However, by using functional diets that strengthen the immune system of fish, farmers can help their stocks cope with disease, environmental shocks and recover faster. As this ultimately improves farm production volumes and ensures an efficient use of feed resources, these diets are becoming ever more integral to farmers’ fish health strategies.
Launched in Norway in 2007, Skretting’s industry leading proactive health diet, Protec, contains active ingredients that act in synergy to enhance the ability of fish to cope with stressful situations, which can be caused by such things as disease, handling, transport and vaccinations. These active ingredients also support the immune systems of fish.
Protec delivers benefits through four modes of effect. First, the immune system is supported, including the stimulation of macrophage activity, helping the fish to resist bacterial infections more effectively as well as enabling them to respond faster to vaccination. Secondly, the feeds contain Skretting’s unique blend of organic acids and plant extracts to stimulate gut health. This is supported by the third mode, which optimises the gut microbiota. The final mode is a supply of anti-oxidants, which work on an intra-cellular level mopping-up the free radicals generated by an immune system fighting a reaction.
The Skretting Aquaculture Research Centre (ARC) in Stavanger, Norway, first started introducing active ingredients in its Response anti-stress feed in 1992. Response was later developed into the group’s Protec and React feeds.
Today Protec diets are widely used for salmonids and other species, with keen users all over the world. In the same year as the Norwegian launch, it was introduced to the UK Atlantic salmon and freshwater trout farming sectors; and a year later it was unveiled in the French market as a supplement in trout and marine grower diets.
“In France, Protec is used to counteract some diseases such as vibriosis in marine fish and sleeping disease in trout. It is used prior to vaccination,” says Skretting Veterinarian Frederic Esnault. “It can also be used in anticipation of difficult environmental conditions such as hot or cold water temperatures or a deficient oxygen level.”
Tackling viral threats
In a controlled viral infection study with pancreas disease (PD) in Atlantic salmon, conducted by the Skretting ARC in 2010, it was confirmed Protec helped reduce the mortality levels in salmon by 70%. Furthermore, combined with a PD vaccination, mortality was reduced by 85%.
According to the ARC fish health researchers, studies confirmed Protec supports the salmon's natural defence mechanisms sufficiently to significantly reduce the degree of heart damage.
Further evidence of the benefits of the use of Protec in combating PD risks appeared in the 2012 Fish Health Report in Norway, which found there was a similar number of outbreaks of the disease in 2011 as in 2010, but customers using Protec reported lower mortality and less impaired growth.
It has also been documented that the number of fish infected with the virus is more than 30% lower when the fish have been fed Protec, and that the infected fish have lower virus levels. This has a positive impact on mortality and recovery. Protec has also been used to help prevent the closely-related heart and skeletal muscle inflammation (HSMI) condition in the spring months after researchers found that feeding Protec reduces the degree of inflammation in the heart and skeletal muscle.
Protec stimulates the fish defence mechanisms, and these are activated regardless of the viral disease to which the fish is exposed.
Australasian successes
Protec was first introduced in Australia more than five years ago. Today it is used in both Australia and New Zealand, where it is fed to Atlantic salmon, Chinook salmon, ocean trout, barramundi and other species for a wide range of conditions.
For salmonids, Protec has proved particularly effective preparing the fish for stressful situations and has contributed to a reduction in mortalities created by extreme environmental conditions. It has also been used to improve the healing of skin and to reduce the impact of Amoebic Gill Disease (AGD).
With barramundi and other marine species, its use leads to an improved winter performance and it is also widely used to support fish transfers.
“In Europe, Protec is the leading health diet with sales increasing every year. This is on the back of well documented results, including: providing benefits during the outbreak of certain diseases in salmon; in offsetting the negative effects of ‘winter syndrome’ in marine fish in the Mediterranean; and in improving growth and disease resistance in juvenile marine fish during transfer,” says Skretting Australia’s Product Manager Dr Nicole Ruff.
“Protec is now widely used as a preventative health option under these scenarios, and the results farmers are reporting back from Europe that fish health is vastly improved, with better survival and overall performance under what previously were challenging circumstances. We want to use the positive experiences from the northern hemisphere in our own local market.”
