The present study was done to evaluate the role of serum muscular enzymes in the determination of the workload in healthy horses, and diagnosis of rhabdomyolysis (ER) cases. Twenty-one draft horses were assessed under the field conditions during rice seedling seasons. Animals were under complete history, physical examination and laboratory evaluation of serum muscular enzymes.  Horses were categorized into 2 main groups; the first group, healthy horses under rice seedling work (n=10). They were examined and sampled 4times/day work. The second group includes horses with exertional rhabdomyolysis under rice seedlings workload (n=11) and they were examined and sampled on admission. Blood samples were collected and as a minimum, serum creatine kinase (CK), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) were evaluated. The obtained results clarified significant alterations in the vital signs in the exertional rhabdomyolysis group in comparison to healthy horses under the same workload in the four examination periods. Additionally, highly significant increase (P ≤0.001) in serum CK, LDH and AST levels in exertional rhabdomyolysis cases in comparison to the healthy horses and to the normal reference limits. While two or more folds increase in the serum muscular enzymes were recorded in healthy horses during workload and 4 h post-work when compared to the pre-work measurements. This, in turn, reflects the great load in healthy horses during rice seedling seasons.