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Biomedical subjects

C S Haley

Publications and source records attributed to C S Haley.

At least 73 records · Page 4Linked to original sources
PubMed1994

Comparisons between peripheral progesterone concentrations in cyclic and pregnant Landrace x large White and Meishan gilts.

Progesterone concentrations were determined in blood samples collected twice daily (at 0900 and 1700 hours) from the day of oestrus (Day 0) until Days 15-24 in ten Landrace x Large White gilts (four cyclic and six pregnant gilts) and eight Meishan gilts (four cyclic and four pregnant gilts). Progesterone concentrations during the early luteal phase tended to be higher in pregnant Meishan gilts than in pregnant Landrace x Large White gilts. Furthermore, when differences in ovulation rate and peak progesterone concentrations were accounted for, maximum progesterone concentrations occurred earlier in Meishan gilts than in Landrace x Large White gilts (P < 0.01); this difference was particularly marked when pregnant animals of the two breeds were compared. In non-mated animals, analyses of the timing and magnitude of progesterone concentrations observed towards the end of the oestrous cycle revealed that the decrease in progesterone concentrations occurred earlier (P < 0.05) in Meishan gilts. Such breed differences in the peripheral progesterone profile may be associated with reduced prenatal mortality, a characteristic of Meishan females.

Animals↗
PubMed1994

Mapping quantitative trait loci in crosses between outbred lines using least squares.

The use of genetic maps based upon molecular markers has allowed the dissection of some of the factors underlying quantitative variation in crosses between inbred lines. For many species crossing inbred lines is not a practical proposition, although crosses between genetically very different outbred lines are possible. Here we develop a least squares method for the analysis of crosses between outbred lines which simultaneously uses information from multiple linked markers. The method is suitable for crosses where the lines may be segregating at marker loci but can be assumed to be fixed for alternative alleles at the major quantitative trait loci (QTLs) affecting the traits under analysis (e.g., crosses between divergent selection lines or breeds with different selection histories). The simultaneous use of multiple markers from a linkage group increases the sensitivity of the test statistic, and thus the power for the detection of QTLs, compared to the use of single markers or markers flanking an interval. The gain is greater for more closely spaced markers and for markers of lower information content. Use of multiple markers can also remove the bias in the estimated position and effect of a QTL which may result when different markers in a linkage group vary in their heterozygosity in the F1 (and thus in their information content) and are considered only singly or a pair at a time. The method is relatively simple to apply so that more complex models can be fitted than is currently possible by maximum likelihood. Thus fixed effects of background genotype can be fitted simultaneously with the exploration of a single linkage group which will increase the power to detect QTLs by reducing the residual variance. More complex models with several QTLs in the same linkage group and two-locus interactions between QTLs can similarly be examined. Thus least squares provides a powerful tool to extend the range of crosses from which QTLs can be dissected whilst at the same time allowing flexible and realistic models to be explored.

Alleles↗
PubMed1994

RFLP and linkage analysis of the porcine casein loci--CASAS1, CASAS2, CASB and CASK.

Restriction fragment length polymorphisms (RFLPs) were revealed at the porcine casein loci with the following combinations of restriction endonucleases and porcine cDNA clones: alpha s1-casein (TaqI); alpha s2-casein (BamHI); and beta-casein (SacI). These RFLPs were shown to be under simple monogenic control by segregation analysis of two- and three-generation families. The CASAS1, CASAS2 and CASB casein loci were also shown to be linked with no recombinant haplotypes observed amongst 77 meioses in Large White and Meishan F1 and F2 crosses. No recombinants were observed in a further 106 meioses that were informative for linkage between CASAS1 and CASAS2.

Alleles↗
PubMed1994

Relationships between components of litter size in unilaterally ovariectomized and intact rabbit does.

