Rflps for Somatotropic Genes Identify Quantitative Trait Loci for Growth in Mice

Restriction fragment length polymorphisms for somatotropic genes were tested for associations with body weight and postweaning growth rate in mice. Polymorphisms for growth hormone (GH) and insulin-like growth factor 2 (IGF-2) genes were identified in stock population lines which had been subjected to long-term selection for high 42-day body weight (H lines) or randomly mated (FP and C lines). Two F2 populations of mice (5F2 and MF2) were generated from crosses between a single H line of mice and two unselected control lines and subsequently, two divergently weight selected sublines were generated from each F2 population. The GHh allele which had originally been fixed in three of four H lines and absent from all FP and C lines was found to have a significant (P less than 0.01) effect on 42-day weight and postweaning growth rate in the F2 populations. However, GHh was associated with lower 42-day weight in the F2 populations, suggesting that the positive association between GHh and weight in the stock population was unique to the high weight selected genetic background of those lines. In agreement with this, the frequency of GHh increased in sublines selected for high 42-day weight and decreased in sublines selected for low 42-day weight. The IGF-2H5 allele was associated with higher weights in a sex-dependent manner in 5F2. In the high selected subline derived from 5F2, a significant increase in the frequency of IGF-2H5 was observed. Therefore this allele, in contrast to GHh, appears to be a positive indicator of growth irrespective of genetic background.     

Direct genetic and postnatal maternal genetic effects on body composition in mice selected for body weight.

Line crossfostering techniques were used to study differences among selected and control lines of mice in direct genetic and postnatal maternal genetic influences on preweaning (day 12) body weight and composition. The lines were selected for high (H6) and low (L6) 6-week body weight and the control line (C2) was maintained by random selection. There were positive correlated responses to selection in both direct genetic and postnatal maternal genetic effects on body weight and weights of all body components (P less than 0.01) except for water and ash weight in H6. The correlated responses in postnatal maternal genetic effects were of the same order of magnitude as those in direct genetic effects. Correlated responses were greater in L6 than in H6. Correlated responses in direct genetic effects were positive (P less than 0.01) for water percent in H6 and ether extract percent in L6, and negative (P less than 0.01) for water percent and lean percent in L6. Correlated responses in postnatal maternal genetic effects were positive for ether extract percent and negative for water percent (P less than 0.01). Correlated responses were far greater in L6 than in H6 and were greater for postnatal maternal genetic effects than for direct genetic effects. Analyses of covariance results indicated line differences in the relative growth rates of the body components.     

Changes in the body composition of mice selected for high and low eight week weight

Summary Body composition was studied in three lines of mice, one selected for high (H) and one for low (L) 8 week weight, and one maintained as an unselected control (C). After 25 generations 8 week weights were 41.2g, 30.6 g and 20.5g for the H, C and L lines. Mice were sampled from the lines and analysed for fat, protein, ash and water at generations 14 and 25. Apart from fat in the H line, there was little alteration due to selection in the relationships between individual body components and total body weight. In the H line, the contribution of fat to body weight gain was considerably increased. Although leaner than the C and L mice at low body weights, H line mice rapidly became fatter with increasing body weight. Selection appeared to reduce the body weight at which fat was deposited at its maximum rate in the H line. The H and C lines were equally fat at body weights of 29.0 g and 21.6 g at generations 14 and 25 respectively. Body weights at points of inflection of the growth curves of the H, C and L lines at generation 25 were 18.3 g, 14.3 g and 12.8 g. The implications of these findings for meat species slaughtered at set weights are discussed.     

Environmental maternal influences on body composition in mice selected for body weight

Summary The effect of the postnatal maternal environment, simulated by rearing mice in litters of three, six or nine, on body weight and body composition was investigated in three lines of mice differing widely in growth rate. The lines were selected for high (H₆) and low (L₆) 6-week body weight while the control line was maintained by random selection. Body weight and weights and percentages of ether extract, water, ash and protein at 21, 42, 63 and 84 days were recorded. With few exceptions, there were positive correlated responses to selection in body weight and in weights of body components. At 21 and 42 days the correlated responses were larger in L₆ mice than in H₆ mice. Body weight and weights of body components were larger for mice reared in litters of three than for those reared in litters of nine. Also, mice reared in litters of six were intermediate in body weight and weights of some of the body components between those reared in litters of three and nine. Differences in body weight and weights of body components due to postnatal maternal environment were small by comparison with differences due to genetic line. There were significant line by maternal environment interactions in body weight at 21 days and in ether extract weight at 21 and 63 days. Line and maternal environment differences in percentages of body components did not follow any consistent trend. The results for percentages of body components were further complicated by line x maternal environment interactions. In general, both line and postnatal maternal environmental differences in percentages of body components diminished with age.Paper No. 5670 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, North Carolina 27650. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Experiment Station of the products named, nor criticism of similar ones not mentioned     

