Effects Of Florfenicol On Humoral Immunity Of ND In Chickens And Its Lesion Of The Immune Organ

As is known drug is one of the most important factors which can affect birds'immunity. Florfenicol as Thiamphenicol's derivative is special antibiotic of animals. Thiamphenicol and chloramphenicol were thought to cause immunodepression so it was banned in many countries and areas. Whether Florfenicol has the same effects is unknown.In order to give poultry farmers some advice on how to utilize florfenicol effectively,it was used on this trial as a preventive drug to observe its effects on the immune system.In this study,120 chickens were divided into four groups in random. No drugs were used to chickens in group A. But chickens in group B, group C and group D were respectively watered 10% florfenicol of commendatory dosage, two times dosage and three times domage for eight days since the third day. The all chickens were immuned with VH on the 7th day, and the antibody titers were detected on the 14th day and the 21th day. At the same time, bursa, spleen, thymus and tonsil were respectively sliced to observe pathological and architectonic changes on the 14th day.The study indicates that the antibody titers of chickens in group A are even on 14th day. And the average titers in group B, group C and group D are 27.3,26.9 and 26.3 separately which is lower than that in group A. The result showed that when being administered in vaccination it can lower the ND antibody level with dosage increasing. The titers on 21th day changed less than that on 14th day. It showed that florfenicol damaged the immune organs irreversiblely in short time.The result showed that florfenicol has no harm to spleen of chickens, but thymus, cortex of bursa, tonsil of Fabricius to some extent were harmed severely. Lymphocytes in cortex of thymus appeared necrotic separately in groups administered florfenicol. And the number of necrotic lymphocytes increased with dosage increasing. So the result showed that florfenicol harmed cortex of thymus, but it has no harm to medulla of thymus to some extent.Lymphocytes in bursa shrinked and appeared necrotic. Further the number of lymphocytes reduced. So it showed that florfenicol can also harm the bursa of chickens in some degree.with dosage increasing, lymphocytes in tonsil appears necrotic and at the same time they drop more and shink severely. It shows that florfenicol can damage tonsil of chickens significantly.The result showed that florfenicol can affect humoral immunity of ND vaccine, and it also damag the immune organs, such as bursa, thymus, tonsil etc.. So florfenicol should be avoided to use before or after immunity and the dosage can't be incresed blindnessly.