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Poultry has commonly been considered highly susceptible to aflatoxins. However, among domestic fowl there is wide variability in specific species sensitivity to these mycotoxins. Comparative toxicological studies in avian species have shown that ducklings and turkey poults are the most sensitive species to aflatoxins, quails show intermediate sensitivity, whereas chickens are the most resistant. Hormesis is a dose-response phenomenon characterized by low-dose stimulation and high-dose inhibition. The low-dose stimulation is typically maximal at only about 30 to 60% greater than controls. Hormesis has been noted in regards to changes in body weight in numerous studies, including those performed for the US National Toxicology Program, with over 50 chemicals. The present paper assesses how relatively low levels of aflatoxin consumption in feed may affect the growth rate of chickens. In general, multiple independent investigations have shown that such aflatoxin consumption affects growth in a hormetic-like biphasic manner with a low dose stimulation and a high dose inhibition. Such observations were then generalized to other toxic agents and animal models, suggesting that low doses of stressor agents induce adaptive responses as reflected in accelerated growth rates. The implications of such hormetic dose responses are briefly discussed.

This study describes the toxicity signs that developed when the diet of male broiler chickens was artificially contaminated with different levels of the mycotoxin ochratoxin A (OTA). Chicks were assigned randomly to three groups of 80 chicks that were fed a diet containing 0 parts per billion (ppb) (control, group 1), 400 ppb (group 2) or 800 ppb (group 3) OTA from day 1 to 5 weeks of age. Signs of ochratoxicosis were assessed on the basis of changes in the following criteria: body weight, relative weights of two representative internal organs (gizzard and thymus), feed consumption, feed conversion ratio, mortality, thyroid activity, blood profile, humoral and cell mediated immunity. Feeding OTA at levels of 400 and 800 ppb (groups 2 and 3) significantly decreased the body weight, thymus weight, feed consumption, feed conversion ratio and thyroxine concentration (P < 0.05). The OTA groups developed anaemia manifested by a significant decrease in the red blood cell count, packed cell volume percentage and haemoglobin concentration (P < 0.05). By the end of the experiment both groups that received OTA showed a 37% reduction in red blood cell count compared with the control group. Furthermore, a significant decrease in the white blood cell count, humoral immune response and cell-mediated immunity was found in both groups fed ochratoxin compared with the control group (P < 0.05). The reduction in the above parameters was more noticeable with time and was proportional to the level of OTA exposure. A significant increase in relative gizzard weight, cumulative mortality and triiodothyronine concentration was found in OTA-fed chicks (P < 0.05). These data provide a description of ochratoxicosis in broilers that should be useful in diagnosis and in improved understanding of the practical implications on broiler performance and health, a problem that can threaten the poultry industry.

The effect of concentration of dietary fat on pigmentation of broiler chickens was investigated in diets containing: 1) 0 or 1.4 micrograms of aflatoxin and 35 micrograms of lutein/kcal of diet; and 2) different levels of dietary fat (0, 2, 4, 6, 8, or 10% cottonseed oil). Serum lutein and its metabolite, 3'-oxolutein, increased with increasing dietary fat until it reached a plateau at 6% fat. Aflatoxin significantly (P less than .05) lowered serum lutein and 3'-oxolutein at all levels of fat. Dietary fat and aflatoxin interacted significantly (P less than .05), with the effect of aflatoxin being greater at the low levels of fat than at the high fat levels. In the toe webs of the birds, the concentrations of lutein and its metabolites, lutein monoester, lutein diester, and 3'-oxolutein responded similarly to aflatoxin and to dietary fat, except that increasing the amount of dietary fat did not spare the effect of aflatoxin on 3'-oxolutein. The effect of chain length and the saturation of fatty acids on the absorption of lutein during aflatoxicosis was investigated in a factorial design for aflatoxin (0 and 4 micrograms/g of diet) and seven fatty acids at 5% of the diet. In control birds, lutein absorption was promoted by lauric = oleic greater than capric = linoleic greater than myristic greater than palmitic = stearic acids. Aflatoxin significantly (P less than .05) depressed the absorption of lutein regardless of the fatty acid present.(ABSTRACT TRUNCATED AT 250 WORDS)