Growth performance, meat quality and activities of glycolytic enzymes in the blood and muscle tissue of calves infected with Sarcocystis cruzi.
Growth performance and the pattern of glycolytic enzymes in the blood plasma were assessed during experimental Sarcocystis cruzi infection (1 x 10(5) sporocysts per calf) in six calves; five calves served as noninfected controls. At slaughter (68 or 88 days post infection), carcass weight, dressing percentages and several parameters of meat quality (pH, color brightness, rigor, water absorbing capacity, water binding capacity) were recorded. Moreover, enzyme activities were measured in muscle homogenates. Weight gain was significantly impaired by the infection. Activities of lactate dehydrogenase (LDH) and aldolase (ALD) significantly increased in the blood plasma of the infected calves during the chronic stage of the disease, while glucose-6-phosphate dehydrogenase (G6PDH) and isocitrate dehydrogenase (ICDH) were not significantly altered. This was accompanied by a significant decrease of enzyme activities in the Musculus longissimus dorsi (LDH, ALD), in the diaphragmatic musculature (ALD, G6PDH) and in the heart (LDH, ALD). Activities of LDH, ALD, ICDH and G6PDH were visualized by enzyme histochemistry within the developing sarcosporidial cysts. However, isoenzymes of parasite origin could not be demonstrated by agar-gel electrophoresis of muscle homogenates or blood plasma. It is concluded that sarcocystiosis of even moderate severity alters the performance of calves but not meat quality. Leakage of glycolytic enzymes from the affected muscles is the probable cause of increased plasma enzyme activities. Although these enzymes are also synthesized by the parasite, the contribution of parasite-derived enzymes to the observed changes of enzyme patterns remains in question.