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At least 1,009 records · Page 56Linked to original sources
PubMed2006

Control of luteinizing hormone and testosterone secretion in a flexibly breeding male passerine, the Rufous-winged Sparrow, Aimophila carpalis.

Rufous-winged Sparrows, Aimophila carpalis, reside in the Sonoran desert and although testicular development is initiated in the spring under the influence of increasing day length, breeding occurs opportunistically in summer in association with heavy rainfall or "monsoon". The aim of this study in free-living male Rufous-winged Sparrows was to establish the relationship between concentrations of plasma luteinizing hormone (LH) and testosterone (T), and breeding associated with heavy rainfall, and to investigate whether breeding is mediated by changes in pituitary gland sensitivity to gonadotropin releasing hormone-I (GnRH) and the recently discovered avian gonadotropin-inhibitory hormone (GnIH). Concentrations of plasma LH and T were relatively low until mid-summer, but increased rapidly and transiently immediately prior to the monsoon which occurred after the summer solstice, when day lengths were decreasing. At this time the birds came into full breeding condition. An injection of chicken GnRH (10 ng) increased plasma LH within 2 min when given before or during the monsoon. An injection of GnIH (1 microg) did not affect plasma LH within 2 min during the monsoon and did not decrease GnRH-elicited LH secretion before or during the monsoon. No experimental treatment affected plasma T concentrations. The data suggest in male Rufous-winged Sparrows that the seasonal increase in plasma LH associated with summer monsoon results from increased stimulation of the pituitary gland by GnRH, rather than from a change in the responsiveness of the gland to GnRH, and that GnIH does not play an acute role in this mechanism. However, a possible chronic role for GnIH in the seasonal control of LH synthesis and secretion through an inhibitory effect on the hypothalamic GnRH system remains to be investigated.

Animals↗
PubMed2006

Linkage disequilibrium mapping in domestic dog breeds narrows the progressive rod-cone degeneration interval and identifies ancestral disease-transmitting chromosome.

Canine progressive rod-cone degeneration (prcd) is a retinal disease previously mapped to a broad, gene-rich centromeric region of canine chromosome 9. As allelic disorders are present in multiple breeds, we used linkage disequilibrium (LD) to narrow the approximately 6.4-Mb interval candidate region. Multiple dog breeds, each representing genetically isolated populations, were typed for SNPs and other polymorphisms identified from BACs. The candidate region was initially localized to a 1.5-Mb zero recombination interval between growth factor receptor-bound protein 2 (GRB2) and SEC14-like 1 (SEC14L). A fine-scale haplotype of the region was developed, which reduced the LD interval to 106 kb and identified a conserved haplotype of 98 polymorphisms present in all prcd-affected chromosomes from 14 different dog breeds. The findings strongly suggest that a common ancestor transmitted the prcd disease allele to many of the modern dog breeds and demonstrate the power of the LD approach in the canine model.

Animals↗
PubMed2001

Recent progress in livestock genomics and potential impact on breeding programs.

Most of the major livestock breeding organizations in the world are actively involved in using the emerging tools for genome analysis to obtain a better understanding of the molecular architecture of their favourite production traits. This is bound to generate a considerable amount of novel biological information that will provide a competitive advantage to those that have access to it. At present, the preferred avenue to exploit this information is via marker-assisted selection (MAS), and several breeding organisations are starting to implement MAS in breeding programs. However, it seems unlikely that the exploitation of genomics information will be limited to MAS in the future. Even though it is difficult to anticipate the ultimate impact of genomics on animal production, it would be very surprising if it were not to revolutionize this industry as it is already revolutionizing the biomedical and plant breeding industries.

Animals↗
PubMed2003

21st century wheat breeding: plot selection or plate detection?

