Welsh Mountain Sheep Research Articles

Genotyping and Whole-Genome Resequencing of Welsh Sheep Breeds Reveal Candidate Genes and Variants for Adaptation to Local Environment and Socioeconomic Traits.

BackgroundAdvances in genetic tools applied to livestock breeding has prompted research into the previously neglected breeds adapted to harsh local environments. One such group is the Welsh mountain sheep breeds, which can be farmed at altitudes of 300 m above sea level but are considered to have a low productive value because of their poor wool quality and small carcass size. This is contrary to the lowland breeds which are more suited to wool and meat production qualities, but do not fare well on upland pasture. Herein, medium-density genotyping data from 317 individuals representing 15 Welsh sheep breeds were used alongside the whole-genome resequencing data of 14 breeds from the same set to scan for the signatures of selection and candidate genetic variants using haplotype- and SNP-based approaches.ResultsHaplotype-based selection scan performed on the genotyping data pointed to a strong selection in the regions of GBA3, PPARGC1A, APOB, and PPP1R16B genes in the upland breeds, and RNF24, PANK2, and MUC15 in the lowland breeds. SNP-based selection scan performed on the resequencing data pointed to the missense mutations under putative selection relating to a local adaptation in the upland breeds with functions such as angiogenesis (VASH1), anti-oxidation (RWDD1), cell stress (HSPA5), membrane transport (ABCA13 and SLC22A7), and insulin signaling (PTPN1 and GIGFY1). By contrast, genes containing candidate missense mutations in the lowland breeds are related to cell cycle (CDK5RAP2), cell adhesion (CDHR3), and coat color (MC1R).ConclusionWe found new variants in genes with potentially functional consequences to the adaptation of local sheep to their environments in Wales. Knowledge of these variations is important for improving the adaptative qualities of UK and world sheep breeds through a marker-assisted selection.

Optimising Large Animal Models of Sustained Atrial Fibrillation: Relevance of the Critical Mass Hypothesis.

BackgroundLarge animal models play an important role in our understanding of the pathophysiology of atrial fibrillation (AF). Our aim was to determine whether prospectively collected baseline variables could predict the development of sustained AF in sheep, thereby reducing the number of animals required in future studies. Our hypothesis was that the relationship between atrial dimensions, refractory periods and conduction velocity (otherwise known as the critical mass hypothesis) could be used for the first time to predict the development of sustained AF.MethodsHealthy adult Welsh mountain sheep underwent a baseline electrophysiology study followed by implantation of a neurostimulator connected via an endocardial pacing lead to the right atrial appendage. The device was programmed to deliver intermittent 50 Hz bursts of 30 s duration over an 8-week period whilst sheep were monitored for AF.ResultsEighteen sheep completed the protocol, of which 28% developed sustained AF. Logistic regression analysis showed only fibrillation number (calculated using the critical mass hypothesis as the left atrial diameter divided by the product of atrial conduction velocity and effective refractory period) was associated with an increased likelihood of developing sustained AF (Ln Odds Ratio 26.1 [95% confidence intervals 0.2–52.0] p = 0.048). A receiver-operator characteristic curve showed this could be used to predict which sheep developed sustained AF (C-statistic 0.82 [95% confidence intervals 0.59–1.04] p = 0.04).ConclusionThe critical mass hypothesis can be used to predict sustained AF in a tachypaced ovine model. These findings can be used to optimise the design of future studies involving large animals.

