If you plan on getting your leather wet (think dog collars and horse tack) then you need neatsfoot oil. Leather loves it.
When you apply neatsfoot oil remember that if the leather has neatsfoot oil soaked into it then it can't absorb water. Simple as that!
Where I list an item as being 'natural oiled' then this is the oil I use.
Apply with a sponge, lots of light coats are better than one heavy one.
Have fun but remember this is an oil and don't get it anywhere it doesn't belong...
If in doubt, try on a small corner before 'splashing it all over'.