Transpiration is a function of humidity, circulation and temperature... there is no pumping, rather moisture is drawn from the tree by the atmosphere. So under cool humid conditions transpiration would also be slower than during warm dry conditions. Like John said -- no leaves, no transpiration.
I would also consider the landscape position and soil conditions. If the soil is wet because it is compacted, that is different than if it is wet because it is at the bottom of a hill. It could be that your rotational grazing will increase
root activity by pasture plants, increase worm activity, and reduce hoof compaction, making your site less wet, IF soil porosity is what is making your soil wet.