Validated quantitative trait loci for eggshell quality in experimental and commercial laying hens.

Compromised eggshell quality causes considerable economic losses for the egg industry. Breeding for improved eggshell quality has been very challenging. Eggshell quality is a trait that would greatly benefit from marker-assisted selection, which would allow the selection of sires for their direct contribution to the trait and would also allow implementation of measurements integrating a number of shell parameters that are difficult to measure. In this study, we selected the most promising autosomal quantitative trait loci (QTL) affecting eggshell quality on chromosomes 2, 3, 6 and 14 from earlier experiments and we extended the F2 population to include 1599 F2 females. The study was repeated on two commercial populations: Lohmann Tierzucht Rhode Island Red line (n = 692 females) and a Hy-Line White Plymouth Rock line (n = 290 progeny tested males). We analyzed the selected autosomal QTL regions on the three populations with SNP markers at 4-13 SNPs/Mb density. QTL for eggshell quality were replicated on all studied regions in the F2 population. New QTL were detected for eggshell color on chromosomes 3 and 6. Marker associations with eggshell quality traits were validated in the tested commercial lines on chromosomes 2, 3 and 6, thus paving the way for marker-assisted selection for improved eggshell quality.

Quantitative trait loci affecting eggshell traits in an F(2) population.

Good eggshell quality is important for both table egg quality and chicken reproductive performance. Weak eggshells cause economic losses in all production steps. Poor eggshell quality also poses increased risk for Salmonella infections. Eggshell quality has been a difficult trait to improve by traditional breeding, as it can be measured only for females and it is difficult and expensive to measure. Breeding for improved shell quality may therefore benefit from the use of marker-assisted selection. In an effort to find markers linked to eggshell quality, we have used an F(2) population of 668 females to map quantitative trait loci (QTL) affecting eggshell traits (eggshell deformation, breaking force, weight). By using 160 microsatellite markers on 27 chromosomes, we found 11 genome-wide and 15 suggestive QTL for shell traits measured at different times during production. Loci affecting the deformation were found on chromosomes 1, 2, 6, 10, 14 and Z. Loci affecting the breaking force were detected on chromosomes 2, 3, 10, 12 and Z. Loci affecting the shell weight were detected on chromosomes 6, 12, 24 and Z. Each QTL explains between 1.5% and 4.6% of the phenotypic variance, adding up to 10-15% of total phenotypic variance explained for the different traits. No epistatic effects were observed between loci affecting eggshell traits. Because the effects for quality are mainly additive, these results provide a basis for further characterization of the loci to identify closely linked markers to be used in marker-assisted selection.

Parent-of-origin specific QTL--a possibility towards understanding reciprocal effects in chicken and the origin of imprinting.

Reciprocal effects for sexual maturity, egg production, egg quality traits and viability are well known in poultry crosses. They have been used in an optimal way to form profitable production hybrids. These effects have been hypothesized to originate from sex-linked genes, maternal effects or a combination of both. However, these may not be the only explanations for reciprocal effects. Recent mapping of quantitative trait loci (QTL) has revealed autosomal areas with parent-of-origin specific effects in the chicken. In mammals, parental imprinting, i.e. the specifically regulated expression of either maternal or paternal allele in the offspring, is the main cause of such effects. The most commonly accepted hypothesis for the origin of imprinting, the conflict hypothesis, assumes a genetic conflict of interest between the maternal and paternal genomes regarding the allocation of resources to the offspring. It also intrinsically implies that imprinting should not occur in oviparous taxa. However, new molecular genetic information has raised a need to review the possible involvement of imprinting or some related phenomena as a putative cause of reciprocal effects in poultry. Comparative mapping provides strong evidence for the conservation of orthologous imprinted gene clusters on chicken macrochromosomes. Furthermore, these gene clusters exhibit asynchronous DNA replication, an epigenetic mark specific for all imprinted regions. It has been proposed that these intrinsic chromosomal properties have been important for the evolution of imprinted gene expression in the mammalian lineage. Many of the mapped parent-of-origin specific QTL effects in chicken locate in or close to these conserved regions that show some of the basic features involved in monoallelic expression. If monoallelic expression in these regions would be observed in birds, the actual mechanism and cause may be different from the imprinting that evolved later in the mammalian lineage. In this review we discuss recent molecular genetic results that may provide tools for understanding of reciprocal differences in poultry breeding and the evolution of imprinting.

Fishy taint in chicken eggs is associated with a substitution within a conserved motif of the FMO3 gene.

