The only sitting U.S. Senator with a DVM will not seek re-election in 2012, considering he is ensnared in fallout from a sex scandal.

Sen. John Ensign, (R-Nev.), stated in a news conference that he wants to shield his family from what likely would be an “exceptionally ugly” campaign. “… There are consequences to sin,” Ensign told the press during his resignation speech.

As a political figure, Ensign’s fall from grace is significant considering that prior to his troubles, his name had been bantered about as a possible 2012 presidential candidate.

The senator could not be reached for comment concerning how issues affecting veterinary medicine might fare in Congress, now that he no longer will be an advocate on Capitol Hill. Ensign graduated from Colorado State University’s veterinary medical program in 1985 and opened a veterinary practice in Las Vegas before entering politics.

For months, Beltway Republicans have pressured Ensign to resign his post. He is the subject of a Senate Ethics Committee investigation that revolves around his extramarital affair with a former campaign staff member. Another wrinkle: Ensign’s close friend and aide Doug Hampton pleaded not guilty yesterday to charges of violating federal conflict of interest laws related to his job as a lobbyist.

Hampton became a lobbyist after leaving Ensign’s office in 2008, when he discovered the senator was having an affair with his wife. Federal law prohibits high-ranking aides from lobbying the Senate less than a year after ending their position.

Ensign also is believed to have helped Hampton gain clients as a lobbyist, which appears to be a violation of the law. The senator is not charged with wrongdoing; according to Washington-based news reports, the Justice Department has declined to pursue the matter.

Ensign first won his Senate seat in 2000, after spending much of the 1990s in the House of Representatives. He won a second Senate term in 2006, and is the third veterinarian to ever serve in the chamber. Congressman Kurt Schrader, of Oregon, is the only veterinarian in the House of Representatives.

Officials in organized veterinary medicine lament that the profession is losing a staunch ally in the federal government. Last year, Ensign proposed a resolution to create World Veterinary Year, and he’s been an advocate for ending animal fighting as well as a co-sponsor of the National Veterinary Medical Service Act.

But Ensign, with a track record of advocating on the side of veterinary medicine and animal health, has not always fallen into line with positions held by the American Veterinary Medical Association (AVMA).

During the mid-2000s, he parted ways with the AVMA by introducing a bill to ban horses from slaughter for human consumption. In a 2005 interview with the Associated Press, Ensign called the practice of slaughtering horses “barbaric.”

By contrast, the AVMA’s official stance is that without U.S. slaughter facilities, equine exports to Canada and Mexico will increase as numbers of unwanted horses in America climb, making the animals vulnerable to suffering, neglect and inhumane euthanasia.

No horse slaughter facilities operate in the United States today due, in part, to Ensign’s efforts, but that soon could change. A bill in Nebraska calls for creating a meat inspection agency to facilitate horse slaughter and the processing of specialty meats.

As ranking member of the Homeland Security and Government Affairs Subcommittee, Ensign now focuses his efforts toward curbing gang violence and drugs, taking sharp aim at Mexican cartels and efforts to police America’s border. Nevada Rep. Dean Heller has launched a bid to replace the embattled senator.