Donal Tierney has a lot on his plate. The former chief financial officer of Aurivo, the cross-border agribusiness stretching across the north-west, was suddenly promoted to the role of chief executive on January 13 after his predecessor Aaron Forde unexpectedly resigned over the Christmas holidays. Within weeks, global food supply chains faced the threat of Covid-19. The challenge has been steeper for the Sligo-headquartered co-op than for its competitors in the dairy heartlands of the south and east: not only is Aurivo a milk processor, it also runs four livestock marts in counties Mayo, Sligo and Leitrim, where 160,000 cattle…