Shawn Leigh Brown, 38, and Tiarna Maree Airey, 27, were found guilty in the Launceston Magistrates' Court on Tuesday on animal cruelty offences.

RSPCA inspectors visited their Newnham property on September 16, 2019, and issued a notice to comply requiring them to seek veterinary treatment for their Staffordshire named Zoe, improve her food, drink and shelter, parasite treatment and provide a clean living area.

When they attended the property again on October 31, Zoe's condition had deteriorated and she weighed 9.7 kilograms in a "skeletal condition" with ribs, spine and pelvis prominent. She was dehydrated, and her faeces contained shoelaces, cloth and grass.

She was seized from the property, and within two months her weight increased to 17 kilograms after receiving adequate food, nutrition and vet treatment.

In an interview with inspectors, Mr Brown claimed he had still been feeding her but she continued to lose weight, and he didn't know "what was going on with her".

But blood samples taken by a vet showed Zoe had no abnormalities, apart from low calcium and insufficient nutrition.

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She had recently given birth to a litter of eight puppies - three of which died - and four were sold for $100 online without microchips or vaccinations, itself a criminal offence. The court found that her pregnancy was an accident, rather than intentional.

Ms Airey told the court they did not have the means to take Zoe to the vet as neither drive, but she sought a consultation over the phone. A second dog in their yard was not in an emaciated condition.

Prosecutor Malcolm Caulfield said similar cases of neglect were frequently brought to the court in Tasmania, but this case had the added issue of breeding.

"Backyard breeding is an issue that concerns us for this very reason," he said.

"Warnings have been given, offers of assistance have been made, clear direction has been given ... and they have failed."

Zoe was formally surrendered at an April 19 court hearing.

Mr Brown initially pleaded not guilty, which he admitted was because he still wanted to get Zoe back. He attempted to change his plea to guilty on Tuesday, and was subsequently found guilty regardless.

Magistrate Sharon Cure said the fact Zoe quickly put on weight once taken out of their care - in addition to the veterinary reports - was evidence of mistreatment by Mr Brown and Ms Airey.

"The significant fact before me is the vet evidence that in eight weeks ... the dog gained 75 per cent of its weight," Ms Cure said.

"The evidence before me was that this dog was not fed enough for that period of time and was emaciated. You've not complied with the direction to take her to the vet."

The court did not find there were aggravating factors, however.

"The underlying reason for this is a lack of resources for the both of you," Ms Cure said.

"I don't think your conduct was intentional or deliberate.

"Your circumstances are such that this has got on top of you ... that makes you unsuitable."

Mr Brown and Ms Airey were allowed to keep their other dog, provided they get him desexed by the end of July. They were banned from owning any additional dog for eight years.

The RSPCA incurred almost $16,000 in costs while caring for Zoe, which must be paid by Mr Brown and Ms Airey. They were both convicted and fined $1000 each.

Zoe was successfully rehomed.