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D Waddington

Publications and source records attributed to D Waddington.

At least 19 recordsLinked to original sources
PubMed2006

Probability of an egg cracking during packing can be predicted using a simple non-destructive acoustic test.

1. The aim of this investigation was to test the predictive power of the dynamic stiffness measurement to identify eggs which are most likely to crack under field conditions. 2. A representative sample of eggs (n = 1660) was collected from the front of the cages in a commercial battery unit. Egg weight, % damping and dynamic stiffness (Kdyn) were recorded using an acoustic crack detection device. Intact eggs were marked and replaced in the front of the cages. These eggs were subsequently passed through online collection, grading and packing machinery, along with a volume of unmarked eggs. At the end of packing the acoustic test was repeated on the marked eggs, and these were subsequently categorised as being either intact (0) or cracked (1). 3. A logistic regression of the probability of cracking vs Kdyn revealed that as the Kdyn measurement decreases below 15,000 N/m there is a rapid increase in the probability that an egg will crack during routine handling. 4. Additional variables (visit, egg weight,% damping and position in the house (battery [1 to 7], side [1, 2] and tier [1 to 8]) were also fitted to the model but only egg weight, visit and tier effects significantly improved the model fit. 5. This study confirms that the dynamic stiffness measurement can predict the probability of an egg cracking in the field and with high precision. As this measurement also has a high heritability, it could be incorporated into breeding programmes, where it would offer an excellent method to improve eggshell quality and reduce the incidence of cracked eggs.

Acoustics↗
PubMed2005

Heritability and genetic correlation of measurements derived from acoustic resonance frequency analysis; a novel method of determining eggshell quality in domestic hens.

Cracked eggshells result in economic loss and provide a route for pathogenic organisms to enter the egg. Genetic factors that contribute to shell strength are likely to decrease the risk that an egg will crack when subject to insult. A novel measurement, the dynamic stiffness of the eggshell (Kdyn) was examined to determine if it might be used in the genetic selection of hens with improved eggshell characteristics. The measurement is determined from acoustic resonance frequency analysis. The estimates of heritability for the novel measurement of Kdyn were moderately high and ranged from 0.33 to 0.53 depending on the model used for the estimation. The estimates of genetic correlation of Kdyn with eggshell breaking strength (0.49) and static stiffness (0.57) were positive and relatively large as expected. There was a small negative genetic correlation between Kdyn and egg production from 26 to 50 weeks of age (-0.19) and a moderate one from 58 to 74 weeks of age (-0.36). The moderate heritability and relative independence of Kdyn indicates that this measurement could be used successfully in a breeding programme to improve shell quality and to reduce the incidence of cracks.

Animals↗
PubMed2004

Application of AFLP technology to radiation hybrid mapping.

We have investigated the use of AFLP technology as a tool for the high throughput enrichment of Radiation Hybrid (RH) maps. The 3000 rad TM112 bovine RH panel was assayed with 37 EcoRI/TaqI AFLP primer combinations. The number of selective nucleotides used during PCR was increased to seven, to reduce the complexity of the AFLP profile and minimise the overlap between hamster and bovine bands co-amplified from hybrid cell clones. Seven-hundred-forty-seven bovine AFLP bands were amplified that could be distinguished following electrophoresis. Repeatability was tested within and between laboratories on independent template preparations and an error rate of 1.3% found. Two-point linkage analysis clustered 428 AFLP fragments in 39 linkage groups of at least 4 markers. Multi-point maps were constructed for 5 sample linkage groups. The study demonstrated that the AFLP approach could be used to rapidly screen for the most informative clones during panel construction and to increase the number of markers on RH maps, which could be useful for joining linkage groups formed by other markers. The use of AFLP markers as anchor points between existing RH maps and other physical maps, such as BAC contigs, is also discussed.

Animals↗
PubMed2004

A study of association between genetic markers in candidate genes and reproductive traits in one generation of a commercial broiler breeder hen population.

Markers of alleles for three physiological candidate genes for reproductive traits, growth hormone (GHR), gonadotropin-releasing hormone receptor (GNRHR) and neuropeptide Y (NPY) were assessed for the association with the total egg production, number of double-yolked eggs and age at first egg in a single generation of a broiler breeder (Gallus gallus) pedigree dam line. Single-nucleotide polymorphisms and deletions were detected in the GHR, GNRHR and NPY genes. Genotypes were identified using a PCR-RFLP assay. The frequency of restriction enzyme+/-alleles in the population was for GHR 0.68 (NspI-) and 0.32 (NspI+), for NPY 0.78 (DraI+) and 0.22 (DraI-) and for GNRHR 0.54 (Bpu1102I+) and 0.46 (Bpu1102I-). Trait data from a total of 772 hens in 67 sire families from one generation of the pedigree dam line were recorded. However, the analysis used only the offspring of heterozygous sires to reduce the influence of selection and genetic background (n=33 sire families for GHR; n=14 sire families for NPY; n=36 sire families for GNRHR). A dominance effect of NPY on age at first egg and an additive effect of GNRHR on the number of double-yolked eggs were found (P<0.05).

