The veterinarian who attended found the dead calf was poorly grown for its approximate age and its carcass was severely dehydrated and starved, SPCA said.
There was a pool of faeces behind the carcass, indicating calf was down for a long period before its death.
She estimated the calf has died two days earlier and the cause of death was likely to have been dehydration, starved and severe parasite burden.
The second calf was euthanised due to being starved.
A post mortem examination revealed severe chronic malnutrition, and blood and faecal samples confirmed a severe internal parasite burden, SPCA said. The third was also poorly grown and in poor body condition, probably due to a lack of treatment for worms.
The veterinarian concluded that the first two calves had been subjected to unreasonable and prolonged neglect, which would have caused them unnecessary pain and suffering.
SPCA chief executive Ric Odom said this was "extremely disappointing".
" ... the defendant in this case has repeated the same mistakes that led to his conviction in 2011 and inflicted unnecessary pain and suffering on these defenceless animals."
"However, the SPCA is grateful that the judge has extended the period of disqualification this time in the hope that this will save more animals from suffering a similar fate at the hands of the defendant," he said. When interviewed, Smith confirmed he previously received advice from the SPCA and a veterinarian in relation to appropriate care of his farm animals. He agreed that his lack of actions were careless and irresponsible.
"The SPCA hopes that this case will send a message to farmers throughout the country that they must keep on top of their husbandry and fulfil their responsibilities towards their livestock. Your animals are dependent on your care and the consequences of neglect can be extremely serious for them and you," Mr Odom said.
Previously, Smith was convicted of similar charges in 2011 where he pleaded guilty to two charges -- failing to ensure that the physical, health and behavioural needs of a calf were met and a second charge of ill-treating a calf that died as a result of starvation.
He was fined $1200 and disqualified from owning and/or exercising authority over livestock for two years.