This cited claim seems to made by Ward himself in the interview without any study to back it up. While not unreasonable, 27 years is already a very high upper bound achieved by only very few canines, see this list: https://en.wikipedia.org/wiki/List_of_oldest_dogs
Even if we assume there are (multiple) of Ward's dogs reaching this age, it is impossible to claim that the food caused it without a proper study to back this up. It could be just a random occurrence.
Additionally, it is worth to mention that recent research showed that it is possible to prolong the life of mice up to 50%, see this comprehensive list:
It is noteworthy that the highest achieving methods were genetically engineered (in comparison to nutritional) and also that mice have a higher lifespan variability than dogs. A well done recent study could extend the life of mice by 25%: https://www.nature.com/articles/nature16932
In light of that, the claim to prolong the lifespan of dogs only nutritionally by 200-300% seems widely exaggerated.