Ts. Stoev, G. Zhelyazkov
Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 5 June 2021; accepted for publication 10 August 2021)
Abstract. The aim of the present study was to evaluate the effect of the dietary black pepper extract supplement on the survival rate, weight gain, feed conversion ratio (FCR), economic efficiency (ECR) and blood biochemical parameters of rainbow trout, cultivated in a recirculation system. One hundred and twenty rainbow trout were distributed in two experimental variants, with two replicates of 30 fish per each. The average initial live weight of fish from the control group (C) and experimental group (P.n) were 41.55±7.96 g and 41.23±8.38 g, respectively (p>0.05). Trouts were fed extruded feed with granule size of 2 mm. Through lubrication of feed granules with 5 ml sunflower oil per 100 g feed, rainbow trouts from group P.n were supplemented with 1% powdered black pepper extract, whereas control rainbow trouts (С) received feed lubricated with the same amount of sunflower oil. Fish were fed 3 times/daily with the diet, based on 3% of biomass. The trial period was 60 days. Survival rate in trouts from both experimental groups was 100%. At the end of the trial, average live weight of fish from group P.n was by 5.84% higher compared to that of control fish the average weight of which was 117.25±19.15 g, yet differences were not statistically significant (p>0.05). The average individual weight gain of control rainbow trouts was 75.70±11.53 g, which was inferior to that of P.n fish by 8.65% (p>0.05). Better FCR was demonstrated in trouts from the group supplemented with 1% black pepper extract – 0.98±0.02, which was by 10.20% less compared to control fish (p<0.01). The addition of 1% black pepper extract to the feed of rainbow trouts tended to result a trend in better growth performance parameters in this species. ECR of group P.n was by 3.98% better than that of the control fish, which showed an ESR value of 1.51. Blood biochemical parameters of fish from both groups were not consistently different.