Fishy odor of urine and other secretions is a characteristic of trimethylaminuria in humans, resulting from loss-of-function mutations in the flavin-containing mono-oxygenase isoform FMO3. A similar phenotype exists in cattle, in which a nonsense mutation in the bovine orthologue causes fishy off-flavor in cow's milk. The fishy odor is caused by an elevated level of excreted odorous trimethylamine (TMA), due to deficient oxidation of TMA. We report the mapping of a similar disorder (fishy taint of eggs) and the chicken FMO3 gene to chicken chromosome 8. The only nonsynonymous mutation identified in the chicken FMO3 gene (T329S) changes an evolutionarily highly conserved amino acid and is associated with elevated levels of TMA and fishy taint in the egg yolk in several chicken lines. No differences in the expression of FMO3 were found among individuals with different associated genotypes, indicating that the trait is not caused by a linked polymorphism causing altered expression of the gene. The results support the importance and function of the evolutionarily conserved motif FATGY, which has been speculated to be a substrate recognition pocket of N-hydroxylating siderophore enzymes and flavin-containing mono-oxygenases.

Mapping of quantitative trait loci affecting quality and production traits in egg layers.

A mapping population segregating for egg quality traits was created by a line cross between two egg layer lines and screened by a genome scan. The F2 generation consisted of 307 hens, which were scored for egg quality and production traits. The mapping population was genotyped for 99 microsatellite loci, spanning nine macrochromosomes and five small linkage groups. The linkage maps were used in mapping QTL affecting 14 traits, by using multiple markers and a least-squares approach. We detected 14 genomewide significant and six suggestive QTL that were located on chromosomes 2, 3, 4, 5, and, 8 and sex chromosome Z. A significant QTL affecting egg white thinning was found on chromosome 2. For eggshell strength, a significant QTL was found on chromosome Z. For production traits, the most interesting area was on chromosome 4, where highly significant QTL effects were detected for BW, egg weight, and feed intake in the same area. The most significant QTL explains 25.8% of the phenotypic variance in F2 of body weight. An area affecting the age at first egg, egg weight, and the number of eggs was located on chromosome Z.

Evaluation of genetic variability and genetic distances between eight chicken lines using microsatellite markers.

The genetic variability and divergence of eight chicken lines were evaluated using nine microsatellite markers. The chicken lines included three White Leghorn hybrids, three Finnish Landrace lines, a Rhode Island Red line, and a broiler hybrid line. All the microsatellite loci were found to be polymorphic, the number of alleles varying from 4 to 13 per locus and 1 to 10 per line, respectively. Observed heterozygosities ranged from 0.00 to 0.91. The highest (0.67) and lowest (0.29) mean heterozygosity per line was observed in the broiler and in White Leghorn of Mäkelä, respectively. Three of the microsatellite loci deviated from the Hardy-Weinberg equilibrium in some populations. F statistics indicated clearly the subdivision of the total population into different lines. The genetic distances confirmed the classification of Finnish Landraces into different lines. A phylogenetic consensus tree was constructed from resampled data (1,000 times) using the neighbor-joining method. According to the phylogenetic tree, the lines were grouped into three clusters, in which the White Leghorns formed one group, two Landraces a second group, and a Landrace, the Rhode Island Red, and the broiler lines a third group. Allele distribution at the loci does not support either the stepwise or the infinite alleles mutation model, but the distribution pattern was quite irregular at different loci.

Sex-dependent expression of tenascin-C in the differentiating fetal rat testis and ovary.