Selection for components related to body composition in mice: correlated responses

Summary Correlated responses were estimated in each of two replicate lines of mice selected within full-sib families for high (HF) or low (LF) 12-week epididymal fat pad weight as a percentage of body weight (epididymal fat pad percentage), or high (HL) or low (LL) 12-week hind carcass weight as a percentage of body weight (hind carcass percentage). Two replicate control lines (RC) were maintained. Correlated traits were measured in each of the 10 generations of selection. Realized (r_{G R}) and offspring-sire genetic correlations generally were in agreement. In HF and LF, 3–6 week postweaning gain (r_{G R} = 0.36±0.04) and feed intake (r_{G R} = 0.50±0.13) had positive correlated responses, but feed efficiency and feed intake/metabolic body size did not change. Positive correlated responses were found for subcutaneous fat pad percentage, body weight-adjusted subcutaneous fat pad weight and fat percentage in the hind carcass (r_{G R}'s were 1.04±0.13, 0.93±0.13 and 0.90±0.08). In the hind carcass, fat-free dry (protein + ash) percentage showed a small negative correlated response, and fat-free dry weight did not change. In HL and LL, the correlated responses for the above traits were generally opposite to those observed in HF and LF. Litter size, percentage of infertile matings, and preweaning mortality showed no consistent correlated responses in any of the lines, but an index of fitness combining the three traits showed a decrease in all four selection treatments.Paper no. 11057 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, 27695-7601. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticisms of similar ones not mentioned     

Muscle-bone relationships in mice selected for different body conformations

Some muscle-bone relationships were studied in terms of gastrocnemius muscle weight, femur and tibia length and femur and tibia weight in four lines of mice (CBi-, CBi+, CBi/L and CBi/C) artificially selected for different body conformations and in the unselected control line (CBi). CBi- (low body weight--short tail) and CBi+ (high body weight--long tail) lines were divergently selected following the positive genetic correlation between body weight and tail (skeleton) length (agonistic selection). In contrast, CBi/L (low body weight--long tail) and CBi/C (high body weight--short tail) were also divergently selected but against the aforementioned correlation (antagonistic selection). The relationship between bone length and muscle weight was interpreted based on the assumption that the increased tension generated by the longitudinal growth of a bone, brings about an increase in the mass of the muscles attached to it. All CBi+, CBi/C and CBi/L mice showed enlarged femurs and tibias, but only those genotypes simultaneously selected for high body weight (CBi+ and CBi/C) showed heavier muscles than controls. The CBi+ and CBi- genotypes with agonistic selection differ in bone length and muscle weight, as it would be expected of the allometric modification of their body conformation, showing the associated longitudinal bone growth-muscle growth. CBi/C and CBi/L mice, with a non-allometric modification of body conformation, exhibited the same bone length but different muscle weight. Consequently, the antagonistic criterion allowed to confirm that the genetic influence on of the proposed muscle-bone relationships could be modified, thus making it possible to lengthen the bone through selection of a long skeleton and to avoid the correlated effect on muscle mass, by selecting for a low body weight, bringing forth presumptive evidence that both processes were genetically independent.     

Replicated selection for insulin-like growth factor-1 and body weight in mice

Summary Five generations of divergent selection for plasma concentration of insulin-like growth factor-1 (IGF-1) and for 12-week body weight were carried out in mice, including randomly selected control lines for each trait. All lines were replicated once (12 lines in total). Each replicate line consisted of eight male and eight female parents per generation. Litter size was standardized to eight pups at birth. Mass selection was applied in the selected lines and within-family random selection in the control lines. Blood was taken from the orbital sinus of individual mice at 12 weeks of age for IGF-1 assay. Realized heritabilities were 0.10±0.01 for IGF-1 and 0.41 ± 0.02 for 12-week weight. The realized genetic correlation between IGF-1 and 12-week weight was 0.58 ± 0.01, with a phenotypic correlation of 0.38. Although the genetic correlation between IGF-1 and body weight in mice is moderately positive, 12-week weight responded 3.5 times as fast to weight selection as to selection for IGF-1.     

