[Dynamics and causes of mortality in poultry in the Pleven district]

Studied were the various factors causing death and the dynamics of death in two broiler flocks, two parental flocks for broilers, and one flock of market egg layers. Death rate among broilers ranged between 2.17 and 2.98 per cent. It was highest during the first week after which it sharply dropped up to the end of the fattening period. In some flocks it again rose in the 4th to 6th of 8th week owing to the onset avitaminosis E, coccidiosis or Marek's disease. Noninfectious and deficiency diseases were prevailing in broilers. In the layers death rate varied within wide limits, ranging from 15 up to 23.75 per cent. It was highest during the first month and then sharply dropped. However, after the third month it again rose, reaching its maximum by the 6-7th month in connection with the outbreak of Marek's disease. In layers the infectious diseases were slightly prevailing, causing 51 to 57.39 per cent of the total number of deaths. Most widespread of the infectious diseases was Marek's disease, causing nearly 50 per cent of the deaths.