High Weight Line Research Articles

Haplotype Purging After Relaxation of Selection in Lines of Chickens that Had Undergone Long-Term Selection for High and Low Body Weight.

Bi-directional selection for increased and decreased 56-day body weights (BW56) has been applied to two lines of White Plymouth Rock chickens—the Virginia high (HWS) and low (LWS) body weight lines. Correlated responses have been observed, including negative effects on traits related to fitness. Here, we use high and low body weight as proxies for fitness. On a genome-wide level, relaxed lines (HWR, LWR) bred from HWS and LWS purged some genetic variants in the selected lines. Whole-genome re-sequencing was here used to identify individual loci where alleles that accumulated during directional selection were purged when selection was relaxed. In total, 11 loci with significant purging signals were identified, five in the low (LW) and six in the high (HW) body weight lineages. Associations between purged haplotypes in these loci and BW56 were tested in an advanced intercross line (AIL). Two loci with purging signals and haplotype associations to BW56 are particularly interesting for further functional characterization, one locus on chromosome 6 in the LW covering the sour-taste receptor gene PKD2L1, a functional candidate gene for the decreased appetite observed in the LWS and a locus on chromosome 20 in the HW containing a skeletal muscle hypertrophy gene, DNTTIP1.

EFFECT OF SHORT-TERM DIVERGENT SELECTION FOR BODY WEIGHT AT 4 WEEK OF AGE IN JAPANESE QUAIL UNDER NORTH-SINAI CONDITIONS A. EFFECT ON 4 WK OF AGE BODY WEIGHT

The base population of the evaluated Japanese quail was derived from a randomly mated flock. This flock was used for subsequent divergent body weight selection to produce the next three generations (G1, G2, and G3). The resultant investigational birds during the period from November 2016 to November 2017 were produced and raised at the experimental farm, Department of Animal and Poultry Production, Faculty of Environmental Agricultural Sciences, Arish University, Al-Arish, North Sinai, Egypt. Individual selection for body weight at 4 wk of age was applied. The upmost 2/3 ranked birds were considered ‘the high body weight line (HL)’, while the lowest 1/3 ranked ones were considered ‘the low body weight line (LL)’. At 5 wk of age, the selected birds were transferred to cages (1 male and 2 females assigned at random from the same selection category along with avoiding sib mating). The same trend of body weight selection intensity was applied at each generation but within each line. The used experimental diet was a corn-soybean growing diet in a mash form with approximately 23% crude protein and 2850 kcal ME/kg. Feed and water were offered ad libitum. Results indicated that the interaction between body-weight and sex was significant on most evaluated body weights. Furthermore, after three generations of that divergent selection, themagnitude of response to selection showed thatmeans of the third generation surpassed the base population by 15.25% and -22.22% for HL and LL; respectively. Also, the third generation high females surpassed the high males and the difference between them was 8.76%. The response to selection for HL, LL and for divergent body weight at 4 wk were 26.33, -38.13, and 64.46, respectively. However, the low selected line had the highest realized heritability (h2) value (0.64) compared with moderate values in high selected line (0.34 and 0.47). While the ESD / SD ratios showed higher values for HL than LL. The ratio values for LL were very close to unity an indication that natural selection did not influence selection for low 4-wk body weight.

EFFECT OF SHORT-TERM DIVERGENT SELECTION FOR BODY WEIGHT AT 4 WEEK OF AGE IN JAPANESE QUAIL UNDER NORTH-SINAI CONDITIONS B. EFFECT ON GROWTH TRAITS

Base population of the evaluated Japanese quail was derived from a randomly mated flock. This flock was used for subsequent divergent body weight selection to produce the next three generations (G1, G2, and G3). The resultant investigational birds during the period from November 2016 to November 2017 were produced and raised at the experimental farm, Department of Animal and Poultry Production, Faculty of Environmental Agricultural Sciences, Arish University, Al-Arish, North Sinai, Egypt. Individual selection for body weight at 4 wk of age was applied. The upmost 2/3 ranked birds were considered ‘the high body weight line (HL)’, while the lowest 1/3 ranked ones were considered ‘the low body weight line (LL)’. At 5 wk of age, the selected birds were transferred to cages (1 male and 2 female assigned at random from the same selection category along with avoiding sib mating). The same trend of body weight selection intensity was applied at each generation but within each line. The used experimental diet was a corn-soybean growing diet in a mash form with approximately 23% crude protein and 2850 kcal ME/kg. Feed and water were offered ad libitum. Results indicated that the interaction between body-weight-selection-type and sex was significant on most evaluated growth traits. Furthermore, line effect highly significant (P≤ 0.0001) on most evaluated growth traits. Also, the RGR decreased with the advancing in age, and higher values were recorded for both sexes and lines for RGR0-2 and reduced gradually by increasing age, also the high females was higher than males at most studied periods. However, the WG, the higher values were obtained for females in both selected lines where the HL showed higher values than the LL.

