If I use multiple items that have the same description of what they improve, will one override the other? Also, what is the maximum amount of items that I can use on one pregnant wolf?

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Example: I want to use Butcher's Broom (increase defect) and Green Berry (increase defect and boost) on the same wolf to increase her chances even more. Will the affects of one item be erased and covered by the new item, or do they stack?