From 1986 to 1995, we performed drug sensitivity tests on 329 cattle with respiratory infectious disease to indentify the causative bacteria, and we conducted both in vitro and in vivo experiments to determine the effectiveness of various combinations of antibacterial drugs for treating respiratory infectious disease in cattle. Pasteurella, Mycoplasma or Ureaplasma were isolated from 271 (82.4%) of the cattle, and 38% (105/271) of these cattle were infected with a combination of Pasteurella and Mycoplasma or Ureaplasma. Results of tests conducted on cattle in the field to determine the efficacy of administration of only one widely used drug (ampicillin, oxytetracycline, kanamycin or thiamphenicol) for the treatment of respiratory infectious disease were not satisfactory. Therefore, we examined the antibacterial effect of a combination of thiamphenicol (TP), Tylosin (TS) or lincomycin on P. multocida, P. haemolytica and M. bovis in vitro using the checker board method and FIC index. The FIC index for either combination of two of the drugs against the bacteria was less than 1.0 (0.06-1.0), and the combination of these drugs showed a synergistic or additive effect. Moreover, improvement in symptoms was more rapid and the cure rate was significantly higher in cattle treated with a combination of TP and TS than in cattle treated with other antibiotics.

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In newborn piglets, the primary aim of this study is to focus on the relationship between the incidence of uric acid urolithiasis and starvation or low body weight. 1) The results indicated that the outbreak of the disease was not an unusual thing, and that starvation, low body weight and reduced ambient temperature were related to an occurrence of the disease. 2) The results suggested that the occurrence of the disease was related to a hypofunction of liver and kidney, lactic acidosis and increased catabolism of protein accompanying starvation. 3) The results suggested that the occurrence of uric acid urolithiasis in the newborn piglets was attributable to increased purine catabolites due to a starvational condition after birth. 4) The results suggested that increased concentrations and excretions of uric acid in the urine were due to starvation, and a decrease of levels of urinary pH were due to an increase of lactic acid concentrations in the urine. On the basis of the above findings, it is suspected that uric acid urolithiasis in newborn piglets occur because of increased purine catabolism due to starvation.

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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.

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