Effects of mass selection on egg production on some reproductive traits in Japanese quail

Summary Most of the selection studies in Japanese quail have focused on high body weight or short-term egg production. The effect of selection on long-term egg production is not well known. Japanese quail lines were subjected to phenotypic mass selection in different ways over 11 generations and a control group was reproduced by random mating. A high body weight line (HL), a low body weight line (LL) (based on 5-week body weight), a line (L) subjected to selection for egg production (120 day) and a control line (C) were used. Age at sexual maturity, egg weight, total number of eggs for 45 weeks and body weight of the lines were determined. A nonlinear regression analysis using the Grossman egg production function was used for the comparison of egg productions of the flocks.

A short insertion mutation disrupts genesis of miR-16 and causes increased body weight in domesticated chicken.

Body weight is one of the most important quantitative traits with high heritability in chicken. We previously mapped a quantitative trait locus (QTL) for body weight by genome-wide association study (GWAS) in an F2 chicken resource population. To identify the causal mutations linked to this QTL, expression profiles were determined on livers of high-weight and low-weight chicken lines by microarray. Combining the expression pattern with SNP effects by GWAS, miR-16 was identified as the most likely potential candidate with a 3.8-fold decrease in high-weight lines. Re-sequencing revealed that a 54-bp insertion mutation in the upstream region of miR-15a-16 displayed high allele frequencies in high-weight commercial broiler line. This mutation resulted in lower miR-16 expression by introducing three novel splicing sites instead of the missing 5′ terminal splicing of mature miR-16. Elevating miR-16 significantly inhibited DF-1 chicken embryo cell proliferation, consistent with a role in suppression of cellular growth. The 54-bp insertion was significantly associated with increased body weight, bone size and muscle mass. Also, the insertion mutation tended towards fixation in commercial broilers (Fst > 0.4). Our findings revealed a novel causative mutation for body weight regulation that aids our basic understanding of growth regulation in birds.

Stimulation of food intake after central administration of gonadotropin-inhibitory hormone is similar in genetically selected low and high body weight lines of chickens

Gonadotropin-inhibitory hormone (GnIH), first isolated from the brain of the Japanese quail (Coturnix japonica), when centrally administered exerts orexigenic effects in birds. However, the precise mechanisms mediating this effect are poorly understood and limited information is available on this effect in models of body weight dysfunction. Thus, the purpose of the present study was to investigate appetite-associated effects of GnIH in chicks from lines that have been selected for either low or high body weight, and are anorexic or become obese, respectively. Central GnIH injection increased food intake in both lines with a similar magnitude of response. There was no effect on water intake. Hypothalamic GnIH mRNA was greater in the low than high weight lines and was greater in the fasted than fed chicks. GnIH receptor mRNA was similarly expressed in both lines, and was greater in fed than fasted chicks. Thus, although selection for body weight did not alter the effect of GnIH on feeding, fasting increased GnIH mRNA in both lines implying that it is an innate hunger factor.

Delayed feeding after hatch caused compensatory increases in blood glucose concentration in fed chicks from low but not high body weight lines

