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D W Bruce

Publications and source records attributed to D W Bruce.

21 records · Page 2Linked to original sources

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.

Anemia↗

Economic effects of subclinical chicken anemia agent infection in broiler chickens.

To evaluate the economic effects of subclinical chicken anemia agent (CAA) infection on broiler performance, clinically normal broiler flocks were grouped into two categories: A) flocks in which none of 10 birds sampled at slaughter had antibody to CAA, and B) flocks in which six or more of 10 similarly sampled birds had CAA antibody. Production and performance parameters of 25 flocks in each category were compared. No statistically significant differences were found between category A and category B flocks in major production parameters such as sex, feed manufacturer, type of litter, stocking density, and age at slaughter. However, category A flocks achieved 13% (P less than 0.05) greater net income per 1000 birds, 2.0% better feed-conversion ratio (P less than 0.05), and 2.5% (P less than 0.05) greater average weight per bird than category B flocks. No significant differences in hockburn bonus per 1000 birds (a bonus payable to growers whose broilers have the lowest prevalence of contact dermatitis lesions on the hocks) and mortality were found between category A and category B flocks. These results show that subclinical CAA infection has a substantial, statistically significant effect on commercial broiler performance and profitability.

Age Factors↗