The impact of the mineral zeolite on feed conversion and mortality rate on commercially grown rainbow trout

Abstract

The aim of this study was to evaluate the effect of zeolite, added to feed, on feed conversion and mortality rate in commercially farmed rainbow trout. The research was conducted at the Riboexport DOOEL pond in Gostivar, at the Vrutok source. Three pools were included in the study: Group A – without zeolite, Group B – feed with 1 % zeolite, and Group C – feed with 2 % zeolite. The fish were reared under standardized conditions (length 4 m, width 1 m, depth 45 cm, total water volume 1.8 m³, temperature 11 °C, and oxygen concentration 9–11 mg/L). Each pool contained 200 juvenile rainbow trout with an initial weight of 46–48 g and length of 15–16 cm, monitored over a 12-week period. Measurements were taken 8 times, at 14-day intervals. Feed conversion was determined using the Feed Conversion Ratio (FCR), and mortality was recorded numerically. The results are presented using descriptive statistics, showing FCR values of 0.89 for Group A, 0.84 for Group B, and 0.89 for Group C. No mortality was recorded in Groups A and B (0 %), while 3 dead fish (1.5 %) were observed in Group C. The best feed conversion was observed in the group receiving feed with 1 % zeolite. Fish mortality was not related to zeolite application but was attributed to mechanical injuries during manual handling.