7. Toxicity of aflatoxins

AF (AFB1, G1, B2 and G2) concentration, duration of dietary exposure, species, sex, breed, age and health status of animals are different factors that affect toxicity [42, 47]. Young animals are less resistant than older one presumably due to the lack of well-developed hepatic enzymatic systems required to degrade the toxins depending upon the specie [48]. Guinea-pig, duckling and rabbit represent a "fast metabolizing group" actually capable of handling LD50 dose in <12 minutes. Sheep, pig, mouse and chick fall into "intermediate group" metabolizing LD50 dose in few hours [49]. Currently, rat is the only example of a "slow metabolizing group" in which LD50 dose would probably disappear from the liver over a period of days (Hu et al., 2011). AFB1 is classified by IARC [35], as a highly toxic compound (LD50, 1–50 mg/kg body weight) among most species, although it is extremely toxic (LD50 < 1 mg/kg) for some species such as cats, ducklings and rainbow trouts [3].

Ducklings followed by turkey poults, broilers and laying hens are the most sensitive species to AFs as these showed 100% mortality at 1 mg/kg AFB1. Moreover, 0.11–0.2 mg/kg AFB1 decreased 230 and 163 g/bird feed intake and weight, approximately from 0 to 14 days of age, respectively [50]. Goslings, quails and pheasants are ranked at intermediate position regarding sensitivity while chickens appear to be the highly resistant. Ducklings are 5–15 times more sensitive than laying hens, but among layers, certain strains may be as much as 3 times more sensitive than others [38]. Broilers are more susceptible to AF than layers [36, 51]. Aflatoxincontaminated feed affect almost all systems in the body are affected, i.e. interference in bone metabolism resulting decreased bone strength, reduction in bone diameter, decrease in dressed weight and breast yield etc. [52].
