By mid-August 1995, 55% of broiler embryos in North America were vaccinated for Marek's disease using the INOVOJECT system, with 201 INOVOJECT machines placed with 16 of the top 25 poultry producers, providing the industry with the capacity to inject in excess of 400 million eggs per month or about 5 billion eggs per annum. In ovo administration of a bursal disease antibody-infectious bursal disease virus (BDA-IBDV) complexed vaccine to specific-pathogen-free (SPF) embryos was safer and more potent than conventional IBDV vaccine alone because it delayed the appearance of bursal lesions, produced no early mortality, produced higher geometric mean antibody titers against IBDV, and generated protective immunity against challenge. In ovo administration of a BDA-IBDV complexed vaccine to broiler embryos generated antibody titers against IBDV sooner than conventional virus vaccinates, and generated protective immunity against challenge Direct DNA injection of plasmid DNA encoding beta-galactosidase into breast muscle in ovo and posthatch was an effective means to achieve both gene transfer and expression, with potential for the development of gene vaccines using plasmids encoding protective antigens from poultry pathogens. In ovo administration of 800 U chicken myelomonocytic growth factor (cMGF), a chicken hematopoietic cytokine for cells of the monocytic-granulocytic lineages, significantly reduced mortality associated with Escherichia coli exposure within the hatcher when compared to PBS controls (6.1 vs 12.4, P < or = 0.05), but not when compared to a yeast expression control. A procedure was developed enabling injection prior to the onset of incubation without compromising embryo viability. This in ovo injection process has opened up the window of embryo development during incubation for intervention, as illustrated by the 100% male phenotype produced in chicks hatching from eggs injected with aromatase inhibitor prior to incubation. These data illustrate some of the in ovo applications presently in use by the poultry industry, and under development or in research at EMBREX.

Circulating levels of corticosterone were determined in chick embryos from 10 to 21 days of incubation using eggs from a Leghorn breeder flock. In Experiment 1, eggs were incubated from 10 to 20 days for daily embryonic blood collection. To verify stage of development with day of incubation, embryo right middle toe lengths were measured concurrent with blood sampling. Serum from three embryos was pooled into one sample and the corticosterone content of 10 samples per day of incubation was determined using a radioimmunoassay procedure. The levels of corticosterone from day 10 to 14 fluctuated slightly and then increased rapidly until 16 days of incubation. At this time serum corticosterone remained relatively constant through day 18 with an apparent increasing trend up to day 20. The use of toe lengths to assure no day-to-day overlap in embryonic development proved effective. In Experiment 2, newly hatched (day 21) chicks were sorted into four 3-hr periods ranging from early to late hatching. Blood samples were collected from five individual chicks during four 15-min sampling periods for each of the four hatch times. Serum corticosterone levels were not affected by sampling periods or hatch times.

Japanese quail eggs were injected with 1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2,2-trichloroethane o,p'-DDT(1-10 mg),1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane p,p'-DDT (1-10 mg), or, in one study, 0.5 mg chlordecone dissolved in 50 microliters of corn oil on day 1 of incubation. Hatchability was not decreased by o,p'-DDT or p,p'-DDT, as compared to corn-oil-injected controls, but was reduced in progeny of parents injected in ovo with either isomer. Tremor was observed for up to 4 days posthatching only in birds injected with 1.75-10 mg p,p'-DDT or chlordecone. Survivability to 5 weeks posthatch was reduced (less than or equal to 50%) in birds injected in ovo with 6.25-7.5 mg, o,p'-DDT or 1.75-5 mg p,p'-DDT as compared to corn oil (96%). Reproductive behaviors were attenuated in birds injected during development with o,p'-DDT, both DDT isomers decreased the total number of ovipositions, and o,p'-DDT increased the total number of eggshell malformations. Neither body weights nor reproductive organ weights at 12 weeks were affected by injection of either isomer. Exposure to DDT did not affect acquisition of a matched-to-sample food-reinforced response or subsequent responding on a random interval schedule of reinforcement. In another experiment, total circulating erythrocyte numbers were reduced in females after injection in ovo with o,p'-DDT but not after injection with p,p'-DDT. A primary humoral immune response was not affected by in ovo exposure to either isomer of DDT. In ovo exposure to o,p'-DDT but not to p,p'-DDT had long-term and estrogen-like effects on behavior and hematology in Japanese quail. Posthatch primary feather morphology was also altered by embryonic exposure to o,p'-DDT, p,p'-DDT, and chlordecone.

The effects of eggshell cuticle removal and two levels of incubation humidity 28.3 C [50% relative humidity (RH)] and 30.0 C (55% RH) wetbulb temperature (WB) on embryonic mortality and hatchability were determined from broiler hatching eggs laid during 38, 42, 48, and 54 weeks of age. Variables measured were: egg weight loss during the first 17 days of incubation, hatch at Days 19.5 and 20.5 of incubation, hatch of fertile eggs, stage of embryonic mortality, and chick weight at 21.5 days of incubation. Day 0 to 17 percentage egg weight loss was increased when the incubation humidity was lowered and the loss was greater than that observed after cuticle removal. A greater percentage of chicks hatched on Day 19.5 at 28.3 C than at 30.0 C WB. The percentage hatch of 38-week fertile eggs was improved at the higher humidity; the higher humidity also decreased late dead and increased pipped embryonic mortalities. Cuticle removal decreased early dead and increased late dead mortality. At Week 38 cuticle removal and lower humidity resulted in a decrease in chick weight at 21.5 days of incubation. For Weeks 42, 48, and 54 combined, pipped mortality was increased by higher humidity and late dead mortality was increased by cuticle removal. Water loss from the egg was increased by cuticle removal or by lowering incubation humidity from 30.0 C to 28.3 C WB, or by both, but lowering humidity was more effective. Changes in humidity and cuticle removal may affect vital gas exchange to different degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Exposure of chicks to salmonellae in the hatchery and hatchery environment limits the effectiveness of a competitive exclusion (CE) culture treatment. Therefore, in an attempt to apply treatment before chicks are exposed to salmonellae, the CE culture was introduced in ovo to unhatched embryos. An undefined, anaerobically grown CE culture, derived from cecal contents of healthy adult chickens, was diluted 1:1,000 or 1:1,000,000 and inoculated either into the air cell or beneath the inner air cell membrane of 17-day-old incubating hatching eggs. The treated chicks were more resistant than untreated chicks to varying challenge levels of Salmonella typhimurium, indicating that it may be possible to initiate protection of chicks to salmonellae challenge prior to hatching into a contaminated environment.