Two models for competition between age classes.

We consider two lumped age-structured models of juvenile against adult competition, one of which is a compartmental ordinary differential equation (ODE) model and one of which is a system of ODEs with delay derived from the McKendrick partial differential equation (PDE) model. Existence and stability of positive equilibria and existence of oscillatory solutions of both models are studied. Using a competition parameter, which measures the intra-specific competition, we investigate the effects of the competitive interactions between juveniles and adults on the dynamics of the population for both models. We find that these effects are different for the two models and discuss the differences from the modeling perspective. The discussion reveals an interesting relation between the length of the maturation period and the vital rates' dependence on the competition parameter.

An age-structured model of population dynamics with dominant ages, delayed behavior, and oscillations.

"An age-structured model of population dynamics with age-dominance is proposed and analyzed. Existence and uniqueness of solutions are established as well as the uniqueness and local asymptotic stability of steady-states. Conditions for convergence to or oscillation about the steady-state are specified in some cases." (SUMMARY IN FRE)

[Etiopathogenesis and epizootiology of coccidiosis in rabbits]. / Etiopatogeneza i epizootologiia na koktsidiozata po zaitsite.

Studies were carried out on the etiology and epizootiology of rabbit coccidiosis. Three experimental groups of rabbits were infected with intestinal, liver, and mixed intestinal and liver coccidia. The shedding of oocysts and the clinical course of the disease were followed up, with description of the morphologic changes and the results of the biochemical examinations of the blood. A total of eight species of coccidia were established in all cases--Eimeria magna, E. intestinalis, E. piriformis, E. media, E. exigua, E. irresidua, E. perforans, and E. stidae. Predominating were E. magna, E. perforans, and E. irresidua. Results showed that all age groups of rabbits were susceptible to the coccidial infection, mostly the weaned bunnies and young ones aged 2-3 months. It is admitted that under the present conditions of this country's rabbit raising coccidiosis is a disease of a seasonal character. Biochemical investigations of blood taken from experimentally infected rabbits revealed that the changes in the activity of GOT and alkaline phosphatase and in the amount of bilirubin were most pronounced.