Critical factors for non-surgical artificial insemination in sheep

USDA National Animal Germplasm Program is responsible for collecting germplasm from agriculturally relevant species in the US and developing methods for its efficient and effective storage and utilization. Lack of low cost and effective use of assisted reproductive technologies in sheep has been problematic and impacts the effective use of germplasm. While ram semen can be cryopreserved, methods for its use via non-surgical artificial insemination (AI) are not well developed. Consequently, we performed multiple trials to identify methods that result in ewe fertility when using cryopreserved ram semen, synchronized estrous, and timed non-surgical AI to identify factors that influence fertility. Experiment 1 used Black Welsh Mountain sheep and resulted in 51 % of bred ewes lambing. Statistical analysis showed age of the ewe, ram, and interaction of ewe age X time of AI effects were not significant. However, AI time relative to CDIR removal impacted fertility (P < 0.001). In a second experiment using Rambouillet, 11 % of artificially inseminated ewes lambed. A statistical model that included the effects of AI time, ewe age, and the AI time X ewe age interaction was not significant (P > 0.05). Experiment 3 utilized both breeds of sheep and resulted in mean fertility of 48 and 13 % for Black Welsh Mountain and Rambouillet, respectively. Analysis of the fertility results in experiment 3 included the effects of ewe breed, time of AI, ram, and the 2 and 3-way interaction terms. The three-way interaction of ewe breed X ewe age class X AI time was significant (P < 0.001) as were all two way interactions (P < 0.05). Identification of this 3-way interaction indicates that AI methodology is complicated and requires tailoring to specific breeds, ewe ages classes, and AI timing. These results suggest, at least partially, reasoning for highly inconsistent results reported in previous literature and the difficulty in applying the technology in the field. Potential approaches to address these important interactions in search of a more predictable result are discussed.

P935Can we predict the occurrence of persistent atrial fibrillation in large animal models to improve study efficiency?

Abstract Funding Acknowledgements British Heart Foundation Project Grant FS/17/54/33126 Background A key consideration when using animals in research is maximising experimental efficiency to minimise the number of animals required. Large animal models have proven an invaluable tool for establishing pathophysiological mechanisms underpinning atrial fibrillation (AF) and testing novel therapeutics, however animals may be resistant to developing the arrhythmias required. While the relationships between atrial refractory periods, conduction velocity, surface area, and vulnerability to fibrillation have been established in clinical practice, these parameters are not regularly used to design animal studies of persistent AF (PsAF). Purpose We investigated whether routinely collected baseline parameters could be used to improve experimental efficiency in an ovine model, by predicting the development of PsAF as opposed to arrhythmia resistance. The aims were to: reduce the number of animals used in future studies, and avoid prolonged experiments in animals likely to be resistant to AF. Methods All procedures were conducted with respect to the Animals [Scientific Procedures] Act, UK, 1986; and were approved by the local ethical review board. The ovine model consisted of healthy adult Welsh mountain sheep that underwent implantation of a neurostimulator connected via an endocardial pacing lead to the right atrial appendage. The device was programmed to deliver intermittent 30 second bursts of 50Hz and sheep were monitored over an eight week period for PsAF. Eight variables were collected at time of implant including weight (kg), left atrial diameter (LAD; cm), P wave duration (msec), PR interval (msec), atrial effective refractory period (ERP; msec), atrial conduction velocity (CV; m/s), AF inducibility with 50Hz bursts (secs), and rate threshold of atrial action potential alternans (msec). Analysis of the data was performed using multiple logistic regression and receiver-operator characteristic (ROC) curves. Regression coefficients are presented as natural logarithm of odds ratios (OR) with 95% confidence intervals (CI). Results Seventeen sheep were included in this study. Five (29%) developed PsAF whereas twelve (71%) were resistant (non-sustained or no AF). Univariate analysis found none of the parameters alone could predict PsAF, however ERP (OR -0.05, CI -.01 to 0.01, p = 0.089) and LAD (OR 8.1, CI -1.6 to 17.5, p = 0.095) suggested a combination may be predictive. A multivariate analysis using Fibrillation number (calculated as LAD / [ERP X CV]) was predictive (OR 26.9, CI 1.1 to 52.7; p = 0.04], with an area under ROC curve of 0.85 (p = 0.027). Conclusions Fibrillation number can predict the development of PsAF in healthy sheep. Practically speaking, this means animals with: a larger LAD, shorter ERP and slower CV are more likely to develop PsAF. These findings can be used to optimise the design of future studies, particularly by reducing the number of animals required.

