Observations on the influence of intestinal spirochaetosis in broiler breeders on the performance of their progeny and on egg production.

Observations were made on the effect of avian intestinal spirochaetosis (AIS) in eight broiler breeder flocks on the performance of their commercial broiler progeny flocks, and also on the production of eggs and the selection of hatching eggs. The effect of treatment on egg production was analysed. The broiler breeder flocks were examined for the presence or absence of antibodies, spirochaetes and clinical signs of AIS, and correlated with the performance data from 136 commercial broiler flocks produced by them. Broiler flocks from affected breeders with clinical signs of AIS had a poorer feed conversion of approximately 90 g per kg growth, an increased number of weak chicks, slower growth and poorer feed digestion than the offspring of unaffected flocks including those previously infected with AIS but without clinical signs. Breeder flocks with clinical signs produced 7.5% less eggs than unaffected flocks. A larger number of eggs (+ 3%) was considered to have insufficient weight for successful hatching. Treatment of hens before the onset of lay prevented the negative effects on egg production but later treatment was less effective. These findings indicate that AIS in broiler breeder flocks is associated with significant production losses through decreased broiler flock performance and decreased egg production and quality.