Ms McDonagh said her husband acted quickly and took their labrador to an after-hours vet.
"I am very grateful that my children were not in the garden at the time. It could [have] been a very different story otherwise."
A request for support had been filed by the owner and an inspector would be looking into the incident, a spokesman for the SPCA said.
"From the information that we have, the owner said the dog ate half of one of the wrapped packages."
An after-hours veterinary clinic provided appropriate treatment for the dog and he had since recovered.
The SPCA was yet to identify the type of poison that was wrapped in the bacon, the spokesman said.
"It looked like green pellets, it could potentially be rat poison or slug bait, but it will be investigated."
The spokesman added they see about half a dozen poison-related incidents like this a year.
Ms McDonagh said she had also reported the incident to police and Auckland Council.
In a comment on her Facebook post she said police were aware and would be "keeping an eye out".
Auckland Council said it was disappointed to hear about the incident.
"If anyone is having issues with dogs, we ask that they please contact Animal Management, rather than resorting to such drastic measures," it said in a statement to the Herald.
"Animal Management will investigate on receiving a complaint and, depending on the situation, we can undertake a number of actions in response."
Paw Justice co-founder Craig Dunn said this kind of behaviour was "disgusting", but unfortunately it does happen.
"People get annoyed at people's pets and this is how they deal with it."
It was likely the act was committed by someone in immediate vicinity to the dog, Mr Dunn said.
To prevent it from happening again there needed to be a focus on being responsible pet owners, he added.
"Address issues people have raised with you, eliminate what issues you can ... If a cat needs to be locked inside at night, lock it inside. If your dog is barking, ask yourself about its behaviour and why it's barking."