The publicly reported limited application of marker-assisted selection (MAS) in wheat breeding programmes to date is reviewed and contrasted with the current situation, in which it has increasingly become technically feasible to tag almost any gene with a microsatellite assay. Although this capability is starting to have an impact on the conduct of large breeding programmes, a much more profound change in breeding strategy will become possible when single nucleotide polymorphism (SNP) technology has matured sufficiently so that the throughput of molecular marker-based genotyping is able to keep pace with the numbers of plants that breeders routinely handle in the field. We explore the extent to which the genomics revolution might generate a change in the conventional breeding paradigm, which has operated with such success for the best part of the 20th century, and identify the need for a substantial reduction in assay price before MAS is likely to make more than a marginal impact on present practice.

Agriculture↗
PubMed1996

Relationship between genetic diversity in the nematode Trichostrongylus colubriformis and breeding management in ten dairy-goat farms.

Ten dairy-goat farms were investigated in center-west of France for genetic variability of Trichostrongylus colubriformis in relation to breeding management. Farm management data were obtained from a questionnaire. Genetic variability was based on two polymorphic enzymes, malate dehydrogenase (MDH) and glucose-phosphate isomerase (GPI). After their establishment, the farms were subsequently isolated from introduction of strongyle worms as shown in the questionnaire; this was also suggested by the absence of a relationship between genetic variability and distance between farm locations. The genetic variability which was recorded could then be ascribed in part to the influence of management. The breeding management estimates combined the fact that animal breeding was the main economic resource; that goats were or were not the only animal bred; and that there was or was not free access to exercise yards in winter. The farms that were similar on the basis of breeding management, were also similar in the frequency of allozymes, indicating that the chosen allozymes were not neutral in respect to environment. Genetic variability was not related to the frequency of T. colubriformis in the strongyle community, this being possibly due to the fact that our farm samples predominantly harboured T. colubriformis. Between-farm genetic variability was positively correlated to the size of herd (P < 0.01), probably due to the fact that larger herds were originally constituted from several different herds.

Animal Husbandry↗
PubMed1999

Ovarian function in ewes during the transition from breeding season to anoestrus.

Transrectal ovarian ultrasonography was conducted in six Western white-faced ewes for 35 days from the last oestrus of the breeding season, to record the number and size of all ovarian follicles > or = 3 mm in diameter and luteal structures. Blood samples were collected once a day for estimation of serum concentrations of follicle-stimulating hormone (FSH), oestradiol and progesterone. Each ewe had five follicular waves (follicles growing from 3 to > or = 5 mm in diameter) over the scanning period. The duration of the growth phase of the largest ovarian follicles did not differ (P > 0.05) between waves, but follicular static and regressing phases decreased significantly (P < 0.05) after the decline in serum progesterone concentrations at the end of the last luteal phase of the breeding season. The intervals between the five follicular waves were: 9.2+/-0.4, 5.2+/-0.7, 8.3+/-0.8 and 5.8+/-0.7 days; the two shorter intervals differed (P < 0.05) from the two longer intervals. Using the cycle-detection program, rhythmic increases in serum FSH concentrations were detected in all ewes; the amplitude, duration and periodicity of FSH fluctuations did not vary (P > 0.05) throughout the period of study. The number of identified FSH peaks (7.8+/-0.5 peaks per ewe, per scanning period) was greater (P < 0.05) than the number of emerging follicular waves. Serum concentrations of oestradiol remained low (< or = 1 pg/ml) on most days, in five out of the six ewes studied, and sporadic elevations in oestradiol secretion above the non-detectable level were not associated with the emergence of follicular waves. The ovulation rate was lower than that seen during the middle portion of the breeding season (November-December) in white-faced ewes but the transitional ewes had larger corpora lutea (CL). Maximal serum concentrations of progesterone appeared to be lower and the plateau phase of progesterone secretion appeared to be shorter during the last luteal phase of the ovulatory season in comparison to the mid-breeding season of Western white-faced ewes. During the transition into anoestrus in ewes, the endogenous rhythm of FSH release is remarkably robust but the pattern of emergence of sequential follicular waves is dissociated from FSH and oestradiol secretion. Luteal progesterone secretion is suppressed because of fewer ovulations and diminished total luteal volume, but it may also result from diminished gonadotropic support. These season-related alterations in the normal pattern of ovine ovarian cycles appear to be due to reduction in ovarian responsiveness to gonadotropins and/or attenuation in secretion of luteinizing hormone (LH) occurring at the onset of the anovulatory season in ewes.

