Dietary Microbial Muramidase Improves Growth Performance Alone or in Combination with Antibiotic Growth Promoters

The gastro-intestinal tract (GIT) of poultry has a complex and dynamic microbial community consisting primarily of bacteria whose cell wall contains the structural polymer peptidoglycans (PGNs). Bacterial cell wall recycling is a process whereby bacteria degrade their own wall during growth in order to recover released constituents by active transport. These nutrients are then reutilized to either rebuild the wall or to gain energy (Mayer, 2012). However, in both normal and a challenged GI tract environment, PGNs can be accumulated. The consequence of PGNs accumulation on the intestinal lumen remains to be investigated, but it could be speculated that accumulation of bacterial cell wall fragments in the gut could impair nutrient digestion and absorption, and negatively affect animal performance. Muramidases are natural enzymes that hydrolyze PGNs from the bacterial cell wall. Recent studies (Lichtenberg et al. 2017; Goodarzi Boroojeni et al. 2019; Sais et al. 2019) have reported positive effects on broiler growth performance by supplementation with a novel microbial muramidase (MUR) which could hydrolyze the PGNs from bacterial cell wall fragments. The goal of the experiment was to evaluate the effect of a microbial MUR with and without antibiotic growth promoters (AGP), on broiler growth performance.

A 42-day feeding trial was conducted with a male flock of 1600 Cobb 400Y chicks randomly allocated to 64 floor pens (25 birds each). Broilers were fed corn-soybean-meat and bone meal-based diets containing Robenidine as coccidiostat. A three-phase dietary program and four experimental pelleted diets were used: a negative control diet (NC), a NC diet + Bacitracin methylene disalicylate (BMD, 50 ppm), NC diet + MUR (25000 LSU(F)/kg) and a NC diet + BMD (50 ppm) + MUR (25000 LSU(F)/kg). Growth performance parameters were recorded at day 0, 14, 28 and 42 of the study. Data were analyzed by two-way ANOVA and means were compared by the Student-Newman-Keuls.

In the present study, the inclusion of MUR in the diet improved body weight gain (P < 0.001) but not when an AGP was included in the diet (P = 0.923), and no interaction was found between AGP and MUR (P = 0.364). MUR supplementation significantly (P < 0.001) increased BWG by 2.4% and 3.2% compared to the NC and NC + BMD, respectively, but no differences were observed when NC + BMD + MUR. Regarding FCRc, the inclusion of MUR showed again a significant improvement (P < 0.001) but not when AGP was included in the diet (P = 0.472) but this time an interaction between AGP and MUR was observed (P = 0.014) indicating that AGP only improves FCR when it is included with MUR. This combination showed the best FCRc value and one explanation could be that AGPs promote bacterial turnover thereby increasing the PGNs in the gut and consequently providing more substrate for the microbial muramidase.

In conclusion, dietary microbial muramidase alone or in combination with AGPs improves broilers performance.