If you hold a Zab Judah themed Breeder in your kennel you are entitled to re-roll a single training session for any hound that has at least one session available.
Here's how it works
Every time you train a hound you are presented with the outcome of that training session once it has been completed. If you have an eligible Breeder in your kennel and the racer being trained has not re-rolled in the past you will be presented with the option to "Accept" or "Re-Roll" the current training session.
For example, you have a Rare Racer with 97 Speed and you are attempting to train it to 100. You complete your training session and you spin a +1. If you have a Zab Judah themed Breeder in your kennel and the Rare Racer has not completed a Re-Roll in the past then you have the option to discard the current training session and try again for a better result.
It does not cost an extra training session when you opt to re-roll
You are not awarded extra XP or Rabbits when you re-roll
You must decide to re-roll on the training confirmation screen
You only need to hold one Zab Judah themed Breeder in your kennel to unlock this feature for all eligible hounds
An eligible hound is any Racer that has at least one training session available.