Quantitative changes in the lymphoid follicles and lymphocytes of the bursa of Fabricius in White Pekin ducks was studied using 51 birds aged from day old to 155 days. The number of follicles in the tunica mucosa was constant from day of hatch to 58 days of age and decreased thereafter. The size attained is peak value by about 58 days of post-hatch and decreased thereafter.
White Pekin duck, bursa of Fabricius, lymphoid follicles, post-natal development