Growth and body composition changes in mice selected for high post-weaning weight gain on two levels of feeding

Summary Two lines of mice were selected for high post-weaning weight gain (3 to 6 weeks) adjusted for 3 week weight. One line (F) was grown on freely available food and the other (S) on a feeding scale set at the same level for all mice. Food intake of the S line averaged 80% of the F line. The realised heritabilities after 6 generations of selection were 0.38±0.06 and 0.33±0.07 for the F and S lines, respectively. In generation 7, mice from the F and S lines and from an unselected control line (C) were compared on both free and set levels of feeding from 3 weeks to 9 weeks of age. Measurements taken were growth rate, appetite, food conversion efficiency (weight gain/food intake) and body composition (fat, protein, ash, water). The F and S lines grew more rapidly and efficiently than the C line on both levels of feeding, each line performing best on the level of feeding on which it was selected. The average genetic correlation between growth rates of the same line on the two feeding levels was 0.54±0.10. The F line grew 19% faster and was 9% more efficient than the S line on free feeding but the S line grew 15% faster and was 15% more efficient than the F line on set feeding. Relative to the C line, food intake per day on free feeding was 4% higher in the F line and 6% lower in the S line. There was no difference between the lines in food intake/g body weight. The rate of deposition of all body components increased in both selection lines. In the F, S and C lines respectively, efficiencies of gains in body components (10²x gain/food) were 1.79, 1.31 and 1.06 for fat, 1.53, 1.63 and 1.22 for protein and 5.88, 6.45 and 4.98 for protein + water. Apparently energy lost as heat was reduced in both the F and S lines. The partitioning of energy retained was altered in favour of more fat in the F line and more protein in the S line.     

Correlated responses in development and distribution of fat depots in mice selected for body composition traits

Summary Development of adipose tissue in five depots was investigated in mice selected for high or low 12-week epididymal fat pad weight as a percentage of body weight (HF and LF lines), or high or low 12-week hind carcass weight as a percentage of body weight (HL and LL lines). An unselected control line (RC) was maintained. Hind carcass (HC) and fat pads from subcutaneous hindlimb, subcutaneous forelimb, gonads, kidneys and mesentery were dissected and weighed at 4, 6, 9, 12 or 15 weeks of age. Generally, body weight (BW), daily gain (DG), feed intake (FI), feed efficiency (FE) and feed intake/metabolic body weight (FC) were higher (P0.05) in HF than in LF, and in LL than in HL. HF had more fat (as a percentage of BW) than LF in all depots (P-0.01), and asymmetry (P0.01) was detected for gonadal fat. LL consistently had a higher (P0.01) fat percentage than HL, and asymmetry (P0.01) was observed for perirenal fat. At age of selection, ranking of fat depot weights as a percentage of total fat depot weight was not changed by selection; however, gonadal fat accounted for more of the total fat in HF and LL compared with RC, while the opposite was found in LF and HL. HC percentage was higher (P0.01) in HL than LL, and higher (P0.01) in LF than HF. Growth rate of each fat depot relative to BW was not affected by selection. These results demonstrated that selection for proportion of fat in one depot or for HC percentage changed fat percentage in other depots. However, the rate of fat deposition in each depot relative to body weight gain was not altered.     

LH receptor induction and ovulation rate in mice selected for litter size and body weight

Female mice from lines which had undergone long-term single trait and antagonistic index selection for litter size and body weight were analysed for ovulation rate and LH receptor induction. Compared to randomly selected controls, selection for large litter size increased ovulation rate (60%; P less than 0.001) and decreased LH receptor induction per microgram ovarian DNA (87%; P less than 0.01). Selection for large body weight increased ovulation rate (18%; P less than 0.001), but did not lead to a significant correlated response in LH receptor induction. Index selection for large litter size and small body weight increased ovulation rate (14%; P less than 0.01) and decreased LH receptor induction (72%; P less than 0.01), while index selection for small litter size and large body weight did not significantly alter either ovulation rate or LH receptor induction. LH receptor quantities in testes of males from the 5 lines did not exhibit the among-line profile which was observed in ovaries of females. These results confirm the role of ovulation rate in mediation of the positive genetic correlation between litter size and body weight in mice. Increased ovulation rate in mice selected for large litter size may be due to mechanisms associated with LH receptors as well as factors related to growth. In contrast, increased ovulation rate in mice selected for large body weight may be due exclusively to factors related to growth.     

