Differential resistance to Staphylococcus aureus challenge in two related lines of chickens

Trials were conducted to determine whether differential resistance to challenge with Staphylococcus aureus was characteristic of two related lines of New Hampshire chickens differing genetically in size of the bursa of Fabricius. Neonatal small bursa line (SBL) chicks were superior to the unselected Lester J. Dreesen (LJD) line in five of six trials employing intracardiac challenge (chi 2 = 6.3, .05 greater than P greater than .01). Older (7 to 12 wk) SBL chicks, challenged intravenously, had superior resistance than Line LJD chicks in three of four trials where a direct comparison was possible. The mortality rate in Line SBL was 34% in all trials compared with a 54% mortality rate (chi 2 = 11.7, P less than .001) in Line LJD. Moreover, the development of morbidity was more rapid in Line LJD. It is suggested that these lines can be of use in investigations of the nature of resistance to staphylococcal disease.