“The first thing that will go is the sheep,” said Hugh Maguire, a Northern Irish farmer, as he pondered Brexit while leaning over pens packed with livestock ready for export across the border to an abattoir outside Dublin.

“Then it will be the communities,” said Kevin Leonard, a vet, at his practice across the road from the sheep mart in Enniskillen, the birthplace of Arlene Foster, the leader of the Democratic Unionist party.

“The profit margins are so low in the farms. It would be hard for our business – how you see it going forward – and the whole area. I think it would definitely be worse if there was no farming,” said Leonard, himself a small farmer with 500 sheep and 150 cattle.

For him, it is not just the prospect of tariffs on lamb exports in the event of a no-deal Brexit, but the disappearance of the farm subsidy. “The biggest threat is that there will not be subsidies to support farmers here. I have farmers here who can’t pay the vet bill until their payment comes in. Most of the farms here are small. They don’t wash their faces just keeping livestock. They need that EU money to live on,” he said.

As Brexit talks intensify in Westminster and Brussels, it is in places such as the wet and damp hills of Enniskillen that the impact of a decision will be felt hard. Farming in this part of Northern Ireland is barely profitable. Land is poor in the border counties that voted remain, compared with the leave-voting eastern counties.

Government statistics for 2016-17 show farm income for lowland sheep farmers in Northern Ireland was £7,812 a year, a little over one-quarter of the UK median household income of £27,200.

Maguire, who owns and rents farmland and does not want to return to the old days when there was “nothing but trouble” on the border, said: “To be quite honest, nobody knows what’s going on.”

He fears that if tariffs are put on sheep, his sales market is dead. “The first thing that will go are the sheep. Seventy percent of them go south to be killed. If there’s barriers there, the market goes,” Maguire said.

For him, the approach of the DUP is unfathomable. The party does not represent border communities and is threatening the livelihoods of farmers on the border, he said. “The DUP are backing themselves into a corner. They are not going to agree unless it’s their way or no way. They are holding the government to ransom,” Maguire said.

“If people want to remain here and call themselves British, let them, but don’t interfere with life on the borders. We have free trade here now and people from the south can come here and buy their livestock. For the next generation it’s concerning because deal or no deal, it’s going to be worse.”

For sheep farmers in Northern Ireland, the consequences of no deal would be immediate and real, as 50% of all lambs born in Northern Ireland go to the Irish Republic for slaughter. Many farmers would go out of business if tariffs were applied to exports, adding 30% to the price per animal.

Kevin Leonard: ‘The biggest threat is that there will not be subsidies to support farmers here.’ Photograph: Lisa O'Carroll/Guardian

Leonard said: “Brexit – I can’t understand why. If it’s not broken, why fix it? I can’t see any positives in it, to be honest.

“Farming is so important to the community here. They might all be small farmers, but they keep people in the shops going and the other trades, mechanics, merchants. They are the backbone of rural life. If they are not making money then that will be a big problem to communities around here.”

James Johnston, the owner of the Ulster Farmers’ Mart in Enniskillen – who voted to leave the EU – believes the market will settle down after Brexit.

He said there is already an effective border for livestock sales, with paperwork particularly for cattle, but a no-deal Brexit would mean an unwelcome “second border”.

“If all of a sudden sheep are worth 50% less and you are going to see people going out of business, 50% of our business would evaporate,” Johnston said.

He wants political leaders to “at least broach the next few steps” and prepare the farming community for what is to come. People need assurances that support is going to be continued and the uncertainty of Brexit removed, Johnston said. “If Michael Gove came over and made that clear, that would good,” he added.