Genetic analysis of grain and malt quality in an elite barley population

Quantitative trait loci (QTLs) associated with grain weight, grain width, kernel hardness and malting quality were mapped in a doubled haploid population derived from two elite Australian malting barley varieties, Navigator and Admiral. A total of 30 QTLs for grain weight, grain width and kernel hardness were identified in three environments, and 63 QTLs were identified for ten malting quality traits in two environments. Three malting quality traits, namely β-amylase, diastatic power and apparent attenuation limit, were mainly controlled by a QTL linked to the Bmy1 gene at the distal end of chromosome 4H encoding a β-amylase enzyme. Six other malting quality traits, namely α-amylase, soluble protein, Kolbach index, free amino-acid nitrogen, wort β-glucan and viscosity, had coincident QTL clustered on chromosomes 1HS, 4HS, 7HS and 7HL, which demonstrated the interdependence of these traits. There was a strong association between these malt quality QTL clusters on chromosomes 1HS and 7HL and the major QTL for kernel hardness, suggesting that the use of this trait to enable early selection for malting quality in breeding programs would be feasible. In contrast, the majority of QTLs for hot-water extract were not coincident with those identified for other malt quality traits, which suggested differences in the mechanism controlling this trait. Novel QTLs have been identified for kernel hardness on chromosomes 2HL and 7HL, hot-water extract on 7HL and wort β-glucan on 6HL, and the resulting markers may be useful for marker-assisted selection in breeding programs.     

Changes in growth,appetite, food conversion efficiency and body composition in mice selected for high post-weaning weight gain on restricted feeding

Summary This study aimed to test the hypothesis that if animals were fed the same amount over the same time period, selection of the fastest growers would result in a change in the partitioning of metabolisable energy toward more protein and less fat deposition. Two mouse lines (S1 and S2) were selected for high 5 to 9 week weight gain corrected to mean 5 week weight. Appetite variation between mice was eliminated by feeding a fixed amount to each mouse daily. After 6 generations of selection, the lines were compared with an unselected control (C) on restricted and ad libitum levels of feeding for growth rate, appetite, food conversion efficiency and chemical body composition.Realised heritabilities of 5 to 9 week gain were 0.36+ 0.05 and 0.19±0.04 for S1 and S2 respectively. Nine week weights were increased by an average of 13% on both feeding levels. Most of this increase, particularly in S2, occurred before 5 weeks and was therefore outside the period of measurement used in selection. On ad libitum feeding, selection increased food intake per unit time by 6% but there was no increase per unit body weight. Food conversion efficiency (gain/food) increased by 12%. Compared with controls at 9 weeks, 3% more of the body weights of selected mice was fat and 1% less was protein. These differences were reduced but were still in the same direction when comparisons were made at the same body weight. Thus the expected change in energy partitioning toward greater protein and less fat deposition in the S lines did not occur.It was concluded that the increased growth and energy retention in the S lines was brought about by a reduction in maintenance requirement. To achieve the desired change in energy partitioning using a similar selection scheme, higher levels of dietary protein should be fed, and some measure of protein deposition rather than growth rate used as the selection criterion.     

Effect of selection for development rate on reproductive onset in female mice.

This research reports analyses of correlated response in reproductive onset in ICR mice after 23 generations of restricted index selection for divergent body weight gain, early (birth-10 days) or later (28-56 days) in life. Long-term selection altered growth trajectories and 56 day body weight of individuals under different selection regimes in this study. Mice in lines under early selection have the same percentage mature weight at vaginal opening as controls (63%). Vaginal opening is delayed in mice selected for slow early growth, which take longer to reach what appears to be a weight threshold. In contrast, individuals in lines selected for later slow growth undergo vaginal opening at the same age as controls, but at a lower weight and increased percentage mature weight. Pre-compensation or 'counter-balance growth' is observed in these lines, with mice selected for late enhanced growth reaching 52% of mature weight at vaginal opening while mice with late slow growth attain 71% of mature weight prior to vaginal opening. Only 42% of mice with late slow growth attain first oestrus by 56 days. We speculate this is a function of growth rate and fat/lean ratio. Mice with early slow growth show compensatory growth, reaching first oestrus at a similar time to controls. We conclude that selection for growth rate has asymmetrically affected reproductive onset, with lines selected for suppressed gains experiencing delays in the reproductive onset traits measured.     

