I just bought x4 bags of 12kg Hill Science Plan Dog food from Pet Supermarket. At the moment they have a special offer of 2 bags for £50.
I also used discount code 'sale100' which saved me £20 off the £100 - making £20 per bag.
The varieties they have on this offer are:
Adult Large Breed Chicken
Puppy Dog Chicken
Puppy Large Breed Chicken
Don't forget 5% cashback from topcashback and quidco.