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

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  • 1 Department of Animal and Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306;
  • | 2 Large Animal Clinical Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306;
  • | 3 Department of Animal and Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306;
  • | 4 Present address is 171 Normandy Ln, Newport News, VA, 23606;
  • | 5 Department of Animal and Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306;
  • | 6 Present address is 3030 Mt Tabor Rd, Blacksburg, VA, 24060;
  • | 7 Department of Animal and Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306;
  • | 8 Present address is Dept of Equine Science, Otterbein College,Westerville, OH 43081;
  • | 9 Large Animal Clinical Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306;
  • | 10 Department of Animal and Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0306;
  • | 11 Waltham Centre for Equine Nutrition and Care, Verden, Germany.
  • | 12 Present address is Wedehof 1, Holtum-Geest, D-2816, Kirchlinteln, Germany.

Abstract

Objective—To determine lactate breakpoint of horses and test for effects of training and dietary supplementation with corn oil on that breakpoint.

Animals—7 healthy Arabian horses.

Procedures—Horses received a control diet (n = 4) or a diet supplemented with 10% corn oil (4). A training program, which comprised two 5-week conditioning periods with 1 week of rest, was initiated. Submaximal incremental exercise tests (IET) were conducted before the first and after both conditioning periods. Blood samples for determination of blood lactate and plasma glucose concentrations were collected 1 minute before IET and during the 15 seconds immediately preceding each speed change. Data collected were fit to one- and twoslope broken-line models and an exponential model.

Results—Good fits were obtained by application of the broken-line models (adjusted R 2 > 0.92) to blood lactate concentration versus speed curves. Lactate breakpoints increased 41% after training but were not affected by diet. After training, slope 2 and peak blood lactate concentrations were greater in the corn oil group, compared with controls. 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 preceded lactate breakpoints by approximately 1 m/s in the second and third IET.

Conclusions and Clinical Relevance—Lactate breakpoints can be determined for horses, using blood lactate concentration versus speed curves generated during submaximal IET and may be useful for assessing fitness and monitoring training programs in equine athletes. (Am J Vet Res 2000;61:144–151)

Abstract

Objective—To determine lactate breakpoint of horses and test for effects of training and dietary supplementation with corn oil on that breakpoint.

Animals—7 healthy Arabian horses.

Procedures—Horses received a control diet (n = 4) or a diet supplemented with 10% corn oil (4). A training program, which comprised two 5-week conditioning periods with 1 week of rest, was initiated. Submaximal incremental exercise tests (IET) were conducted before the first and after both conditioning periods. Blood samples for determination of blood lactate and plasma glucose concentrations were collected 1 minute before IET and during the 15 seconds immediately preceding each speed change. Data collected were fit to one- and twoslope broken-line models and an exponential model.

Results—Good fits were obtained by application of the broken-line models (adjusted R 2 > 0.92) to blood lactate concentration versus speed curves. Lactate breakpoints increased 41% after training but were not affected by diet. After training, slope 2 and peak blood lactate concentrations were greater in the corn oil group, compared with controls. 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 preceded lactate breakpoints by approximately 1 m/s in the second and third IET.

Conclusions and Clinical Relevance—Lactate breakpoints can be determined for horses, using blood lactate concentration versus speed curves generated during submaximal IET and may be useful for assessing fitness and monitoring training programs in equine athletes. (Am J Vet Res 2000;61:144–151)