Intrinsic properties of muscle satellite cells are changed in response to long-term selection of mice for different growth traits

Satellite cell cultures were derived from mice selected long-term over 70 generations for body weight (DU-6, growth), carcass protein amount (DU-6P, protein) and an index combining body weight and endurance treadmill performance (DU-6+LB, growth + fitness) at 42 days of age and from an unselected control line (DU-Ks). They were grown under identical environmental conditions to examine intrinsic cellular differences in proliferation, protein metabolism and responsiveness to growth factors. Growth kinetics (DNA and protein amounts) were determined over a 12-day period. During exponential growth, all growth-selected cultures grew faster than the control culture: (DU-6+LB=DU-6P)>DU-6>DU-Ks. The differences in DNA and protein levels were maintained until day 8. DU-Ks cultures reached similar levels as the growth (DU-6) and protein (DU-6P) cultures in terms of DNA at day 12 of cultivation. Thus, the cultures from the growth and protein lines, but not from the growth + fitness line, exhibited larger protein:DNA ratios (cell size) than the control cultures. Cell cultures from the selected lines were more responsive to serum and epidermal growth factor in terms of [(3)H] thymidine incorporation into DNA, whereas no stimulation by insulin or insulin-like growth factor-I was detectable in cultures from selected lines or controls. During differentiation, protein metabolism in cultures from selected lines was characterised by higher rates of protein synthesis (PS) and degradation (PD), as measured by [(3)H] phenylalanine incorporation or release, respectively, than in control cells. The ratios of the relative differences from the control in PS and PD were only >1.0 in the growth and protein lines. In conclusion, long-term selection for growth therefore modifies the intrinsic capability of satellite cells for proliferation and protein metabolism, with changes being dependent on the selection trait.     

Growth to sexual maturity of dwarf and nondwarf White Rock chickens divergently selected for juvenile body weight

Summary Growth from hatching to the onset of lay (sexual maturity) was studied in White Plymouth Rock pullets from lines selected for high (HN) and low (LN) 56-day body weight, their reciprocal F₁ crosses, an F₂ cross, and two dwarf populations originating from the HN and LN parental lines. The highest R²s for describing growth for all populations except HN were obtained when body weight was expressed relative to body weight at sexual maturity. Modes of inheritance differed depending on whether patterns of growth were expressed in a chronological time frame or on a physiological basis. Heterosis observed for age at sexual maturity and for body weight after the age when selection was made was not in evidence when ages and weights were expressed as a proportion of those at sexual maturity.This research was supported, in part, by BARD Project No. US-675-83C     

Linking cellular zinc status to body weight and fat mass: mapping quantitative trait loci in Znt7 knockout mice

Zinc transporter 7 (Znt7, Slc30a7) knockout (KO) mice display abnormalities in body weight gain and body adiposity. Regulation of body weight and body fat accumulation is complex, involving multiple genetic and environmental factors. To understand how zinc homeostasis influences body weight and fat deposit and to identify quantitative trait loci (QTLs) that link zinc metabolism to growth and adiposity, we conducted a genome-wide mapping study using male F₂ Znt7 KO mice and wild-type (WT) littermates with a mixed 129P1/ReJ and C57BL/6J genetic background. The mice were fed a semi-purified diet containing 30-mg Zn/kg diet at weaning. Body weights and fat pad weights including epididymal, retroperitoneal, and femoral subcutaneous fat pads were measured at 16 weeks of age. We detected two significant QTLs (p < 0.05) for body weight and fat deposit. One was in the F₂ Znt7 KO population and the other in the F₂ WT population. In Znt7 KO mice, the body weight and fat deposit was significantly linked to a locus on chromosome 7 ranging from 64.3 to 78.3 Mb. In WT mice, a significant linkage of retroperitoneal fat mass was found on chromosome 8 between 14.5 and 63.5 Mb. In addition, several other suggestive QTLs (p < 0.63) for body weight and fat accumulation were detected in Znt7 KO and WT mice. In conclusion, the QTLs identified in this study may provide new hints to uncover the genes linking cellular zinc status to growth and body fat accumulation.     

