Abstract
Changes of immunity in the healthy and diseased cows at periparturient period, and the effects of immunopotentiator on immunity in the periparturient cows were investigated to determine the relationships between immunosuppression in the periparturient cows and occurrence of infectious diseases. Mitogenic responses of peripheral blood lymphocytes (PBLs) against phytohaemagglutinin-P (PHA-P), concanavalin A (Con A), and pokeweed mitogen (PWM) were significantly decreased at periparturient period. Nitroblue tetrazolium (NBT) reductivity of peripheral blood neutrophils (PBNs) and the expression of interleukin (IL)-2 mRNA of peripheral blood leukocytes were also suppressed in the period. Mitogenic responses of PBLs in the mastitic cows and puerperal metritic cows were significantly lower than those in the healthy cows. Suppression of lymphocyte blastogenesis in the healthy and diseased cows was correlated to the increased concentration of serum ketone body, ammonia, and α1-acid glycoprotein, and to the decreased level of serum vitamin E. On the other hand, in the cows administered E-SE (selenium; 25mg and vitamin E; 680IU) and several immunopotentiator such as active egg white product and Bacillus subtilis preparation, the mitogenic responses of PBLs and NBT reductivities of PBNs were significantly higher than those in the control cows at periparturient period. These findings indicate that the immunosuppression in the periparturient cows is related with the occurrence of infectious diseases such as mastitis and puerperal metritis. Futhermore, an administration of immunopotentiator including selenium and vitamin E to pregnant cows is associated with the prevention of immunosuppression and infectious diseasesin the periparturient cows.
