Effects of probiotics on gut (duodenum) morphology of broiler challenged with Salmonella enteritidis. A, positive control; B, negative control; C, probiotic 23 (treatment); D, probiotic IKP111 Probiotic (treatment); E, probiotic 333 (treatment); F, probiotic 23 (preventive); G, probiotic (preventive) IKP 23; H, probiotic 333 (preventive); I, protexin; J, antibiotic.