This experiment used 2 lines of chickens that have been selected 54 generations for either low (LWS) or high (HWS) 8-wk BW from the same founder population, sublines (HWR and LWR) in which selection was relaxed in generation 43 in the selected lines, and crosses (HL and LH) made from generation 54 of HWS and LWS. For 8-wk BW, the difference between lines LWS and HWS in generation 54 was approximately 10-fold, whereas for the relaxed contemporary lines they were approximately 7-fold. Three trials were designed to measure developmental, nutritional, and genetic aspects of blood glucose homeostasis during the first 2 wk posthatch. In trial 1, we measured BW, whole blood glucose (BG), and weights (relative to BW) of liver, pancreas, and yolk sac of chicks fed from day of hatch to d 15. In trial 2, we compared those traits in chicks feed-delayed 72 h posthatch and in chicks without feed delay. In trial 3, we evaluated the effect of a 16-h fast on BW and BG on d 3, 8, and 15. There were higher levels of BG in HWS than LWS, and males than females in the fed state. Delayed access to feed for 72 h after hatch was associated with a dramatic reduction in BG. Feeding triggered a compensatory response whereby LWS displayed greater BG but smaller pancreases (% BW; d 15), compared with the controls. There were maternal effects for BW in both fed and fasted states and the reciprocal crosses exhibited heterosis for BG in the fasted state. These results show that chickens selected for high or low BW differ in BG regulation during the early posthatch period.

GENETIC IMPROVEMENT OF EGG PRODUCTION TRAITS IN DOKKI-4 STRAIN. 2-CORRELATED RESPONSES, HERITABILITY, GENETIC AND PHENOTYPIC CORRELATIONS FOR BODY WEIGHT RAITS.

This present study was carried out during three successive generations to improve body weight through selection in developed Dokki-4 chicken strain and to study correlated response of some economic traits. The chicks in each generation represented two lines, selected line for high body weight and control line. The results showed that body weight at different ages studied were improved in selected more than control line (P < 0.01). There were significant differences (P < 0.05) between generations, lines and sexes body weight (BW), daily weight gain (DG), feed conversion (FC), and body weight measurements (shank length, keel length and body circumference) at 4 , 8 , and 12 weeks. Selection differentials of male 12-weeks body weight were 71.0 gm and 57 gm in the selected generations. The corresponding values for females were 54.0 gm and 48.0 gm. The cumulative realized and expected responses, were 130.3 gm and 28.16 gm for males, and were 83.9 gm and 22.4 gm for females over two generations, respectively. The cumulative realized response to selection for body weight was 26.01, 58.0 and 81.95 for body weight at 4, 8 and 12 weeks of age , 0.92, 1.14, 0.94 and 1.03 for daily weight gain, 0.31, 0.82 and 1.46 for shank length, keel length and body circumference at 12 weeks, while, were with feed conversion -0.89, -1.27 and -1.32 at 4, 8 and 12 weeks of age. Heritability estimates based on sire component of variance (first and second generation) for all traits studied were ranged between high, medium and low values. Positive genetic and phenotypic correlations were found body weight at 12 weeks of age and body weight at different ages, daily weight gain, and body measurements (shank length, keel length and body circumference), the range between the values of high, medium and low. But among body weight and feed conversion were negative. In conclusion, the high positive correlation obtained in this study indicate that an improvement in body weight might lead to an improvement in other traits and body measurements. This is a good indicator of body conformation and may be used in selection programmer.

Stimulation of food intake after central galanin is associated with arcuate nucleus activation and does not differ between genetically selected low and high body weight lines of chickens

Galanin, a 29 residue peptide found in the hypothalamus, causes orexigenic effects in a variety of species. In the present study, we investigated appetite-associated effects of galanin in chicks from lines which have been selected from a common founder population for either low or high body weight. The low line consists of some anorexic individuals and there are obese individuals in the high line. Central galanin caused increased food intake in both lines with the magnitude of response similar in both lines. We also quantified the number of c-Fos immunoreactive cells in several hypothalamic nuclei that are associated with appetite. Only the arcuate nucleus had an increase in the number of reactive cells, a response that was similar for both lines. From these results we concluded that selection for body weight likely did not affect galanin function on induction of feeding in either lines, and that the effect of galanin is associated with arcuate nucleus activation in chicks.

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.

Extremely Different Behaviours in High and Low Body Weight Lines of Chicken are Associated with Differential Expression of Genes Involved in Neuronal Plasticity

