A man, 27, has sexually assaulted his three-year-old daughter, his nine-year-old stepdaughter, the family dog and sexually penetrated chickens.

The father from Adelaide was on Wednesday jailed for his ‘abhorrent’ crimes, sentenced to six-years-and-seven-months in prison.

But he was given a non-parole period of three-and-a-half years, after reductions for a full confession.

Most of the abuse was against his stepdaughter, then aged between nine and 11-years-old, while she was asleep.

An Adelaide man, 27, sexually abused his three-year-old daughter and nine-year-old stepdaughter (stock image)

The man also attempted penetrative sex acts with the family dog.

The man also attempted penetrative sex acts with the family dog (stock image)

The man also committed penetrative sex acts with chickens

The man committed penetrative sex acts with chickens (stock image)

The man was only caught when he wrote a letter to his then-wife, admitting his crimes.

Given time already served and his eligibility for parole, the man will be freed from prison in June 2019.