Two trials were conducted to investigate the effects of dietary ascorbic acid (AA) on the performance of laying hens maintained under high environmental temperatures (32.2 °C and 33.3 °C, respectively), and a third trial was carried out under ambient conditions (12.8 °C to 17.3 °C).Weekly changes in egg yield, shell deformation, percentage of cracked eggs and body weight showed an improvement in the AA-supplemented birds but the differences were non-significant. Egg yield and percentage of cracked eggs were not affected when the diet was supplemented with AA under ambient conditions.

I. Two experiments were conducted to investigate the effect of intestinal coccidiosis (Eimeria acervulina) on blood plasma and tissue ascorbic acid (AA) concentrations in chicks, and a third experiment was carried out to examine the role of dietary AA in this infection.2. Experimental infection with intestinal coccidiosis (Eimeria acervulina) brought about a depletion in the concentration of AA in blood plasma, duodenum, jejunum, ileum, liver and the adrenal glands. Generally, these changes were obtained after the prepatent period of 4-5 d of the infection.3. Dietary AA at 1000 mg/kg prevented the depletion in plasma and tissue AA levels but did not significantly affect adrenal weight.The first indication of a possible requirement for exogenous ascorbic acid (AA) in poultry was made by Holst & Halbrook (1933) who observed that chicks suffering from a scurvy-like disease recovered completely when a diet rich in AA was fed, and they concluded that chickens require AA under certain stress conditions in which synthesis of the vitamin may be impaired. Bell et al. (1941) supported the previously mentioned observation and reported a dramatic recovery in laying hens showing symptoms of leg-weakness, by treatment with AA. In rats, which, like the chicken, also synthesize AA, an exogenous supply of the vitamin has been shown to be beneficial under certain stress situations: Malathi & Ganguiy (1964) demonstrated a better resistance to vitamin A deficiency when exogenous AA was supplied; Gala1 et al. (1974) reported that AA reduced the number of gastric ulcers. In rabbits, Zohdy et al. (1974) indicated that AA tended to abolish electroencephalographic changes induced by experimental atherosclerosis. The purpose of the following experiment was to examine the changes in AA concentrations in blood plasma and tissues of male chicks infected experimentally with intestinal coccidiosis (Eimeria acervulina) and to see whether supplementation with dietary A A has any beneficial effects. This disease was chosen as a form of stress because it is reproducible experimentally, but it is not lethal. The infection involves mainly the upper part of the small intestine (up to the yolk stalk or Meckel's diverticulum) and it was here that depletion of AA occurred with hot climates as a stress factor (Kechik, 1971). MATERIALS A N D METHODSExpt I Eighteen, 7-d-old cockerels of a medium hybrid strain were used in this experiment. They were allowed ad lib. access to food and water and continuous artificial light was used. The food was a commercial-type chick crumb without added coccidiostat. Twelve chicks were infected orally with two million sporulated oocysts of E. acervulina and the remaining six were kept separately as controls. On day 5 of the infection, six of the infected and three of the control chicks were killed and the duodenum, jejunum, liver and adrenal glands immedi-