One challenge, many answers, three approaches

On August 19, an article titled, “Is the way cattle are grazed the key to saving America’s prairies?” made headlines in The Guardian. It describes how cattle are being turned out onto the Zumwalt prairie, the largest surviving native bunchgrass prairie in North America, to find out how grazing can be managed to benefit this ecosystem.

The very next day, folio released an article called, “Animal grazing reducing biodiversity around the world: study.” It summarizes a study showing that livestock grazing reduces the number and diversity of animals that depend on plants.

At first blush, it seems these studies are heading in opposite directions.

“Not necessarily,” says Cameron Carlyle, Associate Professor at UAlberta’s Faculty of Agricultural, Life and Environmental Sciences. “It depends partly on the research question and the approach. Both articles are examining native grassland but the first article focuses on conservation through easements and a particular grazing management system, while the second has a narrower question, only taking into account grazed vs. non-grazed land. If grazing prevents conversion to cultivation, for example, then habitat and biodiversity are likely being conserved even if grazing does reduce biodiversity compared to an ungrazed state.”

Instead, Carlyle is proposing a systems approach to enhancing grassland biodiversity and ecosystem services.

“Our idea,” he continues, “is to align cattle genetics and behaviour with desired landscape outcomes. Cattle behaviour affects landscapes as they decide where to search for food and which plants to eat. There’s some evidence of genetic controls on these decisions, for example, whether individual cows like to feed at top or bottom of a hill. If we can identify the genetic markers for those choices, we can have a better distribution of animals on the landscape or modify their effects on the landscape through the of types of plants they like to eat.”

Carlyle and multidisciplinary team including Livestock Gentec researchers propose to examine the genetic factors determining why cattle select particular habitats and plants, the vegetation traits that drive those choices (such as chemical content and nutrition) and the subsequent effects on microbial processes and ecosystem services. Their theory is that, as well as affecting the cows’ choices in what they eat, secondary plant compounds may also have a profound influence on their microbial symbioses with microbes, and hence digestion outcomes, which can affect production (nutrient uptake and weight gain) and environmental metrics (feed waste and methane emissions, etc.).

“If the condition of the grasslands improves in a way that also improves the producers’ bottom line, he says, “they stand a better chance of being protected than of being converted into cropland or subdivisions.”

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