A sensitivity to grain crises and the rapid and dynamic reactions may be responsible for the apparently somewhat chaotic and uneven growth. Such a characteristic of early medieval demographic evolution is probably partly responsible for the fact that these fluctuations cannot be determined or delimited chronologically. The prevalence of pigs in comparison to sheep and especially to cattle, on both desmesne land and farms held in tenure, points to mixed farming in which the stock economy was subordinate to an agricultural economy centred on grain production. From about the middle of the eighth century onwards, the structure and exploitation of land ownership in the Frankish empire between Loire and Rhine, between Rhine, Elbe and Alps, and in northern and central Italy underwent profound changes. As a result of the dominant role of manorial organisation in agrarian and industrial production, the exchange of goods and trade were also to a large extent dependent on the large estate and its production.