Long-term selection (> 45 generations) for low or high body weight from the same founder population has generated two extremely divergent lines of chickens, the low (LWS) and high weight (HWS) lines, which at the age of selection (56 days) differs by more than nine-fold in body weight. The HWS line chickens are compulsive feeders, whereas, in the LWS line, some individuals are anorexic and others have very low appetites. The involvement of the central nervous system in these behavioural differences has been experimentally supported. We compared a brain region at 0 and 56 days of age containing the major metabolic regulatory regions, including the hypothalamus and brainstem, using a global cDNA array expression analysis. The results obtained show that the long-term selection has produced minor but multiple expression differences. Genes that regulate neuronal plasticity, such as actin filament polymerisation and brain-derived neurotrophic factor, were identified as being differentially expressed. Genes involved in lipid metabolism were over-represented among differentially expressed genes. The expression data confirm that neural systems regulating feeding behaviours in these lines are different. The results suggest that the lines are set in separate developmental trajectories equipped with slightly different nervous systems. We suggest that the lines adapt behaviourally different to changing situations post hatch, such as the transition from dependence on yolk to feeding, in order to obtain energy. The present study has identified and exemplifies the kind of changes that may underlie the extreme differences in such behaviours.

Determination of Body Weight and Some Carcass Traits in Japanese Quails (Coturnix coturnix japonica) of Different Lines

Summary The purpose of this study was to determination of body weight and some carcass traits in Japanese quails (Coturnix coturnix japonica) of different lines. The material used in this experiment was selected from three lines: high body weight line (HL), low body weight line (LL) of 5-week body weight and a random bred control line (C). There were significant differences among the lines in respect to body weight and carcass weight. Highest and lowest body weight and carcass weight were measured in HL and LL lines, respectively. While there were no significant differences among the lines in terms of relative proportion of breast, the sex affected significantly (P<0.01). No significant differences were found in terms of left wing, right wing, neck and back percent of body weight for lines and sexes. Also, there were found significant correlations among the carcass traits..

Long-term divergent selection for 8-week body weight in chickens – a review of experiments

In order to study the effects of long-term selection on genetic parameters, the effect of selection on selected and correlated traits and to develop lines for various physiological, biochemical and molecular genetic studies a comprehensive selection study for body weight in chickens has been conducted at the Biotechnical Faculty of University in Ljubljana. Long-term divergent selection in chickens for 8-week body weight for 31 generations produced a high weight (D+) and low weight (D–) line. Body weight at 8 weeks of age was the exclusive selection criterion. Selection lines were compared for body weight and for unselected traits including carcass traits, feed conversion, egg and meat quality traits, reproduction traits, muscle characteristics, nutritional and physiological traits. This paper describes the most important results of different experiments that were performed on animals from both lines in various generations of selection.

Immunocompetence, Hepatic Heat Shock Protein 70 and Physiological Responses to Feed Restriction and Heat Stress in Two Body Weight Lines of Japanese Quail

The effect of early heat stress either solely or plus feed restriction on the physiological response, antibody titer and hepatic 70-kda heat shock protein expression (HSP 70) of two body weight lines (high and low) Japanese quail chicks were investigated. Chicks of each line were divided into three groups; (1)control, (2) exposure to 39±1oC for six hour (h), form 5 to 21 day of age (DOA) on each of three consecutive d/week (HS) and (3) HS concurrent with 70% feed restriction (HSFR). The results showed that quail chicks of either HS or HSFR exhibited significantly higher respiration rate (RR) compared with the control. While, the rectal temperature (RT) was reduced at 21 DOA, in the HSFR group. The plasma concentrations of total protein, globulin, total lipid, cholesterol, triglycerides and glucose were decreased due to HS or HSFR episode. Likewise, the level of both calcium and phosphorus at 21 DOA. However, at 42 DOA, the HS chicks did not significantly differ from the control. The activities of plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were increased (p<0.05) in treated groups (HS and HSFR) at 21 DOA. Either HS or HSFR showed low Newcastle disease antibody titer and a decrease in relative lymphoid organ weights. Unlike the antibody titer, the H/L ratio was increased in the HS chicks. After heat exposure, HSP 70 density of the high body weight line was immediate and pronounced. The combination of heat stress and feed restriction (HSFR) induced even higher response. While in the low body weight line neither the control nor the heat stress treatment showed any response. Chicks of either HS or HSFR had significantly lower live body weight (LBW) and body weight gain (BWG) and poorer fed conversion ratio (FCR) than the control ones. However, during the recovery period (21 to 42 DOA) the HSFR group was the best (p<0.01) for BWG and FCR. The high line body weight chicks showed significantly higher plasma level of total protein, albumin, globulin and cholesterol at 21 and 42 DOA than the low line. Similarly, higher antibody titers against NDV and productive performance traits throughout the experimental period.

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.

