Posthatching changes in the immunoglobulin A concentration in the jejunum and bile of turkeys

An experiment was conducted to document the age-related changes in IgA concentration in the small intestine of newly hatched turkey poults reared in floor pens and to determine whether infection with stunting syndrome (SS) affects age-related changes. Day-old turkey poults were dose per os with .5 mL of saline carrier (control) or with .5 mL of one of two dilutions (250- or 2.5 x 10(6)-fold) of a "crude" SS-causing inoculum. Inoculation with the 250-fold dilution depressed body weight gain (P less than .01) throughout the experiment and impaired feed efficiency (P less than .05) at 5 and 9 days of age as compared with the control group. After 9 days of age, all inoculated poults utilized feed more efficiently than did control poults (P less than .01). Stunting syndrome did not affect IgA concentrations in either bile or jejunum at any specific age. Age-related changes in IgA concentrations, however, were observed. Bile IgA decreased from 1 to 9 days of age, and then increased until 29 days of age. The IgA concentration in jejunal tissue increased linearly from 1 to 29 days of age (P less than .01), whether expressed as IgA concentration per gram of wet tissue or as percentage of total protein in jejunum. Age-related changes in IgA concentration in both bile and jejunum suggest that the secretory immune system associated with the digestive mucosa is not fully developed at the time of hatch.