Abstract

Antibiotics as growth promoters in poultry diets are currently restricted, so other feed additives, such as prebiotics and probiotics, have been suggested as an antibiotics alternative to improve the performance and gut health of poultry. The current experiment was conducted to study the effects of adding Mannan oligosaccharides (MOS) as a potential replacement for an antibiotic on productive performance, nutrient digestibility, some blood parameters, and caecal microbiota of broiler chickens. For conducting the current research experiment, a total of 180 one–day old Ross broiler chicks were randomly divided into one control group fed a basal diet and four dietary treatments with six replicates for each treatment. The treatment groups were fed a basal diet supplemented with different levels of MOS 0.5, 1, and 2 g/Kg diet and Lincomycin 4.4 mg/Kg diet during 35 days of the feeding trial. With exception of the growing period, the group fed a basal diet supplemented with 2 g MOS/Kg feed had considerably higher body weight and weight gain, while having the lowest feed consumption and best feed conversion ratio compared to the other treatment groups, during all experimental periods. Moreover, dietary supplementation of MOS resulted in a significant decrease in the counts of caecal E. coli and Enterococcus, while Lactobacillus and Yeast bacteria counts were significantly higher, compared to non-supplemented groups. Broiler chicks having a 2 g MOS/kg diet recorded lower values of cholesterol, low-density lipoprotein (LDL), urea, and liver enzymes, including Aspartate transaminase (AST) and Alanine aminotransferase (ALT), while they recorded significantly higher high-density lipoprotein (HDL), compared to the other experimental groups. Group treated with MOS 2 g/Kg feed improved digestibility of crude protein, ether extract, crude fiber, nitrogen-free extract, and organic matter, compared to the control group, Additionally, MOS supplementation also increased the intestinal villi length, width, and crypt depth and decreased intestinal inflammation, compared to the control group. In conclusion, supplementation of MOS at 2 g/kg diet improved growth performance, digestibility, and blood parameters without having adverse effects on the intestine of broiler chickens, comparable to the Lincomycin.