[Dynamics of passive humoral immunity transfer against Marek's disease in the progeny of the grandparent breeding stock of broilers].

In the progeny of the grandparents of broiler type HYBRO, imported by the Dutch firm EURIBRID, neonatal humoral immunity was studied during the whole laying period, i.e. in laying hens at the age of 26-52 weeks. Precipitation test was used to examine 292 samples of sera from the parent chickens of sire stock AB and 299 samples of sera from the chickens of dam stock CD, for the presence of maternal antibodies to Marek's disease virus. The number of positive samples decreased with the growing age of the grandparent generation. In the sire stock it ranged from 41.7 to 82.6% (average number 57.5%); in the dam stock, it was from 50 to 90.9% (average number 71.6%). The average incidence of precipitation antibodies in the dam stock was significantly higher than in the sire stock (p less than 0.05). The relationship between laying hen age and percent incidence of passive antibodies in parent-generation chickens was characterized by a regression line and correlation coefficient. We discuss the problem that the incidence of heterologous passive antibodies in the produced parent-generation chickens can only minimally influence the onset of post-vaccination immunity after application of the Czechoslovak vaccine MARVAK, i.e. passive immunity in these chickens cannot be caused by insufficient prophylaxis in some of Czechoslovak multiplier flocks of broiler type.