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Researchers achieve key step toward new growth promoter for beef cattle

A team of Alberta researchers has cloned the DNA sequence encoding bovine epidermal growth factor (EGF), in a major first step toward the development of a feed additive that would benefit cattle producers.

"Bovine EGF is a naturally-occurring protein with excellent potential to improve feed efficiency and reduce intestinal infection in cattle," says lead researcher Dr. Sylvie Bilodeau-Goeseels of Agriculture and Agri-Food Canada's Lethbridge Research Centre. "By cloning its DNA sequence, we have laid the groundwork for developing this protein as a feed additive for the beef industry."

The achievement was accomplished in a three-year study funded in part by the Canada Alberta Beef Industry Development Fund (CABIDF).

EGF is a peptide or small protein, composed of 53 amino acids. It is a potent stimulant of proliferation for a variety of cell types including intestinal epithelial cells. Experiments in rodents also suggest a role for EGF in the regulation of nutrient uptake by intestinal cells. For example, EGF has been shown to increase the transport of electrolytes, glucose and proline across intestinal membranes.

Epidermal growth factor also has some potential as a prevention/treatment agent for intestinal infections. Oral EGF administration reduced the rate of intestinal infections in rabbits and prevented the reduction in weight gain caused by infection.

In Alberta cow/calf operations, approximately 0.4 percent of animals are lost each year to intestinal disease. That roughly translates to an annual economic loss of more than $500,000. During major outbreaks, the percentage can rise to a high of two percent.

"Reducing the rate of infection - and the resulting deaths - would be a significant savings for producers," says Bilodeau-Goeseels. "Because of the positive effects of EGF on intestinal function, we think it has great potential as a feed additive. But, use of EGF as a feed additive will depend on the ability to produce large quantities and the cost of production."

While the cloning of the DNA sequence encoding bovine EGF is a significant scientific achievement on its own, further research will be needed to determine the biological activity of bovine EGF; for example, its ability to stimulate the proliferation of intestinal cells and increase nutrient absorption by these cells in vitro. Following that, its effects on average daily gain, feed intake, nitrogen uptake and feed efficiency in cattle will be determined.

In recent years, an increasingly competitive marketplace has led to a groundswell of research with the sole purpose of developing technologies that improve the efficiency of livestock and dairy production.

"EGF is an excellent candidate to be one such technology because of its demonstrated ability to increase the efficiency with which food is absorbed by the intestine," says Bilodeau-Goeseels.

The first step of the three-year study was to isolate and clone the bovine EGF genomic DNA sequences, which proved to be more difficult than researchers anticipated.

"We found that the sequence encoding the mature bovine EGF protein is significantly different from the corresponding sequences of other species, which is likely why the bovine EGF coding sequence was so difficult to clone," says Bilodeau-Goeseels.

Following the cloning, researchers successfully inserted the bovine EGF sequences into vectors for expression in both E. coli and P. pastoris with the aim of producing large amount of protein for further studies.

CABIDF is a joint $16.4 million fund of Alberta Agriculture, Food and Rural Development and Agriculture and Agri-Food Canada. The Fund is administered by Alberta Beef Producers and has supported more than 50 projects in five major categories identified to benefit the Alberta beef industry.

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