Development of the bursa of Fabricius in the partridge and pheasant.

Development and regression of the bursa of Fabricius was measured in chukar partridge (Alectoris chukar) and ring-necked pheasant (Phasianus colchicus) from hatch to 40 and 34 weeks of age, respectively. Testes weights were recorded for 8 to 34-week-old pheasants and 12 to 30-week-old chukars. Approximately 12 partridges and 12 pheasants of mixed sex were killed every other week and their bursae measured and weighed. Results indicated that chukar bursal weight peaked at about 10 weeks of age in both sexes and then immediately regressed. Chukar bursal weights were highly correlated with age and body weight from hatch to 11 weeks of age but not after 11 weeks. Male chukar bursal weights decreased more rapidly than those of females (P less than .05). In ring-necked pheasants, maximum body weights were attained at 26 and 20 weeks of age for males and females, respectively. Maximum pheasant bursal weights were attained at 10 and 12 weeks of age for males and females, respectively. Bursal weight declined immediately after maximum bursal weights were attained. Age appeared to be a more important factor than body weight with regards to bursal regression in both the chukar and pheasant.