On Dividing into Diets, Dr. Brad White and Dr. Philip Lancaster explore how a ruminant’s diet influences the production of volatile fatty acids (VFAs), such as acetate, propionate, and butyrate, created through the fermentation of carbohydrates and proteins in the rumen. They explain that different types of feed support different bacterial populations, shifting the balance of VFAs. For example, grain-heavy diets boost propionate levels, while high-forage diets favor acetate. Despite these shifts, overall animal efficiency depends more on the total amount of volatile fatty acids produced than on the specific proportions. The experts note that attempts to manipulate VFA ratios can be expensive and often yield only minor improvements in productivity.