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At least 1,297 records · Page 72Linked to original sources
PubMed1993

Development of an animal model for across-herd genetic evaluation of number born alive in swine.

An animal model and computer software were developed to conduct across-herd genetic evaluations using data from producers participating in the Sow Productivity Index program of the American Yorkshire Club. The final data set consisted of 61,596 litter records from 1986 to early 1990. The animal model included fixed contemporary group effects and random additive direct, service sire, permanent environmental, and residual effects. Additive genetic relationships among animals were included. A separate relationship matrix for service sires and their sires was also included. A data set similar to the Yorkshire field data was simulated to use in testing the animal model. The simulated data set consisted of 40 herds, each with 120 reproducing dams and either four or five sires. Six generations of simulated data were produced, resulting in 20,605 litter records. These records were then evaluated using the animal model for number of pigs born alive. Finally, correlations between the true breeding values from the simulation and the predicted breeding values were computed. The correlation between the 918 true and predicted sire breeding values was considerably lower for the animal model without a service sire effect than when it was included (.53 vs .74, respectively). However, the difference was cut in half (.66 vs .77) when only sires with greater than five daughter records were included. The high accuracy of the animal model with a random service sire effect indicates that the proposed model adequately accounts for the variation found in records for number of pigs born alive.

Animals↗
PubMed1994

Optimal contemporary group structure to maximize genetic progress through genetic evaluation of swine.

Accuracies of sire EPD were calculated for a typical growth trait and a typical maternal trait for alternative contemporary group structures. For a given family size (number of progeny tested for a sire in a contemporary group), accuracy increased as the number of sires increased and as the number of contemporary groups increased. An exponential equation was found to best predict accuracy from the number of sires and groups. Partial derivatives can be used to determine the optimal number of sires and groups for a given economic situation (fixed number of animals tested per group). It is recommended that progeny of at least two sires be represented in each contemporary group, but having more than five sires does not effectively increase accuracy further. Accuracy increases with a larger herd size, as more sires and more groups of pigs are tested. When the number of litters that can be tested is at its limit, accuracy is maximized with a small number of sires, and progeny divided among several contemporary groups. However, accuracy is only part of the herd's genetic improvement. Selection decisions must be made to avoid inbreeding, which can be a problem, particularly in small herds.

Animals↗
PubMed2005

Selection for placental efficiency in swine: genetic parameters and trends.

The objectives of this study were to estimate response to divergent selection for an index of placental efficiency in swine, and to evaluate the effect of placental efficiency on litter size. The selection index (SI) included total born (TB), birth weight (BRWT), and placental weight (PW), and was designed to increase in the high line (H) or decrease in the low line (L) the efficiency of the placental function (PE), defined as the ratio BRWT:PW. (Co)variance components were estimated for direct and maternal additive effects by using an animal model with MTDFREML procedures. Estimated breeding values were calculated by using records on individual BRWT (n = 2,111), PW (n = 2,006), PE (n = 1,677), and SI (n = 1,677). Litter traits were evaluated using records on 193 litters. The model included the fixed effects of contemporary group for all traits, with the addition of sex for individual traits and parity for litter traits. Litter was fitted as an uncorrelated random effect for all traits, and TB was used as a linear and quadratic covariate for BRWT, PW, and PE. Direct heritability estimates from single-trait models were 0.03, 0.25, 0.18, 0.11, and 0.08 for BRWT, PW, PE, SI, and TB, respectively. Estimated breeding values were compared between lines by using a model including generation, line within generation, and replicate within line as the error term. Estimates of genetic divergence were 20.7 +/- 2.7 g, 0.24 +/- 0.03, 0.11 +/- 0.02, and 0.07 +/- 0.02 per generation for PW, PE, SI, and TB, respectively (P < 0.01), but divergence was not significant for BRWT. At Generation 4, direct EBV was higher in L than in H for PW (55.9 +/- 8.7 vs. -24.2 +/- 9.5 g, respectively; P < 0.01) and higher in H than in L for PE (0.58 +/- 0.10 vs. -0.35 +/- 0.09 g, respectively; P < 0.01). However, EBV was not different for BRWT, SI, or TB. These results indicate that PW and PE are susceptible to change by genetic selection; however, the correlated response in TB was an unexpected genetic trend toward a higher TB in L of 0.05 +/- 0.01 piglets per generation (P < 0.01).

Animal Husbandry↗
PubMed1984

Lamb production and its components in pure breeds and composite lines. II. Breed effects and heterosis.

