Relationship between running speed, isoenzymes of serum creatine kinase and lactate dehydrogenase and left ventricular function in stallions.

The purpose of this study was to assess the possible relationship between maximal running speed, serum isoenzyme patterns of creatine kinase (CK) and lactate dehydrogenase (LDH) and echocardiographic indices of left ventricular function. A group of 15 healthy, 3-year-old Maremmano stallions were given a 100 day training programme. At the end of this the animals carried out a maximum speed test and were divided into 2 groups (A and B) according to whether or not they had attained a speed of 15 m/s. Venous blood samples were taken from each horse before exercise (T0), 2 min (T1) and 24 h (T2) after exercise. Total serum activity of CK and LDH was measured and their isoenzyme distribution pattern determined. The day before the speed test echocardiographic examination was carried out at rest to assess the left ventricular function by calculating telediastolic, telesystolic and stroke volume, ejection fraction and stroke index. Statistically significant differences were found for the CK isoenzyme pattern at T2, where Group A showed an increase in the MM fraction (P = 0.003) and a decrease in the MB fraction (P = 0.014). These changes were thought to be linked to an increased membrane leakage due to exercise and not to muscle fibre disruption because the CK and LDH total activities remained within the normal range. In Group A there was also greater left ventricular telediastolic volume (P = 0.044) and length (P = 0.033) at rest as well as a greater stroke index (P = 0.032). We concluded that the evaluation of CK pattern after exercise and of echocardiographic left ventricular function indices at rest made it possible to select for the fastest horses (Group A).

A study of immunologic relationships among serologically heterologous strains of bovine viral diarrhea virus by cross immunity tests.

Three serologically heterologous strains of bovine viral diarrhea (BVD) virus were compared in reciprocal cross immunity tests in calves. Each strain was inoculated into five calves. Thirty-eight days later one calf in each group was reinoculated with homologous virus while the immunity of the remaining four was challenged with the serologically heterologous strains of virus, using two calves for each strain. Of the 12 calves in the cross immunity tests, nine were refractory to immunity challenge with the heterologous viral strains while one in each group responded with mild, atypical signs of BVD. On the basis of immunity testing it appears that significant serologic differences among strains of BVD virus are unrelated to the immunologic properties of the strains. It was demonstrated, moreover, that each of the three strains used in the present study evoked the production of antibody to the heterologous as well as to the homologous strain of virus.