Quantitative assessment and comparison of genetic susceptibility to colibacillosis in meat-type chickens.

Abstract

The aim of this study was to examine whether susceptibility to colibacillosis differs between four meat-type chicken lines, indicating genetic variation in susceptibility. This was achieved by a placebo-controlled E. coli challenge experiment and subsequent comparison of mortality rate, colibacillosis lesions and growth retardation. Commercial broilers were included and functioned as reference group. Susceptibility to colibacillosis was measured after intra-tracheal E. coli506 inoculation at 8 days of age. The experiment was ended at 17 days of age and colibacillosis lesion scoring was performed.Mortality rates in the E. coli inoculated groups were not statistically significant ( P > 0.05) in the period of 8 to 10 days of age. From 11 to 17 days of age and from 8 to 17 days of age mortality did differ significantly between some pure lines ( P < 0.05). Compared to their placebo inoculated chicken line mates, mean body weight of the E. coli inoculated group was significantly lower ( P < 0.05) and uniformity in body weight was also reduced resulting in a greater standard deviation of the mean body weight. Mean body weight also differed significantly ( P < 0.001) between chickens showing different levels of colibacillosis. Mean lesion score (MLS) differed between the chicken types. Between the four meat-type chicken lines susceptibility to colibacillosis differed, indicating genetic variation in susceptibility. The commercial broilers were the least susceptible to colibacillosis as they showed lowest mortality and MLS.