I'd miss Chickens the most. I do love Pigs (Bacon) & Cows (Beef), but Chickens give Eggs (and of course Chicken Meat) and eggs are extremely versatile. Chicken Breast can also be added to a whole lot of things as well.
That said, I think my Chicken & Bacon Pasta Bake would be a lot more bland if it was just Chicken Pasta Bake.