Collagen in two muscles of sheep selected for weight as yearlings

Abstract Collagen concentration and solubility were examined in the semimembranosus and biceps femoris muscles of Romney lambs from the Hight line, a line selected for nine generations on the basis of high body weight at 1 year old. Lambs from the Control (CON) and high body weight (HBW) lines were slaughtered at five ages (0, 42, 70, 274, 365 days). In the semimembranosus muscle, there was no evidence of concentration or solubility differences between the lines at any age, but there was a subtle sex by age interaction, possibly because of increased collagen synthesis in males at puberty. In the biceps femoris muscle, collagen concentration was 14% higher in the HBW line, but there was no difference in solubility. The semimembranosus muscle was shear-tested after cooking to give an objective measure of tenderness. Selection line did not affect shear force. With the semimembranosus muscle, collagen solubility was a better predictor of shear force than collagen concentration, confirming previous work on thi...

Influence of Dietary n-6 and n-3 Polyunsaturates on Lipids in Chickens Divergently Selected for Body Weight

The effects of dietary lipid sources rich in n-6 (soybean oil) or n-3 (menhaden oil) polyunsaturated fatty acids (PUFA) on blood triacylglycerol levels and tissue fatty acid compositions in female chickens from two genetic lines were examined. Triacylglycerol concentrations in the plasma very low density and low density lipoprotein fractions were elevated in the low-weight (LW) chickens compared with the high-weight (HW) group. Chicken heterophil to lymphocyte ratios and total antibody titers to sheep red blood cells at 84 days were not influenced by genetic line or by the dietary lipid fed. Concentrations of C18:1 fatty acid isomers and total monounsaturates were highest in liver and heart tissues of HW chickens. Feeding menhaden oil enriched the plasma, liver, and heart with n-3 PUFA in both genetic lines. The data indicate a difference in hepatic fatty acid metabolism between the HW and LW lines that is unaffected by dietary n-6 or n-3 PUFA.

Chiasma frequency in strains of mice selected for litter size and for high body weight

Chiasma frequency was measured in male mice of three outbred lines: FZt:DU (control); DU:6, selected for increased body weight; and DU:C, selected for high fertility. Chiasma frequency was seen to increase in the high body weight line, but decrease in the high fertility line. In both selected lines the intragroup variance in chiasma frequency increased while in DU:C the intracell variance was lower than in the control.

Correlated Responses in Lines of Chickens Divergently Selected for Fifty-Six–Day Body Weight.: 3. Digestive Enzymes

Levels of amylase, trypsin, chymotrypsin, and lipase in the pancreas and small intestinal chyme were measured in females from four lines of chickens. Two of the lines had undergone 32 generations of divergent selection for 56-day body weight, and in the other two lines selection for high or low weight had been relaxed for 5 generations. The diet used in the present experiment was that under which selection had been practiced (20% crude protein and 2,685 kcal of ME/kg). Comparisons between divergently selected lines at common ages revealed higher enzyme levels for high- than low-weight lines. When comparisons were made at a common body weight (80 ± 5 g) there were no differences between lines. These results suggested that correlated responses in feed intake were mediating the regulation of digestive enzyme levels in the pancreas and in intestinal chyme of growth-selected lines of chickens. Chicks from high-weight lines had elevated enzyme levels after a mild feed restriction compared with those provided ad libitum access to feed. It was hypothesized that hyperphagia associated with the high-weight lines in combination with a mild feed restriction and the associated meal feeding stimulated synthesis and secretion of digestive enzymes.

Abdominal Fat and Testes Weights in Diverse Genetic Lines of Japanese Quail

Six experiments were conducted to investigate abdominal fat levels in mature male and female Japanese quail following selection for 4-wk body weight and to investigate the relationship between testes development and abdominal fat accumulation. The present study utilized P-, T-, and S-line quail selected for more than 75 generations for high 4-wk body weight and also lines divergently selected (16 or more generations) for high (H-SD, H-CD) and low (L-SD, L-CD) 4-wk body weight. Adult males had from two to four times more abdominal fat than females, the reciprocal of abdominal fat patterns in chickens. These differences were observed regardless of the selection environment, direction of selection, or duration of selection. Percentage of abdominal fat was higher in high body weight lines than in low body weight lines, and correlation coefficients between body weight and abdominal fat were moderate to high (mean = .39). Correlations between abdominal fat and testes weights were positive and largest at 5 wk (r = .62).