Comparative effects of dietary muramidase and phytogenics on the growth performance and gastrointestinal functionality of broiler chickens

The objective of the present study was to compare the effectiveness of dietary supplementation of muramidase (MUR) and 2 phytogenic additives on the growth performance, intestinal morphology, bacteria load, and production of short-chain fatty acids (SCFA) of broiler chickens raised under field-like conditions. A total of 6,400 day-old Ross 308 broiler chicks were randomly selected and distributed into 32 floor pens, with 200 chicks (100 males and 100 females)/pen. The treatment groups were an unsupplemented control, and the experimental groups supplemented with MUR at 35,000 LSU(F)/kg of feed, phytogenic 1 (Phyto 1, based on thymol) at 100g/ton feed, or phytogenic 2 (Phyto 2, based on alkaloids) at 60g/ton feed, for a total period of 41 d. A 4-phase feeding program was applied (starter, grower, finisher and withdrawal). The paramenters evaluated were: growth performance, carcass yield, concentration of muranic acid in the jejunum content and excreta, liver enzyme concentration, intestinal morphology, and bacteria enumeration and short and branch chain fatty acids (SCFA and BCFA) in the cecal content. Data were analyzed by ANOVA and Tukey's test was used to separate the means. Soluble muramic acid (MurN) in the jejunum increased with the supplementation of MUR and Phyto 2 when compared to the other groups (P = 0.0001), but only the supplementation of MUR increased the concentration of MurN in the excreta. The supplementation of all feed additives improved the body weight gain and the body weight corrected feed conversion ratio when compared to the control group (P = 0.0001). MUR increased villus heigh (VH) when compared to the control or the other supplemented groups (P = 0.0001), and led to the highest concentration of most SCFA, total BCFA, and total SCFA (P < 0.05). In conclusion, the supplementation of MUR and phytogenics to the diets of broiler chickens improved the growth performance, but MUR, only, was capable of effectively degrading peptidoglycans (PGNs) in both intestinal segments, as well as to increase the abundance of beneficial bacteria and SCFA production.