Divergent Selection For Body Weight Research Articles

Long-term selection of chickens for body weight alters muscle satellite cell behaviors

Muscle satellite cells (SC) are resident stem-like cells that play an integral role in skeletal muscle growth and repair. Understanding how SC maintain their identities and dynamic properties is critical to animal growth. However, the genetic and environmental factors governing SC behaviors and the underpinning mechanisms remain unknown. To explore whether genetic selection influences SC behaviors, we used 2 lines of chickens selected for over 50 generations with over a 10-fold difference in body weight at 56 d of age-the Virginia high weight selection (HWS) and low weight selection (LWS) lines. To study these 2 lines, we performed both in vivo and in vitro experiments. In vivo, we studied the abundance of SC in normal physiological settings and tested their functional roles in muscle regeneration using a muscle injury model. In vitro, we isolated SC from chicken skeletal muscle and assayed their ability to proliferate and differentiate under cultured conditions. Immunohistochemical staining of breast muscle (pectoralis major) revealed that muscle fibers from HWS chickens possessed more SC than those from LWS. Further analysis showed that the SC pool from HWS muscles contained a higher percentage of activated SC compared to that of LWS. When isolated SC from HWS and LWS muscles were cultured, HWS SC exhibited greater abilities to proliferate and differentiate than those SC from LWS. To test whether the observed in vitro differences in SC properties could be confirmed in vivo, we subjected chicken breast muscle to barium chloride to induce muscle injury and regeneration. Consistent with in vitro data, breast muscle in HWS chicken experienced a faster and more robust recovery than that of LWS, as evidenced by quicker regeneration and larger muscle fiber size. Taken together, these findings suggest divergent selection for body weight not only results in correlated responses in SC number, but also changes SC growth kinetics. Further dissection of the molecular mechanism will aid the identification of the target molecules for growth intervention in chickens.

Analysis of a long-term divergent selection for body weight in chickens with an exponential model

Analysis of a long-term divergent selection for body weight in chickens with an exponential model

Cholesterol content in eggs produced by hens divergently selected for body weight (Short Communication)

Abstract. In this work the cholesterol content of chicken eggs produced by two lines (high and low weight) representing the 31st generation of selection for divergent growth was studied. Divergent selection for body weight at 8 weeks of age resulted in changes in egg size and consequently in the weight of egg components. Higher values (P≤0.001) were observed in eggs from the high weight (D+) line for egg weight, albumen, yolk and shell weight. Percent yolk was greater (P≤0.001) and percent albumen was lower (P≤0.001) in eggs from the low weight (D−) line. Eggs from the D− line contained lower (P≤0.001) cholesterol content (mg/ egg, mg/g yolk, mg/g yolk dry matter) than eggs from the D+ line but when cholesterol was expressed in milligrams per gram of egg or per gram of edible egg, differences between the two lines were not significant. Divergent selection for body weight changed the albumen : yolk ratio and a change of this type affected the grams of cholesterol per gram of yolk values.

The Differences in Some Production and Clutch Traits in Divergently Selected Japanese Quails

Summary The aim of the research was to investigate the effects of divergent selection on some production and clutch traits in Japanese quail (Coturnix coturnix japonica). Over 5 generations divergently selected two Japanese quail lines (HBW: High Body Weight and LBW: Low Body Weight) and control line (C) that derivate from a base random bred population were used in this study. Weight of first egg, age at sexual maturity, body weight at sexual maturity, total egg number, total egg weight, clutch length, clutch number, pause length and pause number were determined. Statistically important relationships were estimated among these studied traits except between average egg weight with age at sexual maturity. The HBW and LBW were differentiated in both body weight and egg yields (number and weight) by selection applications. Averages of the body weight and egg weight increased but the egg numbers decreased for HBW, in contrast for LBW through generations. When clutch number, pause number and pause length increased, total egg number and total egg weight decreased. The results of this study indicated that divergent selection for body weight resulted in important changes on some production and clutch traits in Japanese quails.