Anestrus↗
PubMed2002

Breed differences in cochlear integrity in adult, commercially raised chickens.

Two types of chickens are commercially available. Broiler birds are bred to develop quickly for meat production, while egg layers are bred to attain a smaller adult size. Because we have observed breed differences in the response of central auditory neurons to cochlear ablation in adult birds [Edmonds et al. (1999) Hear. Res. 127, 62-76], we examined cochleae from the two breeds for differences in integrity. We evaluated cochlear hair cell structure using scanning electron microscopy and cochlear hair cell function using distortion product otoacoustic emissions (DPOAEs) and the auditory brainstem response. We observed striking breed differences in cochlear integrity in adult but not hatchling birds. In adult broiler birds, all cochleae showed damage, encompassing at least the basal 29% of the cochlea. In 15 of 18 broiler ears, damage was observed throughout the basal 60% of the cochlea. In contrast, cochleae from egg layer adults were largely normal. Two thirds of egg layer ears showed no anatomical abnormalities, while in the remainder cochlear damage was seen within the basal 48% of the cochlea. DPOAEs recorded from egg layer birds showed loss of high frequency emissions in every ear for which the cochlea displayed anatomical damage. Average sound pressure levels in both commercial facilities were 90 dB, suggesting these two breeds may exhibit differential susceptibility to noise damage.

Aging↗
PubMed1992

Breeding and gestation facilities for swine. Matching biology to facility design.

The rate-limiting phase of commercial swine production is breeding. The design of the breeding/gestation facilities influences the capacity of the producer to efficiently manage the breeding stock around the time of service and during the postservice period. Thus, breeding design potentially affects total born litter size and farrowing rates. In general, with original construction and facility renovation, the three principal activities of the breeding/gestation phase of production, (1) boar exposure/estrus detection, (2) breeding, and (3) gestation and pregnancy detection, should be independently considered.

Animal Husbandry↗
PubMed2006

Effect of six decades of selective breeding on soybean protein composition and quality: a biochemical and molecular analysis.

To evaluate the extent of the genetic change and its effects on the seed protein composition of soybean cultivars released during the past 60 years, representative ancestral cultivars and those derived from selective breeding were grown in a side-by-side comparison. Total seed protein content, determined by combustion analysis of nitrogen, revealed a decline in the protein content after decades of selection and breeding. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis comparison of protein profiles of the soybean cultivars indicated that relative expression of most of the seed storage proteins had not varied substantially from the ancestral lines to the present commercial cultivars. There was noticeably less beta-subunit of beta-conglycinin, a protein devoid of sulfur amino acids, in the modern cultivars represented by Mustang, Pioneer 93B09, and Asgrow 3602. Comparison of the amino acid profiles of soybean seed, a benchmark of the protein's nutritional quality, revealed that the ancestral progenitor, G. soja, was significantly higher in cysteine, glutamic acid, histidine, and arginine than either the ancestral or the modern cultivars. Selective breeding over the past 60 years minimally affected the overall amino acid composition. The degree of divergence in the DNA sequence of the genes encoding glycinin and beta-conglycinin in the ancestral and modern cultivars was investigated using Southern hybridization and the polymerase chain reaction. Even though some restriction fragment polymorphisms could be detected, overall, the banding patterns were remarkably similar among the ancestral cultivars and those derived from them, suggesting a high degree of conservation of seed-storage protein genes. The results of our study suggest that selection and breeding for yield during the past 60 years had no major influence on the protein composition, ostensibly because of limited genetic diversity among the parental lines.

