The Food of the Gods, and How It Came to Earth by H.G. Wells

When a strange edible substance appears on a remote island, local farmer Mr. Skinner (John McLiam) and his wife (Ida Lupino) deem it a blessing and feed it to their farm animals. Soon other wildlife such as rodents and insects have eaten the food, which makes anything that consumes it grow in size. These gigantic beasts start terrorizing the island, with an athlete named Morgan (Marjoe Gortner) among those who are fighting for their lives against the gargantuan creatures.