage and/or increased leakage from muscle fibres. However, other studies suggest that starch intake might influence plasma muscle enzyme activity reported postexercise. This study aimed to evaluate the effect of different starch allowances on plasma muscle enzyme activity in Standardbred trotters in professional training. Seventy-six horses from five professional trainers were sampled pre- and postexercise. The trainers had different feeding strategies and fed various amounts of starch to their horses. Postexercise plasma AST activity was higher (p < 0.007) for the high (H) and medium (M) starch allowances (451-967 and 988-1429 g/day, respectively) than for horses with low starch allowances (L) (0-268 g/day) (H:8.1 ukat/L (SE 0.5); M: 8.4 ukat/L (SE 0.5); L: 5.8 ukat/L (SE 0.7) (p < 0.007)). Postexercise plasma CK activity was higher (p < 0.01) for the medium starch allowance group than for the high and low starch allowance groups (H:4.6 ukat/L (SE 0.3); M: 5.9 ukat/L (SE 0.4); L: 3.9 ukat/L (SE 0.4)). In conclusion, this study showed higher plasma muscle enzyme activity of AST and some elevations in CK activity in horses fed high-starch allowances compared to horses fed low allowances or no starch. In addition, muscle enzyme activity increased in response to the duration of high-intensity exercise. Management systems aiming for low levels of plasma muscle enzyme activity could accordingly offer diets with low starch (< 450 g/day) contents and perhaps training regimes with shorter durations of high-intensity exercise. However, the mechanisms behind and the elevations' biological importance, need further investigation.
© 2025 The Author(s). Journal of Animal Physiology and Animal Nutrition published by Wiley‐VCH GmbH.
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Publication Date: 2025-05-06 PubMed ID: 40329464DOI: 10.1111/jpn.14127Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The study investigates if the levels of starch in a horse’s diet are linked to changes in muscle enzyme levels after exercise. The research implied that horses fed higher amounts of starch had elevated muscle enzyme activity when compared to horses fed on low or no starch diets.

Objective of the Research

  • The main objective of the study is to understand the possible influence of differing starch allowances or intake on the activity of plasma muscle enzymes in professional training horses, specifically Standardbred trotters. The researchers aim to observe any correlation between muscle enzyme activity, inferred muscle damage and starch intake levels in the horses’ diet.

Research Design and Methods

  • 76 Standardbred trotters from five professional trainers were chosen for the trial. The trainers used varying feeding strategies and fed different quantities of starch to their horses.
  • Blood samples were taken from the horses before and after exercise activities. Analysis of these samples allowed the researchers to measure the activity levels of specific muscle enzymes: creatine kinase (CK) and aspartate aminotransferase (AST).
  • The horses were classified into three groups based on their starch intake: high (H), medium (M), and low (L). The measured enzyme activities were compared between these three groups.

Findings

  • Results revealed that post-exercise plasma AST activity was significantly higher for horses in the high and medium starch allowance groups than for horses in the low starch allowance group.
  • Post-exercise plasma CK activity was observed to be higher for the group on a medium starch diet compared to those on high and low starch diets.
  • Scientists interpreted these findings to suggest that diets with high amounts of starch might lead to elevated muscle enzyme activity, which implies muscle fibre damage or leakage from muscle fibres.

Implications and Future Work

  • The results suggest that horse trainers may need to consider diet adjustments to optimize muscle health, mainly reducing starch intake (<450g/day) and perhaps altering training regimes to include shorter periods of high-intensity exercise.
  • However, this study is a preliminary investigation, and further research is required to understand the mechanisms behind the observed phenomena and the biological significance of the elevation in muscle enzyme activity.

Cite This Article

APA
Connysson M, Jansson A. (2025). Starch Allowance and Muscle Enzyme Activity in Healthy Standardbred Trotters Trained by Professional Trainers. J Anim Physiol Anim Nutr (Berl). https://doi.org/10.1111/jpn.14127

Publication

Journal of animal physiology and animal nutrition
ISSN: 1439-0396
NlmUniqueID: 101126979
Country: Germany
Language: English

Researcher Affiliations

Connysson, Malin
  • Department of Animal Biosciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Jansson, Anna
  • Department of Animal Biosciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.

Grant Funding

  • This study was supported by Swedish-Norwegian Foundation for Equine Research.

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