Two experiments were conducted to evaluate the effect of virginiamycin (VM, 22 mg/kg of diet) on performance of uninfected (CON) turkey poults and those infected (INO) with stunting syndrome and reared on used woodshavings (Experiment 1) or on clean or used woodshavings (Experiment 2). Virginiamycin improved BW (P less than .001) and feed efficiency (FE) (P less than .05) from 1 to 29 days of age, irrespective of type of litter or disease condition. The increase in BW induced by VM, however, was greatest when poults were kept on used litter, resulting in significant (P less than .05) VM by litter interaction. Induced stunting syndrome depressed BW (P less than .01) to 29 days of age and impaired FE from 1 to 9 days of age (P less than .05) and from 5 to 9 days of age (P less than .01) in Experiments 1 and 2, respectively. Virginiamycin did not prevent early adverse effects of INO on BW and FE, but facilitated notable recovery of INO poults relative to INO poults not fed VM. Virginiamycin increased specific activities of maltase and sucrase of the jejunum of CON poults in Experiments 1 and 2; in Experiment 2, this VM effect was evident irrespective of type of litter. Maltase-specific activity and sucrase were reduced by INO (P less than or equal to .05 and P less than or equal to .01 in Experiments 1 and 2, respectively) and VM did not modify this effect. The maltase and sucrase data suggest that VM improved BW and FE of CON poults, in part, by helping to maintain digestive and absorptive functions of the small intestine during the early growth period, but, in the instance of INO poults, VM was not effective in this regard.

Experiments were done to determine the effect of feeding diets of different ingredient composition to poults experimentally infected with stunting syndrome (SS) at 1 day of age. In Experiment 1, feeding a complex diet (CPX) containing fish meal and sunflower meal as the main protein sources eliminated the adverse effects of SS inoculation on performance traits as compared with SS effects on poults fed a corn and soybean meal (CS) diet. In Experiments 2 and 3, the effects of SS were more severe than in Experiment 1. In these experiments, the CPX diet only partly overcame the adverse effects of SS on performance (i.e., in Experiment 2, growth depressions from 2 to 5 days of age were 90.3 and 59.6% in SS-inoculated poults fed the CS and CPX diets, respectively, as compared with uninoculated, control poults fed the same diets). Properties of the CPX diet that made it effective in reducing the severity of SS were not evident from the results of Experiment 3. Replacing soybean meal with soy protein or canola meal was ineffective as compared with the use of a mixture of sunflower meal, fish meal, meat and bone meal, and corn gluten meal.