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PubMed1997

A sequential-arrivals model of territory acquisition

Birds arrive sequentially at their breeding ground where the nest sites vary in value (measured by reproductive success). Each bird must either choose a vacant site or challenge an occupier for its site. In the latter case we assume the occupier to be the more likely winner. The loser of the contest incurs a cost and must go to a vacant site. The rational strategy for such a contest is found. There is a threshold phenomenon; early arrivals occupy vacant sites, late arrivals fight. This result is intuitively reasonable, but the sequence of sites chosen is complex. A recursive method for specifying the solution is described and applied explicitly to some illustrative cases.Copyright 1997 Academic Press Limited Copyright 1997 Academic Press Limited

Journal Article↗

PubMed2000

A sequential-arrivals model of territory acquisition II.

Birds arrive sequentially at their breeding ground where the nest sites vary in value (measured by reproductive success). Each bird may choose a vacant site or challenge an occupier for its site. In the latter case, the occupier is presumed to be the more-likely winner; the loser incurs a cost and must go to a vacant site. In a previous paper (Broom et al., 1997, J. theor. Biol.189, 257-272), we considered the optimal strategy. However, that optimal strategy was complex and perhaps could not be realized in real bird populations, making possibly costly demands both perceptually and at the coding level. With this in mind we introduce certain restricted classes of strategy, and consider how populations might evolve. Computer simulations of various populations have been performed to model the competition amongst several strategies in the presence of recurrent mutations. Certain combinations of strategies persisted and corresponded approximately to the ESSs found in Broom et al. (1997).

Animals↗

PubMed2002

Genetics of resistance to Meloidogyne incognita in crosses of grape rootstocks.

Progeny testing was used to investigate the value of selected grape varieties as parents in breeding nematode-resistant rootstocks. Six pistillate-flowered rootstocks (Ramsey, Dog Ridge, Harmony, Freedom, 1613C, and 161-49C) and four staminate-flowered rootstocks (Riparia Gloire, 3309C, 1616C, and St. George) were used. Each male was crossed to each female. Six weeks after inoculation with 1,500 second-stage juveniles of Meloidogyne incognita race 3, roots were stained in an aqueous solution of eosin-Y (0.25 gm/l for 1 h). Seedling resistance was measured by counting the number of stained nematode egg masses visible per root system. Nematode reproduction on each cross was calculated as the average number of egg masses on ten seedlings per replicate. The females Harmony and Freedom produced the greatest level of resistance in their seedlings across all male parents. Seedlings of Dog Ridge, Ramsey, and 1613C had intermediate levels of resistance, while seedlings of 161-49C were the least resistant. The male 1616C contributed the greatest resistance to its progeny, while seedlings from crosses with the males Riparia Gloire, 3309C, and St. George had lower levels of resistance. Segregation ratios of resistant and susceptible seedlings are consistent with a single dominant allele model for root-knot nematode resistance.

Journal Article↗

PubMed2005

Effects of climate variation on timing of nesting, reproductive success, and offspring sex ratios of red-winged blackbirds.

Predicting ecological consequences of climate change will be improved by understanding how species are affected by contemporary climate variation, particularly if analyses involve more than single ecological variables and focus on large-scale climate phenomena. I used 18 years of data from red-winged blackbirds (Agelaius phoeniceus) studied over a 25-year period in eastern Ontario to explore chronological and climate-related patterns of reproduction. Although blackbirds started nesting earlier in years with warmer springs, associated with low winter values of the North Atlantic Oscillation Index (NAOI), there was no advance in laying dates over the study. Nesting ended progressively later and the breeding season lasted longer over the study, however, associated with higher spring values of NAOI. As the length of the nesting season increased, offspring sex ratios became more female biased, apparently as a result of females adjusting the sex of the eggs they laid, rather than from sex-biased nestling mortality. Clutch size did not vary systematically over the study or with climate. Opposing trends of declining nest success and increasing productivity of successful nests over the study resulted in no chronological change in productivity per female. Higher productivity of successful nests was associated with higher winter NAOI values, possibly because synchrony between nesting and food availability was higher in years with high NAOI values. Other than the association between the start of nesting and spring temperatures, local weather (e.g., temperature, rainfall) patterns that linked NAOI with reproduction were not identified, suggesting that weather patterns may be complex. Because climate affected most aspects of red-winged blackbird reproduction examined, focusing on associations between climate and single variables (e.g., first-egg dates) will have limited value in predicting how future climates will affect populations.

