The two dated for many years in a joint venture called Merial. But when Merck decided to buy Schering-Plough, which had an animal-health business of its own called Intervet, it sold the full rights to Merial to Sanofi.
After Merck's acquisition, the two decided to give it another go, joining Merial and Intervet to surpass Pfizer
A year later, the deal isn't complete because antitrust regulators are apparently worried about the new company gouging farmers and pet owners in product areas where Merial-Intervet would have too large of a market share.
The two reportedly tried to sell off assets to satisfy regulators, but it appears they couldn't reach an agreement that would satisfy potential buyers and regulators while still making sense for the companies. Genzyme
It's a mixed bag for other pharmas with animal-health businesses: Bayer, Boehringer Ingelheim, Novartis
With Merial-Intervet in the doghouse, Pfizer is the big winner, remaining No. 1 in the animal-health business.
Interested in following the competition for Fido's and Porky's business? Click on the green plus sign next to the tickers in the article to add the stock to My Watchlist, which will help you keep track of all our Foolish analysis on the pharma industry.