Investors have also taken notice of the industry's steady growth. Pfizer's animal health division reported $4.2 billion in sales last year, the most in that category. Merck's animal health unit was second and Sanofi's third. When Pfizer spun off it animal health unit into a separate company in January, it raised $2.2 billion at its initial public offering. The new company, called Zoetis, is now valued at more than $15 billion.