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Biomedical subjects

F W Orthel

Publications and source records attributed to F W Orthel.

8 recordsLinked to original sources
PubMed1988

[Analysis of losses due to subclinical small intestinal coccidiosis caused by Eimeria acervulina and Eimeria maxima under field conditions].

Subclinical coccidiosis of broiler chickens caused by Eimeria (E.) acervulina and E. maxima results in a negative effect on feed conversion and retardation of growth. In the present report investigations in 80 broiler flocks are described in which the relationship between age of infection and economic effects were analysed under field conditions. Under these conditions, infections with E. acervulina and E. maxima were found to have a negative effect on growth and feed conversion, that this negative effect persists and accumulates for approximately three weeks following infection, and is subsequently completely or partly compensated for by increased growth rates. In the present study it was established that the losses due to subclinical coccidiosis of the small intestine in the 80 flocks investigated amounted to 6.4 cents per chicken under conditions occurring in the Netherlands. Ionophorous coccidiostats did not prevent infection with E. acervulina and E. maxima but did prevent infections with E. brunetti, E. necatrix and E. tenella.

Aging↗
PubMed1988

Influence of coccidiosis on growth rate and feed conversion in broilers after experimental infections with Eimeria acervulina and Eimeria maxima.

Under experimental conditions, the effects of subclinical Eimeria (E.) acervulina and E. maxima infections on growth and feed conversion in broilers of different ages were analysed. It was concluded that infection with E. acervulina and E. maxima led to a process which was independent of the age at which the birds were infected. The infection adversely affected growth and feed conversion for 2 to 3 weeks, followed by a recovery period of 2 to 3 weeks when compensatory growth took place. From this study it may be concluded that subclinical coccidiosis in the first weeks of life and in the last week of life of broilers does not lead to appreciable damage on growth and feed conversion. Since coccidiosis cannot be avoided in practice, systems in which broilers contact subclinical coccidiosis either in the first weeks of life or in the last week of life should be aimed for. It is suggested that in a coccidiostat programme an efficient anticoccidiosis agent is particularly desirable in the 3rd and 2nd week before slaughter. Examinations performed one week or less before slaughter can hardly be justified, on the grounds that there is a risk of a negative effect on growth an feed conversion due to subclinical coccidiosis.

Animal Nutritional Physiological Phenomena↗
PubMed1985

The use in practice of inactivated oil emulsion vaccine against infectious bursal disease in broiler breeders and its influence on the progeny: a comparative field trial.

Field trials were conducted to establish the effect of the use of an inactivated oil emulsion vaccine against Infectious Bursal Disease (IBD OEV) in broiler breeder hens, and its effects on their progeny. The performance of 18 broiler flocks, which were the progeny of the IBD OEV vaccinated breeder hens, but which were not vaccinated with a live vaccine against IBD, was equal to that of broiler flocks which were vaccinated with a live IBD vaccine and originated from parent stock that had been vaccinated only against IBD with a live vaccine. In none of the 18 flocks, progeny of IBD OEV vaccinated parents, was IBD diagnosed. In a second stage, 15 broiler flocks were included in the trial: these were derived partly from IBD OEV vaccinated parents, and partly from parents that received only live IBD vaccine at 8-10 days of age. No cases of IBD occurred and all flocks were positive for IBD precipitins at slaughter age. Vaccination with a live vaccine against IBD at the age of 8-10 days had no influence on NCD antibody development after a NCD vaccination at 7 days. No immunosuppressive effect from this type of live live IBD vaccine could be determined under field conditions.

Animals↗
PubMed1977

Comparison of live Newcastle disease vaccines in a simple vaccination and challenge experiment.

Groups of day-old chicks with haemagglutination inhibiting antibodies (HIA) were exposed by the spray method to equal doses of three different live Newcastle disease (ND) commercial vaccines and allantoic preparations of them. After three weeks the HIA response was measured and the chicks were challenged with a pathogenic strain of Newcastle disease virus (NDV). The degree of protection of each bird was compared with its HIA response. The commercial vaccines all provided good protection at identical levels, but significant differences were detected between the allantoic fluid preparations. Two of the commercial vaccines produced significantly better protection than the allantoic fluid preparations. In addition to the protection conferred by HIA antibody, other mechanisms of protection apparently played a part.

Aerosols↗
PubMedDate not supplied

Mycoplasma gallisepticum vaccination-challenge: an egg-production model.

Specific-pathogen-free layer hens in maximum lay were exposed by aerosol to a broth culture of Mycoplasma gallisepticum R' strain. Egg-production loss of greater than 50% was evident 7-14 days following challenge of unvaccinated chickens, with a gradual recovery during the next several days. Various vaccine preparations were tested to determine the effect in the model. All vaccinated chickens exhibited significantly (P < or = 0.05) lower egg-production loss than the unvaccinated controls. The model provides a method for testing treatment effects on egg-production losses resulting from controlled exposure to M. gallisepticum and may be useful in simulating field exposure.

Animals↗