Animals↗
PubMed2003

Bone strength during growth: influence of growth rate on cortical porosity and mineralization.

Although it is well accepted that bone architecture adapts to withstand the loads placed on it, the manner in which this occurs in the immature growing skeleton is not fully understood. To investigate the possible mechanisms, we have compared morphometric differences between tibiae from chickens with fast and those with slow growth potential and also distinguished between the effects of genetic potential and growth rate on their impact on bone quality. Two different fast-growing (ad lib modern) strains, one additionally feed-restricted and one slow-growing (control) strain of chicken, were compared at 15 and 42 days of age. The ad lib modern strains had similar final body weights and were approximately twice the weight of the control and restricted-fed birds. Tibiae from the control and restricted birds had a higher ash content and lower porosity than the ad lib modern strain at 42 days. The porosity was a result of rapid primary osteon formation at the periosteal surface and incomplete infilling of the resultant canal by osteoblasts. When adjusted to average body weight of contemporaries, bones from the control strain and the restricted-fed modern birds were stiffer and at least as strong as those from the fast growing ad lib-fed birds. In conclusion, rapid bone deposition at the periosteal surface was associated with decreased mineralization, increased cortical porosity, and altered biomechanical properties. Our results also indicate that growth rate, and not genetic potential, of the fast growing birds was responsible for the rapid periosteal bone deposition.

Acid Phosphatase↗
PubMed2001

Proinflammatory cytokine expression by Theileria annulata infected cell lines correlates with the pathology they cause in vivo.

Control of Theileria annulata is currently best achieved by the use of live attenuated cell line vaccines. However, the mechanisms underlying attenuation are unclear and there is a need to rapidly produce new cell line vaccines, which could safely and effectively vaccinate cattle against tropical theileriosis. There is increasing evidence to suggest that proinflammatory cytokines produced by T. annulata infected cells play a central role in both pathology and immune evasion. This study aimed to test this hypothesis and to evaluate cytokine expression as a marker of virulence. The pathogenicity and protective efficacy of cloned T. annulata cell lines that expressed different levels of proinflammatory cytokines were compared. In two independent trials using different stocks of T. annulata, cell lines that expressed higher levels of proinflammatory cytokines induced severe reactions, and in some cases death, when used to vaccinate groups of cattle. In contrast, low cytokine expressing lines induced low post-vaccinal reactions. The results clearly demonstrated that cytokine expression by T. annulata infected cells could be used as a marker of virulence and provided strong evidence to support a role for cytokines in the induction of pathology. Both high and low cytokine expressing cell lines protected cattle against heterologous challenge infection, offering the possibility of using cytokine expression to rapidly select new safe, potent vaccines against tropical theileriosis without the need for culture attenuation.

Animals↗
PubMed2001

Age-related changes in fear, sociality and pecking behaviours in two strains of laying hen.

1. Two lines of commercial hybrid layers (Tetra and ISA Brown) were reared from hatch to 30 weeks of age in groups of 8. The objectives of the experiment were to evaluate the significance of the different selection practices involved in the development of the lines and to assess the potential association between selected behavioural states and the potential for feather damage and cannibalism. 2. Behavioural tests related to fear (tonic immobility, novel object, open field), sociality (runway, proximity in the home pen) and pecking (feather bunch and focal observations of inter-bird and environmental pecking) were conducted at 0 to 2, 5 to 7, 12 to 14, 19 to 21 and 29 to 31 weeks of age. Scan sampling of general behaviour was also conducted at these ages. 3. Underlying sociality was greater in Tetras than in ISA Brown hens. 4. There were no apparent overall strain differences in fearfulness although ISA Brown hens showed significantly longer tonic immobility fear reactions than Tetras at 31 weeks of age. 5. ISA Brown hens gave and received more gentle pecks than Tetra hens whereas preening was commoner among Tetras. There were no strain differences in the number of pecks at litter or food. 6. As birds aged they showed less avoidance of novel objects and Tetras, though not ISA Browns, showed progressively shorter tonic immobility responses. Birds of both strains spent less time resting, more foraging (pecking and scratching) and pecked more at the feather bunch at older ages. 7. Measures taken in the TI, open field, runway (social affiliation) and feather bunch tests were stable over time whereas focal observations of pecking at hens and the environment were not. 8. Factor Analysis showed that 3 factors defined by the novel object test, environmental pecking and pecking ata feather bunch explained most of the variation in the correlation matrix between summary measures for the 8 behavioural traits.