Animals↗

PubMed2004

Unintended effects and their detection in genetically modified crops.

The commercialisation of GM crops in Europe is practically non-existent at the present time. The European Commission has instigated changes to the regulatory process to address the concerns of consumers and member states and to pave the way for removing the current moratorium. With regard to the safety of GM crops and products, the current risk assessment process pays particular attention to potential adverse effects on human and animal health and the environment. This document deals with the concept of unintended effects in GM crops and products, i.e. effects that go beyond that of the original modification and that might impact primarily on health. The document first deals with the potential for unintended effects caused by the processes of transgene insertion (DNA rearrangements) and makes comparisons with genetic recombination events and DNA rearrangements in traditional breeding. The document then focuses on the potential value of evolving "profiling" or "omics" technologies as non-targeted, unbiased approaches, to detect unintended effects. These technologies include metabolomics (parallel analysis of a range of primary and secondary metabolites), proteomics (analysis of polypeptide complement) and transcriptomics (parallel analysis of gene expression). The technologies are described, together with their current limitations. Importantly, the significance of unintended effects on consumer health are discussed and conclusions and recommendations presented on the various approaches outlined.

Animals↗

PubMed1999

Cryptic female choice: frogs reduce clutch size when amplexed by undesired males.

In species with internal fertilization, females can 'cryptically' choose (e.g. through sperm selection) which individuals sire their offspring, even when their overt preferences for copulatory partners are overrun by male-male competition and sexual coercion. The experiment presented here reveals that control of paternity after copulation has begun is also possible in species with external fertilization. Females of the hybridogenetic Rana essonae-Rana esculenta (LL-LR) waterfrog complex adjust their clutch size in response to mate type: they release fewer eggs when amplexed by hybrid LR males who--jeopardize successful reproduction--than when amplexed by parental LL males. This reduction in the number of eggs laid can increase a female's residual reproductive value through a second mating in the same breeding season or a larger clutch size in the next year. We argue that cryptic female choice through clutch size adjustment (i) may have evolved more often than previously assumed, and (ii) can arise even where females mate only once during a reproductive period.

Animals↗

PubMed1993

Sister chromatid exchange in the goat (Capra hircus).

Lymphocyte cells from 30 Maltese and Syrian derivative goats (13 males and 17 females) reared in southern Italy underwent sister chromatid exchange (SCE) test. For the 902 cells we studied, the SCE-mean values were 6.6 +/- 3.0 per cell for both breeds. The SCE-frequency did not follow a Poisson distribution. The simultaneous visualization of SCEs and G-bands in the lightly stained chromatid allowed the study of SCE-distribution in chromosomes 1 and X. The number of SCEs in chromosome 1 was significantly higher (P > 0.001) than expected from relative chromosome length. No statistical differences between the numbers of SCEs in the active (early-replicating) and inactive (late-replicating) X-chromosomes of female cells were found.

Animals↗

PubMed2006

A microsatellite-based consensus linkage map for species of Eucalyptus and a novel set of 230 microsatellite markers for the genus.

BACKGROUND: Eucalypts are the most widely planted hardwood trees in the world occupying globally more than 18 million hectares as an important source of carbon neutral renewable energy and raw material for pulp, paper and solid wood. Quantitative Trait Loci (QTLs) in Eucalyptus have been localized on pedigree-specific RAPD or AFLP maps seriously limiting the value of such QTL mapping efforts for molecular breeding. The availability of a genus-wide genetic map with transferable microsatellite markers has become a must for the effective advancement of genomic undertakings. This report describes the development of a novel set of 230 EMBRA microsatellites, the construction of the first comprehensive microsatellite-based consensus linkage map for Eucalyptus and the consolidation of existing linkage information for other microsatellites and candidate genes mapped in other species of the genus. RESULTS: The consensus map covers approximately 90% of the recombining genome of Eucalyptus, involves 234 mapped EMBRA loci on 11 linkage groups, an observed length of 1,568 cM and a mean distance between markers of 8.4 cM. A compilation of all microsatellite linkage information published in Eucalyptus allowed us to establish the homology among linkage groups between this consensus map and other maps published for E. globulus. Comparative mapping analyses also resulted in the linkage group assignment of other 41 microsatellites derived from other Eucalyptus species as well as candidate genes and QTLs for wood and flowering traits published in the literature. This report significantly increases the availability of microsatellite markers and mapping information for species of Eucalyptus and corroborates the high conservation of microsatellite flanking sequences and locus ordering between species of the genus. CONCLUSION: This work represents an important step forward for Eucalyptus comparative genomics, opening stimulating perspectives for evolutionary studies and molecular breeding applications. The generalized use of an increasingly larger set of interspecific transferable markers and consensus mapping information, will allow faster and more detailed investigations of QTL synteny among species, validation of expression-QTL across variable genetic backgrounds and positioning of a growing number of candidate genes co-localized with QTLs, to be tested in association mapping experiments.

