after receiving his education at a local school, he attended marischal college in aberdeen but despite his father's reservations, he sought to follow him in an agricultural career. initially, mccombie's employment was within the extensive family farming business, part of which was transporting cattle to the borders of scotland and into england for fattening. during the 1820s he rented the arable tillyfour farm from his father and began the process of building up his own herd of black polled cattle. the herd already on the farm when he leased it were quality animals and influenced by lord panmure, mccombie blended two types of polled cattle from the aberdeen and angus varieties to form the basis of the black aberdeen angus cattle. mccombie referred to the date he founded his herd as 1832, which was the year his cattle gained a first prize in exhibitions. over five hundred prizes were won by his cattle throughout the uk and at major exhibitions in france. when rinderpest struck northeast cattle herds in 1865, mccombie organised aberdeenshire farmers to raise a compensation fund that made possible the rigorous slaughter policy that extirpated the disease, thus providing the model for modern disease control measures among farm stock.