Principal Lesions and Patterns of Mortality Observed in a Broiler Breeder Flock During the Laying Period

ABSTRACT In any broiler breeder flock, there is always some mortality that is considered to be “normal” during the life of the flock. The aim of this study is to summarize the prevalence and patterns of mortality during the production period. To evaluate the mortality, each dead hen was systematically and completely examined via necropsy. In addition to post mortem evaluation, weights (whole body, liver, spleen and heart) were recorded to correlate the bird’s physical condition with the mortality category or lesion. In general, the variation in mortality was not associated with the specific weight of the organs. However, for specific diseases like fatty liver, septicemia and ascites, there was a correlation with the organ weight of the liver, spleen and heart respectively. Ovaritis was observed to be the most prevalent lesion found in dead hens during the production period followed by ovarian regression (atrophy), peritonitis, internal lay and vent pecking. The two periods with the higher total percentage of morality were onset of lay (25-30 weeks) and end-stage of the production period (56-61 weeks). During the laying period, we mainly observed metabolic disorders followed by infectious lesions. Infectious lesions, including ovaritis and septicemia, were the predominant cause for mortality at the onset production. Vent and feather pecking were also primarily concentrated during the first weeks of the production period. Metabolic diseases were observed in higher prevalence during the latter half of the production period.