Alleles↗

PubMed2004

Quantitative trait loci (QTL) detection in multicross inbred designs: recovering QTL identical-by-descent status information from marker data.

Mapping quantitative trait loci in plants is usually conducted using a population derived from a cross between two inbred lines. The power of such QTL detection and the parameter estimates depend largely on the choice of the two parental lines. Thus, the QTL detected in such populations represent only a small part of the genetic architecture of the trait. In addition, the effects of only two alleles are characterized, which is of limited interest to the breeder, while common pedigree breeding material remains unexploited for QTL mapping. In this study, we extend QTL mapping methodology to a generalized framework, based on a two-step IBD variance component approach, applicable to any type of breeding population obtained from inbred parents. We then investigate with simulated data mimicking conventional breeding programs the influence of different estimates of the IBD values on the power of QTL detection. The proposed method would provide an alternative to the development of specifically designed recombinant populations, by utilizing the genetic variation actually managed by plant breeders. The use of these detected QTL in assisting breeding would thus be facilitated.

Computer Simulation↗

PubMed1995

Development and evaluation of a regression equation of prediction for fat-free soft tissue in heterogenous populations of cattle.

Regression equations to predict kilograms of fat-free soft tissue (the sum of water and protein from chemical analyses) were developed from data collected on 526 steers and heifers. Straightbred animals representing Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental breeds of cattle contributed to the data set. Cattle ranged in slaughter weight and age from approximately 350 to 575 kg and from 13 to 23 mo, respectively. Diets (100% ground alfalfa, 67% ground alfalfa and 33% ground corn or 33% ground alfalfa and 67% ground corn) were cross-classified with breed and sex. Estimative traits included in the equation were warm carcass weight, fat depth at the 12th rib, and body impedance. Carcass soft-tissue samples were taken for determination of chemical constituents. The prediction equation accounted for 94% of the variation in fat-free soft tissue of the carcass. Adjusting for breed-sex-diet contemporary groups increased the R2 value by 2% units. The prediction model was evaluated using data collected on 65 steers sired by Charolais or by Hereford bulls at the Ft Keogh Livestock and Range Research Laboratory (Miles City, MT). Postweaning feeding strategies and slaughter ages varied among these animals. Carcass weight, back fat depth, and resistive impedance measures were recorded. Carcass soft-tissue samples were taken for determination of chemical constituents. Values of estimator variables recorded at Ft. Keogh were used in the regression equation to predict fat-free soft tissue for each animal. The values for kilogram of fat-free soft tissue determined from chemical analysis were regressed on predicted fat-free soft tissue. the results indicate that fat-free soft tissue of carcasses can be accurately predicted using estimative traits that do not diminish carcass value.

Animals↗

PubMed1992

Effect of initial restraint, weaning, and transport stress on baseline and ACTH-stimulated cortisol responses in beef calves of different genotypes.

