There is a process and requirements for keeping livestock on your plot. Have a look at the policy on keeping livestock on the information section, and if you would like further information, have a chat with your site rep or other plot holders who already have livestock.
Worcester Allotment forum has a dedicated volunteer livestock officer who is able to answer queries surrounding keeping livestock. If you have any queries for him, please use the Contact Us now form for this to passed on. Please include your contact details and site.