Effects of a Dietary Multi-Strain Probiotic and Vaccination with a Live Anticoccidial Vaccine on Growth Performance and Haematological, Biochemical and Redox Status Indicators of Broiler Chickens

SIMPLE SUMMARY: Coccidiosis, a parasitic disease caused by protozoa of the genus Eimeria, is one of the most frequently investigated enteric poultry diseases, primarily due to its ubiquity and severe negative effects on the economic efficiency of the poultry industry. Immunoprophylaxis with live anticoccidial vaccines is regarded as an effective tool to control this parasitic disease; however, there is a great reluctance to use this approach in broilers, primarily because of reports of transient reduced performance due to the state of ‘mild coccidial infection’ associated with anticoccidial vaccines. In this context, the administration of some feed additives may be useful as supplementation to improve the health status and immune response. Therefore, the present study aimed to evaluate the effect of dietary supplementation with a probiotic on growth performance, oocyst shedding, and selected blood parameters in broilers vaccinated with a live oocyst vaccine. ABSTRACT: A total of 256 male Ross 308 chickens were assigned to four treatments in a 2 × 2 factorial design with two levels of the anticoccidial vaccine (ACV) Livacox T (none or 1 × dose) with or without dietary supplementation with the probiotic Protexin(®) (P). The growth performance parameters for the test periods (1–21, 22–42, and 1–42 d) and oocyst per gram (OPG) at weekly intervals were analysed. Blood samples were collected at 16 post-vaccination (pv) days to measure selected haematological, biochemical, redox, and immunological parameters. ACV administration worsened the performance parameters of the chickens for 1–21 d pv, while supplementation with P reduced this negative effect with a significant improvement in 1–21 d body weight gain and feed conversion ratio. ACV administration increased % phagocytic cells (%PC), phagocytic index (PI), respiratory burst activity, proportion of monocytes, and activities of aspartate aminotransferase (AST) and lactate dehydrogenase, while it decreased the catalase activity and concentration of malondialdehyde and peroxides. The dietary administration of P significantly increased counts of red blood cells and white blood cells and increased %PC and PI, while it decreased the heterophil proportion, heterophil/lymphocyte ratio (p = 0.059), and alanine aminotransferase and AST activities. The oocyst counts were comparable in all sampling periods, except on 14 d pv, as supplementation with P significantly decreased 14 d OPG, thus indicating a positive influence of P on immunity development. In conclusion, dietary supplementation with P led to improved performance, better immunity, and benefits in health status in broilers vaccinated with the ACV, without interfering with the circulating vaccine strains.