Modifications induced by training and diet in some exercise-related blood parameters in young trotters

Abstract

One consequence of muscular activity is an increase in circulating lactic acid; the interval it takes to return to baseline is an index of the capability for recovery and for the utilization of this catabolyte as oxidable substrate. For the energy demand to be met the diet must provide sufficient energy; its main source for muscle activity sustaining the initial anaerobic contraction is glycogen. However, the considerable activity of aerobic muscle fibers observed in training for endurance as well as trotting races is also sustained by lipids. Their utilization is enhanced by Carnitine, which acts on the transport of fatty acids at mitochondrial level. The present study was designed to investigate the effect of L-Carnitine administration on ten 18-month long yearling (body weight 350–400kg) in pre-qualification training. Three constituted the control group; four received 9g/head/daily of L-Carnitine and three received 12g/head/daily of L-Carnitine. The diet consisted for all subjects in 6 kg hay offered, concentrate (4kg/head/day) and soybean oil (300g/head/day) that provided 98 MJ/d of digestible energy. After one month with the new diet, they were periodically subjected to distance and speed tests. The training workload ranged from 1,600 m to 3,000 m at 650 m/min. Blood samples were collected at rest (AR), immediately after exercise (AE), 20′ (AE1) and 60′ (AE2) afterwards. On plasma the profiles relating to effort (lactic acid, ammonia, CK and AST) was determined. For each subject and test lactic acid production (AE-AR), and the recovery curve of lactic acid were also calculated. On the basis of a Diet*Test factorial scheme, there were no significant differences attributable to diet, while differences influenced by training were significant for lactic acid, ammonia, CK and AST. Of particular interest was the recovery curve of lactic acid when subjects were compared singly on the basis of distance run and time. Decadence time was lowest in horses receiving the higher Carnitine dose and in the more advanced stage of training; more evidently with heavier exercise (3,000 vs 2,000 m). In conclusion, Carnitine administration could have a favorable effect on subjects who have achieved a certain fitness condition and on the occasion of intense and prolonged effort.