Olive Polyphenols Show Promise as Aquaculture Feed Ingredient

Italian researchers have found that sup­ple­ment­ing sea bream feed with a 0.08 per­cent polyphe­nol extract improved the feed con­ver­sion rate by 30 per­cent. Anti-inflam­ma­tory and pro-immu­nity effects were also indi­cated.

The polyphe­nols in ques­tion, hydrox­y­ty­rosol and tyrosol, were extracted from olive milling waste, mak­ing the study another exam­ple of the pos­si­bil­i­ties for the olive indus­try to con­tribute to the cir­cu­lar econ­omy and increase sus­tain­abil­ity.

The study, con­ducted by researchers from the Zooprophylactic Experimental Institute of Umbria and Marche and the University of Perugia’s vet­eri­nary med­i­cine depart­ment, was con­ceived to assess the poten­tial of olive indus­try waste prod­ucts as aqua­cul­tural nutri­tional sup­ple­ments in the con­text of global envi­ron­men­tal con­cerns and the European Green Deal.

The exper­i­ment was con­ducted on 600 gilt­head sea bream, ran­domly assigned to two dietary groups of 300. Each group was then divided into three sub­groups of 100 fish placed in sep­a­rate indoor tanks.

Compared to the con­trol group, fish fed with the exper­i­men­tal diet showed a ten­dency to increase in weight in the inter­me­di­ate phase (117 per­cent weight gain com­pared to 82 per­cent), and a higher weight increase was recorded at the end of the exper­i­ment (177 per­cent com­pared to 125 per­cent).

A sig­nif­i­cant improve­ment in the feed con­ver­sion ratio was also recorded (1.85 com­pared to 1.45).

These results sug­gested that dietary sup­ple­men­ta­tion with olive-derived polyphe­nols can enhance growth while main­tain­ing the fish’s gen­eral health and phys­i­cal wel­fare.

In addi­tion, genetic analy­ses showed that fish fed with the polyphe­nol-based sup­ple­ment improved the gene expres­sion of bio­mark­ers related to immu­nity and metab­o­lism.

The researchers par­tic­u­larly noted the reduc­tion in the pro-inflam­ma­tory gene inter­leukin 12 beta expres­sion and an increased expres­sion of the anti-inflam­ma­tory gene inter­leukin 10.

These results tally with pre­vi­ous stud­ies demon­strat­ing that plant pro­tein-based diets lower the expres­sion of var­i­ous pro-inflam­ma­tory mark­ers and other genes linked to immune defense.

In con­trast, ani­mal pro­tein-based diets, such as fish meal, lead to an increase in gene expres­sion related to inflam­ma­tory medi­a­tors tied to reg­u­lat­ing inflam­ma­tion and acti­vat­ing the nat­ural immune response to infec­tion.

The authors note that the European Union gen­er­ates approx­i­mately 88 mil­lion met­ric tons of annual food waste at an esti­mated cost of €143 bil­lion, with the major­ity orig­i­nat­ing from the food indus­try rather than con­sumers.

This cat­e­gory of waste mate­r­ial is respon­si­ble for eight to ten per­cent of global emis­sions and about six per­cent of the E.U.‘s green­house gas emis­sions, pol­lu­tion and waste pro­duc­tion.

Therefore, they sought to apply the cir­cu­lar bio-econ­omy and sus­tain­able farm­ing con­cepts to aqua­cul­ture.

Extensive research has shown the ben­e­fi­cial effects of fish con­sump­tion due to their nutri­tional pro­file, which is high in pro­tein, polyun­sat­u­rated fatty acids such as omega‑3, and vit­a­mins such as B2 and B6. Fish is an inte­gral part of the Mediterranean diet and other diets asso­ci­ated with health and longevity.

Aquaculture has been mooted as a sus­tain­able means of fish pro­duc­tion. It is often con­trasted favor­ably with tra­di­tional fish­ing and its asso­ci­ated envi­ron­men­tal impacts, par­tic­u­larly over-fish­ing, food-web dis­rup­tion and bycatch – the inci­den­tal cap­ture of non-tar­get species such as dol­phins, marine tur­tles and seabirds.

Recent stud­ies, how­ever, have raised con­cerns about poten­tially harm­ful prac­tices within the indus­try.

Some of the main fac­tors cited are the com­po­si­tion, source and per­for­mance of feeds. Improving the sus­tain­abil­ity of this aspect is there­fore seen as key to improv­ing the sus­tain­abil­ity of the indus­try as a whole.

• Nature Communications