Interspecies differences in the empty body chemical composition of domestic animals

Domestication of animals has resulted in phenotypic changes by means of natural and human-directed selection. Body composition is important for farm animals because it reflects the status of energy reserves. Thus, there is the possibility that farm animals as providers of food have been more affected by human-directed selection for body composition than laboratory animals. In this study, an analysis was conducted to determine what similarities and differences in body composition occur between farm and laboratory animals using literature data obtained from seven comparative slaughter studies (n = 136 observations). Farm animals from four species (cattle, goats, pigs and sheep) were all castrated males, whereas laboratory animals from three species (dogs, mice and rats) comprised males and/or females. All animals were fed ad libitum. The allometric equation, Y = aX^b, was used to determine the influence of species on the accretion rates of chemical components (Y, kg) relative to the growth of the empty body, fat-free empty body or protein weights (X, kg). There were differences between farm and laboratory animals in terms of the allometric growth coefficients for chemical components relative to the empty BW and fat-free empty BW (P < 0.01); farm animals had more rapid accretion rates of fat (P < 0.01) but laboratory animals had more rapid accretion rates of protein, water and ash (P < 0.01). In contrast, there was no difference in terms of the allometric growth coefficients for protein and water within farm animals (P > 0.2). The allometric growth coefficients for ash weight relative to protein weight for six species except sheep were not different from a value of 1 (P > 0.1), whereas that of sheep was smaller than 1 (P < 0.01). When compared at the same fat content of the empty body, the rate of change in water content (%) per unit change in fat content (%) was not different (P > 0.05) across farm animal species and similar ash-to-protein ratios were obtained except for dogs. The fraction of empty body energy gain retained as fat increased in a curvilinear manner, and there was little variation among farm animals at the same fat content of the empty body. These findings may provide the opportunity to develop a general model to predict empty body composition across farm animal species. In contrast, there were considerable differences of chemical body composition between farm and laboratory animals.     

完全或部分的食物剥夺对中华鳖(Pelodiscus sinensis)幼体补偿生长反应的影响:生长率的时间变化模式与体组成的变化

为了探究中华鳖（Pelodiscus sinensis）幼体的补偿生长能力,我们对中华鳖幼鳖（平均湿重9．56g）进行如下6种处理：饥饿0（对照）、1、2、3、4周,或者食物限制4周,即只投喂体湿重百分之一的食物;然后对各组进行饱食处理直到10周的实验结束为止。结果发现在饱食期的第一周各饥饿处理组的特殊生长率均显著高于对照组（P〈0．05）,但是终体重均没有赶上对照组。当饥饿或食物限制结束时,脂肪含量随着饥饿期的延长而降低,灰分和水分则表现出相反的变化趋势：脂肪含量显著低于对照（P〈0．05）,而灰分和水分则显著高于对照（P〈0．05）。蛋白含量则没有显著变化（P〉0．05）。实验结束时,除了灰分外（P〈0．05）,其他个体组成指标均恢复到对照组的水平。以上结果表明中华鳖幼体在饥饿胁迫下首先利用脂肪作为主要能源以维持生存,以及在该研究条件下完全的食物剥夺可以诱发其部分补偿生长反应．而部分食物剥夺则不能诱发此反应。     

Divergent selection on 63-day body weight in the rabbit: response on growth,carcass and muscle traits

The effects of selection for growth rate on weights and qualitative carcass and muscle traits were assessed by comparing two lines selected for live body weight at 63 days of age and a cryopreserved control population raised contemporaneously with generation 5 selected rabbits. The animals were divergently selected for five generations for either a high (H line) or a low (L line) body weight, based on their BLUP breeding value. Heritability (h²) was 0.22 for 63-d body weight (N = 4754). Growth performance and quantitative carcass traits in the C group were intermediate between the H and L lines (N = 390). Perirenal fat proportion (h² = 0.64) and dressing out percentage (h² = 0.55) ranked in the order L < H = C (from high to low). The weight and cross-sectional area of the Semitendinosus muscle, and the mean diameter of the constitutive myofibres were reduced in the L line only (N = 140). In the Longissimus muscle (N = 180), the ultimate pH (h² = 0.16) and the maximum shear force reached in the Warner-Braztler test (h² = 0.57) were slightly modified by selection.