The productivity and well-being of animals can be substantially affected by stress. This is particularly true in the case of beef calves that are subjected to a multitude of stressors over a short period during the first year of life. Perhaps the most often studied stress-responsive variable has been blood corticosteroid concentrations. Factors such as age, gender, genetics, and degree of prior experience, can influence how an animal perceives and responds to a given stressor. Few studies have tried to control these variables, and accordingly, many conflicting results have been published regarding the impact of various stressors on cortisol response. We measured baseline plasma cortisol concentration over a 44-day study in Bos indicus and Bos taurus calves. Plasma cortisol values in Bos indicus calves were higher (32.60 +/- 0.66 ng/ml) than values in calves of Bos taurus (25.81 +/- 0.76) breeding. A precipitous decrease in cortisol concentration was observed 7 days after transport stress in all calves. Baseline cortisol concentration did not provide any indication of the intensity of the various stressors. However, significant differences were readily observed after ACTH administration. On the basis of cortisol secretion, stresses of transport and weaning were similar and were the most stressful to calves, regardless of genotype.

Adrenocorticotropic Hormone↗

PubMed1990

Assessment of respiratory diseases and therapeutic intervention by the forced oscillation technique in feedlot cattle.

The forced oscillation technique was used to study pulmonary function in bulls during naturally acquired pulmonary-gastrointestinal disease complex known as shipping fever and as it was treated with two different antibiotics. Fifteen double-muscled bulls of the Belgian White and Blue breed were investigated. Clinical, serological and pulmonary function values were recorded during and after naturally occurring respiratory disease. Total respiratory resistance (Rrs) and reactance (Xrs) were measured by the forced oscillation technique. The antibiotic ceftiofur (group A, n = 10) and oxytetracycline (group B, n = 5) were given over three days. A large increase of Rrs at low frequencies with a marked negative frequency dependence, an increase of the resonant frequency, and a decrease of Xrs were recorded in the initial stage of the disease. The parameters returned to normal values seven days later. Clinical evidence of recovery was more marked in group A than in group B. These results show that moderate shipping fever induces acute small and large airway obstruction which responds to appropriate antibiotic therapy.

Airway Resistance↗

PubMed1988

Consistent capacity for adrenocortical response to ACTH administration in pigs.

The effect of ACTH administration on plasma cortisol concentrations in purebred and crossbred pigs was investigated. Pigs were given either 25 IU of ACTH or physiologic saline solution IM. Blood samples were collected immediately before and 1 hour after ACTH or saline solution administration. Administration of ACTH resulted in a significant (P less than 0.01) increase in plasma cortisol concentration compared with that resulting from administration of saline solution; mean values after ACTH administration were similar in both breed groups. In contrast, a fivefold range of differences was observed among individual pigs of the same age, sex, and body weight, irrespective of breed group. The type and magnitude of the adrenocortical response was consistent and repeatable in pigs over a 3-month period, suggesting that pigs have a consistent capacity for adrenocortical response to ACTH administration. Development of a dynamic test allowed the high and low responding extremes in a population to be detected. The most suitable dose of synthetic ACTH was established to be 50 IU, and the best time for blood sample collection was 60 minutes after ACTH administration. The classification of individual pigs as high or low responders was repeatable and was not affected by prior short-term exposure to ACTH.

Adrenocorticotropic Hormone↗

PubMed1984

[Changes in plasma parameters in rabbit does as a function of their physiological state and feed rationing].

We followed the evolution of hematocrit and of plasma Na, K, Cl, total protein, creatinine, Pi, alkaline phosphatases, triglycerides, cholesterol, glucose and GPT. The amount of feed given to the rabbit does was restricted to 75 percent of the quantity eaten ad libitum, in similar conditions to those of intensive breeding. This had a slight effect on the values obtained for plasmatic components in healthy rabbits. This was not dependent on the timing of blood collection, nor on the physiological state of the animal. The changes in biochemical composition of the plasma due to pregnancy in healthy rabbit does are: a fall in total plasma protein and cholesterol levels, alkaline phosphatases activity, hematocrit, and a rise followed by a marked fall in plasma triglycerides level. During lactation, these levels return progressively to the values obtained in non-pregnant, non-lactating rabbits.

Alanine Transaminase↗

PubMed1994

Randomly primed PCR amplification of pooled DNA reveals polymorphism in a ruminant repetitive DNA sequence which differentiates Bos indicus and B. taurus.

