ECONOMIC-EFFECTS OF CLINICAL CHICKEN ANEMIA AGENT INFECTION ON PROFITABLE BROILER PRODUCTION

An outbreak of anemia dermatitis syndrome caused by chicken anemia agent (CAA) occurred in 15 broiler flocks. An average of 29% of chickens in these flocks were derived from a common breeder flock. The breeder flock had no antibody to CAA at 20 weeks of age but had seroconverted by 31 weeks. Diseased broiler flocks were derived from eggs laid by the breeder flock between 25 and 30 weeks of age. CAA infection in the breeder flock was subclinical, with no apparent effects on mortality or performance. A strategic program of therapeutic and/or prophylactic antibiotic therapy was begun in affected broiler flocks as soon as the disease was diagnosed. Nevertheless, when the cost of therapy was taken into account, affected broiler flocks had a net income 17.3% to 19.6% lower than normal flocks. Average bird weights were 3.3% to 3.5% lower in affected flocks than in unaffected flocks, and affected flocks had a significantly greater proportion of lighter birds. Average mortality in affected flocks was 2.0% to 2.3% higher than in normal flocks, with peak mortality occurring in the third week of life. There was no apparent effect on feed-conversion ratio.