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Feed efficiency is a major goal for aquaculture sustainability, and selecting fish to genetically enhance this trait would be highly valuable. However, no selective breeding program specifically targeted to feed efficiency exists for farmed fish, mostly because of the difficulty of measuring individual feed intake. However, a negative phenotypic correlation between feed efficiency and weight loss at fasting has been previously demonstrated in sea bass submitted to feed deprivation (FD). We mated sea bass parents selected for their high (FD+) or low (FD-) weight loss at fasting to produce FD+ and FD- progeny, which were reared in a single tank to avoid common environmental effects. At 8 months of age, 1200 of those fish were submitted to three alternating periods of fasting (3 weeks) and re-feeding (3 weeks). Individuals were weighed at the end of each feeding and fasting period. Their line of origin was identified by genotyping of 12 microsatellite markers, resulting in 1130 unambiguously assigned fish (484 FD-, 686 FD+). FD- offspring lost significantly less weight than FD+ offspring in this feed deprivation trial. After that the feed efficiency of eight groups of 50 FD+ fish and eight groups of 50 FD- fish was evaluated in four successive 20-day periods. At the end of the fourth period, 10 fish per tank were sacrificed to evaluate their carcass yield. The FD- fish had a better overall growth and were fatter, and FD+ fish had a better carcass yield. A better feed efficiency was expected for the FD- fish, but differences between the two groups for this trait, measured either with feed efficiency ratio or with residual feed intake, were not consistently significant Although the two lines were clearly divergent for several traits, demonstration of feed efficiency differences between the FD+ and the FD- lines was not consistently observed in sea bass. A second generation of selection may allow further divergence in the lines and reveal differences in feed efficiency. (

Feed efficiency is a major goal for aquaculture sustainability, and selecting fish to genetically enhance this trait would be highly valuable. However, no selective breeding program specifically targeted to feed efficiency exists for farmed fish, mostly because of the difficulty of measuring individual feed intake. However, a negative phenotypic correlation between feed efficiency and weight loss at fasting has been previously demonstrated in sea bass submitted to feed deprivation (FD). We mated sea bass parents selected for their high (FD+) or low (FD-) weight loss at fasting to produce FD+ and FD- progeny, which were reared in a single tank to avoid common environmental effects. At 8 months of age, 1200 of those fish were submitted to three alternating periods of fasting (3 weeks) and re-feeding (3 weeks). Individuals were weighed at the end of each feeding and fasting period. Their line of origin was identified by genotyping of 12 microsatellite markers, resulting in 1130 unambiguously assigned fish (484 FD-, 686 FD+). FD- offspring lost significantly less weight than FD+ offspring in this feed deprivation trial. After that the feed efficiency of eight groups of 50 FD+ fish and eight groups of 50 FD- fish was evaluated in four successive 20-day periods. At the end of the fourth period, 10 fish per tank were sacrificed to evaluate their carcass yield. The FD- fish had a better overall growth and were fatter, and FD+ fish had a better carcass yield. A better feed efficiency was expected for the FD- fish, but differences between the two groups for this trait, measured either with feed efficiency ratio or with residual feed intake, were not consistently significant Although the two lines were clearly divergent for several traits, demonstration of feed efficiency differences between the FD+ and the FD- lines was not consistently observed in sea bass. A second generation of selection may allow further divergence in the lines and reveal differences in feed efficiency. (