A study was performed to evaluate the use of unilateral ovariectomy for the measurement of uterine capacity in rabbits through a comparison of the relationships between ovulation rate, number of implanted embryos, and litter size in unilaterally ovariectomized (ULO) and intact does. Data from 211 ULO and 323 intact does were analyzed. The animals were derived from a synthetic line previously selected on litter size. Laparoscopy was performed on all does during their second gestation 12 d after mating and the number of corpora lutea and implantation sites were recorded. Intact and ULO does had the same ovulation rate, confirming the presence of compensatory ovarian hypertrophy in the remaining ovary of the ULO does. The number of implantation sites in the ULO group (11.3) approached the number found in the control group (12.6). Embryonic survival (until implantation) was lower (P < .01) in ULO does (.77) than in intact does (.88), but fetal survival (after implantation) was the same in both groups. The ULO females produced litters 77% of the size of those of the normal control females. Pre- and postimplantation survivals were not related in intact does but seemed to be related in ULO does through an effect on the number of implantation sites. The coefficient of the regression of number of implantation sites on ovulation rate was positive in control does (.62 +/- .06) and was also positive in ULO does (.31 +/- .07), showing that a higher ovulation rate would have resulted in a higher number of embryos being implanted in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

The genetic basis of response in mouse lines divergently selected for body weight or fat content. II. The contribution of genes with a large effect.

Gene action underlying selection responses has been studied using crossbreeding. Maximum likelihood based segregation analysis has been presented for analysing backcross data for the presence of genes with a large effect. Two sets of divergently selected lines (P-lines for body weight and F-lines for fat content) were reciprocally crossed and the F1s were crossed to the high and low lines to produce all possible backcrosses. Earlier analysis had shown that the difference in body weight at 10 weeks (n = 595) between the high and low P-lines was largely (75-80%) explained by autosomal, additive genes with the remainder explained by additive genes on the X chromosome. Maximum likelihood segregation analysis suggested the presence of a major effect on the X chromosome, but as there was only one round of recombination between the X chromosomes in the forming of the backcrosses, linked genes on the X chromosome could have acted together to give the appearance of a single major gene. The difference in fat content between the F-lines (n = 578) could be explained by autosomal genes of largely additive effect. Segregation analysis suggested the presence of a major gene with complete dominance, but this was attributed to a relationship between the mean and the variance: transformation of the data resulted in only polygenic additive genes being of importance. This study concluded that maximum likelihood based analysis and crosses between selected lines provide a powerful means for studying the gene action underlying responses to selection.

Adipose Tissue↗
PubMed1993

Reproductive performance in relation to uterine and embryonic traits during early gestation in Meishan, large white and crossbred sows.

Previous studies have shown that females of the Chinese Meishan breed and of their F1 cross with European Large White pigs are very prolific, producing about four more piglets per litter than control Large White females. The main cause of this prolificacy is enhanced prenatal survival for a given ovulation rate in Meishan and F1 females and this is controlled by genes of the mother, not those of the conceptus. The objectives of this study were to determine whether genotypic differences in embryo survival were apparent in the period immediately after attachment and to compare embryonic and uterine development at this time. Sows in their third parity (20 Large White, 14 Meishan, 25 Large White x Meishan F1 and 25 Meishan x Large White F1) were killed 20-22 days after mating and their reproductive tracts recovered for further study. There were significant differences between the purebred sows, and crossbred sows were approximately intermediate for the number of corpora lutea (20.7 +/- 0.9, 27.8 +/- 1.1, 22.4 +/- 0.8 and 23.3 +/- 0.8 for the four genotypes, respectively), the number of embryos (15.2 +/- 0.9, 23.4 +/- 1.1, 17.2 +/- 0.8 and 18.8 +/- 0.8, respectively) and the proportionate embryo survival (0.74 +/- 0.04, 0.84 +/- 0.04, 0.78 +/- 0.03 and 0.82 +/- 0.03, respectively). There was a negative association within genotype between embryo survival and the number of corpora lutea. Adjusting for the genotypic difference in the number of corpora lutea increased the genotypic differences in embryo survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Genetic basis of prolificacy in Meishan pigs.

