Bacteriocins lauded to enhance cattle efficiency

Bacteriocins—safe and natural antibiotics, produced by bacteria as a means of self-defence—soon could be used to enhance efficiency in cattle, say scientists with the Agriculture and Agri-Food Canada’s Lethbridge Research Centre.
“Bacteriocins are a product of competition and are commonly found in the rumen,” says Dr. Ron Teather, a rumen microbial biotechnology scientist with AAFC.
Research is aimed at identifying bacteriocins that can be used to inhibit undesirable rumen bacteria, thereby increasing feed efficiency and reducing greenhouse gas emissions from cattle.
Bacteriocins help keep yogurt from spoiling and help preserve silage. Bacteria produce these natural antibiotics to prevent competing organisms from settling on their “turf,” and they are found in almost all environments.
Bacteriocins first were discovered by the dairy processing industry, which noticed that some bacteria used in food fermentation—in making sour cream, for example—were better than others at preventing spoilage of the food.
Bacteriocin production is more common in some groups of bacteria than others, says Dr. Teather. In the rumen, each feed component attracts a specialized group of bacteria that is focused on degrading that component.
“If we know the preferred feed of specific bacteriocin-producing bacteria, we can supplement the diet accordingly, giving the bacteriocin-producers an advantage in the charge to inhibit undesirable organisms,” he notes.
Several hundred strains of rumen bacteria that produce different bacteriocins have been identified. Compared to “man-made” antibiotics, bacteriocins tend to be quite specialized. They have a narrow spectrum of activity and only inhibit one or two other organisms.
Another distinct feature of bacteriocins is that they are proteins. Once these proteins leave the rumen environment, the animal can digest them to supplement its nutrition and there is no residue.
There are a variety of mechanisms by which bacteriocins inhibit other species, says Dr. Teather. Most commonly, bacteriocins target other organisms’ cell membrane.
“The bacteriocin basically pricks holds in the membrane so that small molecules leak out of the cell. When the cell can no longer maintain its energy metabolism, it dies.”
Three specific bacteriocins have been examined on a genetic and molecular level for their potential to enhance rumen metabolism, he says.
Coincidentally, a lot of bacteria that are involved in silage fermentation are bacteriocin-producers, he adds.
“We came up with the idea to try and introduce selected bacteriocin-producers into silage in order to produce bacteriocins in the feed itself. These experiments are currently underway and it will be another couple of years before we have conclusive data.
“We hope to move on to small animal trials within three to four years.”
Although the primary focus of the current study is to reduce greenhouse gas emissions from cattle, Dr. Teather expects to observe improved feed efficiency, as well.
“By shifting rumen fermentation in a direction that will reduce emissions, you make more energy available to the animal instead of losing it as gas,” he says. “And the degree to which an animal utilizes the energy in its feed is a measure of efficiency.”

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