Stunting syndrome in broilers: physical, physiological, and behavioral aspects.

The effect of stunting syndrome (SS) on young broilers induced by orally administering an inoculum prepared from intestines of SS-affected broiler chicks was studied in two experiments. Depression of growth, feed intake, and feed utilization, respectively, was negatively related to the age of inoculation, i.e., highest at posthatch inoculation (63, 57, and 61%), and intermediate at the ages of 3 (42, 45, and 50%) and 7 d (29, 34, and 53%), whereas at the age of 14 d inoculation was ineffectual and the inoculated chicks performed similarly to the naive controls. Eating behavior was determined by periodically recording the number of chicks in each treatment group exhibiting this behavior, i.e., pecking mash in the feeder or pecking the litter. Eating activity was much higher in inoculated chicks (about 20 to 24%) than in the naive controls (6 to 12%) and as with performance negatively related to the age of inoculation. In chicks inoculated at the age of 14 d, eating activity was quite similar to that of the naive control chicks. Noninoculated chickens raised in the same room as their inoculated counterparts were infected by the disease agents. In some respects the consequences of horizontal infection were similar to those observed in inoculated chicks, i.e., depressed feed intake, growth, and feed utilization and a heavier heart, crop, proventriculus, gizzard, intestine, and gastrointestinal contents. In contrast, the activities of the pancreatic digestive enzymes were more similar to those of the naive controls than to those of the inoculated groups. At the age of 14 d, activities of amylase, trypsin, chymotrypsin, and lipase in the pancreas were lower in the inoculated than in the naive control birds. At the age of 21 d, the results were reversed and activity in the inoculated birds was higher than in the naive control birds. During both periods, the activity of pancreatic lipase was higher in the naive controls than in the inoculated birds. The hyperactivity estimated via a determination of eating activity suggests that SS is an affliction not only of digestion but also of metabolism.