Wellington — New Zealand's $400 million meat trade to the United States is under assault for the second time in a year. Alarm bells rang Oct. 23 when news filtered through that the US House of Representatives had passed, by a devastating 211-to-168 vote, a farm bill amendment that could wreck New Zealand's vital meat exports to the US.
Just two months ago New Zealand reluctantly signed the GATT Subsidies Code, which bars government subsidies for exports. The signing headed off a threat from the American Woolgrowers' Association to seek duties on New Zealand lamb. In the view of the grower group, the lamb was subsidized.
If New Zealand had not signed it, something it had refused to do on grounds the code discriminates against farm-based economies, the American wool people might have sought a ban on importing New Zealand lamb because of the damage they say it does to the US domestic industry.
No sooner had the ink dried on that signing than another cloud loomed over the entire meat trade in the form of an amendment by a US congressman, Glenn English (D) of Oklahoma. Mr. English's amendment sought to ban all imports of meat produced with the use of agricultural chemicals and drugs not used in the United States.
New Zealand immediately went on the offensive. Its ambassador to Washington, Frank Gill, said, ''We will have to fight this right down the line.''
Prime Minister Robert D. Muldoon's administration is counting on the Reagan administration to help eliminate the threat. There was intensive lobbying against it on Capitol Hill by Mr. Reagan's men.
A presidential veto of the entire four-year farm bill is one of New Zealand's main hopes for preventing what could be a disaster to its fragile, farming-based economy.
Officials have branded the amendment ''an outright protectionist move that amounts to a nontariff trade barrier inconsistent with our obligations under GATT (the General Agreement on Tariffs and Trade).''
US concern over possible economic retaliation from countries affected by the amendment would appear unfounded, at least from New Zealand's point of view.
New Zealand imports less than $48 million of foodstuffs a year from the US. Said Ambassador Gill: ''I don't think we would be inclined to retaliate, but others might.''
The amendment could also further sour trans-Tasman relations between Australia and New Zealand.
One immediate reaction in Wellington was that the Americans were retaliating because of the Australian meat scandal. It was recently discovered that some Australian beef exports to the US contained horsemeat. There have always been fears that the fallout from the scandal could damage New Zealand's own beef trade with America.
News of the threat could not have come at a worse time for the Muldoon administration. The government is preoccupied with fighting to to remain in office in a vital general election in six weeks.
Moreover, the overseas-trade minister, Brian Talboys, who has so often ''gone into bat'' against protectionist forces in the US, is in the twilight of a long and distinguished career. Whether he will continue the battles of the past until his retirement day Nov. 28 remains to be seen, but this current threat leaves the government vulnerable, with no experienced negotiator of Mr. Talboys's class available to step in.