Some might notice these days that Swiss cheese slices have been lacking their signature holes. The distinguishable feature has made the cheese one of the most recognizable dairy products around.
According to a Swiss agricultural institute, microscopic specks of hay are the cause of the holes in the cheese. The hay particles create the holes as the milk matures. Because milking methods have transitioned into more hygienic, automated systems, there have been a decline in cheese holes in the last 15 years.
Scientists can, however, add various amounts of hay dust to regulate the number of holes in the cheese. Y'know, for nostalgic purposes.