Evidence that bacteria are not causative agents of stunting syndrome in poults

Two experiments were conducted to determine the effect of removing bacteria, including long segmented filamentous organisms (LSFO), from inoculum known to induce stunting syndrome (SS) in poults. Experiment 1 consisted of two identically designed trials. In each trial, each of four treatments was assigned to an isolator. Three treatments consisted of dosing, by crop intubation, groups of 1-day-old poults with unfiltered SS inoculum or filtrate of inoculum passed through .45- or .20-micron microfilters. Uninoculated poults were dosed with inoculum carrier, saline. Experiment 2 was done in battery facilities. Three rooms were used and each room housed one of three treatment groups. Triplicate pens of 10 poults each within each room were dosed by crop intubation with saline (uninoculated), unfiltered inoculum, or filtrate from .20-micron filtration. As compared with uninoculated poults, weight gain through 7 days was reduced 20% (P less than .05) by unfiltered and filtered inocula in both experiments. Jejunal maltase activity also was decreased (P less than .01) by unfiltered and filtered inocula. Feed efficiency (FE) was not determined in Experiment 1, but in Experiment 2, FE from 1 to 14 days of age was impaired by inoculum, irrespective of filtration. This effect was not evident during the 14- to 20-day period. The observation that the adverse effects of giving filtered inoculum to poults were the same as those caused by unfiltered inoculum indicated that bacteria, including LSFO, were not primary causative agents of the SS experimentally induced in poults.