Productive traits, blood biochemical parameters and meat quality of rainbow trout (Oncorhynchus mykiss W.) fed with supplement of nutmeg extract (Myristica fragrans)

Ts. Stoev, G. Zhelyazkov*

Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, Students campus, 6000 Stara Zagora, Bulgaria

(Manuscript received 2 September 2020; accepted for publication 16 November 2020)

Abstract. The aim of the present study was to evaluate the effect of the dietary nutmeg extract (Myristica fragrans) supplement on the survival rate, weight gain, feed conversion ratio (FCR), economic efficiency (ECR), blood biochemical parameters, chemical composition and fatty acid profile of rainbow trout (Oncorhynchus mykiss W.), cultivated in a recirculation system. One hundred and sixty rainbow trouts were distributed in two experimental variants, each with two replications with 80 fish in one group. The average initial live weight of trouts from control (C) and experimental (E) groups was 13.43±0.33 g and 13.46±0.29 g, respectively. Fish were reared in concrete tanks with effective volume of 0.8 m3, part of a recirculation system. Trouts were fed „Aqua garant UNI“ extruded feed produced by Garant-Tiernahrung Gesellschaft m.b.H. – Austria, with pellet size of 2 mm. The feed of fish from the experimental group was supplemented with 1% powdered nutmeg extract (P.I.C.Co LTD), by lubricating the pellets with 5 ml sunflower oil/100 g feed. Control rainbow trouts received feed lubricated with the same amount of sunflower oil. Fish from both groups were fed 3 times daily and their ration was 3% of body weight. The experimental period lasted 60 days. The dietary supplementation of rainbow trouts with nutmeg extract had a negative impact on growth performance and economic efficiency of farming of the species. Final live weight and average individual weight gain were lower, and FCR and ECR values were inferior vs controls. The nutmeg extract had also an adverse effect on water content and dry matter of meat from supplemented fish. A positive effect was demonstrated only on meat fat content, which was substantially lower compared to that of control fish. Despite the higher SFA as well as lower UFA, MUFA, PUFA, n-6 and n-3 fatty acid content of trout meat that received nutmeg extract with feed, the PUFA/SFA and n-6/n-3 ratios remained within the favourable range for human nutrition, e.g. >0.4 and <5, respectively.

Effect of dietary phytoextracts supplementation on the chemical composition and fatty acid profile of rainbow trout (Oncorhynchus Mykiss w.), cultivated in recirculation system

  1. Georgieva, G. Zhelyazkov, Y. Staykov, D. Georgiev

 

Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6014 Stara Zagora, Bulgaria

 

DOI: 10.15547/ast.2018.03.041

(Manuscript received 7 June 2018; accepted for publication 28 August 2018)

 

Abstract. The present research aimed to examine the effect of dietary phytoextracts supplementation on the chemical composition and fatty acid profile in the meat of rainbow trout (Oncorhynchus mykiss W.), cultivated in a recirculation system. The fish were divided into 6 groups: one control (C) and five experimental groups in the food of which phytoextracts of curcumin (EC), paprika (EP), thyme (ET), oregano (EO) and garlic (EG) were added. The inclusion of phytoextracts had no significant effect on growth parameters of fish from EC, EP, ET, EO and EG groups (P>0.05). No statistical differences on water content, protein and lipids were observed in the meat of fish from the control and the experimental groups (P>0.05). Statistically significantly higher value of the dry matter was established in ET group in comparson with C, EC, EP, EO and EG groups (P≤0.001). The values of ash were significantly lower in fish from all experimental groups compared to the control group. The inclusion of phytoextracts did not affect the fatty acid profile of fish from EP, EO and EG groups (P>0.05). Exceptions are EC and ET groups, which had the lowest value of C18:3n-3 α-linolenic compared to those from the control group (P≤0.05, P≤0.001).