Effect of dietary supplementation of mannanoligosaccharides on growth performance, ileal microbial counts, and jejunal morphology in broiler chicks exposed to aflatoxins

• Aflatoxin challenge reduced weight gain and feed efficiency in broiler chickens.
• Supplemental MOS ameliorated retarded growth in aflatoxin-challenged chicks.
• The lowest bacterial count and greatest villi height were assigned to unchallenged birds.
• Supplemental MOS decreased ileal bacteria counts in aflatoxin-challenged broilers.

The present study was conducted to evaluate the effects of dietary inclusion of mannanoligosaccharides (MOS) on growth performance, ileal microbial population, and jejunal morphology in aflatoxin-challenged broiler chicks. A total of 336 seven-day-old Ross broiler chicks were randomly assigned into 7 experimental treatments with 4 replicates of 12 chicks each. Experimental treatments consisted of a control group (unchallenged group), and a 2×3 factorial arrangement of treatments, including 2 aflatoxin levels (0.5 and 2 ppm) and 3 supplemental MOS levels (0, 1, and 2 g/kg). Broiler chicks were challenged with a mix of aflatoxins during 7–28 d of age. Results showed that increasing aflatoxin level resulted in a marked decrease (P<0.01) in average daily feed intake (ADFI) and subsequent average daily gain (ADG); consequently it impaired (P<0.001) feed conversion ratio (FCR). Dietary MOS supplementation increased ADFI (P<0.01) and ADG (P<0.001) in aflatoxin-challenged chicks, resulted in the improvements in FCR values. The retarded ADG was ameliorated by inclusion of 2 g/kg of MOS into the diet of aflatoxin-challenged broiler chicks. Although incremental levels of aflatoxin decreased (P<0.05) carcass yield, dietary supplementation of MOS up to 2 g/kg resulted in an increase in carcass yield. Contamination with 2 ppm aflatoxin resulted in increases (P<0.001) in ileal enumerations of Escherichia coli, Salmonella, Klebsiella, and total negative bacteria at both 28 and 42 d of age. Although the lowest bacterial count was assigned to the control (unchallenged) group, supplemental MOS decreased ileal bacterial populations in aflatoxin-challenged broiler chicks. Dietary supplementation of 2 g/kg of MOS was more effective (P<0.05) in depression of ileal microbial counts in broiler chicks challenged with 0.5 ppm aflatoxin. Incremental levels of aflatoxin resulted in considerable (P<0.001) decreases in villi height, villi height to crypt depth ratio, villi absorptive area, and apparent villi absorptive area. Moreover, dietary aflatoxin contamination increased crypt depth, goblet cell counts, and lymphoid follicular diameter. These changes, however, were partly modulated by dietary MOS supplementation up to 2 g/kg. The present results indicated that although aflatoxicosis reduced growth performance, dietary inclusion of MOS ameliorated the retarded growth via suppressing ileal pathogenic bacteria and enhancing absorptive surface area in broiler chicks.