Ewe performance was compared for five pure breeds of sheep (Finnsheep, F; Rambouillet, R; Dorset, D; Targhee, T; Suffolk, S) and the crosses in development of two maternal composite lines (C1 = 1/2F1/4R1/4D and C2 = 1/2F1/4T1/4S). The data involved 10,959 breeding season records of 4,219 ewes by 412 sires. Ewe production and the components (fertility, litter size, neonatal and preweaning lamb survival and mean lamb weaning weight) were adjusted for age and standardized across season of lambing and years. The D and F ewes produced more weight of lamb/ewe exposed than R, S and T ewes because of higher D and F fertility, higher D lamb survival and larger F litters. First cross and inter se generations of C1 and C2 ewes averaged 17 to 27% higher fertility than the parental mean. Litter size averaged about one lamb higher for F than for other pure breeds, but only slightly higher for C1 and C2 than for the mean of F and other breeds. Lower neonatal survival for F than for other breeds and crosses was associated with the larger F litters and with 2 to 8% positive heterosis in the crosses. Preweaning survival of suckled and nursery lambs was low for F and S and positive heterosis ranged from 9 to 19% in crosses. Mean lamb weaning weights were highest for S, lowest for F, with little heterosis in crosses. Crossbred ewes reared .3 to .4 more lambs than mean for parental pure breeds. Heterosis in C1 and C2 ranged from 11 to 28% for lambs born, 27 to 43% for lambs weaned and 29 to 44% for weight of lamb weaned/ewe exposed. Decline in heterosis with inter se mating of crosses was no greater than expected from the reduction in predicted heterozygosity.

Animals↗
PubMed1989

Class I alleles of the bovine major histocompatibility system and their association with economic traits.

A total of 179 Holstein cows from the Agriculture Canada Research Branch herd at Ottawa and 271 progeny-tested Canadian Holstein bulls were typed for 37 lymphocyte antigens. Each antigen appears to be controlled by a distinct, codominant allele of the bovine lymphocyte antigen (BoLA)-A locus, which is a class I locus of the bovine major histocompatibility system. Only 10 and 16 alleles were present in Holstein cows and bulls, respectively. The association between bovine lymphocyte antigens and economically important traits was examined in gene substitution models. Separate models were used for the cow and bull data. The substitution of the W6.1 allele for the W10 allele was associated with increased protein yield in the milk in both analyses. The results were also consistent with a previous report that the presence of the W10 allele was associated with increased fat percentage compared with some, but not all, of the other alleles. However, more research is necessary to confirm these findings and to determine the biological mechanisms underlying these associations.

Age Factors↗
PubMed1994

Estimation of genotype effects for milk proteins with animal and sire transmitting ability models.

The objective of this work was to estimate the contribution of milk protein genotype to production traits of Holstein cattle. Two approaches were employed. The first was based on an animal model analysis of milk records in which cows were genotyped for milk protein variants. The second approach was the analysis of PTA of sires in which the sires were genotyped for their milk protein variants. Results of the animal model analysis agreed qualitatively with previously published analyses of cow records, indicating only a minor contribution of milk protein genotype to production traits. Qualitative similarity was also found between the analysis of sire transmitting abilities and the animal model. Algebraic results suggested, however, that an indirect analysis of published sire transmitting abilities does not provide unbiased estimates of differences in milk protein genotypes. Although analysis of PTA is simple, only a direct analysis of genotyped cows with an animal model provides unbiased estimates of genotype differences.

Animals↗
PubMed1996

Influence of male broiler breeder dietary energy intake on reproduction and progeny growth.

A study was conducted to test the effects of dietary energy intake on reproduction in genetically similar broiler breeder males and on the subsequent growth of their progeny. Fifty-nine 1-d-old pedigree broiler breeder male chicks were raised to breeding age. At 33 wk of age, 33 males were chosen and placed in one of three groups of 11 males per group and fed either 370, 330, or 290 kcal per bird per d. Each group contained both full and half brothers and had similar 6- and 33-wk mean body weights. There was a significant negative effect of decreased dietary energy intake on sperm concentration and total live sperm per milliliter of ejaculate, whereas there was no significant effect on ejaculate volume or percentage dead sperm per ejaculate. Four groups of hens (21 wk of age) with 18 hens per group, were randomly assigned to each male dietary treatment group. Hens were artificially inseminated with 50 microL neat pooled semen from one of the three male treatment groups. There was a significant linear effect of diet on fertility, with no significant effect on hatch of fertile, hatch of eggs set, or embryonic mortality. There was no effect of sire energy intake on offspring body weights at 0, 3, or 6 wk of age. Hens were similarly artificially inseminated and sperm penetration determined for 9 consecutive d postinsemination. There was a significant quadratic relationship between sperm penetration of the perivitelline layer overlying the germinal disc and day postinsemination for each of the three male treatment groups. In addition, mean sperm penetration was 62.3, 42.9, and 6.6 holes in the germinal disc perivitelline layer for the high, medium, and low energy groups, respectively. Following 16 wk of dietary energy treatment, there was a significant linear effect of diet on mean testes weight, mean testes weight as a percentage of male body weight, and male body weight.

Animals↗
PubMedDate not supplied

Multilocus sequence data reveal extensive phylogenetic species diversity within the Neurospora discreta complex.

