Replacing bacitracin zinc antibiotic with symbiotic additive in pullet diet

Abstract

Context Currently, since the use of antibiotics as growth promoters in animals has been banned worldwide, it is necessary to use other additives that indorse an adequate balance of the intestinal microbiota, so as to render better results in nutrient acquisition and health of poultry, yielding adequate growth and performance. Aim The study evaluated the effects of dietary supplementation with symbiotics during the grower phase, to replace bacitracin zinc. Methods The experiment included a total of 684 pullets of the Dekalb White strain, from 6 to 15 weeks of age, distributed in a completely randomised design, with five treatments, and eight replications of 18 birds each. The treatments were composed of two base diets, namely one of corn and soybean meal (reference diet, RD), and another of meat and bone meal (MBM), in addition to two more diets based on MBM, one with an addition of 0.05% of bacitracin zinc (Bac Zn), and the other with 0.1% of symbiotic provided to two groups, including one group that had already consumed the symbiotic since the first day of life (starter phase, Symb-S), and the other that started to consume at the beginning of the experiment (grower phase, Symb-G). Performance, blood variables, nutrient metabolisability, weights of organs of the immune and digestive system, and measurement of length (intestine and caecum) were determined. Data were compared using orthogonal contrast. Key results The birds fed with the RD diet presented a worse overall performance and coefficients of apparent metabolisability of dry matter (CAMDM) (6–10 weeks) than did those fed the MBM diet. Birds fed with the Bac Zn diet showed better bodyweight gain (6–15 weeks), coefficients of apparent metabolisability of gross energy (CAMGE) and CAMDM (6–10 weeks) than did those fed the MBM diet. Birds fed with symbiotic diets had better responses in blood biochemistry variables (alkaline phosphatase, total proteins) than did those fed the Bac Zn diet. Conclusion The use of symbiotics since the starter and grower phase can replace the use of Bac Zn, without affecting the biochemical and metabolic responses of the pullets. Implications Symbiotics improved utilisation of diet nutrients, maintenance of physiological homeostasis, and growth of pullets.