This paper reviews the literature on the response of young domestic fowl to various food restriction patterns. Emphasis has been given to anatomical, endocrine and immunological factors and their interactions with the genetic background. Under restricted feeding (limitation of the amount or time of access to food) chickens learn quickly to ingest the allocated quantity of food within a short period of time. When exposed to a single sequence of food removal and restoration, body weight losses are reduced for non-adapted compared with adapted individuals, for light breeds compared with heavy breeds, and for older compared with younger chickens. Adaptation to food restriction includes increased capacity and slower evacuation of the gastrointestinal tract (mainly the storage organs) to increase the supply of nutrients during the periods of food deprivation; increased hepatic lipogenesis and glycogen synthesis during the feeding cycle; and decreased heat loss on days of food deprivation. Synthesis and secretion of digestive enzymes in response to intermittent feeding has been found to be population dependent and consistent with the hypothesis that the amount of intestinal chyme mediates the synthesis and excretion of digestive enzymes from the pancreas. Numerous hormones are directly or indirectly involved in the metabolic responses to food restriction. Hyperinsulinaemia, increased plasma levels of growth hormone, triiodothyronine, thyroxine and plasma prolactin have been observed after the reintroduction of full feeding. It is suggested that the altered hormonal environment induced by food restriction contributes to a metabolic situation that may enhance immunocompetence.

Chicken anaemia virus (CAV) is a small, naked, icosahedral virus with an SS-DNA genome of 2.3 kb. The virus infects very young chicks (vertically by transovarial transmission) and causes anaemia, immunosuppression and skin lesions (CAV syndrome). The virus also infects older birds (by horizontal transmission) with no apparent signs of infection, although growth may be affected. In Australia the CAV syndrome is currently controlled by exposure of breeding stock to wild-type virus (no attenuated virus is available). The authors are currently investigating CAV-specified proteins and an attenuated virus vaccine and developing an ELISA for antibody detection with the Division of Animal Health, CSIRO.

Chlamydiosis of domestic poultry (chickens, pheasants, guinea fowl, quail, ducks, geese, and turkeys) is reviewed with emphasis on psittacosis as an occupational disease. The article covers literature from 1940 to 1994. The potential risks of transmission of C. psittaci from poultry to man are discussed, and clinical diseases caused by C. psittaci infection in man are briefly reviewed. Ducks, sometimes without clinical signs, and turkey flocks usually conspicuous for ornithosis during transport or processing, are the most likely sources for poultry transmitted psittacosis. Isolation of the chlamydia, both from man and birds, is the best method for confirmation of the diagnosis. In humans an easier, but less reliable, way is the demonstration of a significant titre rise in properly spaced paired serum samples combined with clinical symptoms. False positive results can occur with the complement fixation test (CFT) commonly used. It has to be remembered that there is a high prevalence of antibodies to different Chlamydia spp. in the population, and that the genus-specific antigen used in the CFT recognizes antibodies to all these pathogens and antibodies resulting from prior infections. More specific serological tests should be favoured, and highly sensitive and specific DNA detection methods, currently mostly used in research, will probably replace tests like the CFT. Case reports of outbreaks of the disease especially among poultry plant workers are compared. With awareness of the problem, employees knowing the clinical signs of psittacosis both in poultry and man, modern abattoir machinery, good sanitary conditions, and early treatment with effective drugs when necessary, the disease risks can be minimized.

A major goal of many poultry producers is to attain good flock liveability. Historically, most poultry producers have manipulated environmental conditions and management to maximize bird health. In the past two decades there has been much research into nutritional regimes that improve bird health through immunomodulation. Commercial poultry environments contain ubiquitous micro-organisms that continuously challenge the immune system. Nutritional supplements that enhance immune system function may improve flock performance and be economically advantageous. This paper reviews the literature on zinc-methionine and the avian cellular immune system. Current knowledge of the effects of zinc on many animal models is reviewed and a hypothetical mechanism for the action of zinc-methionine on this system is discussed.