Research in France and in the UK confirms the prolificacy of the Chinese Meishan breed to be about three to four piglets greater than that of control Large White females. Crossbreeding studies clearly indicate that this breed difference is due to genes acting in the dam and not in the litter itself. There is high heterosis for litter size in F1 Meishan x Large White crossbred females, such that their litter size is similar to or greater than that of purebred Meishan females. There is some discrepancy between studies about whether the Meishan female has a higher ovulation rate than does the Large White breed and this can be attributed in large part to the different basis upon which breed comparisons have been made. Nevertheless, there may be real genetic differences between Meishan pigs exported to different countries. In young gilts at comparable numbers of oestrous cycles after puberty, the ovulation rate is similar in Meishan and Large White gilts, but in older gilts, and particularly in multiparous sows, Meishan pigs have a higher ovulation rate in British studies. Once comparisons of prenatal survival between breeds have been adjusted for any breed difference in ovulation rate, the main cause of prolificacy in Meishan pigs can be seen to be an enhanced level of prenatal survival. Crossbreeding studies show that this is controlled by the maternal genotype and not that of the embryos. The advantage in prenatal survival to the Meishan pig is clearly present in the post-attachment period (after day 20 of gestation), but may also be present earlier in gestation. Results from a study presented here suggest that Meishan sows have a higher uterine capacity than do Large White sows and this allows them to maintain their higher number of attached embryos through gestation. F1 Meishan x Large White crossbred females achieve their high litter size via a different route than do purebred Meishan females. These animals have a lower ovulation rate and fewer attached embryos than do purebred Meishan sows, but a very low level of fetal loss allows them to produce litters of similar size. The low level of fetal loss in F1 females appears to be due to the higher uterine capacity of F1 females compared with purebred Meishan sows.

Animals↗
PubMed1992

A simple regression method for mapping quantitative trait loci in line crosses using flanking markers.

The use of flanking marker methods has proved to be a powerful tool for the mapping of quantitative trait loci (QTL) in the segregating generations derived from crosses between inbred lines. Methods to analyse these data, based on maximum-likelihood, have been developed and provide good estimates of QTL effects in some situations. Maximum-likelihood methods are, however, relatively complex and can be computationally slow. In this paper we develop methods for mapping QTL based on multiple regression which can be applied using any general statistical package. We use the example of mapping in an F(2) population and show that these regression methods produce very similar results to those obtained using maximum likelihood. The relative simplicity of the regression methods means that models with more than a single QTL can be explored and we give examples of two lined loci and of two interacting loci. Other models, for example with more than two QTL, with environmental fixed effects, with between family variance or for threshold traits, could be fitted in a similar way. The ease, speed of application and generality of regression methods for flanking marker analysis, and the good estimates they obtain, suggest that they should provide the method of choice for the analysis of QTL mapping data from inbred line crosses.

Animals↗
PubMed1992

Methods of segregation analysis for animal breeding data: a comparison of power.

Maximum likelihood segregation analysis provides potentially the most powerful method for the detection of segregating major genes. Segregation analysis requires the comparison of the likelihood of the data under the combined model (allowing both polygenic and major gene genetic variation) with the likelihood of the data under the polygenic model (allowing only polygenic genetic variation). In this study three approximations to the combined model likelihood were compared using simulated data, both with and without a segregating major gene, containing observations on paternal half-sibs. The use of Hermite integration to replace the integration in the combined model likelihood provided the most powerful test for a major gene. Two approximations, based on extensions of linear-mixed-model theory and estimating transmitting abilities for sires, were also considered. These approximations were less powerful than the use of Hermite integration, although the approximation estimating a transmitting ability for each major genotype for the sires was an improvement over the approximation estimating a single transmitting ability. For each approximation the frequency of detection of a major gene depended on the proportion of the genetic variance explained by the simulated major gene and whether the major gene caused the distribution to be skewed.

Alleles↗
PubMed1992

Methods of segregation analysis for animal breeding data: parameter estimates.

Three approximations to the combined model likelihood (including variation due to both polygenes and a major gene) used in segregation analysis were compared in their ability to estimate the parameters describing the model. Paternal half-sib data simulated under four different combined models were used. In general, when a combined model provides the best explanation of the data the parameter estimates from all three approximations investigated are, on average, in good agreement with the values simulated. The use of Hermite integration to replace the integration in the combined model likelihood provided the parameter estimates closest to those stimulated. The other two approximations, based on extensions of linear mixed-model theory, gave estimates further from the expected values, however, these latter two methods can estimate transmitting abilities for the sires directly from the analyses. The three approximations are similar in their ability to genotype sires at the major locus. On average, with the models studied here, about 65 per cent of sires can be successfully genotyped.

Alleles↗
PubMed1992

Maximum likelihood mapping of quantitative trait loci using full-sib families.

