INDIVIDUAL FEED INTAKE AND BODY WEIGHT GAIN RELATIONSHIP ACCORDING TO GENETIC ORIGIN AND REARING TEMPERATURE IN EUROPEAN SEA BASS DICENTRARCHUS LABRAX
C. Rodde*1,2,3, M. Vandeputte3,4, F. Allal3, M. Besson3,4, A. Vergnet3, F. Clota3,4 and H. de
Verdal1
1 CIRAD, UMR 116 ISEM, Montpellier Cedex 5, France, 2 Worldfish, Penang, Malaysia, 3 MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Palavas-les-Flots, France, 4 GABI, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France. Contact : charles.rodde@cirad.fr
Introduction
Fish feed accounts for around 50% of intensive fish farming costs, and fish feed production and consumption have a strong environmental impact. Using breeding programs to improve feed efficiency could highly increase aquaculture sustainability. Still, it is likely that individual feed intake (FI), body weight gain (BWG) and their interrelation could change substantially depending on the genetic background and on the rearing temperature. Genetics by environment interactions were already demonstrated on the growth of European sea bass (Vandeputte et al, 2014). Here, we studied three European sea bass populations: Atlantic Ocean (AT), West Mediterranean sea (WM) and East Mediterranean sea (EM) at two temperatures (18 and 24°C) in order to 1) assess the differences in the relationship between FI and BWG for each population, temperature and population by temperature interaction and 2) determine the variations of such traits at individual level.
Material and methods
We used 200 European sea bass from the three sea bass populations (62 AT, 66 WM, 72 EM). At the beginning of the experiment, fish were seven-months old and weighing 21.4 ± 8.3 g. These fish were reared in individual aquaria in order to permit individual FI measurement, as described by Besson et al (2019). Among these 200 fish, 100 were reared at 18°C and 100 were reared at 24°C. We firstly identified the ad libitum (ADL) feeding rate of each fish (100% ADL) by adjusting rations weekly over a four-weeks period. Each fish was then fed to 100 % ADL for 22 days, and then 80%, 60%, 40%, 20% and 0% ADL for 10-11 days at each level. Individual FI and BWG were measured at each level and FI and BWG relative to metabolic body weight were calculated (MBW=(Wi x Wf)0.4, with Wi and Wf initial and final weights, Saravanan et al, 2012)
We first studied the intercept and slope of the linear relationship between BWG and FI with an analysis of covariance. To assess individual variations within each interaction, parameters of the linear relationship between BWG and FI were then calculated for each individual and compared. Finally, residuals of the linear relationship between BWG and FI were calculated using the whole dataset and corrected for population and temperature effects. The Pearson’s correlation between residuals ad libitum (res100%ADL) and during fasting (res0%ADL) was estimated. All the analyses were performed using R software.
Results
There was no significant difference in slope in the relationship between BWG and FI (Figure 1) between populations, temperatures, and population by temperature interactions. A significant difference in intercept was found between populations (P < 0.001) and between temperatures (P < 0.001), but interactions was not significant (P > 0.05)
EM fish had a significantly higher intercept than WM (P < 0.01) which had a significantly higher intercept than AT (P < 0.001). Fish reared at 18°C had a significantly higher intercept (P < 0.001) than those reared at 24°C.
At individual level, within each population by temperature interaction, coefficients of variation of intercept and slope were ranged between 15% and 25% and between 15% and 29% respectively.
Finally, Pearson’s correlation between res100%ADL and res0%ADL was not significantly different from 0 (r = -0.08).
Discussion and conclusions
Given the observed homogeneity of slope between populations, temperatures and interactions, it can be considered that a given increase in FI will lead to a similar increase in BWG, whatever the population or the rearing temperature. Moreover, intercept was higher at 18°C than at 24°C: we can make the hypothesis that maintenance costs are lower at 18°C. Similarly, intercept differences between populations may be explained by different maintenance costs. Actually, several phenotypic traits were already demonstrated as significantly different between these populations (Vandeputte et al, 2014). No genetics by environment interaction seemed to be involved in the relationship.
Furthermore, as measuring FI is complex in fish, we tried to find an easier trait (loss of weight during fasting, expressed by res0%ADL) to select for in a breeding program. As the correlation between res100%ADL and res0%ADL was not significant, weight loss during fasting cannot be used to predict which individual fish would have the best growth performance at its ad libitum FI. However, the present experiment was done using really specific rearing conditions: fish were juveniles and isolated (which induces stress). Correlation estimates may be biased by the time lapse existing between measurements done at different feeding levels.
Nevertheless, this study generated key information for breeding programs. A broad individual variability was existing in the relationship between BWG and FI, suggesting opportunities for selective breeding, if this variability is of genetic origin.
References
Besson, M., Allal, F., Chatain, B., Vergnet, A., Clota, F., Vandeputte, M., 2019. Combining individual phenotypes of feed intake with genomic data to improve feed efficiency in sea bass. Frontiers in Genetics 10.
Saravanan, S., Schrama, J.W., Figueiredo-Silva, A.C., Kaushik, S.J., Verreth, J.A.J., Geurden, I., 2012. Constraints on energy intake in fish: the link between diet composition, energy metabolism, and energy intake in rainbow trout. Plos One 7.
-1 0 1 2 3 0 1 2 3 FI (in % of MBW/day) B W G ( in % o f M B W /d a y) Temp 18 24 Pop AT EM WM
Vandeputte, M., Garouste, R., Dupont-Nivet, M., Haffray, P., Vergnet, A., Chavanne, H., Laureau, S., Ron, T.B., Pagelson, G., Mazorra, C., Ricoux, R., Marques, P., Gameiro, M., Chatain, B., 2014. Multi-site evaluation of the rearing performances of 5 wild populations of European sea bass (Dicentrarchus labrax). Aquaculture 424–425, 239– 248.
