These three dinosaur egg-looking things are enteroliths (also called bezoars) from the stomach of one horse. What it is is essentially like a pearl that forms in the gut of a horse (or ruminant like a cow) around a foreign body. They form in layers over time and are made of a chalky sort of material. All three of these were removed from the same horse via colic surgery--the horse is now fine. In the bottom one, the owners chipped off some layers so you can get a sense of how they're formed.
To give you an idea of scale, that's my size 8 boot right next to them. Crazy.