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Four hundred thirty-two 1-day-old specific-pathogen-free chicks were randomly divided into 36 groups of 12. All chicks were given 0.2 ml of Newcastle disease antiserum (hemagglutination-inhibition [HI] titer 1:5120) by injection into the yolk sac at hatch. Half of the groups received 0.2 ml of Enterococcus faecalis (4.0 x 10(8) colony-forming units/ml) by injection into the yolk sac at hatch (treatment). The remaining 18 groups received no bacteria (control). Two treatment groups and two control groups were weighed, bled, killed, and yolk sac weighed daily for the first 9 days of life. Feed was weighed at placement and at the end of the trial. Blood was tested for packed cell volume (PCV), total plasma protein, and Newcastle disease HI titer. No significant difference was observed between treatment and control groups for chick body weight, PCV, and feed consumption. Total plasma protein and retained yolk weight were significantly higher for treatment groups over control (P < 0.01 and P < 0.0001, respectively). Also, the geometric mean serum HI titer (log2) for Newcastle disease antibody was significantly higher in the control chicks vs. the treatment chicks (P < 0.01).

Inactivated Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV) were incorporated into water-in-oil emulsion vaccines alone or as a bivalent vaccine. Twenty-week-old broiler breeder chickens that had received previous live virus vaccination with NDV and IBDV were injected intramuscularly with the monovalent or bivalent vaccine. The antibody titers to either the monovalent vaccine or bivalent vaccine increased rapidly and then remained at high levels for the duration of the 40-week trial. There were no practical differences in amplitude or duration of the antibody response to either antigen used alone compared to that of the bivalent combination. Progeny hatched from the vaccinated breeders possessed maternal antibody levels at one day of age comparable to those of the hens at the time the eggs were laid. The maternal antibody titers declined at a steady rate until they reached negligibly detectable levels at approximately 3 weeks of age. This trend held true without regard to the initial antibody titer.

Sera tested for hemagglutination-inhibition (HI) activity against Newcastle disease virus (NDV) and infectious bronchitis virus (IBV) and virus-neutralizing (VN) activity against infectious bursal disease virus (IBDV) and viral arthritis (VA) virus were collected from a wide variety of accessions into the Diagnostic Services Laboratory, Poultry Disease Research Center, University of Georgia. The sera were then segregated according to HI or VN titer to NDV, IBV, IBDV, or VA virus and stored frozen at -20 C until tested by two commercial enzyme-linked immunosorbent assays (ELISAs). There was good correlation of mean Flockchek ELISA titers or EIA Systems sample-to-positive (S/P) ratios with specific HI or VN titers. Flockchek ELISA profile group 3 and EIA Systems mean S/P ratio of 1.12 corresponded to what were considered in our lab to be minimum protective titers for each antigen against virulent challenge in our area.

COMBSCORES determined using the ImmunoComb solid-phase immunoassay were compared with hemagglutination-inhibition (HI) titers specific for Newcastle disease virus (NDV) and infectious bronchitis virus (IBV) and with mean enzyme-linked immunosorbent assay (ELISA) titers determined using Agritech Systems, Inc., ELISA. COMBSCORES for NDV and IBV increased proportionately in a stepwise manner as HI titers increased. The ImmunoComb solid-phase immunoassay was ablt to produce endpoint titers on sera with NDV-HI titers of 0 through 320 and IBV-HI titers of 0 through 1024 without reaching the maximum S-value. The ImmunoComb showed good correlation with the HI assay and the Agritech ELISA and should prove to be a useful tool for serological profiling, either alone or in conjunction with the HI test or commercial ELISA.

ImmunoComb scores are highly correlated to hemagglutination-inhibition (HI) titers against infectious bronchitis virus and Newcastle disease virus. Statistical calculations permit using an individual COMBSCORE to predict the corresponding HI titer value. Tables are presented to facilitate the transformation of COMBSCORES into HI titers.

A survey of antibodies against infectious bursal disease virus (IBDV), infectious bronchitis virus (IBV), Newcastle disease virus (NDV), and reovirus (RV) was conducted in broiler-breeder flocks and selected progeny broiler flocks utilizing the enzyme-linked immunosorbent assay. Marked differences in antibody titers between different breeder flocks were related to differences in vaccination programs. Poor performance in some progeny broiler flocks was related to low antibody titers against IBDV in the source breeder flocks. Progeny broiler flocks in which there was a high incidence of condemnations for airsacculitis had elevated antibody titers against IBV. A few progeny broiler flocks that experienced high mortality due to gangrenous dermatitis had no antibody titers against IBDV at processing. Antibody titers against RV were very variable and could not be related to any production problems.