Determination of the lactate breakpoint during incremental exercise in horses adapted to dietary corn oil.

The research examined the lactate breakpoint in horses during incremental exercise and explored the effects of training and a diet supplemented with corn oil. The study found that lactate breakpoints increased after training and were greater in horses with a diet supplemented with corn oil.

Experimental Design

• The research involved seven healthy Arabian horses, which were divided into two groups. One group received a control diet (four horses) while the remaining three were fed a diet supplemented with 10% corn oil.
• Both groups of horses underwent a training program, consisting of two 5-week conditioning periods separated by a week of rest.
• Submaximal incremental exercise tests (IET) were conducted on the horses before the first conditioning period, and after both conditioning periods to monitor changes in fitness levels.
• Blood samples were collected 1 minute prior to the IET and during the 15 seconds immediately before each speed change to determine blood lactate and plasma glucose concentrations.

Data Analysis and Results

• Data collected were fit to single and double-slope broken-line models and an exponential model to create curves of blood lactate concentration versus speed.
• The broken-line models provided good fits (adjusted R2 > 0.92) to the blood lactate and speed curves.
• After the training program, lactate breakpoints increased by 41%, suggesting higher fitness levels.
• Horses in the corn oil group had higher slope 2 (indicative of a steeper rise in lactate concentration at higher speeds) and peak blood lactate concentrations compared to the control group post-training.
• The mean blood lactate concentration at the breakpoint was not affected by training or diet.
• Plasma glucose concentration versus speed curves also fit the broken-line models, and glucose breakpoints (the speed at which glucose concentration starts increasing sharply) preceded lactate breakpoints by about 1 m/s in the second and third IET.

Conclusions

• The lactate breakpoints of horses during submaximal IET could be successfully determined using blood lactate concentration versus speed curves.
• These breakpoints could serve as useful indicators for assessing fitness and monitoring the efficacy of training programs in equine athletes.
• The increase in lactate breakpoints after training and a higher breakpoint in the corn oil group post-training suggests that endurance training and corn oil supplementation might enhance physical performance.