https://phys.org/news/2018-07-dinosaur-dinner.html

The team grew dinosaur food plants, such as horsetail and ginkgo, under high levels of carbon dioxide mimicking atmospheric conditions similar to when sauropod dinosaurs, the largest animals ever to roam Earth, would have been widespread.

An artificial fermentation system was used to simulate digestion of the plant leaves in the sauropods' stomachs, allowing the researchers to determine the leaves' nutritional value. The findings, published in Palaeontology, showed many of the plants had significantly higher energy and nutrient levels than previously believed.