Aflatoxin and Wildlife

In Texas, the regulatory limit for aflatoxin in feed to be used for whitetail deer and other wildlife is currently set at 50 ppb, (parts per billion).  Since there is considerable confusion about exactly what constitutes a safe and/or practical level, this number has been changed at least a couple of times in recent years.  Prior to the passage of new regulations which went into effect on September 1, 1999, for example, the allowable limit was 100 ppb.    Presumably, this legal threshold may be different in other states, and in other parts of the world. 

Relatively little quantitative research has been documented on the effects of aflatoxin on various species of wild animals and birds.  A very thorough short-term research project was conducted on the effects of aflatoxin on young whitetail deer that were fed a ration containing 800 ppb of aflatoxin over an eight week period.  Fourteen 4-to-5-month-old whitetail deer fawns were selected for the test, since it is generally agreed that young animals are more sensitive to the effects of aflatoxin than older animals.  The conclusion of the researchers was that, in general, though a wide variety of subclinical effects were noted, no major effects were recorded.  An article describing this research project in detail was published in the Journal of Wildlife Diseases in 1997, and is titled EVALUATION OF LOW-LEVEL AFLATOXIN IN THE DIET OF WHITE-TAILED DEER, by C. F. Quist, E. W. Howerth, J. R. Fischer, R. D. Wyatt, D. M. Miller, and V. F. Nettles. 

Interestingly, it has been observed that the presence of low levels of aflatoxin in the diet of whitetail deer and some livestock, (cattle and hogs, for example), often improves feed efficiency--that is, even though feed intake will be lowered, weight gained per unit of feed will be increased, when aflatoxin is added to the diet.  At least this effect has been documented for the initial stages of feeding trials--long term effects may depend on the level of aflatoxin present in the diet.  This effect tends to offset the reduction in feed intake so often cited as a characteristic result of aflatoxin ingestion.  An explanation of this phenomenon does not appear to have ever been documented in the literature.

Note that while feed with up to 50 ppb aflatoxin may be legally fed to wild turkeys, quail, and other wild birds, in many areas in the USA, (where baiting or supplemental feeding is legal--in many locations it is not), some wildlife experts feel that any feed with aflatoxin in excess of 20 ppb should not be used for this purpose.  Very young birds, (turkey, quail, etc.), especially, seem to be more vulnerable to the effects of aflatoxin.  Interestingly, domestic chickens seem to be very tolerant of aflotoxin in their diets.

A two-week study involving groups of 4-month-old wild turkeys that were fed rations containing up to 400 ppb aflatoxin led to the conclusion that even 100 ppb of aflatoxin in the diet of young wild turkeys can cause undesirable effects, with statistically more significant effects at the 400 ppb aflatoxin level.  The study was published in a paper presented at the 1997 Wildlife Disease Conference in St. Petersburg, Florida, and was authored by Charlotte F. Quist, Jeremy V.Kilburn, Denise I. Bounous, Victor F. Nettles, and Roger D. Wyatt.

Significant mortality rates in wild birds such as turkeys, quail, ducks, and geese, have been reported when relatively high aflatoxin levels exist in their feed.   Documented research in this area, however, seems to be somewhat limited.

Research done by the Caesar Kleberg Research Institute in South Texas on newly hatched bobwhite chicks, showed high mortality rates in a matter of days when they were fed milo containing up to 100 ppb aflatoxin.