Could serum glucose be a selection criterion in Nile tilapia breeding programs

Abstract Consumers, researchers, and organizations worldwide have expressed increasing concern about the conditions under which farm animals are raised and handled. The development of tools for selecting animals better conditioned to their environment is a strategy to increase animal wellbeing. This study investigated the use of blood glucose as possible selection criteria to achieve better conditioning of fish to the farming environment. We carried out four experiments. The first experiment evaluated serum glucose levels during a 24 h fasting period. Then, heritability estimates and other genetic parameters for blood glucose level (GL) and live weight (LW) were determined (Experiment II). Using the genetic parameters it was possible to identify two distinct groups: animals with a low estimated breeding value (EBV) for GL and those with a high EBV for GL. The expression of genes encoding catalase (CAT) and glucose transport 1 (GLUT1) were assessed and compared between groups (Experiment III). In the fourth experiment, the response of genetic groups to handling stress was assessed. The heritability estimate of GL (0.26) and the positive and significant correlation between GL and LW (0.32) indicated that GL has sufficient genetic variability for use as a selection criterion. Genetic gains in both traits were evidenced by good responses to direct and correlated selection. CAT expression did not differ between groups (Low and High EBV for GL). On the other hand, GLUT1 expression was higher in the high EBV (0.013 AU) than in the low EBV group (0.005 AU). As shown by their good response to handling stress and high performance, fish in the high EBV group were better conditioned to the environment. The relationships between animal performance, the environment, and blood glucose observed in this study indicate that Glucose can be use as a indicator of better use of glucose and better adaptation to stress situations in Nile tilapia.