QTL analysis of body composition and metabolic traits in an intercross between chicken lines divergently selected for growth

The high- and low-growth lines of chickens have been developed from a single founder population by divergent selection for body weight at 56 days of age for more than 40 generations. The two lines show a ninefold difference in body weight at selection age and several interesting correlated selection responses such as altered body composition and metabolic differences. We have generated a reciprocal intercross comprising >800 F2 birds. In a previous study, we reported the detection of 13 quantitative trait loci (QTLs) affecting growth. Here we report QTLs for body composition (fat deposition, muscle development), weight of internal organs, and metabolic traits (plasma concentrations of glucose, insulin, cholesterol, glucagon, triglycerides, and IGF-I). Most of the QTLs with convincing statistical support mapped in the vicinity of growth QTLs. One of the most interesting observations was that the type of reciprocal cross had highly significant effects on body weight at hatch and on plasma concentrations of glucose, cholesterol, insulin, and IGF-I, but it had no significant effect on body weight at 56 days of age. The reciprocal cross explained between 15 and 35% of the phenotypic variance for weight at hatch and for plasma concentrations of glucose and insulin. The observed pattern indicated that these effects were caused by maternal effects or by genetic differences in mitochondrial DNA.

Many QTLs with minor additive effects are associated with a large difference in growth between two selection lines in chickens

Two growth-selected lines in chickens have been developed from a single founder population by divergent selection for body weight at 56 days of age. After more than 40 generations of selection they show a nine-fold difference in body weight at selection age and large differences in growth rate, appetite, fat deposition and metabolic characteristics. We have generated a large intercross between these lines comprising more than 800 F2 birds. QTL mapping revealed 13 loci affecting growth. The most striking observation was that the allele in the high weight line in all cases was associated with enhanced growth, but each locus explained only a small proportion of the phenotypic variance using a standard QTL model (1.3-3.1%). This result is in sharp contrast to our previous study where we reported that the two-fold difference in adult body size between the red junglefowl and White Leghorn domestic chickens is explained by a small number of QTLs with large additive effects. Furthermore, no QTLs for anorexia or antibody response were detected despite large differences for these traits between the founder lines. The result is an excellent example where a large phenotypic difference between populations occurs in the apparent absence of any single locus with large phenotypic effects. The study underscores the need for powerful experimental designs in genetic studies of multifactorial traits. No QTL at all would have reached genome-wide significance using a less powerful design (e.g. approx. 200 F2 individuals) regardless of the nine-fold phenotypic difference between the founder lines for the selected trait.

Long Term Selection for Small Body Weight in Japanese Quail II: Changes in Reproductive Traits from 60 to 65th Generations.

Establishment of small body size poultry is an important strategy, which leads to effective management of bird-colonies and less feed consumption. And also it would be a useful experimental tool for elucidating an evolutionary mechanism causing the change in body size. In Saga University, a divergent selection for body weight at 6 weeks of age had been performed for 65 generations in Japanese quail. And three lines were established : large body weight (LL) line, randomly selected control (RR) line and small body weight (SS) line. Breeding of SS line started with the individuals selected from RR line (Okamoto et al., 1989a ; b). We have aimed to investigate the changes in reproductive traits during a long term selection for small body weight, and the results from 60 to 65th generations have been described in this report. Body weight of SS line was consistently smaller than that of RR line in every generation, and the following differences were observed over most generations. Fertility and hatchability in SS line were significantly lower than in RR line (P<0.01). The raising rate in early stage of growth after hatch tended to be lower in SS line than in RR line, but viability after sexual maturation in SS line remained at high level. Age at first egg in SS line was significantly delayed as compared with that of RR line (P<0.01), and total number of the eggs laid until 100 days of age in SS line was significantly lower than that of RR line (P<0.01). Total weight of the eggs laid until 100 days of age and average egg weight from 91 to 100 days in SS line were significantly lower than those in RR line (P<0.01). Genetic fitness (Falconer and Mackay, 1996) tended to decrease progressively in SS line though drastic increase was observed temporarily at 64th generation. Consequently, it has been concluded that long term selection for small body weight reduces genetic merits, particularly in reproductive traits such as fertility, hatchability, raising rate and sexual maturation, indicating that it is difficult to maintain the production of healthy adult birds at a higher level in the miniaturized line.

