Noise when pulling off with heavy load

Hi All,
I have a 110 2004 TD5 which has recently began being used for transporting cattle in trailer, whenever I set off forward or in reverse with the extra weight there is a loud squealing/slipping noise but once it starts moving it stops. The sound has also happened when stopped dead and put into hard lock and then setting off (without the extra weight). I’m scratching my head trying to work out what it could be. I’ve read some posts and boost leaks and warped manifolds were mentioned but surely the noise would be happened more frequently than just when setting off? Any ideas would be much appreciated cheers

Can you work out where about it is coming from, front, middle or back? Someone outside as it happens could help.

Release bearing?

How about auxiliary belt and associated parts if you say it also happens on full lock with no trailer?
Don't buy cheap parts or you will be doing it again.