A maximum likelihood method is presented for the detection of quantitative trait loci (QTL) using flanking markers in full-sib families. This method incorporates a random component for common family effects due to additional QTL or the environment. Simulated data have been used to investigate this method. With a fixed total number of full sibs power of detection decreased substantially with decreasing family size. Increasing the number of alleles at the marker loci (i.e., polymorphism information content) and decreasing the interval size about the QTL increased power. Flanking markers were more powerful than single markers. In testing for a linked QTL the test must be made against a model which allows for between family variation (i.e., including an unlinked QTL or a between family variance component) or the test statistic may be grossly inflated. Mean parameter estimates were close to the simulated values in all situations when fitting the full model (including a linked QTL and common family effect). If the common family component was omitted the QTL effect was overestimated in data in which additional genetic variance was simulated and when compared with an unlinked QTL model there was reduced power. The test statistic curves, reflecting the likelihood of the QTL at each position along the chromosome, have discontinuities at the markers caused by adjacent pairs of markers providing different amounts of information. This must be accounted for when using flanking markers to search for a QTL in an outbred population.

Animals↗
PubMed1992

A comparison of rate and uniformity of embryo development in Meishan and European white pigs.

A comparison was made of the rate and uniformity of development of embryos recovered from Meishan and European white sows. The time of ovulation was estimated to be 34.3 and 49.0 h after the onset of oestrus in large white and Meishan sows, respectively. Embryos were recovered from a total of 38 Meishan and 37 European pigs between 18 and 219 h after the estimated time of ovulation. Embryos recovered after 18-59 or 44-82 h were classified into one of 11 stages (from early fertilization to early blastocyst), and the maximum blastocyst diameter was measured for embryos recovered 140-219 h after ovulation. There was no evidence of a difference between the genotypes in the stage or size of embryos at these times or of large differences between the genotypes in the extent of variation in embryo stage within females, although a minority of European white females had very variable embryos. As the differences between the embryos of the Meishan and the European white were small, it seems unlikely that greater uniformity of Meishan embryo development is a major cause of the higher prenatal survival in that breed.

Animals↗
PubMed1992

The potential role of molecular genetic manipulation in the improvement of reproductive performance.

Revolutionary opportunities for the modification of animal performance are being created by the development of new methods for embryo manipulation and the application of molecular biology. This paper reviews the potential application of these procedures for the improvement of reproductive performance in livestock. There are three sections: a consideration of the methods of molecular manipulation that are available at present and those that seem likely to become available, a discussion of the modifications to hormonal systems and, finally, an analysis of candidate genes for manipulation of seasonality, number of ovulations, sex ratio and prenatal survival. The analysis points to a number of ways forward. Many of the most promising opportunities will depend upon the isolation of embryonic stem cells or the establishment of alternative methods of site-directed mutation. In most cases, the genes of interest have not yet been cloned and much remains to be learned about the molecular regulation of reproduction. A greater understanding seems likely to reveal the inadequacies of some of the present suggestions, but it is also certain to reveal further opportunities. However, in the longer term, there seems to be a real prospect of modification of at least some of these aspects of reproductive performance by molecular means.

Animals↗
PubMed1991

Use of DNA fingerprints for the detection of major genes for quantitative traits in domestic species.

The detection of marker loci linked to major genes or quantitative trait loci (QTL) of large effect in farm animal populations is of great potential value, both because it allows the easy manipulation of the major genes and because it provides a possible route to their ultimate isolation. At present the number of markers available is limited in farm animals. DNA fingerprints provide a promising source of informative marker loci and have the advantage that several loci can be detected on a single Southern hybridization. The disadvantage of DNA fingerprints is the difficulty in determining allelism of DNA fingerprint bands in different pedigrees and the fact that not all potentially resolvable loci can be resolved in a single pedigree. With probes capable of detecting 50 randomly distributed loci, about 50% of the genome of a typical domestic mammal might be expected to be closely linked to a marker (at a distance of 0.2 Morgans or less). If a proportion of DNA fingerprint loci prove to be clustered near chromosomal telomeres or elsewhere in the genome, coverage will be less. In order to detect linkage to a major gene, sires known or suspected to be heterozygous are used to produce large half-sibships, all animals in the pedigree are DNA fingerprinted and the phenotypes of the offspring are recorded. Where several heterozygous sires are available, sires can be selected in an attempt to maximize the number of marker loci resolved. The optimum number of sires needed to produce pedigrees will depend upon the size of the major gene, the number of DNA fingerprint probes available and the characteristics of the DNA fingerprints produced, but often one or two pedigrees will be optimum. Monte Carlo simulation was used to explore the power of detection of linkage between a major gene and a marker locus in a backcross. Maximum likelihood and analysis of variance of mean differences between marker genotypes were of similar power, but maximum likelihood provided reasonable estimates of the major gene effect and its linkage to the marker under some circumstances. One hundred offspring informative for the segregation of a marker would provide reasonable power for the detection of a gene causing a difference between the heterozygote and the homozygote of at least one within-sire, within-genotype standard deviation when linkage was very close (0.05 or less).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Direct responses in males and correlated responses for reproduction in females to selection for testicular size adjusted for body weight in young male lambs.