Effects of divergent selection for body weight at a fixed age on histological, chemical and rheological characteristics of rabbit muscles

The aim of this study was to investigate the main carcass traits, and some of the histological, chemical and rheological characteristics of two muscles in two lines of rabbits divergently selected for body weight at 63 days of age. At slaughter, live body weight (+13%) and weights of semitendinosus (ST) and longissimus lumborum (LL) muscles (+13 and +8%, respectively) were heavier in the heavy line (HW) than in the light line (LW). At the same time, mean cross-sectional area of constituent myofibers was 6% larger in ST muscle from HW compared to LW lines; however, the number of myofibers remained steady in both lines. Shear force value was increased by 20 and 8% in ST and LL muscles, respectively, in HW compared to LW lines. Ultimate pH values in both muscles were similar for both lines. No effect of selection was denoted for intra-muscular fat content of ST muscles. This study suggests that selection for live body weight at a fixed age of slaughter affected muscle weight by myofiber hypertrophy and caused slight modifications of rheological properties of the muscles.

Divergent selection for body weight and yolk precursor in Coturnix coturnix japonica. 12. Heterosis in reciprocal crosses between divergently selected lines

A selection experiment was started using Japanese quail to study the genetics of BW and plasma yolk precursor (measured by total plasma phosphorus; TPP). Lines were divergently selected for 4-wk BW (HW and LW) or plasma TPP (HP and LP). Sublines of HW were developed by continuing to select the males for increased 4-wk BW while selecting the females for increased (HW-HP line) or decreased (HW-LP line) TPP. The purpose of the present study was to determine the inheritance of traits associated with growth and reproduction in reciprocal crosses between the divergently selected lines and sublines. Reciprocal crosses were made between the HW and LW, HP and LP, and HW-HP and HW-LP lines. Traits measured included BW at various ages, age at sexual maturity, egg production, ovarian follicular development, egg weight, TPP, wet and dry liver weights, and occurrence of smooth muscle tumors in the ligaments of the oviduct. The HW line differed from the LW line in all traits measured except TPP and weight of smooth muscle tumors. No offspring were obtained from the HW x LW matings (male listed first). In the LW x HW cross, heterosis was negative for BW through sexual maturity and age at sexual maturity. Positive heterosis was observed for egg production, egg weight, and occurrence of smooth muscle tumors. Differences between the HP and LP lines were observed in the selected trait (TPP) and some correlated traits (BW at some ages, age at sexual maturity in females, egg production, and number and total weight of ovarian follicles). Positive heterosis in the HP and LP crosses was observed for BW, egg production, egg weight, and number of ovarian follicles whereas negative heterosis was observed for TPP and age at sexual maturity in females. The HW-HP and HW-LP lines differed in the selected traits and some correlated traits (egg weight and weights of the liver and smooth muscle tumors). Positive heterosis in the crosses was observed for BW, egg production, and liver weights whereas negative heterosis was evident for age at sexual maturity and TPP.

Responses to Long-Term Divergent Selection for Eight-Week Body Weight in Chickens

Thirty-six generations of divergent selection for body weight at 8 wk of age resulted in approximately an eightfold difference between the high (HWS) and low (LWS) lines for this trait. In both White Plymouth Rock lines, selection intensities declined over generations, with responses about five times greater during the first 18 than the last 18 generations of selection in Line HWS and about two times greater in Line LWS. Also, responses to selection were more irregular in the later than in earlier generations. Sexual dimorphism of body weight (male:female) was greater for Line LWS than HWS. A randombred control line (AC) maintained concurrently with the selected lines did not exhibit environmental trends across generations. Relaxed lines, established at different generations of selection, were used to evaluate effectiveness of selection and monitor environmental changes over short periods.

Effects of age and divergent selection for body weight on muscle protein turnover in chickens

Effects of age and divergent selection for body weight on muscle protein turnover in chickens

Growth and development of lines of Japanese quail ( Coturnix coturnix japonica) divergently selected for body weight at 4 weeks of age

1. 1. Divergent selection for body weight resulted in significant increases and decreases in body weight and the relative weight of the pectoralis major breast muscle in heavy (HW) and light weight (LW) strains of Japanese quail compared with a randombred control strain (R1). 2. 2. The relative weights of the abdominal fat pad and total carcass lipid were increased in the HW strain, particularly in the females. 3. 3. Sexual maturity was similar in HW and R1 hens but was delayed in the LW hens. HW hens laid significantly more double-yolked eggs.