Skretting Australia felt there were common challenges to fish farmers where Proteccould play a pivotal role in improving fish health and performance, says Ruff. And over the past two years in particular, some thorough local R&D and documentation has further strengthened the position of the product in the market.
Between April and July 2012, a laboratory trial was conducted at the University of Tasmania’s Aquaculture facility. The study investigated the use of some experimental diets (variations of Protec-based feeds) to mitigate mortality caused by Neoparamoeba perurans, the causative agent of AGD.
Fish fed the control and two experimental feeds for four weeks were challenged with N. perurans in a standard challenge model. At the conclusion of the challenge trial, salmon fed the experimental diets achieved a significantly improved survival rate compared to those fed the control diet. In fact, the relative survival was 27% higher using the experimental diets.
This was the first study in the world to demonstrate diet manipulation can actively play a role in reducing mortality caused by AGD.
Meanwhile, numerous commercial trials have demonstrated the beneficial effects of Protec. As an example, post-stress (exhaustive exercise) levels of secondary stress response parameters (blood lactate and glucose) were reduced by more than 10% in triploid Atlantic salmon parr and by 30% in large barramundi when fed Protec. From a practical point of view, leading up to periods of known stress, such as handling, grading and vaccination, Protec can be used as a strategy to help recover from these results, says Ruff.
Reducing mortalities
Skretting Chile has accrued around 20 years experience using functional diets, which were the predecessors to Protec. One very important stage of the diets’ development was in 2007, when a serious outbreak of infectious salmon anaemia (ISA) threatened Chilean salmonid stocks. Protec was launched the same year with a solid scientific background generated by Skretting ARC. It focused specifically on the fish health issues of local aquaculture, says Dr Ronald Barlow, Technical Manager, Skretting Chile.
Several controlled trials were performed to measure the efficacy of the diet on the pathogens and illnesses that were damaging local aquaculture. The trials were run by independent laboratory ADL Diagnostic against the ISA virus, the fungus Saprolegnia spp. and against four bacteria - Vibrio ordalii, Aeromonas salmonicida, Flavobacterium psychrophilum and Piscirickettsia salmonis.
“The results proved the efficacy of the diet on the fish, reducing the number of pathogens,” says Barlow. “Protection of the primary fish barriers (skin and mucus) was another positive effect related to defence mechanisms and immune and non-immune specific responses.”
From the outset, Skretting Chile strongly recommended farmers use the diet as part of a broader sanitary strategy, created specifically for conditions and challenges at the sea sites.
“The producers started to progressively use the diet at the end of the last decade, adopting the preventive concept as an alternative way to produce fish. The functional diet is recommended to be given continuously for four to six weeks to fish facing critical periods of stress, such as vaccinations, grading, transport and extreme environmental conditions,” says Barlow.
The Protec strategy for every site and customer is built using Skretting’s Data Feed tool – software that estimates the outbreak probability according the site and proximity of SRS and IPN illnesses.
Barlow adds that while there are many variables that affect fish health, such as water quality, site management, the local climate and environment as well as the interaction with other animals, analysis shows there is a strong correlation between the use of Protec and reduced mortality rates.
Using public data supplied in an official report of ‘Caligidosis (Sea Lice) Situation in High Surveillance Sites’, another clear association was found between the use of Protec and a reduction in the number of parasites detected among adults and juveniles in stocks of both Atlantic salmon and trout. This report included information on 270 sea sites together with the Skretting Chile database.
Protec has been a major success story in the Chilean market. Over the past six years, the diet has been used with Atlantic salmon, Pacific salmon and trout in many different farming regions and it has helped farmers limit the impacts on their production systems.
“Even though it is only used for a short period in the life of the fish, Protec represents a significant proportion of our sales, and more than 90% of our customers have used it,” says Claudia Gatica, Marketing Deputy Manager, Skretting Chile.
Skretting’s progress in the field of nutrition will be further extended in October this year when the next generation of Protec goes on sale in Norway. The new product was launched at the Aqua Nor aquaculture technology exhibition held in Trondheim, Norway, in August.
