Local trainers are heavily favoured to win this year's Melbourne Cup, but not with a locally-bred horse.

Only 10 of the first 50 horses in the Cup weights released on Tuesday were bred in Australia or New Zealand with 22 of the 40 foreigners now trained here.

As a result bookmaking firm Sportingbet Australia rates the chances of an Australian-trained winner at $1.37.

An overseas-trained winner of Australia's greatest race is rated a $2.95 chance.

The reasoning is based on massive support for the Irish-bred stayer Puissance De Lune.

Since last November, the Warrnambool-trained galloper has dominated betting on the $6.2 million race - a situation that remained unaltered after the announcement of weights.

Puissance De Lune has been handicapped on 54.5kg, a hefty impost for a horse who has beaten questionable opposition in his best wins, and one who was beaten fair-and-square at his latest start.

"I thought it would be less," said his rider Glen Boss.

"I'd hoped for 53.5 and I thought he'd probably get 54.

"But he's good enough to win it with that weight."

Most of the major firms report heavy backing for Puissance De Lune with around 20 per cent of all money bet on the Cup for the Darren Weir-trained entrant.

TAB Sportsbet spokesman Adam Hamilton said price assessors were inclined to ease Puissance De Lune from the $5.50 quoted before the release of handicaps, but the weight of money prevented any generosity.

"We've taken a long list of bets on Puissance De Lune and it's getting longer," he said.

The nearest runner to Puissance De Lune in betting is last weekend's Dato Tan Chin Nam Stakes winner Fiorente at $8.50 after $17 was bet a week ago.

With the six-year-old coming into the Cup in the anticipated weight range with 55kg, his prospects have risen again.

Fiorente, another Irish-bred, looks well weighted in comparison to last year's winner Green Moon who is up 4kg in the handicaps from 2012 to 57.5kg, although he carried to 54.5kg to victory because his rider Brett Prebble was 1kg overweight.

Chief handicapper Greg Carpenter honoured the 2011 Melbourne Cup champion Dunaden with the topweight of 58.5kg, 4kg more than he carried in his win and 0.5kg less than a year ago when he started favourite and finished 14th to Green Moon.

Red Cadeaux, the runner-up in 2011 and eighth last year has 56.5kg.

While the form of the top three in the handicaps is relatively easy to assess, Carpenter described the recent import Sea Moon as a vastly different proposition.

"He's one of the most challenging horses I've had to handicap in a Cup," Carpenter said.

Sea Moon, a dual Group Two winner in England, is yet to win at the highest level, but is the highest-rated galloper among the 134 entries.

He has 56.5kg in the Cup.