Sorry I was slow to respond there. For the prevalence of cattle in the British Isles I have as my evidence an article published by Emania, the bulletin of the Navan Research Group, called 'Evidence of Dairying at Dún Ailinne' by Finbar McCormick. In it evidence is presented for a dairy-cattle based economy, he skips over a bit of the evidence of the cattle based economy in general and goes staright to his proff of the emphasis placed on dairy but it's useful because Dún Ailinne was one of the capitals/royal sites of Ireland during the period you're looking at (so was Navan Fort). It provides strong evidence for the importance of cattle from its numerical data.
For the Germans the writings of Caesat and Tacitus as well as accounts of the Cimbri-Teutones migration and battles with Gaius Marius.
In both cultures the penalty for murder was a payment of cattle (Tacitus writes in Germania:
http://www.fordham.edu/halsall/source/tacitus1.html), the Irish habit of doing this is well recorded and extended well into the Middle Ages (it was still practiced in the 14th century). Other evidence includes the focus on cattle-raiding in Irish mythology, one of the most important stories being the Tain of 'The Cattle Raid of Cooley' (
http://en.wikipedia.org/wiki/T%C3%A1..._C%C3%BAailnge).