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Dietary microbial 6-phytase concentration effects broiler growth, short-chain fatty acid profile, and intestinal histomorphology

Hamid Raei , Fatemeh Azari Ghaleh Joogh, Shahram Golzar Adabi , Mohammad Amir Karimi Torshizi

Abstract

Context; The dietary inclusion of inorganic phosphates to provide dietary phosphorus, besides increasing the cost of feed, leads to the release of excess phosphorus into the environment causing pollution. Aim; This study was conducted to determine the effects of dietary phytase concentration on growth, caecal short-chain fatty acids (SCFA) profile, tibia bone mineralisation, nutrient digestibility, and intestinal histomorphology of Ross 308 broilers. Methods; Treatments consisted of a negative control (NC) diet containing 1.2 and 1.1 g/kg of available phosphorus (avP) for the grower and finisher periods, respectively; a positive control (PC) diet containing 4.2 and 3.8 g/kg of avP for the grower and finisher periods, respectively, provided via dicalcium phosphate (DCP), and DCP in the PC diet was replaced with four levels of phytase at 500, 1000, 1500 and 2000 FTU/kg. Both NC and PC diets contained the same levels of avP for the starter period (0-10 d). Key results; At 1 to 41 d, body weight gain (BWG), feed intake (FI), and feed conversion ratio (FCR) were negatively affected in NC birds (P < 0.01). FCR was significantly lower by 3.1 and 3.7% in PC-1500 and PC-2000 birds respectively, compared to PC at 1 to 41 d (P < 0.01). Dietary supplementation of phytase significantly increased villus height, villus width, and villus surface area in PC-2000 birds compared to the PC group (P < 0.05). A significant increase in lactic acid and total aerobic bacteria counts was observed with increasing the level of phytase (P < 0.01). The inclusion of phytase in the diet resulted in a notable elevation in the concentrations of acetate, propionate, butyrate, branched-chain fatty acids (BCFA), and total SCFA (P < 0.05). Conclusion; In addition to enhancing growth performance, the incorporation of phytase into broiler diets with low avP can optimize intestinal morphology, regulate caecal microflora composition, and elevate the caecal concentration of SCFA. Implication; Higher phytase concentration exceeding commercial recommendations are likely to have increased beneficial effects on broiler performance.

AN24017  Accepted 18 March 2025

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