| The aim of this study was to evaluate effects of microbial aerosol on ducks' welfare and shed light on the establishment of microbial aerosol concentration standards for poultry breeding. A total of 600 one-day old cherry valley ducks were randomly divided into five groups(A, B, C, D and E) with 120 ducks in each one. In order to obtain objective data, each group has three replications. Different microbial aerosol concentrations in different groups were formed by controlling ventilation and bedding cleaning frequency. Group A was set as a control group, and the sanitary conditions were deteriorating gradually in the four treatment groups from group B to E. Six-stage Andersen impactor was used for the detection of aerosol concentration of aerobe, fungi, gram-negative bacteria, and AGI-30 microbial air sampler for the detection of endotoxin. Physiological stress levels of the ducks were evaluated by detecting adrenocortieotropic hormone(ACTH) in serum. Correspondingly, the production performance indicators like average daily gain, ratio of feed, slaughter index and so on were tested and evaluated to analyze the influence of environmental factors on the duck body. In order to assess the effects of bioaerosol factors on ducks, welfare indicators including fluctuating asymmetry(FA), appearance and gait as well as the lactobacilli cecal concentration were evaluated. In order to assess the immune function of meat ducks, immune indicators including H5 HIV antibody titer, IgG, IL-2, T-lymphocyte transformation rate, lysozyme and immune organ indexes were measured. Correlation coefficients(Person's) were also calculated to evaluate the relationships among airborne bacteria, fungi, endotoxin and production indicators, animal welfare indicators and immune indicators, respectively. The results indicated that when the concentration of microbial aerosol reach the level of group D(i.e. airborne aerobe: 2.96 × 105 CFU?m-3, airborne fungi: 2.63 × 104 CFU?m-3, airborne gramnegative bacteria: 3.09 × 104 CFU?m-3, airborne endotoxin: 41.78 × 103 EU?m-3), the ACTH levels of serum, feed weight ratio, death rate of meat ducks of above group as compared with the control group increased significantly or very significantly(P<0.05 or P<0.01); the daily gain, breast muscle percentage, carcass weight, slaughter rate of the meat duck were significantly reduced(P<0.05 or P<0.01); the ducks in this group had significantly decreased cecal lactobacilli concentration(P < 0.05) and significantly increased the appearance and gait scores, wings fractional anisotropy(FA) value, comprehensive FA value, Esherichia coli concentration and Salmonella concentration(in 6-week old)(P < 0.05 or P < 0.01); the ducks in this group had significantly increased serum IgG level(P < 0.05) and significantly decreased serum IL-2 concentration, T-lymphocyte transformation rate and spleen index(P < 0.05 or P < 0.01). The results indicated that a high level of microbial aerosol in the sheds not only significantly affected the production performance of meat ducks, and significantly reduced the daily gain, breast muscle percentage, carcass weight, slaughter rate of the meat duck, and significantly increased feed weight ratio, death rate of meat ducks; but also made a negative impact on the level of animal welfare of meat ducks, and significantly reduced the concentration of cecal lactobacilli concentration and significantly increased the appearance and gait scores, wings fractional anisotropy(FA) value, comprehensive FA value, Esherichia coli concentration and Salmonella concentration(in 6-week old); in the mean time, a high level of microbial aerosol significantly affected the immune level of meat ducks, and it caused immune overload, delayed the time of antibody titer peak's appearance, reduced the protection of vaccine and so on. Furthermore, the microbial aerosol parameters of group D(i.e airborne aerobic bacteria(2.96 ×105 CFU?m-3), airborne fungi(2.63 ×104 CFU?m-3), airborne gram-negative bacteria(3.09 ×104 CFU?m-3) and airborne endotoxin concentration(41.78 ×103 EU?m-3) could be preliminarily used as an upper limit concentration of the bioaerosol in the ambient air quality control for the healthy breeding of meat ducks. |
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