Growth performance, biochemical blood parameters and meat quality of rainbow trout ( Oncorhynchus Mykiss W. ) fed with licorice ( Glycyrrhiza Glabra L. ) supplemented diet

Abstract

Licorice (Glycyrrhiza glabra) is medicinal plant characterized with sweet flavor which has been used in Bulgarian traditional medicine to improve the condition of the digestive tract and could positively affect digestibility and assimilation of feed nutrients in human and animal organisms. The studies connected with the effect of licorice in fish are limited. The aim of current study was to find the effect of feed supplemented with licorice Glycyrrhiza glabra on growth performance, blood parameters and meet quality in rainbow trout (Oncorhynchus mykiss W.), raised in the recirculation system. The fish were fed with two feeds: control feed (CF) - without the addition of supplement and experimental feed (EF), with supplementation of 300 mg.kg-1 licorice in pellets. The stocking density of rainbow trout in recirculation system was 50 pcs.m-3. The initial average weight of fish in CF variant was 13.30 ±3.07 g and in EF variant was 13.40±3.55 g without differences being statistically significant (p≥0.05). The continuation of the experiment was 60 days. The average final weight, meat quality, and blood biochemical parameters were measured at the end of the experiment. The SGR and FCR were also calculated. Fish from the experimental group fed with a supplement of licorice had with 8.54% higher average final weight compared to the parameter’s value in trouts from the control variant (p<0.05). SGR in rainbow trout’sfrom experimental variants was higher with 6.9% compared to the value of SGR in fish from CF variant. The blood biochemical parameters in experimental trouts were not significantly affected by supplementation of licorice extract. The average values of glucose, ASAT, and ALAT in control variant were higher respectively with 3.96%, 57.2% and 10.3% compared to values in these parameters measured in the blood of fish from the experimental variant, but differences were not statistically proven (p≥0.05). The meat quality parameters were affected from the addition of licorice in feed for trouts and the moisture, fat, and ash quantities were higher respectively with 2.49%, 36.4% and 12.5% compared with the average values of these parameters found for fish from CF group (p<0.05). The extract from licorice added to feed for the feeding of rainbow trout increases the growth of fish and affect the meat quality parameters (p<0.05), but did not affect significantly the blood parameters (p≥0.05).