Effects of selecting for litter size and body weight on the components of litter size in mice

Divergent selection for the total number of young born in the first three litters (TNY-3) and for 6-week body weight in mice resulted in different changes in the components of first litter size. Selection for large TNY-3 increased the number of ova shed while pre-natal losses were not modified. Selection for small TNY-3 caused both a decrease in ovulation rate and an increase in post-implantation mortality. Divergent selection for body weight modified ovulation rate in the same direction as body weight. Embryo survival declined in both lines selected for body weight. That decline was caused by an increase in pre-implantation mortality in the case of the high line, and by an increase in post-implantation mortality in the low line.

Divergent Selection for Body Weight and Yolk Precursor in Coturnix coturnix japonica.: 5. Correlated Responses in Adult Body Weight, Liver Weight, Ovarian Follicle Production, and Carcass Composition of Laying Hens

Laying female quail of five strains (R-l, randombred control; HP and LP, high or low concentration of egg yolk very low density lipoprotein (VLDL) precursor in laying females: HW and LW, high or low 4-week body weight) were sampled after 120 days of egg production for body weight, liver weight, ovarian follicle production, and carcass composition. Body weight change during the reproductive period was associated with starting body weight, but not with yolk VLDL precursor (total plasma phosphorus). Egg production was slightly depressed in both the HW and HP strains. Liver weight was associated with body weight. Percent dry matter of liver was not different between strains, Liver as a percentage of body weight was slightly greater in the HP strain. Egg and yolk weights were associated with body weight but not with concentration of yolk VLDL precursor. Ovarian follicle number and weight were also influenced by body weight but not by concentration of yolk VLDL precursor.Carcass composition was influenced by body weight. The larger HW strain contained more fat and less protein than the smaller LW strain after 120 days of egg production.

Divergent Selection for Body Weight and Yolk Precursor in Coturnix coturnix japonica.: 4. Correlated Responses in Carcass Composition and Carcass Yield of Progeny During Growth

Carcass composition (protein, fat, ash, and percent dry matter), component parts, and dressing yield were determined in lines of quail undergoing divergent selection for yolk precursor, growth, or egg production. Carcass weights and yield percentages were greatest in the line selected for increased 4-week weight and lowest in the line selected for decreased 4-week weight. Carcass weights and yields were not affected by selection for yolk precursor or egg production. Carcass percent protein was lower and percent fat higher in the line selected for increased 4-week body weight but unaffected by divergent selection for yolk precursor or egg production. Percent ash did not vary with genetic changes in body weight, yolk precursor, or egg production.

Divergent Selection for Body Weight and Yolk Precursor in Coturnix coturnix japonica.: 3. Correlated Responses in Mortality, Reproduction Traits, and Adult Body Weight

Egg production, mature body weight, egg weight, yolk weight, fertility, hatchability, and mortality during the early growing period were compared in strains of Japanese quail. The strains were either a randombred control (R1) that served as the base population or strains divergently selected for high (HW) or low (LW) 4-week body weight or high (HP) or low (LP) plasma phosphorus (yolk precursor) early in the laying period.Changes in 4-week body weight in HW and LW were associated with corresponding changes in mature body weight, yolk weight, and total egg weight. Egg production decreased in HW, but there was no significant change in LW. Mortality increased in LW and decreased in HW. Egg production of HP declined at a rate similar to that observed in HW. No other consistent significant changes occurred in the phosphorus strains. Fertility and hatchability did not exhibit significant strain differences in the fifth generation of selection.

Divergent Selection for Body Weight and Yolk Precursor in Coturnix coturnix japonica: 2. Correlated Responses in Plasma Lipoproteins and Lipids

Lipoproteins from generations five and six of Japanese quail (Coturnix coturnix japonica) divergently selected for increased (HW) or decreased (LW) body weight at 4 weeks of age or increased (HP) or decreased (LP) plasma yolk precursor at the initiation of egg production were separated into fractions of d<1.006 and d>1.006. A randombred control (R1) was also sampled. Total lipids (TL), neutral lipids (NL), and phospholipids (PL) were determined. The NL's of the d<1.006 lipoprotein fractions were also analyzed for cholesterol esters (CE), triglycerides (TG), cholesterol (C), and a fraction of minor lipid components including digycerides (DG+). A correlation of .960 between total plasma phosphorus and TL of the d<1.006 lipoprotein fraction was observed. No strain effect was note d for TL, NL, or PL for either generation in the d>1.006 fraction. In the d<1.006 fraction, TL, NL, and PL all varied concurrently, with the order being HP > HW, LW, R1> LP. Percent NL and PL did not vary with strain in the S5 generation in the d<1.006 fraction. In the S6, the HP strain had a higher % NL and lower % PL in the d<1.006 fraction. No differences in % NL and PL were noted for the d>1.006 fraction. In the d<1.006 fraction all lipid classes in the NL's tended to vary together.It was concluded that selecting for total plasma phosphorus in laying female Japanese quail is effective in quantitatively but not qualitatively altering the d <1.006 lipoprotein levels in the laying hen plasma, without affecting the d>1.006 lipoprotein levels. It was also concluded that selecting for body weight for six generations did not affect laying female lipoprotein concentration.