Feed efficiency is a major goal for aquaculture sustainability, and selecting fish to genetically enhance this trait would be highly valuable. However, no selective breeding program specifically targeted to feed efficiency exists for farmed fish, mostly because of the difficulty of measuring individual feed intake. However, a negative phenotypic correlation between feed efficiency and weight loss at fasting has been previously demonstrated in sea bass submitted to feed deprivation (FD). We mated sea bass parents selected for their high (FD+) or low (FD-) weight loss at fasting to produce FD+ and FD- progeny, which were reared in a single tank to avoid common environmental effects. At 8 months of age, 1200 of those fish were submitted to three alternating periods of fasting (3 weeks) and re-feeding (3 weeks). Individuals were weighed at the end of each feeding and fasting period. Their line of origin was identified by genotyping of 12 microsatellite markers, resulting in 1130 unambiguously assigned fish (484 FD-, 686 FD+). FD- offspring lost significantly less weight than FD+ offspring in this feed deprivation trial. After that the feed efficiency of eight groups of 50 FD+ fish and eight groups of 50 FD- fish was evaluated in four successive 20-day periods. At the end of the fourth period, 10 fish per tank were sacrificed to evaluate their carcass yield. The FD- fish had a better overall growth and were fatter, and FD+ fish had a better carcass yield. A better feed efficiency was expected for the FD- fish, but differences between the two groups for this trait, measured either with feed efficiency ratio or with residual feed intake, were not consistently significant Although the two lines were clearly divergent for several traits, demonstration of feed efficiency differences between the FD+ and the FD- lines was not consistently observed in sea bass. A second generation of selection may allow further divergence in the lines and reveal differences in feed efficiency. (

Selective breeding to improve residual feed intake (RFI) in sea bass (Dicentrarchus labrax) is a major goal that would optimize economic gain while minimizing the environmental impact of production. Due to the difficulty in accurately measuring individual feed intake, no selective breeding program has yet been started. In a previous study, we identified a criterion phenotypically related to RFI variations: the loss of weight during feed deprivation, FD. Moreover, an additional composite criterion (CC) integrating both FD and weight gain during subsequent re-feeding (RF) was closely related to RFI, even though the relationship was only close to significance (P=0.06). The aim of the present study was to estimate the heritability of these two traits, in order to complete the analysis of their pertinence as indirect criteria for use in a selective breeding program to improve RFI. We set up a full factorial mating design combining 41 sires and eight dams to produce mixed families offspring, which were all raised in the same tank. At 50g. 1300 individuals were individually tagged and a fin clip was sampled for DNA extraction and parentage reassignment using five to six microsatellite loci, which showed they originated from 261 families. The evolution of individual body weight was recorded during a growth period of three weeks, followed by successive periods of three weeks feed deprivation and three weeks ad libitum re-feeding, repeated twice. Phenotypic and genetic correlations between the two feed deprivation periods or the two re-feeding periods were moderate (r = 0.45-0.51, and 0.71-0.73 respectively for phenotypic and genetic correlations) indicating that FD and RF are relatively repeatable. FD, RF and CC heritabilities were of the same magnitude (0.23 +/- 0.04, 0.19 +/- 0.04 and 0.22 +/- 0.04, respectively), and sufficient to consider the use of such criteria in a future breeding program.

No commercial breeding programs have yet started to improve feed utilization efficiency in fish, mainly because of the difficulty in accurately measuring individual feed intake in fish reared in groups. Our general goal is to propose indirect criteria to be used for breeding of commercial lines. In a previous study undertaken with rainbow trout clones, a genetic correlation was detected between residual feed intake (RFI), and body weight variation during successive periods of feed deprivation (FD) and re-feeding (RF). To assess the pertinence of such indirect criteria for future breeding programs, we set up a large experiment using sea bass (Dicentrachus labrax), a recently domesticated species with broad genetic diversity. The objectives of the present study were to analyze the relationship of FD and RF with RFI, and to assess the consistency of such indirect criteria over time and their correlation with carcass quality. Fish originating from a full factorial design combining eight dams and 41 sires, were raised in the same tank. At 306 days post fertilization 2000 fish were individually tagged and their body weight recorded over a growth period of three weeks, followed by two successive periods of three weeks of feed deprivation and three weeks of ad libitum re-feeding. Fish performances were then classified, FD-, FD+, RF- and RF+ for fish exhibiting loss (FD) or gain (RF) of weight relatively lower (-) and higher (+) than the population mean. Fish were sorted into four groups (FD-/RF-, FD+/RF+, FD-/RF+, FD+/RF). Each of the 4 groups was split between three replicated tanks of 50 fish. Body weight gain and feed intake were measured for each replicate every three weeks over a six months period to estimate residual feed intake. The fish then underwent a period of three weeks of feed deprivation followed by a period of three weeks of ad libitum re-feeding. At the end of each period, individual weight gain variations were recorded, as well as muscle fat using ultrason

