الفهرس 
1. IntroductionOnly 14 pages are availabe for public view
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Abstract
This study aimed to compare a recombinant HVT- IBD (Vaxxitek®) with a traditional vaccination program against infectious bursal disease in commercial broiler chickens under Egyptian field conditions. 36000 broiler chicks with maternal immunity, sourced from the same 35 week’s old cobb breeder flock were used. 18000 chicks were vaccinated at the hatchery with rHVT-IBD SC and 2 hours later followed by inactivated ND vaccine SC also, transferred to the farm and placed in a house. The other 18000 chicks were vaccinated SC with an inactivated ND only at the hatchery, transferred to the farm and placed in another house under the same conditions. A registered attenuated intermediate vaccine at 8 days in drinking water and a registered attenuated intermediate plus vaccine in drinking
water at 15 days were delivered as a traditional IBD vaccination program for this house.
Other prophylactic programs including vaccinations against ND, IBV and H5 were the
same at the farm. We investigated performance parameteres at slaughter age (36days) and
some laboratory parameters at the ages of 1, 14, 21, 28 and 34 days. At 36 days, rHVTIBD
vaccinated chickens had lower total mortality including culls by 2 %. Weight gain
was heavier by 15 grams. Feed Conversion Ratio (FCR) was better by 0.1 point.
Production Number (PN) was better by 21.57 points. Better bursal integrity was evident in
rHVT-IBD vaccinated chickens at 28 and 34 days by bursal body weight ratios. There was
no significant difference in the spleen/body weight ratios at weekly intervals until slaughter
age. The detection of IBD genome in bursas by PCR technique showed negative results in
all samples. At 34 days, High and homogonous antibody titer was achieved by both
programs without significant differences using ProFlok® Plus IBD Ab test kit which
detects anti-VP2 antibodies. This high and homogenous antibody titer was achieved by
rHVT-IBD vaccine 1 week earlier than the traditional IBD vaccination program. ProFlok®
IBD Ab test kit demonstrated at 34 days that only approximately 28 % of the samples from
the chickens vaccinated with rHVT-IBD tested positive with lower antibody titer.
whereas, 100% the samples from the chickens vaccinated with traditional IBD program
tested positive with significant higher antibody titer. Such type of kits detects mainly anti-
VP3 antibodies after a natural infection or vaccination with live vaccines. Biochek IBD
ELISA demonstrated that the target antibody titers was acheivied at 28 days (one week
earlier) by rHVT-IBD vaccinated chickens. Both ProFlok® IBD and Biochek IBD ELISA
could be used to differentiate birds vaccinated with rHVT-IBD from birds infected or
vaccinated with modified live vaccines. rHVT-IBD didn’t interfere with IBD maternal
antibody. No significant differences were detected regarding the antibody titers against
ND, IBV or H5 in post-vaccination seroconversion using ELISA for IBV and HI test for
ND and H5 subtype of AI.