MORTALITY AND DISEASE STATUS IN HY-LINE AND ISA-BROWN STRAINS OF LAYER CHICKENS REARED IN CAGE SYSTEM IN BANGLADESH
Mortality and disease status in Hy-Line (n= 3450) and ISA-Brown (n = 250) strains of layer chickens were carried out in three commercial layer farms in the district of Mymensingh from day-old to 65 weeks age of birds from September 2003 to December 2004. The management including housing, hygienic measures, vaccination practices, diseases occurred and mortality were observed and recorded daily. Diseases and disorders were diagnosed based on the disease history, clinical signs, characteristics necropsy lesions, morbidity and mortality rates, and laboratory investigations including bacteriological and parasitological examinations. The morbidity and mortality of chickens caused by different diseases and disorders were statistically analyzed on the basis of farms, strains of birds, age and seasons. An overall 32.38% (n = 1198) morbidity and 21.30% (n = 788) mortality was recorded among 3700 chickens. Etiological analysis showed that the highest mortality caused by bacterial diseases (7.08%), followed by viral diseases (5.81%), fungal diseases (2.18%), mycoplasmosis (1.89%), parasitic diseases (1.83%) and nutritional and other disorders (2.48%). Specific diseases and disorders caused mortality in chickens included Salmonellosis (3.14%), Colibacillosis (2.51%), Fowl cholera (0.46%), Infectious coryza (0.41%), Necrotic enteritis (0.59%), Infectious bursal disease (2.19%), Newcastle disease (1.76%), Avian leukosis (0.73%), Fowl pox ( 0.51%), Mareks disease (0.62%), Aspergillosis (1.54%), Aflatoxicosis (0.65%), Mycoplasmosis ( 1.89%), Ascaridiasis (0.22%), Tapeworm infection (0.16%), Coccidiosis (1.32%), Ectoparasitosis (0.14%), Nutritional deficiency (0.68%), Ascites, Hydropericardium hepatitis syndrome (0.49%), Cannibalism (0.27%), Egg peritonitis (0.22%), Egg bound disorder (0.43%) and Heat stroke and cold (0.41%). Diseases caused highest mortality during laying period (8.43%), followed by growing (6.32%), pullet stage (4.65%) and brooding (3.78%) ages. Both the morbidity and mortality rates in ISA-Brown strain (62.60% and 37.20%) were found significantly (p < 0.01) higher in comparison to Hy-Line (30.17% and 20.14%) strain of chickens. Seasonal influences on mortality in layer type chickens showed significantly (p < 0.01) highest mortality during summer (8.57%), followed by winter (6.51%) and rainy (6.22%) months. It may be concluded that the infectious diseases even with vaccination associated with high morbidity and mortality in commercial egg type chickens in Bangladesh.
Bangl. J. Vet. Med. (2011). 9(1): 01-16