Symbiotic can replace zinc bacitracin in diets for layer-type chicks

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Context Antibiotics are being prohibited as additives in poultry diets. Therefore, poultry farmers have been searching for other alternatives, such as symbiotics, to include in broilers and laying hens diets. In contrast, symbiotics have not been tested in laying-type chicks, especially symbiotics composed of three groups of bacteria, yeast and two prebiotics. Aim This study examined the effects of replacing zinc bacitracin with symbiotic supplementation on the performance variables, haematology and blood biochemistry variables, and the weight of the immune and digestive systems in layer-type chicks. Methods A total of 1040 female layer-type chicks from 1 to 5 weeks of age were evaluated in a completely randomised design, four treatments and 10 replicates of 26 birds. The treatments consisted of two basal diets (one composed of corn and soybean meal [control diet] and another similar to the first diet, except with the addition of meat and bone meal [MBM]), and two diets based on MBM: one with 0.05% zinc bacitracin (ZnBc) and another with 0.1% symbiotic. Data were subjected to analysis of variance and means were compared by orthogonal contrasts. Key results MBM provided higher mean bodyweight, weight gain and creatinine levels, but lower liver weight, caecum length and gamma-glutamyl transferase levels than in the birds fed the control diet. From 1 to 14 days, ZnBc provided greater bodyweight and weight gain than MBM. From 1 to 28 and 1 to 35 days, ZnBc resulted in higher bodyweight and weight gain, but lower feed intake and feed conversion ratio than birds fed the MBM diet. ZnBc decreased alkaline phosphatase, and increased creatinine levels and gamma-glutamyl transferase. From 1 to 14 and 1 to 21 days, 0.1% symbiotic provided a better feed conversion ratio than in the birds fed the ZnBc diet. The 0.1% symbiotic supplementation resulted in lower liver and fabricius bursa weights, higher mean alkaline phosphatase, and lower globulin, gamma-glutamyl transferase and aspartate transferase levels than ZnBc. Conclusion The symbiotic is effective for female layer type-chicks, fulfilling the purpose of replacing ZnBc. Implications Symbiotics used in chicks’ diets from the first day of life can replace antibiotics to maintain physiological homeostasis and protect them from possible stress situations.