Farmed Tilapia See Growth, Meat Quality Boost From Nerolidol Supplement

Adding supplemental nerolidol to diets of farmed tilapia\r\nimproves fish growth and performance along with increasing meat quality,\r\nresearchers say.

A team of researchers from the Federal University of Santa\r\nMaria, the State University of Santa Catarina and the Franciscan University,\r\nSanta Maria in Brazil explored the influence of both dietary free and\r\nnanoencapsulated nerolidol on the performance and fatty acid profile farmed Nile\r\ntilapia.

 “The aim of this\r\nstudy was to evaluate whether dietary supplementation with free or\r\nnanoencapsulated nerolidol improves growth performance, meat antioxidant status\r\nand fillet fatty acid profiles in Nile tilapia,” ​the researchers said.

The researchers found that adding 1 mL nanoencapsulated\r\nnerolidol/kg of feed increased the final body weight and growth rate for fish\r\ncompared to those on the control diet. Fish receiving the supplemented feed had\r\nlower lipid peroxidation levels and reduced reactive oxygen species in meat.

The meat antioxidant capacity for peroxyl radical was\r\nsmaller in fish on diets supplemented with nanoencapsulated nerolidol compared\r\nto fish on the control diet, they said.

Catalase activity in tissue was increased while hydrogen peroxide\r\nlevels fell for fish on diets with 1mL free nerolidol/kg of feed and feed\r\nsupplemented with nanoencapsulated nerolidol compared to those eating the\r\ncontrol diet.

All fish on supplemented diets displayed lower levels of\r\nsaturated fatty acids (SFA) compared to results for fish receiving the control\r\ndiet, they said. However, the total content of monounsaturated fatty acids\r\n(MUFA) increased for supplemented fish.

“It appears that nanoencapsulation of nerolidol exerted\r\npotent benefits for fish health, manifesting as improvement in growth\r\nperformance and reduction in meat ROS [reactive oxygen species] and LPO [lipid\r\nperoxidation] levels in fish fed with nerolidol nanospheres,” ​the researchers\r\nsaid. “Both forms improved meat quality based on reduction of SFAs and\r\nincreases in MUFAs, suggesting that dietary supplementation with\r\nnanoencapsulated nerolidol is a compelling approach to improving fish health\r\nand meat quality.”​

Alternatives to AGPs​

Aquaculture is a rapidly growing food production sector\r\nglobally, witnessing an average annual growth rate of 5.8% from 2000-2016 and\r\nproviding about 80m tons of fish by 2016, the researchers said.

Aquaculture production provides a source of protein and\r\nessential micronutrients for humans, they said. Compared to terrestrial\r\nanimals, fish is a source of essential fatty acids, including polyunsaturated\r\nfatty acids.

However, expanding aquaculture production has been\r\naccompanied by the use of semi-intensive or intensive farming systems, which\r\nare stressful conditions for fish that may increase the chance of disease\r\noutbreaks and high rates of fish mortality, they said.

“Enhancing fish health is a major concern of fish farmers;\r\nuntil some time ago, this end was achieved primarily using antibiotics;\r\nhowever, this practice is currently discouraged because of the emergence of\r\nantibiotic-resistant bacteria, environmental side-effects, alterations in\r\nmicrobial communities, and accumulation in edible tissues,” ​they said. “Today,\r\nthe search for unconventional and more environmentally-friendly growth\r\npromoters as alternatives to antibiotics are compelling methods to promote\r\nanimal health and well-being in order to sustain safer and more productive\r\naquaculture.”​

Why add nerolidol to fish feed?​

Manufactured drugs are starting to be replaced with natural\r\nproducts and nutritional additives that enhance the antioxidant system, the\r\nresearchers said. These include essential oils and their isolated compounds\r\nlike sesquiterpenes.

“Sesquiterpenes are C-15 terpenoids that occur as\r\nhydrocarbons or in oxygenated forms such as alcohols, ketones, aldehydes, acids\r\nor lactones in nature; they are important constituents of essential oils, with\r\nmany applications in fish production,” ​they said. “Nerolidol\r\n(3,7,11-trimethyl-1,6,10-dodecatrien-3-ol) is an aliphatic sesquiterpene\r\nalcohol with several pharmacological properties in mammals, including\r\nneuroprotective, trypanocidal, antimicrobial and antioxidant properties.”​

No research has been done exploring the use of isolated\r\nnerolidol ub fish, but the compound is found in Lippia alba​ essential oil,\r\nwhich is used as a fish anesthetic, they said.

