2 field trials for the study of the possible effects of avian leukosis control measures on production characteristics

: Two field trials were performed to study possible effects of the lymphoid leukosis (LL) control programme as carried out in the Netherlands, on production characteristics. Progeny groups of selected ALV-negative, congenitally non-shedding, hens and progeny of conventional flocks were divided into flocks either to be reared in conventional conditions or in isolation for a period of eight weeks followed by controlled exposure (vaccination) with ALV. Detrimental effects on production characteristics attributable to the LL control programme were not observed in the two trials. The LL control procedure was successful in the prevention of lymphomas and elimination of congenital ALV shedding. Differences in egg production between LL control groups and conventional flocks were not observed. This was presumably due to the absence or too small a number of ALV-infected hens in the conventional flocks. Relatively low immunoglobulin class IgA levels were observed in serum samples of chickens which were reared in isolation for a period of eight weeks. Quantitative differences in immunoglobulin classes IgG and IgM were not perceptible between samples from chickens which were reared in isolation and those reared in conventional conditions.