In England at least, it's not always necessary if your carriage of the animals is not in relation to an economic activity (eg, it's your hobby.)
it's definitely a hobby, I daren't work out the costings - suffice to say it must be in the animals' favour 
In truth, if it weren't for the subsidies, I suspect most farmers could say the same - but in their case I don't think trading standards would accept that as an excuse for not having a transport license!
