Cattle trains (with cattle !) were quite common on the South Wales mainline well into the 1960s. I recall long trains of cattle wagons carrying imported Irish livestock from Fishguard Harbour to various destinations in the east and north. These always ran under control orders (ie they were not in the working timetable) and were quite often duplicated or occasionally triplicated. One one occasion I remember a very large train full of noisy cattle passing through Ferryside with a brake vans in the middle and the rear, headed by two County Class 4-6-0s - obviously two trains combined. There was also a regular Wednesdays only Carmarthen-Crewe cattle train. Latterly (from about 1962) this was formed almost entirely of BR standard horseboxes, mostly in Southern green livery, and was worked by a Stanier Class 5MT or 8F.
A decent cattle train is next on the list for my modelling project - the trains I remember from the 1950s in South West Wales.
David R