Can mix feeding cause bad bacteria to grow in dog's guts?

All of us have bacteria in our guts – our ‘microbiome’ – and our dogs are no different. The better our diet is, and the more variety that’s included, the healthier our microbiome is. A healthy microbiome, which consists of ‘good’ bacteria helps to protect against ‘bad’ bacteria growing in the gut, as the friendly bacteria outcompetes the pathogenic bacteria for resources.