| Summary: | 碩士 === 國立屏東科技大學 === 畜產系所 === 97 === The objectives of this study were to understand the effects of antibiotics on growth performance, immune responses and anti-immflammatory properties of broilers. In this experiment, 320 day-old Arbor Acres broilers were randomly allocated to four treatments × four replicates with 20 birds in each pen. The 4 treatments were: basal diet (control), basal diet + nosiheptide (NHT), basal diet + oxytetracycline (OTC), and basal diet + tylosin. Feed and water were provided ad libitum. The same experiment were repeated twice. Birds were weighed individually at 3 and 6 wks of age and four birds were randomly selected from each treatment for measurement of relative organ weight, immunoglobulin concentrations, and specific antibody titration of sera. The results showed that the body weight and relative organ weight were no significant difference between groups at 3 and 6 wks of age. Values of serum IgG and IgM of broilers at D 21 were increased by dietary supplementation of antibiotics. The supplementation of antibiotics significantly increased the secondary response of antibody titration against sheep red blood cells.
In order to compare the immune ability of different antibiotics administration, the immflammatory challenge had been introduced to this study. Two hundred microliter of croton oil and olive oil mixture were inoculated to young chicks at the age of 35 days, and the body weight gain from D35 to D42, and relative organ weight of spleen and bursa were recorded at the age of 42 days of noninjected control and croton oil injected birds in different dietary treatment groups. Leukocyte populations and serum cytokines concentration were analysed at individual time at 0 (before croton oil injection)、16、41, and 168 h post croton oil treated. The results showed that the body weight gain had promoted 10%, 11%, and 14% in NHT, OTC, and tylosin treated than control group respectively. Croton oil injection significantly decreased the relative organ weight of bursa comparison of the noninjected control in basal diet group. The relative bursa weight were no significant difference between antibiotic groups chicks with or without croton oil injection. Croton oil treatment had decreased the percentage of lymphocyte and increased the percentage of monocyte, heterophil, eosinphil, and heterophil to lymphocyte ratio at 16 h post injection. Comparison of the concentration of IFN-γ、IL-6、TNF-α, and IL-10 of serum, the results indicated that croton oil treatment had increased those cytokines concentration in blood, but the addition of antibiotics significantly moderate the increased concentration of these proinflammatory or anti-inflammatory cytokines. To sum up, the administration of antibiotics did not influence the broiler growth performances but could moderate the decrease of body weight gain and relative bursa weight after oil challeged and decreased the level of proinflammatory cytokines in serum which were stimulated by croton oil injection.
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