Relationships between age, body weight, and season of the year and the incidence of sudden death syndrome in male broiler chickens.

The aim of this study was to examine relationships between the incidence of sudden death syndrome (SDS) in male broiler chickens and age, body weight, and season of the year. The data used were from 23 experiments conducted from July 1982 to June 1987 involving a total of 89,988 chickens aged 1-day to a maximum of 70 days. All chickens that died during the experiments were necropsied and the incidence of SDS noted. Incidence of death from SDS as a percentage of mortality ranged from 1.31 to 9.62% among experiments. Death rate from SDS showed a significant increase with body weight. The SDS mortality rate reached a maximum when birds were between 21 and 27 days of age. Death rate from SDS increased up to about 21 days and remained between 80 and 86/100,000 chickens per day to 39 days, with a gradual decline to the end of the observation period (63 days), when it was 54/100,000 per day. Death rate from SDS may be related to the month in which the experiment started, with the highest mortality occurring in January and the lowest in July. Correlations between death rates from SDS and other causes were not significant.