[Effect of various breeding conditions on the development of respiratory syndrome in calves].

In two experimental rearing houses with new-born non-colostral calves, separated from their mothers at birth and artificially fed colostrum or colostral whey, the epizootological situation was very favourable throughout the time of observation. The respiratory syndrome occurred in both cases as a result of the long-term worsening of microclimatic conditions and failure to adhere to the principle of the all-in all-out system. The etiology of the disease was of a complex character, involving virus PI-3, IBR, and bacteria, and its arising reminded of the exacerbation of latent virus infection. The primary role of the PI-3 virus in the arising of the disease was documented by complex laboratory examination. As distinct from the large-capacity calf-house with continual operation where the PI-3 virus and the same bacteria participated in the arising of the respiratory syndrome, which was not controlled, in the experimental calf-houses it was sufficient to adjust the microclimatic conditions, to disinfect the stables, and to adhere strictly to the priniciple of the all-in all-out system. The proposed method of the rearing of "minimum-morbidity calves" appears to be promising for use in the prevention of respiratory infections in calves and its further testing in large-capacity calf-houses is considered as desirable.