The process of in ovo injection significantlyincreased relative liver weight on day 0, suggestive of asignificant role for the liver during immune stimulation.The liver produces acute phase proteins in response tocytokines such as IL–1 and IL–6. It also produces someof the complement proteins and is an important antigen–trapping site, particularly of antigens arriving from thegut, as may be the case after in ovo vaccination into theamniotic fluid. Stimulation of the immune response hasbeen associated with diversion of amino acids to theliver for uptake, and an increase in hepatic blood flow(Spurlock 1997).There were significant effects of day of collectionon the amount of HVT recovered from spleens ofvaccinated birds, with a rapid increase in concentrationfrom days 0 to 14, followed by a plateau at relativelyhigh viral copy numbers on day 35. Results from thepresent study revealed that the amount of HVTrecovered, even on day 0, and the onset of viraemia didnot differ between treatments with either 4000 or 8000pfu of HVT.The increase in concentration of HVT recoveredfrom spleen samples of vaccinated birds over time isconsistent with the results of Sharma and Burmester(1982). In their study, the amount of HVT recoveredfrom birds 10 days post–vaccination was greater thanthe amount recovered seven days post–vaccination.The results of this study are also consistent with thedữ liệu của Hồi giáo et al. (2004) vào HVT nội dung của cáclá lách của tiêm phòng nuôi gà thịt lên đến ngày 35 bài-tiêm phòng. Các nghiên cứu tất cả đề nghị liên tụcbản sao của HVT trong máy chủ lưu trữ theo thời gian, tối thiểucho đến ngày 49 tuổi. Ngược lại, Witter và Offenbecker
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