Previous observations of morphological, reproductive and genetic variation have suggested that Neurospora discreta, as presently circumscribed, might represent a diverse complex of multiple species. To investigate this hypothesis we examined the phylogenetic relationships among 73 fungal strains traditionally identified as N. discreta. Strains were chosen from across the morphological, ecological and geographical ranges of the species. Sequence data were obtained from three unlinked nuclear loci, and phylogenetic species recognition was applied to the dataset using protocols that have been shown to be reliable for identifying independent lineages and delineating species of Neurospora. The results demonstrate that the present circumscription of N. discreta includes at least eight separate phylogenetic species. This research also reveals an abundance of previously unrecognized genetic diversity within the genus, characterizes the interspecific evolutionary relationships and contributes to a fuller understanding of species diversity in Neurospora.

Genetic Variation↗
PubMed2006

Parasexuality in asexual development mutants of Aspergillus nidulans.

The parasexual cycle with parameiosis has been characterized previously by the occurrence of genetic recombination and haploidization inside heterokaryotic hyphae prior to conidial formation. The aim of current research was to characterize, through genetic and cytological analyses, an asexual development mutant strain of A. nidulans and to use it to obtain parameiotic segregants. Analyses showed the medusa phenotype of the B84 strain, whose mutant allele was mapped in the chromosome I. The heterokaryons B84(med)//G422(med+) and B84(med)//G839(brl) were formed in liquid MM+2% CM and inoculated in the appropriate selective media. Two mitotic segregant groups were obtained: aneuploids and haploid stable recombinants. Mitotic segregants, wild-types, and developmental mutants, which did not produce new visible mitotic sectors in the presence of Benomyl and which showed normal meiotic behavior during the sexual cycle, were classified as parameiotics.

Aspergillus nidulans↗
PubMed1994

Medical resource allocation: rationing and ethical considerations, Part II.

The proliferation of medical technology during the past decade has doubtless surpassed that of any other recent period. We have witnessed and are continuing to witness rapid advances in human genetic engineering, reproductive technology, and biomedical intervention in the life process. Our population has benefitted from this technology as a result of its ability to extend the life of individuals, particularly the elderly sector of our society. This technological proliferation has caused philosophers, physicians, engineers, and policy strategists to focus upon questions of ethics and mortality relating to their application. In approaching the ethics of rationing, consideration must be given to both the deontological concepts of the individual and the utilitarian principles of societal preservation. This article continues a discussion of the issues of resource allocation that was begun in the February 1994 issue of Physician Executive.

Advance Directives↗
PubMed1999

The modulation of DNA content: proximate causes and ultimate consequences.

The forces responsible for modulating the large-scale features of the genome remain one of the most difficult issues confronting evolutionary biology. Although diversity in chromosomal architecture, nucleotide composition, and genome size has been well documented, there is little understanding of either the evolutionary origins or impact of much of this variation. The 80,000-fold divergence in genome sizes among eukaryotes represents perhaps the greatest challenge for genomic holists. Although some researchers continue to characterize much variation in genome size as a mere by-product of an intragenomic selfish DNA "free-for-all" there is increasing evidence for the primacy of selection in molding genome sizes via impacts on cell size and division rates. Moreover, processes inducing quantum or doubling series variation in gametic or somatic genome sizes are common. These abrupt shifts have broad effects on phenotypic attributes at both cellular and organismal levels and may play an important role in explaining episodes of rapid-or even saltational-character state evolution.

Animals↗
PubMed2001

[Molecular diagnosis of fragile X syndrome with polymerase chain reaction: application of a diagnostic protocol in 50 families from northern Spain].

OBJECTIVES: The aim of this study was to develop a rapid, non-radioactive and effective method for the molecular diagnosis of fragile X syndrome (FXS) by the polymerase chain reaction (PCR) of the CGG repeat and to establish a protocol to be used in: a)ruling out FXS in patients with non-specific mental retardation; b)determining the exact genotype of affected individuals; c)studying all at-risk individuals from families with FXS and identifying asymptomatic carriers, and d)offering accurate genetic and reproductive counselling to families with FXS. MATERIALS AND METHODS: Samples from 438 individuals from 50 families with FXS were studied using three different PCR tests: the first to detect ethidium bromide through ultraviolet light, the second to detect digoxigenin and CSPD after blotting and hybridisation with the (CGG)5 oligoprobe, and the third to amplify and detect the DXS548 microsatellite. RESULTS: Of the 438 individuals studied, 121 had full mutations (60 males and 61 females), 86 had pre-mutations (7 males and 79 females), 16 showed mosaic patterns and 215 had no mutations. PCR techniques amplified up to 120-150 repeats, and direct study with probes was required when no bands or only one band was detected in females. PCR was more accurate than genomic DNA Southern blot analysis in pre-mutated carriers. In one family, recombination between the FRAXA locus and the DXS548 microsatellite was found. CONCLUSIONS: These non-radioactive PCR protocols permit rapid and accurate diagnosis of FXS. They and are especially useful in prenatal diagnosis and in the identification of carriers.

Adult↗