Effects of Lactanase on the plasma lactate response to intense exercise in horses

Abstract

A commonly held belief is that lactate production during exercise limits performance via fatigue. The current study aimed to assess the effects of a supplement marketed as performance enhancing (Lactanase®) on equine exercise performance and plasma lactate concentrations. Lactanase was expected to alter exercise performance and plasma lactate. Eight healthy, unfit Standardbred horses (four geldings and four mares, 9±3 years, 489±33 kg, mean ± standard error) were administered Lactanase (5 doses of 25 g) top-dressed on a commercial pelleted ration or unsupplemented pellets (Control) in a cross-over design experiment. Doses were administered over a four-day period and horses performed a graded exercise test on the fourth day following the final dose of either Lactanase or control. Blood samples (20 ml) were obtained via jugular catheter 30 min prior to exercise, immediately prior to exercise, in the last 10 s of each incremental exercise step, and 5 and 60 min post-exercise. Samples were frozen at -80 °C until further analysis. Data were analysed using a two-way repeated measures ANOVA. Statistically different means were separated using Student-Newman-Keuls and Dunnetts. No differences (P>0.05) in total run time were observed following Lactanase administration. Plasma lactate increased (P<0.05) when horses reached a speed of 7 m/s and remained elevated through 60 min post-exercise. There was no effect (P>0.05) of Lactanase on the plasma lactate response during exercise. Similarly, supplementation did not affect (P>0.05) plasma glucose or total protein at any time point. Exercise did increase plasma total protein (P<0.05), but it returned to baseline levels by 60 min post-exercise. Plasma glucose was elevated (P<0.05) post-exercise. These results indicate Lactanase administration does not alter the lactate response or the total run time to fatigue during intense incremental exercise in horses.