Abstract: Accumulated O(2) deficit (AOD) and plasma lactate accumulation rate (PLAR) are alternative methods for estimating net anaerobic energy utilisation (NAEU) in exercising horses. How they compare or their accuracy is unknown. Objective: We hypothesised net anaerobic energy utilisation calculated by PLAR (NAUE(PLAR)) is equivalent to NAUE estimated by AOD (NAUE(AOD)). Methods: Six Thoroughbred horses ran at identical supramaximal speeds (118% aerobic capacity) until exhaustion for 2 runs while breathing normoxic (NO, 21% O(2)) or hyperoxic (HO, 26% O(2)) gas. Jugular blood was sampled at 15 s intervals to measure plasma lactate concentration. Horses also ran at incremental submaximal speeds from 1.7-11.0 m/s to determine the linear relationship between speed and O(2) consumption to estimate O(2) demand for AOD calculations. Results: Maximum O(2) consumption of horses increased 11.6 ± 2.3% in HO and NAEU(PLAR) and NAUE(AOD) decreased 38.5 ± 8.0% and 46.2 ± 17.7%, respectively. The NAEU(PLAR) in NO was 114.5 ± 27.4 mlO(2) (STPD) equivalent/kg bwt contributing 23.5 ± 3.7% to total energy turnover and in HO was 70.9 ± 19.8 mlO(2) (STPD) equivalent/kg bwt contributing 14.6 ± 3.8% to total energy turnover. The NAUE(AOD) in NO was 88.6 ± 24.3 mlO(2) (STPD) equivalent/kg bwt contributing 19.9 ± 2.1% to total energy turnover and in HO was 56.2 ± 19.1 mlO(2) (STPD) equivalent/kg bwt contributing 10.9 ± 4.3% to total energy turnover. Overall, NAEU(AOD) was systematically biased -23.5 ± 16.8 mlO(2) (STPD) equivalent/kg bwt below NAEU(PLAR). Total energy demand estimated by PLAR was 11.1 ± 5.4% greater than that estimated by AOD and was higher in every horse. Conclusions: The NAUE(PLAR) estimates average 40.0 ± 29.6% higher than NAUE(AOD) and are highly correlated (r(2) = 0.734), indicating both indices are sensitive to similar changes in NAEU. Accuracy of the estimates remains to be determined. Multiple considerations suggest NAUE(AOD) may underestimate total energy cost during high-speed galloping, thus biasing low the AOD estimate of NAEU.
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The study examined the comparison of net anaerobic energy utilisation in horses during exercise, estimated by two methods: plasma lactate accumulation rate and accumulated oxygen deficit. The research aimed to determine if these methods produced equivalent results.
Methods
Six Thoroughbred horses were exercised at identical supramaximal speeds until they reached exhaustion, under two different conditions: normal oxygen (NO) levels and hyperoxic (HO) conditions with 26% oxygen.
Jugular blood was sampled at 15-second intervals to measure plasma lactate concentration. This data was used to calculate the plasma lactate accumulation rate (PLAR), an estimate of net anaerobic energy utilisation (NAEU).
The horses also ran at varying submaximal speeds, from 1.7-11.0 m/s, to find the linear relationship between speed and oxygen consumption, which was used to estimate the oxygen demand for the accumulated oxygen deficit (AOD) calculations.
Results
The amount of oxygen consumed by the horses increased by an average of 11.6% under hyperoxic conditions.
The NAEU calculated through both methods decreased when the horses were breathing hyperoxic gas, suggestive of a reduced reliance on anaerobic energy production under these conditions.
The NAEU estimated by the PLAR method was systematically biased, measuring higher than the AOD method by an average of 23.5 mlO2 equivalent/kg body weight.
A comparison of total energy demand estimates revealed that the PLAR method estimated 11.1% greater demand than the AOD method. This difference was consistent across all six horses in the study.
Conclusions
The net anaerobic energy utilisation estimated by the PLAR method averaged 40% higher than the estimates obtained by the AOD method. However, the results from both methods were highly correlated, which indicated that both are sensitive to similar changes in NAEU.
The accuracy of these two methods in estimating NAEU remains to be determined, with a suggestion that the AOD method may underestimate the total energy cost during high-speed galloping.
Cite This Article
APA
Ohmura H, Mukai K, Takahashi T, Matsui A, Hiraga A, Jones JH.
(2011).
Comparison of net anaerobic energy utilisation estimated by plasma lactate accumulation rate and accumulated oxygen deficit in Thoroughbred horses.
Equine Vet J Suppl(38), 62-69.
https://doi.org/10.1111/j.2042-3306.2010.00261.x