The cellular mechanisms controlling sexual differentiation of fetal gonads are poorly understood. By examining the protein and mRNA expression of tenascin-C in correlation with the immunocytochemical detection of alpha-smooth muscle actin (alpha-SMA) and basement membrane heparan sulfate proteoglycan (HSPG) we demonstrate a clear-cut sex-and development-dependent expression pattern of tenascin-C in the rat testis, ovary and mesonephros. Immunocytochemistry and in situ hybridization of tenascin-C in 15-day-pc fetal testis and ovary showed protein and mRNA accumulation within the mesenchyme of the mesogonadal connection. In addition to the male and female mesonephros, some labeling could also be seen within the testicular tunica albuginea and intraovarian mesenchymal septa. In the 17-day-pc testis abundant accumulation of tenascin mRNA and protein appeared in the tunica and mediastinum testis, but not at all in the intratesticular mesenchyme. A similar pattern was still seen in the newborns where, however, a decrease in the anti-tenascin immunoreactivity of the tunica and mediastinum could be demonstrated. In contrast to the testis, expression of tenascin in 17-day-pc ovaries was widespread within the hilus and the entire intragonadal mesenchyme where it continued to accumulate also in newborns. Northern blot analysis of tenascin-C mRNAs showed one message of 8.0 kb in the 15-day-pc male and female gonads. An additional weak signal of 6.5 kb was seen in the female mesonephros. In the 18-day-pc testis, the 6.5-kb signal appeared stronger than the 8.0-kb signal. In contrast to the testis, the 6.5-kb message was weak in the developing ovary where the 8.0-kb signal had an intense peak on the day 18 pc. Further, in the ovary, mesenchymal accumulation of HSPG coincided with the spatial distribution of tenascin. In the testicular tunica and in the mesenchyme of the male and female genital ducts expression of tenascin was parallel with the differentiation of smooth muscle tissue, detected by labeling for alpha-SMA, which also indicated the tenascin-negative myoid cells of the testis. Our results indicate that tenascin expression in the fetal rat internal genitalia is involved in the differentiation of smooth muscle cells but not intratesticular myoid cells. In the ovarian mesenchyme, tenascin-C may have a specific function in the dynamic remodeling of the ovarian cords.

Genetic variation of residual feed consumption in a selected Finnish egg-layer population.

The purpose of the study was to estimate the heritability of residual feed consumption (RFC) and the genetic correlations between RFC and economically important traits. The genetic progress after four generations of selection for RFC and the changes in economically important traits were also investigated. A selection experiment for RFC was carried out from 1983 to 1987. The total data consisted of 3,750 birds and 2,661 records. The (co)variance components were calculated using derivative-free bivariate animal model restricted maximum likelihood (REML). Breeding values were estimated for calculating genetic progress in RFC and correlated responses in the other traits. The heritability of RFC calculated from the whole recorded period (16 to 42 wk) and using all 2,661 records was .46 (+/- .04). The genetic correlations between RFC and egg mass, number of eggs, egg weight, and body weight were not significant. The genetic correlation between RFC and feed consumption was .50 (+/- .04). The breeding value estimates indicated a moderate genetic progress in RFC due to selection. Feed consumption was decreased and body weight gain showed reduction in the last two generations. No change could be found in egg mass, number of eggs, egg weight, age at first egg, or body weight.

Cumulative prevalence of urinary characteristics in very old people.

We studied in 1982 six urinary characteristics in very old inhabitants of Tampere, Finland, born in 1892 or earlier (N = 167). The majority (N = 132) of the subjects had also been studied in 1977 and 1978. The abnormalities were quite transient during the 5-year period. The cumulative percentage of those who had urinary infection was high in respect of bacterial culture and pyuria. Positive bacterial culture (> or = 10(5)/ml) could be detected in over half of the cohort, and pyuria (> 5/HPF) in 76%. Although persistence of albuminuria and haematuria was individually relatively rare in all three surveys, their cumulative percentages were 36% and 34%, respectively, during the 5-year period. Use of indwelling catheter was significantly more frequently connected with bacteriuria and haematuria than with albuminuria or pyuria.

Annual injection of vitamin D and fractures of aged bones.

In order to investigate the effect of a supplementation of vitamin D in the prophylaxis of fractures of the bones of aged people, an annual intramuscular injection of ergocalciferol (150,000-300,000 IU) was given to two series of aged subjects: first to 199 (45 male) of 479 subjects (110 male) aged more than 85 years who were living in their own home, and second to 142 (29 male) of 320 (58 male) subjects aged 75-84 and living in a home for aged people. This prospective series was divided into treatment groups according to month of birth. These injections were given annually from September to December in the years 1985-1989, two to five times to each participant. The fracture rates, laboratory values, vitamin D levels, possible side effects, and mortality were followed until October 1990. A total of 56 fractures occurred in the 341 vitamin D recipients (16.4%) and 100 in 458 controls (21.8%) (P = 0.034). The fracture rate was about the same in both outpatient and municipal home series. Fractures of the upper limb were fewer in the vitamin D recipients, 10/341 = 2.9% (P = 0.025), than in the controls, 28/458 = 6.1%, during the follow-up. A similar result was obtained in fractures of ribs, 3/341 = 0.9% and 12/458 = 2.6%, respectively. Fractures of the lower limbs occurred almost as frequently, 31/341 = 9.1%, among the vitamin D recipients as among the controls, 49/458 = 10.7%. The fracture rate was higher in females (22.2%) than in males (9.5%). The fractures were fewer in the vitamin D recipients only in females.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum vitamin D level after an annual intramuscular injection of ergocalciferol.