By amplification of pools of DNA representative of different bovine populations with single short oligonucleotide primers of random sequence, we were able rapidly to identify markers which distinguish the two major subspecies of domestic cattle, Bos taurus and B. indicus. One of the marker polymorphisms was found to be in a novel, dispersed DNA sequence which occurs in several ruminant species. The marker will assist in the detection of crossbreeding between Zebu and B. taurus types where this threatens a potentially valuable trypanosomiasis-resistant B. taurus genetic resource in West Africa. In addition, the marker will be useful for exploration of the evolutionary relationships of the major subspecies of domestic cattle. The general approach used to identify population-specific DNA polymorphisms has potentially broad application in definition of species, breeds and populations and will be of generic value in studies of genome evolution.

Animals↗

PubMed1979

Clinical comparison of skin testing and the radioallergosorbent test in dog-sensitive patients using mixed and breed-specific antigens.

A study of clinical history, intradermal test end points and RAST values with six different dog antigens was made in 20 patients and 5 control subjects. Skin testing was found to be more useful clinically than the RAST. Considerable variability among mixed epidermal extracts was noted. There was no apparent advantage to testing with three individual-breed extracts studied, compared to the most potent mixed epidermal antigen. The results of this study suggest that further efforts toward standardization of potency, methods of preparation and, possibly, breed composition of dog allergenic extracts are required to develop improved allergens for clinical use.

Animals↗

PubMed1995

Individual multilocus genotypes using microsatellite polymorphisms to permit the analysis of the genetic variability within and between Italian beef cattle breeds.

We investigated the genetic variability within and between cattle breeds. The polymorphisms of 17 microsatellites were studied in 220 unrelated animals belonging to four Italian beef cattle breeds (Chianina, Marchigiana, Romagnola, and Piemontese). Variations of allelic frequencies were examined to characterize the breeds and their relationships. Wahlund coefficients, Polymorphism Information Content values, and Haldane exact test for Hardy-Weinberg proportions were calculated. The results show that the Hardy-Weinberg equilibrium is not always maintained. Moreover, in addition to the classical genetic distances, a new method, based on the consideration of a multilocus genotype of each animal, was set up to measure the genetic similarity between animals or within groups of animals. All the results showed that, whereas Chianina occupies an intermediate position and Piemontese is the most distinct of all four breeds, Marchigiana and Romagnola display the strongest similarity. The new method also provides evidence that average similarities are always higher within breeds than between breeds. By comparing pairwise the multilocus genotypes, it was also possible to discriminate the individuals with higher or lower genetic similarities so that each breed could be subdivided into two groups of animals in relation to their similarity to the average breed multilocus genotype. High similarities between breeds were detected, somewhat surprisingly, when the most homogeneous groups of each breed were compared. The microsatellite multilocus genotype is particularly efficient in evaluating the between- and within-breeds genetic similarities and for subgrouping genetically more homogeneous animals.

Alleles↗

PubMed1997

Inheritance of hypoxic exercise tolerance in mice.

All mammals tested, when exposed acutely to a degree of hypoxia above some threshold, exhibit a reduced capacity to perform work. Chronic hypoxic exposure is usually associated with some degree of acclimation resulting in partial recovery of the preexposure work capacity. The present study reports that, among mice, interindividual variability in recovery of ability to tolerate a standardized hypoxic exercise [t(et); time elapsed in treadmill exercise in hypoxia until 4-s failure to avoid a grid configured to deliver a mild aversive current (0.15 mA)], after 8 weeks' exposure to half-atmospheric pressure, is influenced predominantly by two unlinked genes of major effect. Two approaches were taken toward genetic characterization. In one, a maximum-likelihood procedure was applied to 11 models of genetic determinacy in the t(et) distributions of BALB/cBy (C) and C57BL/6By (B6) parental inbred strains, their F1 hybrid, and the backcross (BC) generations. Breeding tests of the resulting candidate "best-fit" major locus inheritance models involved repeated cycles of selecting, as the progenitor of a new BC generation, the male with the highest value of the test variable in the previous BC generation, and breeding him to C females. Mice from each of four distinct phenotypes appearing in BC3 were bred to C mice, producing distributions expected from two-locus segregation. The second approach was based upon CXB/By RI strain distribution pattern and derivative breeding tests to reveal phenotypic distributions consistent with two-locus inheritance of tet. Melding these results with a positional cloning strategy may permit relating a behavioral difference to specific heritable elements and identifying their products as the (partial) physiological substrata of the behavior.

Animals↗