Amino Acids↗
PubMed2001

Evaluation of synchronization of oestrus based on gonadotrophin-releasing hormone and its potential use for fixed-time breeding in Tuli beef cows.

The objective of the experiment was to compare the reproductive post-partum performance of beef cows synchronized for oestrus using prostaglandin F2alpha (PGF2alpha) alone or with a gonadotrophin-releasing hormone (GnRH)-based drug. Fifty-five post-partum lactating Tuli cows were randomly allocated to three groups. Two groups were synchronized using either two injections of PGF2alpha (500 microg Prosolvin per injection) given 11 days apart (group 1), or GnRH (12.5 microg Receptal per injection) followed 6 days later by an injection of 500 microg PGF2alpha (group 2). The cows were bred by artificial insemination 12 h after they were observed in oestrus. Group 3 was synchronized as for group 2, but a second injection of GnRH was given 54 h after the PGF2alpha injection, at which time the cows were bred by artificial insemination (AI) without detection of oestrus. Blood samples were taken from the cows in group 3 and analysed for progesterone concentration to establish which cows were cycling and in oestrus before and at the time of breeding. Detection of oestrus and breeding by AI was done over 60 days. There were no significant differences (p>0.05) among the three groups in the first service and total conception rates. The percentage of cows in oestrus within 10 days of the synchronization treatment was not significantly different (p>0.05) between groups 1 and 2. The progesterone concentrations in the cows in group 3 showed that only those that were cycling at the start of the experiment responded to the synchronization treatment and conceived after fixed-time breeding. These results suggest that combinations of PGF2alpha and GnRH may be of value in synchronizing oestrus and controlling breeding in Tuli cows. However, the benefit might be greater if only cows that are known to be cycling are bred in this way.

Animals↗
PubMed2001

Cross-fostering and cross-breeding of HAB and LAB rats: a genetic rat model of anxiety.

Recently, two Wistar rat lines, bred and selected for either high (HAB) or low (LAB) anxiety-related behavior on the elevated plus-maze, were described as a novel psychopathologic animal model. The behavioral and neuroendocrine responses to exposure to an emotional stressor were markedly enhanced in HAB rats compared with LAB rats, thus resembling patients suffering from psychiatric diseases. The present study focused on the developmental and genetic basis of the line-specific differences by using cross-fostering and cross-breeding approaches. For the cross-fostering paradigm, neonate HAB offspring were nursed by a LAB foster mother, and vice versa, until weaning. In the cross-breeding approach, HAB females were mated with LAB males, and vice versa, to create an intermediate F1 generation. Thereafter, the F1 animals were strictly sibling-mated to produce a segregating F2 generation. At 10 weeks of age, anxiety-related behavior of all animals was tested on the elevated plus-maze. The robustness of emotionality was assessed in rats of both lines throughout their entire lifetime. Serving this purpose, the frequency of ultrasound isolation calls, indicative of the emotionality of newborn rats, was monitored in regularly-fostered HAB and LAB pups on postnatal day 11. In addition, the timecourse of anxiety-related behavior was studied by repeated testing on the elevated plus-maze at the ages of 10 weeks, 6 months, 16 months, and 19 months. The cross-fostering approach failed to reveal behavioral differences between regularly and cross-fostered HAB and LAB rats, indicating no line-specific differences in maternal care or maternally-influenced development, at least after postnatal day 1. In contrast, cross-breeding resulted in F1 and F2 offspring displaying intermediate behavioral patterns on the elevated plus-maze which were exactly in between those shown in HAB and LAB control rats, thus confirming a genetic basis of the differences in anxiety. Cross-breeding revealed no differences related to the gender of the offspring or to the line-derivation of sire or dam, indicating an autosomal, rather than heterosomal, heredity of the divergent emotionality in HABs and LABs. Further, we were able to show stable and robust emotional differences in rats of both lines during their entire lifetime. HAB rats showed an enhanced frequency of ultrasound isolation calls on postnatal day 11 (p < 0.05) and a lower open arm exploration of the elevated plus-maze throughout adulthood (p < 0.01) compared with the same-aged LABs. In conclusion, the extremely divergent anxiety levels of HAB and LAB rats are maintained during their whole lives and are determined genetically, rather than being learned. These findings may be important for further studies on the genetic basis of emotionality.

