My rehabbed Jack Russell mix ran after my 5 ISA Browns one day because they managed to get out of the run. I didn't panic, even though I knew at least 1 would be caught. That's what JRs do, it's built into them and hard to break.
Or so I thought!
The next scene was 5 fluffy orange featherballs surrounding a terrified little dog. When she got free of them she ran up the steps, into the house and under my bed where she stayed for nearly 2 hours.
Since then she "played" with them a bit, i.e. ran after them until they turned on her, then ran away. But now she doesn't even do that.
When John the duck starts having his way with a chicken, Poppy runs at him and he stops that behaviour. Then he and Poppy have a back and forth chase. She barks and chases him, then he turns and chases her. Sooner or later they just stop and go on with their lives.
Flash forward to my 3 ducklings who held her attention from first pip to almost full grown. Once they got big enough to run around the yard I leashed her and let her follow them but if she got too close I pulled her back and said NO. I knew I couldn't trust her though, because of the holes she tried to dig under their pen.
Eventually I let her loose with them in the yard and she looked more like a Border Collie than a JR, following them around but not biting them. Last week she simply stopped bothering them completely!