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The present study was conducted to evaluate the effect of two different β-mannanases on growth performance and nutrient retention of broiler chickens fed a diet with low energy and amino acid density. A total of 312 one-day-old male broiler chickens (Ross 308) were placed in floor pens and fed a standard starter diet for 16 days. They were then randomly moved to stainless steel cages and distributed into three groups, with 13 replicates of 8 chickens each. The control group received a corn-soybean meal-based grower diet with reduced metabolizable energy by ∼100 kcal/kg and a 10-12% reduction of digestible amino acids (lysine, methionine, and threonine). Titanium oxide was added at 0.5% of diet as an indigestible marker. The other groups were fed the same diet supplemented with either β-mannanase A derived from Thermothelomyces thermophilus (100 g β-mannanase/MT grower diet) or β-mannanase B derived from Paenibacillus lentus (350 g β-mannanase/MT grower diet). The trial lasted for 7 days from d 17 to d 23, comprising 4 days of acclimatization followed by 3 days of sample collection. Final body weight (d 23), body weight gain (d 17-23), and feed intake (d 17-23) of broiler chickens did not differ among the groups. However, both β-mannanases significantly improved the feed conversion ratio during d 17-23 (P = 0.039) and nitrogen retention (P = 0.028) in broiler chickens compared to the control group. Moreover, dietary supplementation with β-mannanase A significantly increased dry matter retention (P = 0.050), organic matter retention (P = 0.028), and nitrogen-corrected apparent metabolizable energy (AMEn; P = 0.033) compared to the control group. In conclusion, supplemental β-mannanase, regardless of the product, improved the growth performance of broiler chickens by improving nutrient retention and dietary AMEn.

ABSTRACT: The present study was undertaken to evaluate the efficacy of 2 graded levels (0.03 and 0.05% of diet) of a monoglyceride blend containing butyric, caprylic, and capric acids in broilers’ diet for optimizing gut structure and animal growth performance. For this purpose, a total of 210, one-day-old male Ross 308 broiler chicks were randomly allocated to 3 experimental treatments using 7 replicates each and 10 birds/replicate. The treatment groups involved supplementation of blend of short and medium chain fatty acids at the level of 0, 0.03, and 0.05% of the diet for 42 d. The incorporation of mixes of monoglycerides into broilers’ diet linearly improved BWG between d 0 and 21 (P = 0.034). At the end of trial, however, no significant changes were observed in performance indexes (BWG, FI, FCR). Jejunal morphometric parameters (villus height, crypt depth, and their ratio) remained unaltered with the monoglyceride supplementation on d 21. The results further showed that monoglycerides supplementation increased the goblet cell counts along the jejunal villi (P = 0.034) and crypt regions (P = 0.022), as well as it effectively modulated the mRNA abundances of tight junction protein (ZO-1, P = 0.033) and nutrient transporters (SGLT, PePT1; P = 0.005, 0.023, respectively) in the jejunum. Moreover, the downregulation in mRNA abundance of TNFα (P = 0.030) was observed with the monoglyceride supplementation. The SCFAs analysis of cecal contents showed no notable differences with monoglyceride blend supplementation when compared to the unsupplemented group. Collectively, high goblet cell numbers in the jejunum along with downregulation of the mRNA abundances of pro-inflammatory cytokines, upregulation of tight junction proteins, and nutrient transporters showed favorable responses of low doses of monoglycerides blend in broiler feeding. Further studies should be conducted in different rearing conditions to examine the effectiveness of such low levels of a monoglyceride blend in the modulation of gut structure, its functionality and animal performance.