Previous research suggests that using nanotechnology or\r\nloading nerolidol into nanospheres could increase the compound’s antioxidant\r\ncapacity, they said.

“Nanotechnology is a science devoted to the design,\r\nsynthesis, characterization and application of materials that possess a\r\nfunctional organization on the nanometric scale (10−9 m); where the reduction\r\nof particle size at nanometric scale increases the particle reactivity and\r\nalters the pharmacological properties of active principles,”​ the researchers\r\nsaid. Nanotechnology is starting to be used to improve the “production,\r\nprocessing, storage, transportation, traceability, safety and security”​ for\r\naquafeed, they added.

“Shah and Mraz (2019) reported that nanotechnology is a\r\ncompelling alternative to avoid the excessive usage of antibiotics, for\r\nidentification of new natural bioactive compounds that could be used as growth\r\npromotors,”​ they said. The technology can be used to improve the efficacy of\r\nbioactive compounds and provide for a targeted and sustained release.

The researchers’ hypothesis was that nerolidol’s antioxidant\r\nproperties would improve fish health, boost Nile tilapia growth performance, improve\r\nmeat antioxidant status and the fatty acid profile in fish fillets.

Feeding trial ​

During the feeding trial, 200 Nile tilapia fingerlings\r\nreceived one of five trial diets for 60 days. The diets used a commercially\r\navailable nerolidol and contained 38% protein.

The trial feeds included a non-supplemented control diet\r\n(Group A) comprised of meat and bone meal, soybean meal, corn and rice bran,\r\nthe control diet supplemented with 0.5mL/kg of feed free (Group B) or\r\nnanoencapsulated nerolidol (Group D), or the control diet with 1 mL/kg of feed\r\nfree (Group C) or nanoencapsulated nerolidol (Group E).

Fish were weighed and measured at the start and end of the\r\nfeeding trial, they said. Weight gain, growth rate (SGR), condition factor\r\n(CF), percentage of fish survival and feed intake (FI) were calculated.

A selection of fish on every diet was collected at the end\r\nof the trial to sample muscle fillets, the researchers said. Tissue was\r\nassessed for meat reactive oxygen species (ROS), meat hydrogen peroxide concentration,\r\nmeat lipid peroxidation levels (LPO), meat carbonyl protein content and meat\r\nantioxidant capacity against peroxyl radicals (ACAP).

Fish fillets were also checked for meat superoxide dismutase\r\n(SOD) activity, meat catalase activity (CAT), muscle protein content and fatty\r\nacid profile, they added.

Results​

Overall, fish receiving the diet with 1 mL/kg feed\r\nnanoencapsulated nerolidol had increased weight gain and a higher final mean\r\nweight compared to fish on the control diet, the researchers said. Tilapia on\r\nthat diet had lower ROS and LPO levels compared to control group fish.

However, no major differences were noted based on diet for\r\nsurvival, feed intake or condition factor, they said.

“These data suggest that nanoencapsulation of nerolidol\r\npromotes fish health by promoting growth and reducing free radical production\r\nand lipid damage,”​ the researchers said. “Free and (particularly)\r\nnanoencapsulated nerolidol enhanced muscle/meat enzymatic and non-enzymatic\r\nantioxidant systems.”​

Meat hydrogen peroxide concentration was reduced for fish on\r\nthe 1mL free nerolidol/kg feed, 0.5mL nanoencapsulated and 1mL nanoencapsulated\r\ndiets, they said. Fish on all diets had similar protein carbonylation levels.

Fish receiving diets with encapsulated nerolidol had higher\r\nmeat ACAP levels and CAT activity increased for those fish and tilapia on the\r\ndiet with 1mL free nerolidol, they said.

But there were no major differences found for SOD activity\r\nregardless of diet.

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Supplementing diets with either type of nerolidol lowered\r\ntotal saturated fatty acid levels and increased the amount of monounsaturated\r\nfatty acids, they said. However, all fish had similar results for the sum of\r\npolyunsaturated fatty acids (PUFA).

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