Age Factors↗
PubMed2000

Effects of repeated restraint in Japanese quail genetically selected for contrasting adrenocortical responses.

Behavioral and adrenocortical responses to repeated mechanical restraint were compared in 28-day-old to 31-day-old male Japanese quail from two genetic lines divergently selected for reduced (low stress, LS) or exaggerated (high stress, HS) plasma corticosterone (C) responses to brief immobilization. Restraint in a metal crush cage for 5 min elicited immobility and silence in all the birds. Circulating C levels were considerably higher in quail of both lines following restraint than in the undisturbed controls of either line. As expected, both the behavioral and physiological effects were more pronounced in HS than in LS birds. Struggling increased with repeated restraint in HS and LS quail, thus suggesting behavioral habituation to the stressor in both lines. On the other hand, a line effect on the pattern of adrenocortical responses was revealed upon subtracting the change in plasma C concentrations from Day 1 to Day 4 in the undisturbed controls from the corresponding change in restrained birds. Thus, unlike LS quail, in which there were no detectable effects of repeated restraint, the adrenocortical responses of HS birds showed evidence of experience-dependent sensitization. Our results demonstrate the importance of the background genome in determining the patterns of the behavioral and adrenocortical responses elicited by repeated exposure to stressful stimulation. The present results and those of previous studies could be explained in one or both of two ways: that underlying fearfulness is lower in LS than HS quail or that they adopt active or passive coping strategies, respectively. Our findings may also have important implications for poultry welfare and productivity. @ 2000 Elsevier Science Inc.

Adrenal Cortex↗
PubMed2000

Differences in gene density on chicken macrochromosomes and microchromosomes.

The chicken karyotype comprises six pairs of large macrochromosomes and 33 pairs of smaller microchromosomes. Cytogenetic evidence suggests that microchromosomes may be more gene-dense than macrochromosomes. In this paper, we compare the gene densities on macrochromosomes and microchromosomes based on sequence sampling of cloned genomic DNA, and from the distribution of genes mapped by genetic linkage and physical mapping. From these different approaches we estimate that microchromosomes are twice as gene-dense as macrochromosomes and show that sequence sampling is an effective means of gene discovery in the chicken. Using this method we have also detected a conserved linkage between the genes for serotonin 1D receptor (HTR1D) and the platelet-activating factor receptor protein gene (PTAFR) on chicken chromosome 5 and human chromosome 1p34.3. Taken together with its advantages as an experimental animal, and public access to genetic and physical mapping resources, the chicken is a useful model genome for studies on the structure, function and evolution of the vertebrate genome.

Animals↗
PubMed2000

Dietary effects on bone quality and turnover, and Ca and P metabolism in chickens.

The responses of skeletal health and blood calcium (Ca) and phosphorus (P) status to different dietary calcium and available P (avP) contents were examined in 2-week-old chickens. High avP content resulted in more inorganic P (P(i)) and less ionised Ca (Ca(2+)) in the blood. Birds on low Ca and high avP diets showed a higher incidence of tibial dyschondroplasia and hypocalcaemic rickets and were therefore assumed to be hypocalcaemic. However the molar Ca:P ratio in bone was closer to the expected 1.67:1 in diets high in avP. No significant dietary mineral content effect was found on bone mineral content, or breaking strength, within the range of diets used. Results suggest that variations in molar Ca:P ratios in bone have little effect on mechanical competence, and that diets for this strain should be higher in Ca, and could be lower in avP, than current recommendations.

Amino Acids↗
PubMed2000

Skeletal development in the meat-type chicken.

