Effect of Exercise on Biochemical Factors in Healthy and Diseased Horses 

Clinical pathology is frequently used in horses for assessing fitness to race and to screen for diseases that may affect performance. The performance or output of an equine athlete is determined by many complicated interdependent biological and physiological processes. Understanding how these process function and relate to each other is mandatory if the horse is to be effectively trained and managed during its working or competitive life (Warwick, 2004). On the basis of such considerations, the purpose of this study was to investigate changes of some biochemical parameters: aspartate amino transferase (AST), alanine amino transferase (ALT), alkaline phosphatase (ALP), gammaglutamyl transferase (GGT), lactate dehydrogenase (LDH), creatinine kinase (CK), total protein (TP) and glucose in healthy and horses suffering from upper respiratory tract infection, before and after exercise.

To study the effect of exercise on the serum biochemical parameters in ten clinically normal Thoroughbred (6 geldings, 4 mares) of similar age group (6-9 years) were selected as control (Group I) and were compared with ten Thoroughbred (7 geldings, 3 mares) those affected with upper respiratory tract affections (5 Left Laryngeal hemiplegia, one Dorsal displacement of the soft palate, one Epiglottic entrapment, one Pharyngeal lymphoid hyperplasia, one Guttural pouch empyema, one Rostral displacement of palatal arch) with similar age group (6-9 years) were selected as clinical group (Group II).
       
Blood samples (10 ml in a vacutainer without anicoagulant) were collected from each horse at rest and after exertion (which was fifteen minutes) induced by lunging, canter, trotting or hand rolling. Serum was separated and used for estimation of the biochemical parameters. The value of the alanine amino transferase and asparate amino transferase was estimated as per the technique described by Varley et al., (1980). The alkaline phosphatase was estimated by IFCC method (Tietz et al., 1983). Modified Biuret and Dumas method (Varley et al., 1980) was followed for estimating serum total protein. The glucose was estimated by orthotoludine method (Bauer, 1982). The lactate dehydrogenase and Gamma glutamyl transferase was estimated by Szasz method (Szasz et al., 1976). Creatinine kinase was estimated by Wroblewsk and La Due method (Wroblewsk and La Due, 1995). The data were analyzed by paired and unpaired t-Test.

In this study, a significant increase in AST, GGT, LDH, CK and TP values and there was a significant decrease in Glucose value were observed after exercise in group I (Table 1a). A significant increase in AST, GGT, CK and TP values and there was a significant decrease in ALT, ALP and Glucose values were observed after exercise in group II (Table 1a). The increased values (after exercise) for AST, GGT, CK, LDH and TP were well within the physiological limit. This could possibly due to short sampling interval for the collection of pre and post exercise blood sample, (which was fifteen minutes) and no major metabolic changes associated with liver and bone alterations can be expected, with in the short sampling period. Snow and Harris (1988) reported that though there were increase in serum biochemical parameters, the value remained within the reference limits. Similar findings were observed in the present study also. The values observed in the control group horses (Table 1a) were in agreement with standard reference values observed by Sribhen et al., (2007).
 

       
The reduction in glucose level was due to the energy expenditure associated with the exercise. Rose (1982) stated that reduced glucose values reflected utilization of glucose in excess of replacement by glucogenolysis in horses after exercise. Though there was significant reduction in the ALT and ALP levels after exercise, they were within the physiological normal range. Since the sampling interval is too short, no major metabolic changes associated with liver and muscle metabolism.
       
No significant differences were observed in the levels of AST, ALT, ALP, GGT, LDH and TP between the groups before and after exercise (Table 1b). However decrease in the creatinine kinase was found to be significant in group II when compared to that group I before and after exercise (Table 1b). The decreased value of CK in clinical group, before and after exercise was within the normal range. A significant increase in glucose value was found in group II when compared to that group I before exercise (Table 1b). The increased value of glucose before exercise was within the normal range. The values observed in the clinical group horses (Table 1b) were in agreement with standard reference values observed by Sribhen et al., (2007).
 

All authors declare that they have no conflict of interest.