Using physiological and zootechnical profiles to evaluate welfare in farmed rainbow trout Oncorhynchus mykiss (Walbaum) under stressful conditions

Abstract

The welfare of farmed animals, and more recently of farmed fish, is a growing concern in current society. Changes in living conditions represent one of the most stressful situations in fish production. It is crucial to develop tools to evaluate welfare in farmed fish throughout the various situations observed during the production cycle. The present work aims to select relevant parameters in order to evaluate the welfare of trout, by describing the physiological and zootechnical profiles of rainbow trout Oncorhynchus mykiss (Walbaum) populations during adaptation to a new environment. Ten days after transferring seven groups of farmed trout to a laboratory setting, a principal component analysis was performed on five parameters: plasma cortisol level (PCL), hepatosomatic index (HI), growth (G), food intake (FI) and food conversion ratio (FCR). PCL and FCR were positively correlated and were both negatively correlated with FI and G. FI and G were positively correlated. HI was not correlated with any other parameter. PCL was considered as being at basal levels. Descriptive statistics and the principal component analysis suggest measuring PCL, G, FI and FCR to be a relevant strategy for evaluating the welfare of trout when adapting to a new environment. The study demonstrates the relevance of this approach in evaluating specific profiles related to the welfare of farmed animals.