Δ13c in Muscle, Liver, and Adipose Fin and Their Relationship to Weight Change During Both Growth and Starvation in Rainbow Trout (oncorhynchus Mykiss), after Feeding a Diet Low in 13C

A 35-day experiment was conducted with a total of 105 rainbow trout (Oncorhynchus mykiss) with an average initial weight of 192.9 g, sampled over four time points (day 7, 14, 21, and 28) to study the relationship between respectively, 813C in muscle, liver, and adipose fin and relative weight gain, when fed a diet based on plant C3 ingredients, with a lower level of 813C compared to the baseline diet. From day 28 to 35, seven fish per tank were starved to investigate the effect of starvation on 813C in muscle, liver, and the adipose fin. Relative weight gain (as a proxy for feed efficiency) significantly (P < 0.0001) affected 813C in muscle and liver, respectively, implying that a diet with a lower natural abundance (compared to the baseline diet) can be used to phenotype feed efficiency. Moreover, the change in 813C due to weight loss was considerable in liver (2.6%o), but only 1.7%o in muscle under starvation.