An annual intramuscular injection of ergocalciferol (150,000 IU) normalized low serum (25(OH)D concentrations in elderly people for 1 year. The treatment had a slight effect on serum 24,25(OH)2D levels but no effect on 1,25(OH)2D levels.

Body weight and the three-year prognosis in very old people.

We studied prospectively the three-year prognosis of persons aged 84-88 years living in their own homes in the city of Tampere, Finland in 1981-84. Out of the target population 722 persons (64 per cent), 181 of them male (25 per cent), participated in the initial survey. A re-examination was carried out annually for the next three years. Increased mortality was observed for subjects with body mass index less than or equal to 22.0 kg/m2, statistically significantly in women but not in men. Mortality was not increased in those with body mass index greater than or equal to 30.0 kg/m2 in either sex. Low body mass index was associated with mortality due to stroke. Low body mass index was related to permanent hospitalization and also to failure to cope with living at home. On average, body weight was somewhat reduced during the follow-up period. Both a loss and a gain in weight by two kilograms or more during the first follow-up year were associated with increased mortality but not with institutionalization during the next two years.

Blood pressure in the very old.

Seven hundred and twenty-four people (541 female, 183 male), aged 84-88 years and living at home in the city of Tampere, Finland, accepted our invitation to be examined in the outpatient department of the local geriatric hospital. These subjects were re-examined annually, and their fate was followed for 3 years. The blood pressure level was a prognostic sign for mortality during the first year after its measurement. The lowest mortality rate was found among those subjects with systolic blood pressure between 140 and 169 mmHg and diastolic blood pressure between 70 and 99 mmHg. Blood pressures outside of these ranges were associated with increased mortality rates, particularly cardiac and coronary mortality. The mortality rate was especially high among those whose systolic blood pressure had decreased to low levels in the year before, but was lower in those whose systolic blood pressure had decreased from high to middle levels (140-169 mmHg) than in those with consistently high systolic blood pressure. Eventual institutionalization was more common in those with low systolic blood pressure.

Blood pressure and five year survival in the very old.

During 1977-8 we measured blood pressure in 561 old people (83% of those aged 85 or more living in Tampere) and analysed their five year survival according to their blood pressure group. The subjects were divided into six groups on the basis of their blood pressures (from less than 120 to greater than 200 mm Hg systolic, from less than 70 to greater than 110 diastolic). The greatest mortality was observed in those in the lowest systolic and lowest diastolic groups. Mortality was least in subjects with systolic pressures of 160 mm Hg or more and diastolic pressures of 90 mm Hg or more. The most essential finding in this series of the very old was an increased mortality in the lowest blood pressure groups.

Blood glucose and diabetes mellitus predicting mortality in persons aged 85 years or above.

The population aged 85 years or over (n = 674) living in Tampere, Finland was surveyed in 1977-1978. In an investigation of the prognostic survival of new and previously diagnosed diabetic patients, the levels of blood glucose were analysed in 558 persons, 99 men and 459 women. The relative sex- and age-adjusted survival rates were evaluated at the 5-year follow-up. The mortality after 5 years of the 17 new diabetics at home did not differ significantly from that of the 225 non-diabetics at home. The mortality of 30 patients with previously diagnosed diabetes mellitus was higher than that of the non-diabetics. The survival prognosis of the diabetics on antidiabetic medication did not differ from that of those on diet. An increased risk of mortality was found in this series in previously diagnosed diabetics and--most unexpectedly--in non-diabetics with the lowest fasting blood-glucose levels.

Electrocardiographic findings and 5-year cardiovascular mortality in very old people.

The electrocardiograms (ECGs) of 558 individuals, 83% of the total population aged 85 years or over in the city of Tampere in 1977, were assessed according to the Minnesota code in a health survey. The underlying causes of death were identified from the death certificates during the following five years. The total mortality rate was 70%, while the cardiovascular mortality was 51%. The lowest 5-year mortality from cardiovascular and cardiac diseases was observed in subjects with no codable or only minor ECG abnormality in the initial examination. The highest cardiovascular mortality rate was found in individuals with atrial fibrillation, atrioventricular blocks and left or right bundle branch block. The cardiac mortality was related to left or right bundle branch block and atrial fibrillation. Mortality from stroke showed the highest association with clockwise rotation and left high R waves.