Abstract:
27A lNFLUENCE OF AUSTRALIAN INFECTIOUS BRONCHITIS VIRUSES ON GROWTH OF MALE BROILER CHICKENS G. AFANADOR, R. B. CHUBB and D. J. FARRELL Catch-up or compensatory growth occurs during recovery after severe dietary restriction i n broilers[McCartney a n d Brown,1977]. Previously,we reported an adaptive response to infectious bronchitis virus(lBV) characterized by changes in body weight[BWl,feed intake and energy metabolism (Afanador et a1,1991].Two experiments were carried out to quantify on a large scale either the changes in growth rate or on general performance of male surviving broilers after they were vaccinated by eye-drop method at 2 days(d) with VicS-strain IBV(10 4~2EID50/birdI and challenged by the same route using T-IBV strain(l04*6ElD5O/bird) at 15 d of age. Vaccination resulted in significantly[P<O.OS) lower BW in vaccinated-challenged[VC) group than in both control(C) an unvaccinated-challenged(UC) broilers at 15 d of age. Challenge resulted in a further reduction in BW of VC and UC broilers compared to C group at weekly intervals until 28 d of age(P<O.O5).Following infectious bronchitis(lB),BW approached normal in VC and UC surviving male broilers(Figure 1). At 15 d of age,feed intake was reduced significantly (P<O.O5) by vaccination. Challenge decreased feed intake in UC group more than in VC group,but both groups were significantly(P<0.05) different to C group at 42 d of age.Water intake was higher in both UC and VC broilers compared to C group. Carcass weight and abdominal fat pad were reduced by challenge in absolute terms(Pt0.05) It is concluded that decreased feed intake was a well characterized response to vaccination or challenge with IBV.Compensatory growth occurred during recovery after infection`but surviving broilers did not regain lost weight at 42 d of age. AFANADOR,G.,CHUBB,R.B. and FARRELL,D.J.(1991).Proc.Aust.Poult.Sci.Symp.,p.75,ed.D.Balnave[Univ. of Sydney Printing Service). McCARTNEY,M.G. a n d BROWN,H.B.(1977I.Poult.Sci.56:713. Department of Biochemistry,Microbiology and Nutrition,University of New England,Armidale,N.S.W. 2351
