Effects on exercise response, fluid and acid-base balance of protein intake from forage-only diets in standardbred horses.
Abstract: High-energy forage might be an alternative to concentrates for performance horses and such forage can be produced by an early cut. However, early cut forage is high in crude protein (CP), which may result in an excessive CP intake. Objective: To investigate how CP intake affects nitrogen (N), fluid and acid-base balance, and exercise response in horses fed high-energy forage diets. The hypothesis was that high CP intake causes acidosis, and alters fluid balance and response to intensive exercise. Methods: Two forage-only diets based on high-energy grass forage were fed for 23 days in a crossover design to 6 Standardbred horses in racing condition. One forage diet provided a high (HP) CP (16.6%) intake and the other diet provided recommended intake (RP) of CP (12.5%) for racehorses. The horses had intensive exercise twice and slow exercise 1-3 times every week. At the beginning and end of each period, faeces and urine were collected for 48 and 72 h, respectively and analysed for dry matter, pH and N content. At Days 19 and 23 in each period 2 race-like exercise tests were performed, a standardised treadmill test and a field test on a race track. Blood samples were taken before, during and after the tests and analysed for sodium (Na), potassium (K), chloride (CI), total plasma proteins (TPP), TCO2, urea, pH and lactate. The strong ion difference (SID) was calculated and heart rate and respiratory rate was also recorded. Results: There was a decrease in urinary pH and an increase in N excretion, blood urea, water intake, urine volume and faecal water content on the HP diet. Total water intake was higher than the increase in urinary and faecal water loss indicating increased evaporative losses on the HP diet. During the exercise tests there were no significant differences between diets in TPP, plasma lactate, blood Na, K, Cl, TCO2, pH, SID and respiratory or heart rates. Conclusions: Feeding a forage-only diet with a CP intake corresponding to 160% of the requirement caused an increase in N excretion within 36-48 h after the diet was introduced and alterations in fluid and acid base balance at rest. Conclusions: The increased urine and probably also evaporative fluid losses suggest that feeding a HP diet will cause an unnecessary challenge for horses during prolonged exercise.
Publication Date: 2007-04-04 PubMed ID: 17402499DOI: 10.1111/j.2042-3306.2006.tb05620.xGoogle Scholar: Lookup
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- Journal Article
- Randomized Controlled Trial
- Research Support
- Non-U.S. Gov't
Summary
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This research explores the impact of high protein (HP) intake from forage-only diets on nitrogen balance, fluid balance, acid-base balance, and exercise reaction in race-ready Standardbred horses. The findings indicate that an excessive protein intake alters fluid and acid-base balance and increases nitrogen excretion in horses, which may potentially challenge horses during extended exercise.
Study Design and Methods
- The study was conducted using a crossover design, with two diets based on high-energy grass forage fed to six Standardbred horses in racing condition over 23 days. These diets differed mainly by their crude protein (CP) percentage: one with a high CP intake (16.6%) and one with the recommended CP intake (12.5%) for racehorses.
- The horses were subjected to both intensive exercises twice a week and slow exercises one to three times a week. Several biological variables were monitored to assess the horses’ health and response to the diets.
- Faeces and urine were collected at the start and end of each trial period and analyzed for dry matter, pH, and nitrogen contents. Other measurements taken included heart rate, respiratory rate, and blood analysis before, during, and after the exercises. Specific blood components measured were sodium, potassium, chloride, total plasma proteins, TCO2, urea, pH and lactate. The strong ion difference was also calculated.
Study Outcomes
The results demonstrated several impacts of a high protein intake from a forage-only diet.
- The HP diet resulted in a decrease in urinary pH, indicating a disruption in acid-base balance within the body.
- There was an increase in nitrogen excretion, suggesting that the HP diet led to an unnecessary nitrogen load that had to be eliminated from the body.
- Increased intake of water, more significant urine volume, and higher faecal water content were observed with the HP diet, suggesting alterations to fluid balance in the body.
- Despite these changes, exercise-related responses such as heart rates, respiratory rates, and various blood markers (including sodium, potassium, chloride, and lactate levels) didn’t significantly vary between the two diets.
Conclusions
- In summary, this study suggests feeding horses a forage-only diet with a high protein intake, at around 160% of the recommended dietary requirement, caused increased nitrogen excretion and alterations to both fluid and acid-base balance.
- The consequences of these changes potentially pose unnecessary challenges for horses undertaking prolonged exercise.
- However, this high protein intake did not significantly impact the horses’ physiological response to exercise in the short term.
Cite This Article
APA
Connysson M, Muhonen S, Lindberg JE, Essén-Gustavsson B, Nyman G, Nostell K, Jansson A.
(2007).
Effects on exercise response, fluid and acid-base balance of protein intake from forage-only diets in standardbred horses.
Equine Vet J Suppl(36), 648-653.
https://doi.org/10.1111/j.2042-3306.2006.tb05620.x Publication
Researcher Affiliations
- Deptartment of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Box 7018, S-750 07 Uppsala, Sweden.
MeSH Terms
- Acid-Base Equilibrium / physiology
- Animal Nutritional Physiological Phenomena
- Animals
- Cross-Over Studies
- Dietary Proteins / administration & dosage
- Dietary Proteins / adverse effects
- Dietary Proteins / metabolism
- Dose-Response Relationship, Drug
- Drinking
- Feces / chemistry
- Horses / metabolism
- Hydrogen-Ion Concentration
- Male
- Nitrogen / metabolism
- Physical Conditioning, Animal / physiology
- Urinalysis / veterinary
- Urination / drug effects
- Urination / physiology
Citations
This article has been cited 5 times.- Saastamoinen M, Särkijärvi S, Suomala H. Protein Source and Intake Effects on Diet Digestibility and N Excretion in Horses-A Risk of Environmental N Load of Horses.. Animals (Basel) 2021 Dec 15;11(12).
- Zhu Y, Wang X, Liu B, Yi Z, Zhao Y, Deng L, Holyoak R, Li J. The Effect of Ryegrass Silage Feeding on Equine Fecal Microbiota and Blood Metabolite Profile.. Front Microbiol 2021;12:715709.
- Jansson A, Harris P, Davey SL, Luthersson N, Ragnarsson S, Ringmark S. Straw as an Alternative to Grass Forage in Horses-Effects on Post-Prandial Metabolic Profile, Energy Intake, Behaviour and Gastric Ulceration.. Animals (Basel) 2021 Jul 24;11(8).
- Mok CH, Urschel KL. Amino acid requirements in horses.. Asian-Australas J Anim Sci 2020 May;33(5):679-695.
- Ringmark S, Skarin A, Jansson A. Impact of Year-Round Grazing by Horses on Pasture Nutrient Dynamics and the Correlation with Pasture Nutrient Content and Fecal Nutrient Composition.. Animals (Basel) 2019 Jul 29;9(8).
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