Broiler lines divergently selected for digestive efficiency also differ in their susceptibility to colibacillosis

Increasing feed efficiency of broiler chickens by selective breeding could lead to decreased feed cost and reduced environmental impact of poultry production. At INRA, two broiler chicken lines (D+/D-) were divergently selected for their digestive efficiency. Strong differences were shown between both lines for the anatomy and histology of the digestive tract, and for the intestinal microbiota composition. In the present study, we investigated whether this selection also had an effect on susceptibility to colibacillosis, which is one of the main causes of economic losses in poultry production. The broiler lines D+/D- were challenged with an avian pathogenic Escherichia coli strain. A first experiment was conducted to assess the 50% lethal dose by subcutaneous infection of hatchlings, whereas a second experiment reproduced colibacillosis by infecting air sacs of 23-day-old chicks. The 50% lethal dose was very low for both lines. However, the line with the higher digestive efficiency (D+) was the less susceptible to colibacillosis. This result is interesting for selection purposes and opens the way to integrative genetic studies of the interactions between digestion efficiency and resistance to colibacillosis.