Aging↗
PubMed2006

[The influence of the socio-economic structure of the breeding farms of Franches-Montagnes horses on the conditions of husbandry].

The socio-economic structure of the breeding farms of Franches-Montagnes horses (FM) in Switzerland is evaluated on the basis of an investigation carried out in 2002 by the Swiss FM breeding federation. Questionnaires were sent to 3500 of its members and the results include data from 968 breeding enterprises, housing a total of 3965 FM. The quality of the husbandry of FM varies according to factors such as the altitude and the geographical situation of the farms and studs. Socio-economic parameters, such as the role of FM in the business, their use (breeding, driving, riding) and the age and level of professional education of the owners may also have an effect on standards of husbandry. The results show that the owners for whom FM represent a source of income more frequently keep their horses in standing stalls, but give them more time to exercise at liberty than the horses belonging to amateur breeders. Younger and better educated breeders are more likely to house their animals in groups.

Altitude↗
PubMed2006

[Evaluation of the quality of husbandry of Franches-Montagnes horses in their breeding farms].

The quality of husbandry of Franches-Montagnes horses (FM) in Switzerland is evaluated on the basis of an investigation carried out in 2002 by the Swiss FM breeding federation. Questionnaires were sent to 3500 of its members and the results include data from 968 breeding enterprises, housing a total of 3965 FM: 46.1% were breeding mares (61.0% with foal at foot), 26.5% young stock, 1.3% stallions and 26.0% non breeding stock (74.6% of which were pleasure horses and 25.4% working horses). 57.6% of the FM were housed in individual boxes with or without permanent outdoor access, 25.4% were hold in groups with or without permanent outdoor access, the remaining 17.0% were kept in standing stalls. 95.0% of the FM had at least visual contact with other equines and 99.2% had sufficient light in their stable. 88.1% were stabled on long stalk straw, while only 4.3% were bedded on other materials other than straw. The average time spent at pasture per horse and per week ranged from 96.5 +/- 51.6 hours in summer to 27.2 +/- 26.7 hours in winter. On average, a FM is used for 8.3 +/- 6.5 hours per week. Horses with an paddock at their disposal spend an average of 39.8 +/- 45.9 hours there per week.

Animal Husbandry↗
PubMed2026

Translating functional molecular knowledge into crop-breeding success.

Historical plant breeding, which optimizes phenotypes through selective crossing guided by phenotypic evaluation and molecular markers, is limited by evolutionary constraints that hinder rapid crop improvement. A new paradigm, precision breeding, circumvents these limitations by targeting genetic variants through functional molecular knowledge. To generate this knowledge at scale, sequence-based deep learning leverages high-quality genome sequence data to predict variant effects at base-pair resolution. When linked to agronomically important traits, these predictions enable breeders to prioritize variants for precision selection or editing. Although it is still in the early stages of development, we foresee three key applications for this approach: introgressing genes from distant breeding pools, purging deleterious mutations and designing new plant ideotypes. Looking ahead, refined computational models will facilitate targeted editing and the systematic redesign of complex physiological processes to address emerging breeding goals under shifting environmental conditions.

Crops, Agricultural↗
PubMed1998

Polymorphism of Old Kladruber horses, a surviving but endangered baroque breed.