No commercial breeding programs have yet started to improve feed utilization efficiency in fish, mainly because of the difficulty in accurately measuring individual feed intake in fish reared in groups. Our general goal is to propose indirect criteria to be used for breeding of commercial lines. In a previous study undertaken with rainbow trout clones, a genetic correlation was detected between residual feed intake (RFI), and body weight variation during successive periods of feed deprivation (FD) and re-feeding (RF). To assess the pertinence of such indirect criteria for future breeding programs, we set up a large experiment using sea bass (Dicentrachus labrax), a recently domesticated species with broad genetic diversity. The objectives of the present study were to analyze the relationship of FD and RF with RFI, and to assess the consistency of such indirect criteria over time and their correlation with carcass quality. Fish originating from a full factorial design combining eight dams and 41 sires, were raised in the same tank. At 306 days post fertilization 2000 fish were individually tagged and their body weight recorded over a growth period of three weeks, followed by two successive periods of three weeks of feed deprivation and three weeks of ad libitum re-feeding. Fish performances were then classified, FD-, FD+, RF- and RF+ for fish exhibiting loss (FD) or gain (RF) of weight relatively lower (-) and higher (+) than the population mean. Fish were sorted into four groups (FD-/RF-, FD+/RF+, FD-/RF+, FD+/RF). Each of the 4 groups was split between three replicated tanks of 50 fish. Body weight gain and feed intake were measured for each replicate every three weeks over a six months period to estimate residual feed intake. The fish then underwent a period of three weeks of feed deprivation followed by a period of three weeks of ad libitum re-feeding. At the end of each period, individual weight gain variations were recorded, as well as muscle fat using ultrason

No commercial breeding programs have yet started to improve feed utilization efficiency in fish, mainly because of the difficulty in accurately measuring individual feed intake in fish reared in groups. Our general goal is to propose indirect criteria to be used for breeding of commercial lines. In a previous study undertaken with rainbow trout clones, a genetic correlation was detected between residual feed intake (RFI), and body weight variation during successive periods of feed deprivation (FD) and re-feeding (RF). To assess the pertinence of such indirect criteria for future breeding programs, we set up a large experiment using sea bass (Dicentrachus labrax), a recently domesticated species with broad genetic diversity. The objectives of the present study were to analyze the relationship of FD and RF with RFI, and to assess the consistency of such indirect criteria over time and their correlation with carcass quality. Fish originating from a full factorial design combining eight dams and 41 sires, were raised in the same tank. At 306 days post fertilization 2000 fish were individually tagged and their body weight recorded over a growth period of three weeks, followed by two successive periods of three weeks of feed deprivation and three weeks of ad libitum re-feeding. Fish performances were then classified, FD-, FD+, RF- and RF+ for fish exhibiting loss (FD) or gain (RF) of weight relatively lower (-) and higher (+) than the population mean. Fish were sorted into four groups (FD-/RF-, FD+/RF+, FD-/RF+, FD+/RF). Each of the 4 groups was split between three replicated tanks of 50 fish. Body weight gain and feed intake were measured for each replicate every three weeks over a six months period to estimate residual feed intake. The fish then underwent a period of three weeks of feed deprivation followed by a period of three weeks of ad libitum re-feeding. At the end of each period, individual weight gain variations were recorded, as well as muscle fat using ultrason

