In the 18th century they crossbred with Shorthorns; fully grown crossbreeds weighed to . Some graziers of the Craven highlands also visited Scotland, for example Oban, Lanark and Stirling, to purchase stock to be brought down the drove roads to the cattle-rearing district. In the summer of 1745 the celebrated Mr Birtwhistle had 20,000 head driven from the northernmost parts of Scotland to Great Close near Malham, a distance of ca . In 1818 the Craven Heifer, bred for meat on the Bolton Abbey estate remains to this day the largest and fattest cow of her age ever shown in England, weighing . In modern times dairy farming has predominated and after the 1970s Holstein Friesians became the most popular breed weighing ca 1600 pounds (725 kg). Crops Pollen analysis shows that the peak of arable agriculture in Craven was 320–410 AD, but outbreaks of pestilence in the 6th century and in the 7–8th century resulted in a shift away from ploughing to grazing. However, the Anglo-Saxon Chronicle records the Danish Viking settlers "were engaged in ploughing and making a living for themselves." Cultivation lynchet terraces and ridge-and-furrow fields of the Middle Ages are visible alongside many villages particularly in Wharfedale and Malhamdale and tithe records show they grew crops of oats, barley and wheat and in rotation, beans and peas. However, the wool boom of the 16th century caused most arable land to be turned into pasture. In the 18th century miller's records show they had to import wheat to grind and sell as flour but the farmers still grew oats for it formed the principle article of their subsistence, some made into bread and puddings but mostly cooked as oatcakes. Administration In the 18th century the national Board of Agriculture commissioned a survey of agriculture in the region, with a view of improving it. It was published in 1793 as General view of the Agriculture of the West Riding of Yorkshire, a 140-page book detailing every factor. The wide variety of soil composition resulted in tithes ranging from 6 shillings up to 3 pounds per acre and farms leasing from 50 to 500 pounds per year. It details by parish quantities of cattle and crop produced, their rotation and market value. The report recommended more wheat and turnips; more sheep and of better breed; criticized poor drainage and design of farm buildings and taught principles of farm management.