Effects of divergent selection for body weight on bone length and diameter in mice

SUMMARYThe length and diameter of the humerus, ulna, femur and tibia were studied at generations 10 and 14 in lines of mice selected for high and low body weight at 10 weeks of age.Although some deviations from control were not significant, a general pattern of correlated responses was evident. The divergences of high and low line means for bone length and diameter were significant in the four bones, confirming the contribution of these parameters to genetically determined alterations in body weight. Maternal effects did not affect bone length and diameter and heterosis was not important in the genetic control of these parameters. Unlike bone length, bone diameter continued to diverge in response to the additional four generations of selection. There may therefore be differences in the quantitative genetic control of bone length and diameter and consequently in the control of endochondral and intramembranous ossification.

Selection in Small Populations of Chickens

The results of a 10-year multi-selection experiment with White Leghorn and Fayoumi chickens are reported. The study includes 5 single-trait Leghorn lines, 3 single-trait Fayoumi lines and 2 two-trait Leghorn lines. The traits selected were high egg rate (2 lines), body size (2 up lines, 1 down line), egg size (2 up lines, 1 down line), high body weight—low egg weight (one line) and low body weight—high egg weight (one line). All lines were maintained by 8 sire matings except the high egg-rate lines maintained by 16 sires. Selection responses were measured as deviations from the Cornell Randombred Control. Even though full-sib and half-sib matings were avoided, inbreeding increased 1.6 to 1.9% per generation in the 16-sire lines and from 1.6 to 2.3% in the 8-sire lines. On the average, body weight declined 20 g, egg weight 0.6 g. and rate of egg production 2.3% for each 10% increase in inbreeding.Average selection differentials in each line were from ⅔ to one standard deviation per generation, and the response to divergent selection for body weight and egg weight was asymmetrical. Likewise, the correlated responses to selection were asymmetrical. The effective population numbers per line were large enough to give good realized heritability estimates except for the egg rate lines. The realized heritabilities were (1) for egg rate, 0.07 ± 0.04 (Leghorn), 0.03 ± 0.14 (Fayoumi), (2) for high body weight, 0.32 ± 0.04 (Leg) and 0.49 ± 0.09 (Fay), (3) high egg weight, 0.25 ± 0.03 (Leg) and 0.43 ± 0.07 (Fay) and (4) low egg weight, 0.59 ± 0.03 (Leg).The experiment with the two-trait lines was designed to examine the question of antagonistic selection, i.e., selection for two traits in opposition to the sign of the genetic correlation between them. The response to antagonistic selection was more restricted for the low body weight and high egg weight combination than vice versa. This resulted from the physical incompatibility of these two traits. Finally, the response to antagonistic selection did not seem to be rigidly controlled by the strength of the genetic correlation between the two traits.

Effects of divergent selection for body weight on fibre number and diameter in two mouse muscles

SUMMARYThe effects of selection for increased or decreased body weight in mice, at 5 or 10 weeks of age, on the fibre number, fibre diameter and weight of the m. sternomastoideus and m. anterior tibialis muscles were studied. Unselected control mice were also included. Significant effects were detected in the case of each of the traits. However, the magnitude of any particular correlated response to selection varied between muscles and between selection ages in an unsystematic fashion. Most of the changes in muscle weight resulting from selection were attributable to positively correlated changes in fibre number but they were also accompanied by changes in fibre diameter in some cases.The correlated responses described indicate the difficulty of predicting how selection for body weight changes will influence cellular structure of any given muscle.Phenotypic correlations between muscle fibre number and diameter were essentially zero. The phenotypic correlations between muscle weight and fibre number and fibre diameter were positive.Sex had no effect on fibre number but had an effect on fibre diameter which depended on the particular muscle and the age of the animal.