You can feed a Chihuahua the best feed in the world, give him all the vitamins in the world, Shoot him up with the best testosterone his whole life, pump horse steroids through his veins till they explode. He may be the biggest Chihuahua in the world, but he will still be 1/8 the size of the smallest Great Dane.
You can never cheat genetics
Here is an old study I found where the University of Wisconsin in 1899 cross bred "Razorback" hogs "trapped in Indian country" with several domestic breeds and tested the growth rate versus feed consumed of the pure breds versus hybrids.
" A comparison of the different breeds and crosses represented in this experiment is given in table No VI The Razor back Poland China cross bred pigs ate the most grain made the greatest average gain had much the
larger quantity of internal fat and the greatest thickness of surface fat on outside of body.
The Yorkshires were ahead in requiring the least amount of food per 100 lbs gain.
The Razor back pigs ate the least grain made the smallest gains and required the greatest amount of feed for 100 lbs gain, while at the same time they had the second largest quantity of internal fat.
The cross bred Razor back Berkshire pigs stand third on the list in amount of feed eaten and gains made They also come third in thickness of external fat and show the least amount of internal fat"
The study starts on page 45
https://books.google.com/books?id=hy2yExBHNIEC&pg=RA2-PA46&lpg=RA2-PA46&dq=university+of+wisconsin+razorback+hogs+study&source=bl&ots=S7kcRXqxck&sig=ACfU3U0jp1GL2tqanB3kRKCxd1WEB4bhjw&hl=en&sa=X&ved=2ahUKEwjvzqTesa7wAhVXaM0KHbE6CicQ6AEwCXoECAcQAw#v=onepage&q=university%20of%20wisconsin%20razorback%20hogs%20study&f=false
