Research on Fungal Growth Stimulants for Domestic Animals in China

ABSTRACT

Anabolic estrogens are used in animal production world-wide to enhance rapid growth and improve feed efficiency. These methods have become essential tools for increasing meat production while reducing feed costs. They have been especially important in improving the efficieny of beef cattle production and they have been used in many parts of the world. It has been estimated that it would cost livestock producers in the U.S. over two billion dollars to forego the advantages of these growth promoting implants.

Compounds are approved for use in the U.S. including, 17-beta estradiol (Compudose), 17-beta estradiol benzoate (Synovex-S) and Zeranol. Estradiol is the normal estrogenous hormone in humans and animals. Zeranol is an industrial reduction product made from zearalenone, a mycotoxin produced by the corn pathogen Fusarium graminearum (Gibberella zeae). Zeranol (Ralgro) was approved by the FDA in 1969 for use as a growth promoter in cattle and sheep (Federal Register, 1969).

The relatively high cost of Ralgro on the commercial market has precluded its use in many developing countries such as China. However, as a part of FAO/UNDP Project CPR/85/038 “Growth Stimulants for Domestic Animals” I had the opportunity to participate for the past 3 years in a research program at the Beijing Research Institute for Nutritional Resources to develop a large scale zeranol production capability for China. Our project carried out research on strain selection and mutation in F. graminearum for improved zearalenone yields in shorter fermentation cycles. This program was very successful, and all objectives of the project were achieved. Zearalenone production by freshly isolated strains from nature ranged from 0.90 to 3.20 g/l in surface culture (vermiculite) to 0.43 to 0.73 g/l in submerged culture. We carried out conventional mutation studies for selection of high zearalen one-producing strains of F. graminearum in 1987 and 1988. Strain № 23157, selected after a long series of studies using U.V., NTG, and EMS mutation and protoplast mutation studies produced high levels of zearalenone both in surface (44.63 g/l) and submerged culture (21.30 g/l) under appropriate environments. Pilot scale zeranol production and large scale testing in cattle and sheep in many parts of China are now in progress.