A team of international researchers examined the use of date palm fruit extract and probiotics, alone and in combination, to promote the immune system in farmed sea bass as a replacement for antibiotic use. They also looked at how it could be included in feed.
“The aim of this work was evaluated the effects of the dietary date palm fruit extracts administration, alone or in combination with [probiotic] Pdp11, on immune and antioxidant status European sea bass (Dicentrarchus labrax), one the major cultured fish species in the Mediterranean area,” said the researchers.
The group found that combining the feed additives could generate an immunostimulant response in farmed fish.
“The mixture diet could potentially be considered of great interest as immunostimulant diet to use as food additive for farmed fish,” noted the authors. “Future research is needed to obtain enough information about synergistic effect of plant extracts and probiotics in farmed fish and the possible protective effects after in vivo challenges to pathogen bacteria.”
Farmed fish provides about half the fish and seafood eaten today, said the researchers. However, the aquaculture industry faces several sustainability challenges.
Large farming operations can be plagued by disease concerns, infections and stress-related mortality, they said. One way to address these health challenges is through the use of immuno-stimulants which are seen as an alternative to other treatments and vaccines.
Preventive measures look to promote fish immune systems and protect animals from some disease challenges, wrote the authors. They also can be a more environmentally friendly feed additive.
“Plant extracts have been reported as anti-stressors, growth promoters, appetite stimulators, enhancement of tonicity and immunestimulation, maturation of culture species and anti-pathogen properties in aquaculture fish due to active principles (e.g. alkaloids, terpenoids, tannins, saponins, etc.),” said the researchers. “Furthermore, plant extracts can be considered as an alternative to other substances (such as antibiotics or chemicals) used to control aquaculture diseases.”
Date palm fruit has long been used to promote good health in countries in the Middle East and Asia, they said. “Recently, several phytochemical studies have shown that date fruits contain anthocyanins, phenolic substances, sterols, carotenoids, flavonoids, vitamins, enzymes and high amounts of carbohydrates, compounds that demonstrated its great potential as a natural immunostimulants,” added the team.
Little work has examined its use as a feed supplement in fish, they said. The group also looked at use of the probiotic Shewanella putrefaciens (Pdp11) as different types are known to provide health benefits.
In the trial, a group of 48 European sea bass were split into tanks and given one of four experiment diets, said the researchers. Tests ran for a period of two and four weeks after a 15-day adaptation period, said the researchers.
Diets included a control, the Pdp11 109 cfu g−1 supplemented diet, a diet with date palm fruit (100 g kg−1) additive and a combination diet that included both supplements, they said.
Date palm fruit extracts and Pdp11 were not purchased commercially, they said. The feed additives were dissolved in cod oil and sprayed on feed before use and the control diet was sprayed only with cod oil.
Sample fish were collected two and four weeks after the start of the feed trials, said researchers in the study.
Harvested fish were weighed and measured and samples of blood were taken, they said. Anti-oxidant and pro-oxidant statuses were measured along with anti-protease activity, peroxidase activity, total serum immunoglobulin M levels (IgM) and gene expression.
Fish demonstrated an immune response after four weeks with just the date palm additive, said the researchers. However, the mixed additive offered a boost to genetic immune functioning.
The biological antioxidant potential was increased for fish getting either the probiotic or palm fruit extract diets, for both time periods, they said. But, bacteriostatic activity was not altered.
“Protease and antiprotease activities were not modified by the tested diet, except for fish fed 2 weeks the mixture diet, in which this activity was statistically significantly decreased, respect to the levels of this activity recorded for the other experimental groups,” they said.
Fish getting the palm fruit additive showed an increase in haemolytic complement activity after two weeks and the group getting both treatments saw a decrease after four weeks, said researchers in the study. Cellular immune parameters were altered by the additives.
The expression of several genes including rbl and sod were upregulated in fish getting the probiotic after two weeks, said the researchers. Genes il-1B and hep also were up-regulated in fish getting the probiotic and the combined treatment at two weeks and at four weeks fbl, hep, rbl, il-1B, sod and lyz were up-regulated in the mixed diet and for fish getting the fruit.
“No significant variations were found on the seric peroxidase activity and total IgM level of European sea bass specimens after being fed with the tested experimental diets for 2 or 4 weeks,” they said.
Source: Fish & Shellfish Immunology
Title: Impact of date palm fruits extracts and probiotic enriched diet on antioxidant status, innate immune response and immune-related gene expression of European seabass (Dicentrarchus labrax)
Authors: F.A. Guardiola, C. Porcino, R. Cerezuela, A. Cuesta, C. Faggio, M.A. Esteban,