Gorgan University of Agricultural Sciences and Natural Resources Poultry Science Journal 2345-6604 14 1 2026 01 01 Effects of Feed Restriction and Prebiotic Supplementation on Growth Performance, Immune Responses, Microbial Population, and Intestinal Morphology of Broiler Chickens 91 99 7408 10.22069/psj.2025.23702.2335 EN Ali Maddahian Animal Science Research Department, Gilan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran 0000-0002-7674-4888 Reza Naseri Harsini Animal Science Research Department, Gilan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran Hamed Kioumarsi Animal Science Research Department, Gilan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran Seyed Mousa Saadat Mirqadim Animal Science Research Department, Gilan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran Houshang Dehghanzadeh Animal Science Research Department, Gilan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran Hassan Khamisabadi Animal Nutrition and Physiology Research Department, Animal Science Research Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran Journal Article 2025 05 31 This study examined the effects of feed restriction and prebiotic supplementation on broiler chickens’ performance, immune response, gut microbiota, and intestinal morphology. A total of 240 one-day-old male Ross 308 broilers were randomly assigned to four treatments: control (C), feed restriction (FR), prebiotic supplementation (P), and a combination of prebiotic supplementation with feed restriction (FR+P). The prebiotic contained mannan-oligosaccharides (MOSs) and beta-glucans at 0.1% of the diet. Feed restriction was set at 80% ad libitum intake during the second week. The findings indicated that prebiotic supplementation increased the feed intake and weight gain, particularly during the early growth phase (p< 0.05). Feed restriction resulted in low daily weight gain and impaired cellular immune response (p< 0.05); however, these detrimental effects were partially mitigated by prebiotic supplementation. The FR+P group treated at 21 days had higher counts of Lactobacillus with lower coliform counts in the cecum (p< 0.05). Moreover, prebiotic supplementation improved intestinal morphology as indicated by an increase in villus height and crypt depth of the duodenum and jejunum with a significant effect in the FR+P and P groups (p< 0.05). The FR+P group recorded the highest villus height of the duodenum at 21 days, whereas the highest jejunal villus height and duodenal crypt depth were observed in the P group at 42 days (p< 0.05). The cell-mediated immunity, as determined by footpad swelling following the injection of PHA, was greatly enhanced in birds fed prebiotics compared to birds with feed restriction alone (p< 0.05). Overall, prebiotics, particularly with feed restriction, enhanced gut health, immune function, and intestinal morphology, suggesting their potential in broiler production. https://psj.gau.ac.ir/article_7408_6d5e64d8e11f961e7f8d92c3ebc76fe8.pdf