Estudo comparativo de lotes de frangos vacinados com diferentes programas contra bronquite infecciosa

Abstract

Over the 37 years during which vaccines containing the Massachusetts strain were the only ones available and widely used, controlled clinical studies, field experiments, and other scientific investigations revealed their limited efficacy in addressing the challenges of Infectious Bronchitis (IB) present in Brazil. However, in 2016, the introduction of a new viral strain, the BR-I, homologous to the most prevalent challenges in the field, brought promising results. The aim of this study is to evaluate, through a retrospective study on 110 batches of broilers from 4 Brazilian companies, the performance of the vaccination program containing the BR-I strain under field conditions, comparing it with vaccinated flocks with the conventional program using the Massachusetts vaccine. To achieve this, variables of zootechnical performance and sanitary condemnations were used for a comparative economic simulation. Additionally, linear correlations between serological titers against bronchitis and variables of interest were investigated. No significant correlations were observed between these variables and serological titers. The results revealed significant differences between the vaccination programs regarding serological titers (p-value = 0.014), daily weight gain (p-value = 0.041), adjusted feed conversion (p-value = 0.034), partial condemnations due to airsacculitis (p-value = 0.004), and condemnations due to repulsive appearance (p-value = 0.014). Through economic simulations, a substantial saving of US$1,564.82 was observed for each flock of 19,500 broilers in favor of the vaccination program utilizing BR-I. The data were analyzed through parametric and non-parametric tests, as well as linear models, to investigate the complex relationships between the variables. The results obtained from the comparison tests of means, whether parametric or non-parametric, were consistent with the results of the linear models, reinforcing the conclusions of these models. However, it is relevant to highlight exceptions in the variables of slaughter age and daily weight gain, where the results differed between the comparison tests of means and the linear models. This disparity suggests that these variables may be influenced by factors not covered by the parametric and non-parametric analyses, highlighting the complexity of the relationships between the variables and the need for a more in-depth statistical analysis to adequately understand the observed patterns.