Clinical and Gross Pathological Investigations of Internal Laying in Commercial Layer Chicken

摘要

Avian oviduct is a tubular organ and its muscular contraction responsible for recurring ovum transportation, egg formation, oviposition, sperm transport and fertility. Any defect in oviduct motility may have a great bearing on the above said functions and also results in internal laying or ectopic oviposition. Modern commercial layer are highly prolific and susceptible to internal laying however their prevalence, nature and significance is not known. Hence a study was undertaken to assess the prevalence and clinico-pathological aspects of internal laying in commercial white leghorn layer chicken in Namakkal region of India. A total of 5145 carcasses of white leghorn layers, above 20 wks age from 255 flocks were examined for various oviduct abnormalities for a period of four years (2006 to 2009). Among all the cases examined for reproductive tract abnormalities, 51 (0.99%) cases from nine flocks revealed internal laying with an overall drop in egg production, morbidity and mortality of 0.5 to 1.0%, 0.5 to 1.0% and 0.2 to 0.5 % respectively between 21 and 80 wks. of age. Necropsy examination revealed distended abdomen, few to numerous, partial as well as fully formed eggs along with yolk materials in the peritoneal cavity. On the basis of oviduct lesions, the causes of internal laying were identified as thin shelled eggs (33.33%), salpingitis (27.45%), vent trauma (17.65), heat stress (3.92%), oviduct neoplasm (1.96%) and unknown cause (15.69%). Microbial analysis of samples revealed the presence of Escherichia coli in cases associated with salpingoperitonitis. Internal laying was noticed in layers with highest occurrence in 21–30 wk. (25.49%) and 41-50 wk. (21.57%) of age and during summer season (49.02%). It was concluded that the presence of eggs in the abdominal cavity and lesions in the shell gland and vagina indicates the functional alterations of the distal parts of reproductive tract could be responsible for internal laying