Response-Inhibition During Problem Solving in Sheep (Ovis Aries)

Response inhibition is a behavioural skill that is important for flexible behaviour and appropriate decision making. It requires the suppression of a prepotent, but inappropriate action, in order to achieve a more advantageous outcome. Response inhibition has been tested in many animal species using the cylinder task. This task requires the self-driven inhibition of an impulse to obtain a visible food reward via a detour, rather than a direct but blocked route. We have shown previously using the stop-signal task that sheep can successfully interrupt an already-started response, if a reward is going to be restricted. However, it is not known if sheep can show self-driven response inhibition in a task that provides a reward independent of performance. Here we tested two groups of sheep on the cylinder task (11 Lleyn sheep: aged 8 months; 8 Welsh mountain sheep aged ~8 years old). Sheep were trained using an opaque cylinder and all sheep successfully learned the task. When response inhibition was tested using the transparent cylinder, all sheep performed significantly better than chance, but the older sheep showed a reduced number of correct responses compared to the young sheep (72.5±5.0% and 86.4±4.3% respectively). The results show that sheep have a mechanism for self-regulating their actions in order to retrieve food faster.

Response-inhibition during problem solving in sheep

Author(s): Knolle, Franziska; Goncalves, Rita P.; Davies, Emma L.; Duff, Amy R.; Morton, A. Jennifer | Abstract: Response inhibition is a behavioural skill that is important for flexible behaviour and appropriate decision making. It requires the suppression of a prepotent, but inappropriate action, in order to achieve a more advantageous outcome. Response inhibition has been tested in many animal species using the cylinder task. This task requires the self-driven inhibition of an impulse to obtain a visible food reward via a detour, rather than a direct but blocked route. We have shown previously using the stop-signal task that sheep can successfully interrupt an already-started response, if a reward is going to be restricted. However, it is not known if sheep can show self-driven response inhibition in a task that provides a reward independent of performance. Here we tested two groups of sheep on the cylinder task (11 Lleyn sheep: aged 8 months; 8 Welsh mountain sheep aged ~8 years old). Sheep were trained using an opaque cylinder and all sheep successfully learned the task. When response inhibition was tested using the transparent cylinder, all sheep performed significantly better than chance, but the older sheep showed a reduced number of correct responses compared to the young sheep (72.5±5.0% and 86.4±4.3% respectively). The results show that sheep have a mechanism for self-regulating their actions in order to retrieve food faster.n

"Patient reported outcomes" following experimental surgery-using telemetry to assess movement in experimental ovine models.

ABSTRACTMany potential treatments for orthopedic disease fail at the animal to human translational hurdle. One reason for this failure is that the majority of pre‐clinical outcome measurements emphasize structural changes, such as gross morphology and histology, and do not address pain or its alleviation, which is a key component of treatment success in man. With increasing emphasis on “patient reported outcome measurements (PROM)” in clinical practice, in this study we have used two different telemetric methods (geolocation and Fitbark activity trackers, Kansas City, MO) to measure movement behavior, i.e., an indirect PROM, in an ovine osteoarthritis induction and an osteochondral defect model performed in adult female Welsh Mountain sheep. This study demonstrates that both systems can be used to track movement and activity of experimental sheep before and after surgery and that the Geolocator system recorded a decrease in distance moved and activity at the end of the experimental period in both models. The Fitbark activity tracker also recorded significant alterations in movement behavior at the end of these studies and this method of recording showed a correlation between Fitbark data and radiography, macroscopic and histological scoring (well recognized outcome measurements), particularly in animals with large (10 mm) defects, i.e., more severe pathology. These results suggest that telemetry is able to track movement behavior in experimental sheep and that the methodology should be considered for inclusion in outcome measures in preclinical orthopedic research. © 2017 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:1498–1507, 2018.

Increased Ca buffering underpins remodelling of Ca2+ handling in old sheep atrial myocytes.

