black and brown piglets

[sandyshore]

i have two 3 month old piglets, both were the same size when i got them. one is an iberian type black pig and the other is brown, both are female.

both eat the same amount of food but the brown pig is huge, very fat and dosent do much exercise apart from eating, the black pig is always running around, escaping, playing with the dog and is much thinner. is this normal, are the black pigs as a breed thinner than other pigs? or should i call the vet?

thanks