Study of the TVN changing procedure and total bacterial load of the Rainbow trout (Oncorhynchus mykiss) deit under environmental conditions

Sanchuli, Mina; Sudagar, Mohammad; Hajibeglou, Ali; Nahavandi, Reza; Zakariaee, Hamideh

Volume 17, Issue 2 (Summer 2025) 3 2025, 17(2): 64-78 | Back to browse issues page

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Sanchuli M, Sudagar M, Hajibeglou A, Nahavandi R, Zakariaee H. Study of the TVN changing procedure and total bacterial load of the Rainbow trout (Oncorhynchus mykiss) deit under environmental conditions. 3 2025; 17 (2) :64-78
URL: http://jmb.ahvaz.iau.ir/article-1-1016-en.html

Study of the TVN changing procedure and total bacterial load of the Rainbow trout (Oncorhynchus mykiss) deit under environmental conditions

Mina Sanchuli

Department of Aquaculture, Faculty of Fisheries and Environment, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.

Abstract: (194 Views)

Rainbow trout (Oncorhynchus mykiss) is one of the most important farmed fish species worldwide for cold-water aquaculture, and maintaining the quality of its consumed diet is of great importance. The present study was conducted to measure volatile nitrogen as an important indicator of protein degradation and to evaluate the trend of changes in the total bacterial load of the diet under environmental conditions in spring 1402 (2023) at the Genetics and Biotechnology Laboratory of the Faculty of Fisheries and Environment, Gorgan University of Agricultural Sciences and Natural Resources. In this study, random time treatments including 0, 2, 4, 6, 8, and 10 weeks with five replicates were considered, and volatile nitrogen and bacterial load were measured over a 70-day period. Volatile nitrogen was determined using the standard macro-Kjeldahl method, and bacterial load was measured using conventional culture-based laboratory methods. Plates were incubated for 24–48 hours at 37 ± 3 °C. To ensure data normality, the Kolmogorov–Smirnov test was applied, and in the case of normal distribution, data were analyzed using one-way ANOVA at a 95% confidence level (P < 0.05). First, overall differences among means were identified, and then Duncan’s multiple range test was used to separate the groups. The results showed an increasing trend in bacterial load up to week 6, with a statistically significant difference (P < 0.05) compared to the week-zero treatment. Measurement of volatile nitrogen revealed a statistically significant difference (P < 0.05) from week zero to the end of the experiment, and the results indicated a direct relationship between total bacterial load and volatile nitrogen content. Overall, the crude protein of rainbow trout feed remained unchanged for a certain period at a temperature of 20–25 °C and constant humidity; however, after two weeks, bacterial growth increased, leading to protein degradation, release of volatile nitrogen, and a decline in the initial desirable quality of the diet. Therefore, it is recommended that fish feed be purchased for short-term use, such as two weeks and at most one month, for feeding fish.

Keywords: Rainbow trout, diet, Total Volatile Nitrogen, bacterial load.

Full-Text [PDF 849 kb] (114 Downloads)

Type of Study: Research | Subject: Fisheries
Received: 2025/04/25 | Accepted: 2025/07/11 | Published: 2025/07/11