Pigs
All the pigs in the world get up on their back legs and join civilisation as we know it. Humankind rapidly comes to the conclusion that they're several magnitudes of intelligence greater than us, and it would probably be a good idea to stop eating them, in case they take over and start farming us!
Things you might miss....
Bacon mmmm
gammon mmmmm
sauages mmmm
ham mmmmmmm,
Cows
The Hindu deity Ganesh manifests and anyone caught slaughtering a cow gets trampled by his great big all-seeing elephant feet!
No more...
Steak (rare takes on a completely different meaning)
Roast beef
Mince (and that means spaghetti bolognese and chilli!)
Sheep
OIV (ovine immunodeficiency virus) spreads like the plague it is from the Welsh mountains to the furthest corners of the earth. No more sheep means no more lamb!
No Irish Stew
No more herb encrusted haunch of lamb
No more doner kebabs
No more lamb biriyani

Poultry
Well, this is coming anyway.
Farewell to...
drumsticks, KFC, thanksgiving turkey, beer chicken, no more spicy wings!
Seafood
The white seal leads all the denizens of the deep to a secret sea where man never comes.
Fish and chips gone!
Prawn cocktail gone!
Salmon fishcakes gone!
Chowder gone!
Any one would be a tragedy, but which would you miss most, and which forbidden dish would mean life loses all its colour?