Analysis of MHC class I and class II polymorphism, as well as data from other polymorphic systems (non-MHC lymphocyte alloantigen, blood groups systems, biochemical polymorphisms and microsatellite loci), was used to characterize the extent and distribution of the genic polymorphism of Kladruber horses. A breed-characteristic distribution of the MHC polymorphism was found. The repertoire of defined MHC class I specificities was restricted, especially in the grey subpopulation and in stallions, but a high frequency of blanks suggests the possible existence of undetected specificities. Despite the small population size and a relatively high degree of inbreeding, high heterozygosity in MHC haplotypes has been conserved. The extent of polymorphism and the degree of heterozygosity in other loci were also relatively high. A comparison of the two existing subpopulations, grey and black, at all the loci tested, including RAPD markers, characterized them as genetically distinct, although clearly related. The genetic distances between them were of the same order of magnitude as between distinct breeds. The results may be useful in defining short-term and long-term breeding policy within the breed and for further studies of associations with disease and other traits.

Animals↗
PubMed2001

Breeding virus resistant potatoes (Solanum tuberosum): a review of traditional and molecular approaches.

Tetraploid cultivated potato (Solanum tuberosum) is the World's fourth most important crop and has been subjected to much breeding effort, including the incorporation of resistance to viruses. Several new approaches, ideas and technologies have emerged recently that could affect the future direction of virus resistance breeding. Thus, there are new opportunities to harness molecular techniques in the form of linked molecular markers to speed up and simplify selection of host resistance genes. The practical application of pathogen-derived transgenic resistance has arrived with the first release of GM potatoes engineered for virus resistance in the USA. Recently, a cloned host virus resistance gene from potato has been shown to be effective when inserted into a potato cultivar lacking the gene. These and other developments offer great opportunities for improving virus resistance, and it is timely to consider these advances and consider the future direction of resistance breeding in potato. We review the sources of available resistance, conventional breeding methods, marker-assisted selection, somaclonal variation, pathogen-derived and other transgenic resistance, and transformation with cloned host genes. The relative merits of the different methods are discussed, and the likely direction of future developments is considered.

Animals↗
PubMed2001

The subspecific origin of the inland breeding colonies of the cormorant Phalacrocorax carbo in Britain.

The establishment of cormorant breeding colonies inland within south-east Britain since 1981 is a matter of major conservation and pest management concern. This study was initiated to investigate the subspecific origin of two recently established breeding colonies. The analysis examined sequence variation of the control (D-loop) region of the mitochondrial genome. Samples of tissue were obtained from 334 individuals from across the species range in western Europe from both subspecies (Phalacrocorax carbo carbo and P. c. sinensis) and 84 birds from two inland breeding colonies in Britain. Single-strand conformation polymorphism (SSCP) was used to assess mitochondrial variation among samples, revealing four haplotypes. The samples from the traditional breeding colonies clustered into three distinct phylogeographic groupings: Norway-Scotland, Wales-England-Iles des Chausey and the rest of Continental Europe. These results only partly agree with the traditional subspecific taxonomic groupings and are slightly at variance with results using microsatellite DNA frequencies, and a hypothesis using results from both studies is advanced. The subspecific origin of the inland colonies was investigated using maximum likelihood and Bayesian models.

Animals↗
PubMed2001

Macrogeographic patterns of breeding system diversity in the Daphnia pulex group from the United States and Mexico.

Studies on the biogeographical patterning of reproductive systems promise to extend understanding of the factors which modulate breeding system transitions. Two closely allied cladoceran crustaceans, Daphnia pulex and D. pulicaria, show varied modes of reproduction, with populations reproducing by either cyclic or obligate parthenogenesis. Prior studies have provided a detailed understanding of their breeding system diversity in the polar and cold temperate regions of North America. The present investigation extends this analysis, characterizing breeding systems and clonal diversity at sites throughout the United States and Mexico. Genotypic diversity in these southern areas was high, but only diploids were detected, indicating that polyploids are restricted to the north. F(1) hybrids and their two parental species were present in most areas, although their frequencies varied geographically. Hybrids invariably reproduced by obligate asexuality, but both parental taxa showed regional shifts in their breeding system. The complexity of these latter patterns suggests that they reflect the interplay of historical factors and selection.

Animals↗