Selective breeding to improve residual feed intake (RFI) in sea bass (Dicentrarchus labrax) is a major goal that would optimize economic gain while minimizing the environmental impact of production. Due to the difficulty in accurately measuring individual feed intake, no selective breeding program has yet been started. In a previous study, we identified a criterion phenotypically related to RFI variations: the loss of weight during feed deprivation, FD. Moreover, an additional composite criterion (CC) integrating both FD and weight gain during subsequent re-feeding (RF) was closely related to RFI, even though the relationship was only close to significance (P=0.06). The aim of the present study was to estimate the heritability of these two traits, in order to complete the analysis of their pertinence as indirect criteria for use in a selective breeding program to improve RFI. We set up a full factorial mating design combining 41 sires and eight dams to produce mixed families offspring, which were all raised in the same tank. At 50g. 1300 individuals were individually tagged and a fin clip was sampled for DNA extraction and parentage reassignment using five to six microsatellite loci, which showed they originated from 261 families. The evolution of individual body weight was recorded during a growth period of three weeks, followed by successive periods of three weeks feed deprivation and three weeks ad libitum re-feeding, repeated twice. Phenotypic and genetic correlations between the two feed deprivation periods or the two re-feeding periods were moderate (r = 0.45-0.51, and 0.71-0.73 respectively for phenotypic and genetic correlations) indicating that FD and RF are relatively repeatable. FD, RF and CC heritabilities were of the same magnitude (0.23 +/- 0.04, 0.19 +/- 0.04 and 0.22 +/- 0.04, respectively), and sufficient to consider the use of such criteria in a future breeding program.

Selective breeding to improve residual feed intake (RFI) in sea bass (Dicentrarchus labrax) is a major goal that would optimize economic gain while minimizing the environmental impact of production. Due to the difficulty in accurately measuring individual feed intake, no selective breeding program has yet been started. In a previous study, we identified a criterion phenotypically related to RFI variations: the loss of weight during feed deprivation, FD. Moreover, an additional composite criterion (CC) integrating both FD and weight gain during subsequent re-feeding (RF) was closely related to RFI, even though the relationship was only close to significance (P=0.06). The aim of the present study was to estimate the heritability of these two traits, in order to complete the analysis of their pertinence as indirect criteria for use in a selective breeding program to improve RFI. We set up a full factorial mating design combining 41 sires and eight dams to produce mixed families offspring, which were all raised in the same tank. At 50g. 1300 individuals were individually tagged and a fin clip was sampled for DNA extraction and parentage reassignment using five to six microsatellite loci, which showed they originated from 261 families. The evolution of individual body weight was recorded during a growth period of three weeks, followed by successive periods of three weeks feed deprivation and three weeks ad libitum re-feeding, repeated twice. Phenotypic and genetic correlations between the two feed deprivation periods or the two re-feeding periods were moderate (r = 0.45-0.51, and 0.71-0.73 respectively for phenotypic and genetic correlations) indicating that FD and RF are relatively repeatable. FD, RF and CC heritabilities were of the same magnitude (0.23 +/- 0.04, 0.19 +/- 0.04 and 0.22 +/- 0.04, respectively), and sufficient to consider the use of such criteria in a future breeding program.

No commercial breeding programs have yet started to improve feed utilization efficiency in fish, mainly because of the difficulty in accurately measuring individual feed intake in fish reared in groups. Our general goal is to propose indirect criteria to be used for breeding of commercial lines. In a previous study undertaken with rainbow trout clones, a genetic correlation was detected between residual feed intake (RFI), and body weight variation during successive periods of feed deprivation (FD) and re-feeding (RF). To assess the pertinence of such indirect criteria for future breeding programs, we set up a large experiment using sea bass (Dicentrachus labrax), a recently domesticated species with broad genetic diversity. The objectives of the present study were to analyze the relationship of FD and RF with RFI, and to assess the consistency of such indirect criteria over time and their correlation with carcass quality. Fish originating from a full factorial design combining eight dams and 41 sires, were raised in the same tank. At 306 days post fertilization 2000 fish were individually tagged and their body weight recorded over a growth period of three weeks, followed by two successive periods of three weeks of feed deprivation and three weeks of ad libitum re-feeding. Fish performances were then classified, FD-, FD+, RF- and RF+ for fish exhibiting loss (FD) or gain (RF) of weight relatively lower (-) and higher (+) than the population mean. Fish were sorted into four groups (FD-/RF-, FD+/RF+, FD-/RF+, FD+/RF). Each of the 4 groups was split between three replicated tanks of 50 fish. Body weight gain and feed intake were measured for each replicate every three weeks over a six months period to estimate residual feed intake. The fish then underwent a period of three weeks of feed deprivation followed by a period of three weeks of ad libitum re-feeding. At the end of each period, individual weight gain variations were recorded, as well as muscle fat using ultrason