A special study just completed by a task force of agricultural scientists for CAST (Council for Agricultural Science and Technology), a national scientific organization, has looked in depth at the effect on the environment of selenium supplementation of animal feeds.

The CAST report followed the proposed reversion to old selenium-use standards by the government, which was a response to concerns about selenium toxicity to wildlife that had occurred at the Kesterson Reservoir in California and some other localities.

The scientists found no evidence that supplemental selenium use for farm animals and poultry, including feedlot concentrations, was involved in any environmental problems.

Selenium is an essential nutrient, the report says. It has been used in supplemental feeding, injections, and other means for 20 years in the United States and some other countries. The level of permitted usage has been increased several times for producers of animals and poultry over the years because experience showed this was necessary for good animal health. At these levels, its use has been both “effective and safe” for meat animals and poultry, safe for consumers, and has not been shown to negatively impact the environment.

The scientists urge the U.S. Food and Drug Administration (FDA) to retain feed additive regulations that have been in effect since 1987 and to abandon its plan to revert to prior, lower-level selenium standards.

The FDA’s action would roll back the approved level of selenium supplementation in animal feeds from 0.3 to 0.1 parts per million in the diet dry matter, to take effect in September 1994.

The CAST report says researchers have found that environmental problems linked with selenium tend to be “localized” and are prevalent in areas where natural factors such as high levels of selenium in rocks and soils are involved.

The excess selenium at the Kesterson Reservoir in the San Joaquin Valley of California, where young waterfowl had high mortality and where reproductive problems were found, was due to “recycling” of irrigation runoff water and related factors involving high levels of selenium and other soil salts found in the valley, rather than to livestock or poultry operations.

“There was no evidence that livestock selenium supplementation practices were a factor,” said Oregon State University animal scientist James E. Oldfield, chair of the CAST task force.

The scientists point out that in some countries like Finland and New Zealand, soil selenium is deficient and fertilizers have been supplemented with selenium for 20 years or more to enable the harvest of crops and forages containing adequate amounts of selenium for normal animal health. Oldfield noted that this practice has not led to environmental problems, even though it adds more selenium than does direct animal use. “If there was a problem, you’d expect it to show up there,” Oldfield added.

The CAST report assessed the amounts of selenium used in livestock practices as very small compared to that entering the environment from other sources. The scientists noted that as supplemental selenium passes through animals, it changes to forms that are less available biologically, which helps control any environmental buildup.

The CAST authors termed selenium as “vital” in basic life processes including growth and reproduction. They noted that minute amounts of this micronutrient element benefit meat animals and fowl when included in their feed, or when they are otherwise treated with this substance. Also, the scientists said, selenium is known to help create resistance to some infectious diseases.

Now the specialists fear that reducing the use of this additive to former legal levels will hamper efficient production of meat animals and poultry.

The report suggests any reversion in the use of this feed additive could be a costly mistake for the United States. It could affect the profitability of livestock and poultry enterprises, adversely impacting the nation’s supply of food, and make domestic meat and poultry producers less competitive nationally and globally.

“Risks and Benefits of Selenium in Agriculture” was written by a task force of five scientists, chaired by James E. Oldfield of the Department of Animal Sciences, OregonState University, Corvallis, Oregon. Four additional scientists served as credited reviewers.

The full 6-page Issue Paper is available for $3.00 from CAST, 4420 West Lincoln Way, Ames, IA 50014-3447, (515) 292-2125. CAST is a nonprofit consortium comprised of 30 member scientific societies in food and agricultural science and many individual, student, company, nonprofit, and associate society members.