1. This study ascertained how bone of modern meat-type chickens develops under typical commercial conditions and compares development with that in genetic precursor stock. 2. A modern fast-growing selected strain and a slower-growing control strain were used. Birds were weighed weekly. A random sample was taken from each population at a range of ages up to 39 d. 3. A tibiotarsus from each bird was X-rayed and its dimensions and estimated resistance to bending were determined. Cortical bone samples were ashed to measure total mineral, calcium and phosphorus content. Cortical samples were also taken for porosity assessment. 4. As expected, the selected strain grew faster and heavier than the control strain. Despite this, both strains demonstrated similar periods of rapid bone formation (days 4 to 18) and mineralisation (days 4 to 11), and achieved similar estimates of resistance to bending. 5. However, cortical bone of the selected strain was less well mineralised and more porous than that of the control strain and showed a significant increase in the molar Ca:P ratios above the expected range of values during the first 2 to 3 weeks of life. 6. Despite production of bones with the correct dimensions for load support, the relatively poor density and mineral content of bone in the selected strain is likely to reduce effective breaking strength of the tibiotarsus. Possible reasons may be either inadequate dietary supply of Ca and P or impaired utilisation of the minerals due to a rapid growth rate or genetic factors.

Animals↗
PubMed2000

A chromosome-based model for estimating the number of conserved segments between pairs of species from comparative genetic maps.

Comparative genetic maps of two species allow insights into the rearrangements of their genomes since divergence from a common ancestor. When the map details the positions of genes (or any set of orthologous DNA sequences) on chromosomes, syntenic blocks of one or more genes may be identified and used, with appropriate models, to estimate the number of chromosomal segments with conserved content conserved between species. We propose a model for the distribution of the lengths of unobserved segments on each chromosome that allows for widely differing chromosome lengths. The model uses as data either the counts of genes in a syntenic block or the distance between extreme members of a block, or both. The parameters of the proposed segment length distribution, estimated by maximum likelihood, give predictions of the number of conserved segments per chromosome. The model is applied to data from two comparative maps for the chicken, one with human and one with mouse.

Animals↗
PubMed1999

The dynamics of chromosome evolution in birds and mammals.

Comparative mapping, which compares the location of homologous genes in different species, is a powerful tool for studying genome evolution. Comparative maps suggest that rates of chromosomal change in mammals can vary from one to ten rearrangements per million years. On the basis of these rates we would expect 84 to 600 conserved segments in a chicken comparison with human or mouse. Here we build comparative maps between these species and estimate that numbers of conserved segments are in the lower part of this range. We conclude that the organization of the human genome is closer to that of the chicken than the mouse and by adding comparative mapping results from a range of vertebrates, we identify three possible phases of chromosome evolution. The relative stability of genomes such as those of the chicken and human will enable the reconstruction of maps of ancestral vertebrates.

Animals↗
PubMed1999

Ability of laying hens to jump between perches: individual variation and the effects of perch separation and motivation on behaviour.

1. This study investigated the ability and the behaviour of laying hens jumping between perches 2 different distances apart using hungry and satiated birds to determine whether behaviour and success were related to motivation. 2. Four groups of 10 birds (Lohmann brown) trained to jump from one perch to another were subjected 4 times to each of the experimental treatments (2 perches with a distance of either 50 or 150 cm between them) whilst either hungry or satiated, controlling for time of day and order of presentation. 3. The behaviour of each bird on the 1st perch was observed for a maximum of 2 min or until the bird jumped from the perch. The outcome of each jump, number of head movements and steps, incidence and duration of calling, and activity score were recorded. 4. The probability of birds jumping was less at the greater distance and was not affected significantly by other experimental factors. 5. Head movements were more frequent in birds which jumped, at the shorter distance, in motivated (hungry) birds and in the morning rather than the afternoon. 6. More stepping was performed by birds which jumped and at the shorter distance; there was no significant effect of motivation or time of day on stepping rate. 7. Birds called more at the greater distance and this was interpreted as indicative of frustration. 8. Subjective scores for activity were lower when perches were separated by the greater distance and when birds were satiated (less motivated) rather than hungry. 9. Agitated head movements and stepping activity thus occurred mainly when birds were motivated and on the point of jumping whereas calling was associated with an apparent inability or unwillingness to jump.

Animals↗
PubMed1999

Analysis of telomere length in Dolly, a sheep derived by nuclear transfer.

We have used a (TTAGGG) oligonucleotide probe to demonstrate that ovine telomeres are composed of (TTAGGG) repeat arrays and to compare the terminal restriction fragment lengths of sheep derived by natural mating and nuclear transfer. Here we show that ovine somatic telomeres decrease in length with age, and that Dolly, derived by the transfer of 6-year-old adult somatic nucleus, exhibits diminished terminal restriction fragment lengths. The decrease is consistent with the age of the donor tissue and telomere erosion during in vitro culture. Nuclear transfer does not restore telomere lengths. Dolly otherwise appears physiologically and phenotypically normal for her breed and age. We further report on apparent telomere lengthening in sheep, occurring during the first year in naturally derived lambs.

Journal Article↗