RÉSUMÉ
Fertile eggs were obtained from three different broiler breeder flocks with different levels of virus neutralizing antibodies to infectious bursal disease virus. Egg yolk from these flocks was tested for antibody titers by the virus neutralization test. Flock I eggs had no antibodies, flock II had medium level antibodies (1:200-1600; geometric mean = 1:975), and flock III had a high level of antibodies (1:1600-6400; geometric mean = 1:3365). Chicks from the above flocks were challenged each with 10(2) 50% embryo infective dose of the IN serotype 1 variant virus at 1, 2, and 4 wk of age and examined at 5 and 11 days postchallenge. The average organ/body weight ratios were calculated and statistically analyzed. Chicks with no maternal antibodies were not protected at any age. Chicks with medium levels of maternal antibodies were protected when challenged at 1 and 2 wk of age. Chicks with high levels of maternally derived antibodies were protected when challenged at all the ages tested. The above results were statistically significant (P < 0.05).
Sujet(s)
Infections à Birnaviridae/médecine vétérinaire , Poulets , Virus de la bursite infectieuse/immunologie , Maladies de la volaille/immunologie , Maladies de la volaille/prévention et contrôle , Facteurs âges , Animaux , Anticorps antiviraux/métabolisme , Infections à Birnaviridae/immunologie , Infections à Birnaviridae/prévention et contrôle , Embryon de poulet , Femelle , Immunité acquise d'origine maternelle , Virus de la bursite infectieuse/classification , Tests de neutralisationRÉSUMÉ
The growth hormone (GH) secretagogue activity of variable dosages of clonidine (16.5, 50, 150, and 450 micrograms/kg of body weight), given orally mixed with the daily food ration, was evaluated in young and old dogs. Significant (P less than 0.05) increase in plasma GH concentration was detected at all dosages tested in young dogs and in response to all but the lowest dose tested in the old dogs fed the clonidine-containing diet. Old dogs had plasma GH concentration that exceeded that of young dogs when higher doses of clonidine were used. A clonidine (100 micrograms/kg)-supplemented diet was fed to middle-aged dogs twice daily for 30 days. Significant (P less than 0.01) increase of plasma GH concentration was observed on the first day of the feeding trial, but was undetectable by day 30. After feeding the clonidine-enhanced diet for 30 days, the effects on thymic morphology were variable, and there was no effect on plasma thymulin titer. Clonidine-fed dogs had significantly increased lymphocyte blastogenic responsiveness to mitogens, compared with that of control dogs, when evaluated as stimulation index.