Yes, you can safely give Bryonia 30c or a lower potency. Bryonia is a good all-round remedy for animals if the cough is obviously worse for movement and warmth. This remedy can be given 3-4 times daily for up to 7 days, but stop earlier on distinct improvement and, if necessary, repeat later.

Wim

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Homeopath for people and animals.
(Sorry, Wim no longer works here.)