The South Australian Research & Development Institute (SARDI) has partnered with Port Fairy abalone farm Southern Ocean Mariculture, Aquafeeds Australia and Tarac Technologies following a successful laboratory trial last year.
Steam-distilled grape marc (SDGM), registered as Acti-Meal, is the heat-treated skins, pulp, seeds and stems of grapes left over after making wine. Once known as a waste product, South Australia-based Tarac Technologies has developed a process to turn grape marc into a range of value-added products, including grape spirit, grapeseed extract, grapeseed oil, stock feed and soil improvers.
During a three-month lab trial at a water temperature of 22°C, greenlip abalone fed an experimental formulated diet containing 5-20% SDGM displayed greater growth performance and feed utilization compared to those on a commercial diet. The abalone on the SDGM diet showed a 6% improvement in biomass gain and a 2.9% increase in shell growth rate compared with abalone fed a commercial diet.
The grape marc-fed abalone also outperformed the other abalone in food conversion ratio, which is the amount of food consumed compared with the amount of weight gained. Abalone on the commercial feed returned a ratio of 0.81 g of feed per gram of growth, while just 0.67 g of the feed containing 20% grape marc was required per gram of growth.
Sixteen concrete raceways were each stocked with 100 kg of abalone on Dec. 18-20, 2017, to start a six-month farm trial. At the time, the abalone, which were about a year old and halfway through their growing cycle, weighed about 18 g and were about 48 mm long. The abalone in eight of the raceways are being raised on a 20% SDGM diet, while the other eight raceways receive a standard commercial feed.
SARDI nutrition and feed technology associate professor David Stone said early indications would not be known until the first official weight check was recorded in February.
“All we know at the moment is the animals are feeding well, and everyone’s happy. They are accepting the food, there have been no mortalities and they are growing well,” he said.
“We’ll look at it every month to get an idea, but at the end of the six months, the bulk weight is going to be the main interesting part and the economics associated with the way they grow, such as the food conversion ratio, growth rate, feed intake and survival,” Stone said.
The feed comes in pinhead-sized granules for baby abalone and larger flat pellets for more mature abalone and lasts in the water for 24 hours or more to allow for overnight feeding.
The farm trial is being funded by a $100,000 grant through the South Australian River Murray Sustainability Program, while the lab study was funded through the South Australian Government Functional Food Focus Program.
Stone said one of the major challenges facing aquaculture is finding sustainable food sources that minimize the use of marine ingredients. He said using a waste product such as SDGM goes part of the way toward achieving this.
“You don’t want to be taking 2 kg of fish from the ocean to produce 1 kg of fish in a farm,” Stone explained. “The other bonus here is that we are removing something that costs $500-800 (per metric ton) and replacing it with what is effectively a waste product that costs $250-400/mt; it’s a price reduction with a growth benefit.”
Tarac Technologies processes more than 120,000 mt of grape marc and 40 million liters of distillation wine at its three locations to produce about 10 million litres of grape spirit a year.
The Barossa Valley, Australia, company exports up to 80% of its grape spirit, primarily to North America and Europe, and also supplies more than 50 boutique distillers around Australia.
As a byproduct of those processes, Tarac produces about 130,000 mt of SDGM each year, which is also used as a soil conditioner or stock feed.