Selection based upon testicular diameter adjusted for body weight at 6, 10 and 14 weeks of age was used to produce two lines of sheep, with either high or low testicular size. Ten generations of selection were carried out and the estimate of the realized heritability of the selection criterion was 0.53 +/- 0.01. There were significant positive correlated responses to selection for testicular diameter at 6, 10 and 14 weeks of age, but the correlated responses in body weight at these ages were negative. In mature females, there were significant negative correlated responses to selection in premating body weight in the 1st, 2nd and 3rd breeding season and in the day of the first oestrus in the 2nd breeding season. Litter size per ewe mated had a small positive correlated response to selection in the second breeding season. This latter response appeared to be due to a positive correlated response in fertility, ewes from the High-line having a significantly higher probability of conceiving to a single mating than those from the Low-line. There was no significant correlated response in ovulation rate or litter size per ewe lambing and the genetic correlation between these traits and the selection criterion is likely to be close to zero. This may be due to the adjustment for body weight used, but it is possible that, in any event, body weight in young rams may be a better predictor of female ovulation rate than testicular diameter. These results do not rule out the possibility that testicular size in rams older than those selected would provide a good predictor of genetic merit for female ovulation rate.

Animals↗
PubMed1990

Embryo survival and conceptus growth after reciprocal embryo transfer between Chinese Meishan and Landrace x Large White gilts.

Embryos were transferred between Meishan and Landrace x Large White (control) gilts on Day 4 or 5 to establish approximately equal numbers of all four possible combinations of donor breed and recipient breed. The breed of the donor gilt significantly (P less than 0.01) affected embryo survival with 44.5% of transferred Meishan embryos and 69.6% of transferred control embryos surviving to Day 30 +/- 1. There was no influence of the breed of the recipient gilt on the proportion of embryos which survived. These differences in embryo survival between the two breeds could not be explained by differences in (1) the number of embryos transferred, (2) the stage of development of the embryos transferred, (3) the interval between ovulation and transfer or (4) the degree of asynchrony between donor and recipient gilt. On Day 30 +/- 1 embryos from control donors developed into longer fetuses (P less than 0.01) with larger allantoic sacs (P less than 0.05) than did embryos from Meishan donors. Fetuses in control recipients were longer (P less than 0.01), heavier (P less than 0.001) and had larger allantoic sacs (P less than 0.05) than fetuses occupying Meishan uteri. The interaction between breed of donor gilt and breed of recipient gilt did not significantly affect conceptus growth. These results suggest that Meishan pig embryos may be less tolerant to routine embryo transfer procedures than those of control gilts, that the genotype of the dam does not affect the proportion of embryos surviving to Day 30 +/- 1, and that both fetal and maternal factors affect conceptus growth.

Animals↗
PubMed1989

Study of LH response to GnRH in the young male as a criterion of genetic merit for female reproduction in sheep.

A high and a low response line in sheep were selected on the basis of the mean concentration of LH in 10-week-old Finn-Dorset ram lambs after an i.v. injection of 5 micrograms GnRH. After 8 male generations the mean LH response of the high line was more than 5-fold that of the low line and the heritability of the selected trait was estimated at 0.44 +/- 0.015. Highly significant line differences in mean LH response to GnRH were also found in males at 20 weeks of age and females at 10 and 20 weeks of age and the genetic correlations between the four LH response traits appear to be close to unity. Large line differences in the mean FSH response to GnRH were also found in both males and females at 10 and 20 weeks of age. Selection had little effect on the physical characteristics of lambs. High-response line ewes entering their first breeding season at about 7 months of age showed oestrus earlier in the season and had higher ovulation rates and numbers of lambs born per ewe lambing than did low-response line ewes. In the second breeding season, at about 19 months of age, the only line difference was a higher ovulation rate early in the breeding season in high-line ewes. It is suggested that these changes may be mediated by a more rapid response in high-line ewes to increased GnRH stimulation at puberty or at the beginning of the breeding season.

Animals↗