Abstract: This study selected feed efficiency ratio (FER) and residual feed intake (RFI) as indicators of feed utilisation efficiency, and assessed their genetic parameters in Litopenaeus vannamei fed a diet containing 5% fishmeal and 35% protein. A total of 45 families were selected for a 42-day feeding trial. A total of 900 shrimp (20 animals per family) were held in individuals. Feed intake and body weight of all the individuals were collected to calculate FER and RFI. The variance components for these traits were estimated using a univariate animal model and average information restricted maximum likelihood method, and genetic (phenotypic) correlations between traits were estimated by bivariate analysis. The study found that the individual RFI under the low-fishmeal and low-protein diet ranged from –0.09 to 0.03 g/d. The individual FER ranged from 15.39% to 78.17%, with an average of 38.08%. The individual average daily feed intake (DFI) was between 0.16 and 0.28 g/d and the individual average daily gain (ADG) was between 0.03 and 0.15 g/d. The family RFI ranged from –0.029 to 0.015 g/d, with considerable variation among families. The family FER ranged from 56.57% to 71.23%, with more minor differences. Without partitioning the common environmental effects, the heritability estimates of RFI and FER were between 0.3 and 0.4, and those of ADG and DFI were around 0.47. The genetic correlations of RFI with FER and ADG were 0.179±0.212 and 0.333±0.193, respectively, showing weak positive correlations, which were not significantly different from zero (P > 0.05). The genetic correlation between RFI and DFI was highly positive (0.772±0.084). The genetic correlation (0.936±0.027) between FER and ADG was extremely strong, and that (0.545±0.157) between FER and DFI was moderate. There was also a high positive genetic correlation between ADG and DFI (0.705±0.111). The phenotypic correlation between RFI and ADG was close to zero, and that (–0.220±0.049) between FER and RFI was weak. Considering the potential overestimation of heritability due to not partitioning common environmental effects, RFI, FER and ADG still exhibited some genetic variation. This suggests that breeding for feed utilisation efficiency and growth in L. vannamei under the low-fishmeal and low-protein diets is feasible. Given the genetic correlations among traits, selecting for growth traits while directly selecting for RFI could enhance the feed utilization efficiency of L. vannamei on low-fishmeal and low-protein diets. Additionally, selecting for growth traits can indirectly improve FER.