Cases of "horrific neglect" dominate the RSPCA's annual cruelty review in Wales, with cases up from 94 in 2005 to 126 in 2006.
It is believed this horse's hooves had not been trimmed in 10 years
The review has also highlighted an increase in the mistreatment of horses.
The review said RSPCA inspectors dealt with a "shocking catalogue" of crimes, including a cat killed in a washing machine and a mummified dog.
But the RSPCA said the Animal Welfare Act in March had made an impact, and allowed inspectors to intervene sooner.
Among the complaints investigated for the 2006 review were that of a dog that died of starvation in a cupboard in Ebbw Vale, Blaenau Gwent.
The 27-year-old owner was jailed for four months in May for abandoning his black and tan cross breed bitch after losing his keys to a council house.
The dog was shut in a small room in the property for three weeks and suffered an "agonising" death, the court heard.
WALES ANIMAL CRUELTY 2006
126 cases reported (up from 94 in 2005)
193 defendants reported (up from 131)
25 cautions (up from 19)
56 defendants convicted (down from 73)
79 convictions (down from 119
16 defendants convicted in west Wales (up from 10)
Plaster had been gouged from the room's walls, indicating the animal had tried to escape.
In another case, a stallion's hooves were found to have overgrown by more than one metre (3ft 3in) in what an RSPCA officer called the worst case of its kind she had seen.
Its owner, aged 62, of Pembrokeshire, was banned from owning horses for three years, fined £1,000 and told to pay £1,800 costs after admitting causing unnecessary suffering in November 2006.
Martyn Hubbard, RSPCA superintendent for the Wales and the west, said neglect was the most common form of cruelty.
"Animals depend totally on their owners to meet their day-to-day needs. Ignoring this basic responsibility has heart-breaking consequences," he said.
"These cases defy belief. It's so shocking to discover animals that have starved to death, simply because their owners couldn't be bothered to feed them."
The increase in cruelty against horses was also "particularly disturbing", said Mr Hubbard.
"The magnificent creatures have very specific needs in terms of feeding, exercise, habitat and veterinary attention.
"As with cruelty against other animals, we will not stand by and watch them suffer silently in fields and stables".
Cruelty statistics for Wales and England showed a general increase in offences against horses, up 33% on the previous year.
But there were some positive trends, with offences against dogs and cats down by 15.6% and 9.5% respectively.