Pan Chang-cheng, a member of the Taiwan Solidarity Union (TSU) and a Pingtung county councilor, was joined by several dozen TSU members in the protest. They urged the incoming government to reject the market-opening request by the United States.
The protesters also asked the new government, which will be led by the Democratic Progressive Party (DPP) and sworn in May 20, to replace its agriculture minister-designate, Tsao Chi-hung, with someone else.
Pan argued that the move to open Taiwan's market to American pork containing ractopamine will affect not just the health of Taiwanese people, but also the livelihoods of local swine breeders.
If the market is opened, prices for Taiwanese pork will drop by 50 percent, he said, urging the new government to "rein itself in on the brink of the precipice."
Pan vowed to lodge another protest in front of the Presidential Office with the participation of swine breeders and 100,000 pigs from around the country if the new government decides to open the country's doors to U.S. pork containing traces of ractopamine or other leanness-enhancing drugs.
He also urged President-elect Tsai Ing-wen and Premier-designate Lin Chuan to replace Tsao as head of the Council of Agriculture before they assume the office, questioning the competence of the former Pingtung magistrate.
During Tsao's service in Pingtung in 2005-2014, the county saw one of Taiwan's worst food safety breaches in history, Pan said, referring to the discovery in September 2014 of cooking oil that had been adulterated with recycled waste oil and animal feed oil.
"How can a person who failed to be a good county chief serve as head of a council that is in charge of national affairs?" he asked.
Chang Chao-lin, head of the TSU's youth affairs department, said during the protest that pork accounts for 50 percent of Taiwan's total meat consumption, and added that his party will fight for the benefits of Taiwan's people to the end.
The AIT represents U.S. interests in Taiwan in the absence of diplomatic links between the two countries.
The issue resurfaced after Tsao said in an April 21 interview with the United Daily News that Taiwan cannot shut its doors to U.S. pork containing ractopamine forever in the face of globalization, confirming the DPP's about-face on the issue.
The U.S. has hinted that Taiwan must accept imports of pork with ractopamine in order for trade ties to be expanded.
Kurt Tong, principal deputy assistant secretary for the Bureau of Economic and Business Affairs at the U.S. Department of State, said during a visit to Taiwan in late March that "pork is certainly one of the important issues" in trade relations between the two countries.
The U.S. had previously insisted during President Ma Ying-jeou's first term from 2008 to 2012 that Taiwan's ban on imports of American beef containing ractopamine be lifted before trade ties could be advanced.
The DPP adamantly opposed lifting the ban at that time, until the Codex Alimentarius Commission, a United Nations body that sets food standards, voted 69-67 in July 2012 to allow ractopamine residue in pigs, cattle and turkeys.
Taiwan formally eased its ban on U.S. beef imports with traces of ractopamine in July 2012, soon after the Codex vote, leading to the resumption of talks under the Taiwan-U.S. Trade and Investment Framework Agreement (TIFA), which had been suspended since 2007.
But both the DPP and the Ma government continued to support "zero tolerance" on pork imports, which the incoming Tsai administration now seems willing to compromise on to further advance Taiwan's international trade interests.