Key points Ageing is associated with an increased risk of cardiovascular disease and arrhythmias, with the most common arrhythmia being found in the atria of the heart.Little is known about how the normal atria of the heart remodel with age and thus why dysfunction might occur.We report alterations to the atrial systolic Ca2+ transient that have implications for the function of the atrial in the elderly.We describe a novel mechanism by which increased Ca buffering can account for changes to systolic Ca2+ in the old atria.The present study helps us to understand how the processes regulating atrial contraction are remodelled during ageing and provides a basis for future work aiming to understand why dysfunction develops. Many cardiovascular diseases, including those affecting the atria, are associated with advancing age. Arrhythmias, including those in the atria, can arise as a result of electrical remodelling or alterations in Ca2+ homeostasis. In the atria, age‐associated changes in the action potential have been documented. However, little is known about remodelling of intracellular Ca2+ homeostasis in the healthy aged atria. Using single atrial myocytes from young and old Welsh Mountain sheep, we show the free Ca2+ transient amplitude and rate of decay of systolic Ca2+ decrease with age, whereas sarcoplasmic reticulum (SR) Ca content increases. An increase in intracellular Ca buffering explains both the decrease in Ca2+ transient amplitude and decay kinetics in the absence of any change in sarcoendoplasmic reticulum calcium transport ATPase function. Ageing maintained the integrated Ca2+ influx via I Ca‐L but decreased peak I Ca‐L. Decreased peak I Ca‐L was found to be responsible for the age‐associated increase in SR Ca content but not the decrease in Ca2+ transient amplitude. Instead, decreased peak I Ca‐L offsets increased SR load such that Ca2+ release from the SR was maintained during ageing. The results of the present study highlight a novel mechanism by which increased Ca buffering decreases systolic Ca2+ in old atria. Furthermore, for the first time, we have shown that SR Ca content is increased in old atrial myocytes.

Peripheral Blood Mononuclear Cells Enhance Cartilage Repair in in vivo Osteochondral Defect Model.

This study characterized peripheral blood mononuclear cells (PBMC) in terms of their potential in cartilage repair and investigated their ability to improve the healing in a pre-clinical large animal model. Human PBMCs were isolated with gradient centrifugation and adherent PBMC’s were evaluated for their ability to differentiate into adipogenic, chondrogenic and osteogenic lineages and also for their expression of musculoskeletal genes. The phenotype of the PBMCs was evaluated using Stro-1, CD34, CD44, CD45, CD90, CD106, CD105, CD146 and CD166 cell surface markers. Osteochondral defects were created in the medial femoral condyle (MFC) of 24 Welsh mountain sheep and evaluated at a six month time point. Four cell treatment groups were evaluated in combination with collagen-GAG-scaffold: (1) MSC alone; (2) MSCs and PBMCs at a ratio of 20:1; (3) MSCs and PBMC at a ratio of 2:1 and (4) PBMCs alone. Samples from the surgical site were evaluated for mechanical properties, ICRS score and histological repair. Fresh PBMC samples were 90% positive for hematopoietic cell surface markers and negative for the MSC antibody panel (<1%, p = 0.006). However, the adherent PBMC population expressed mesenchymal stem cell markers in hypoxic culture and lacked CD34/45 positive cells (<0.2%). This finding demonstrated that the adherent cells had acquired an MSC-like phenotype and transformed in hypoxia from their original hematopoietic lineage. Four key genes in muskuloskeletal biology were significantly upregulated in adherent PBMCs by hypoxia: BMP2 4.2-fold (p = 0.0007), BMP6 10.7-fold (p = 0.0004), GDF5 2.0-fold (p = 0.002) and COL1 5.0-fold (p = 0.046). The monolayer multilineage analysis confirmed the trilineage mesenchymal potential of the adherent PBMCs. PBMC cell therapy was equally good as bone marrow MSC therapy for defects in the ovine large animal model. Our results show that PBMCs support cartilage healing and oxygen tension of the environment was found to have a key effect on the derivation of a novel adherent cell population with an MSC-like phenotype. This study presents a novel and easily attainable point-of-care cell therapy with PBMCs to treat osteochondral defects in the knee avoiding any cell manipulations outside the surgical room.

Assessment of genetic relationship between six populations of Welsh Mountain sheep using microsatellite markers

This study investigated the genetic relationship between 6 populations of Welsh Mountain sheep: 5 phenotypic breed-types within the Welsh Mountain (WM) sheep breed, which have each been bred in specific geographic areas of Wales, and the Black Welsh Mountain sheep breed. Based on DNA analysis using 8 microsatellite markers, observed heterozygosity levels were similar to those expected in livestock populations subjected to selective breeding (0.530-0.664), and all but one population showed evidence of inbreeding. Using Bayesian cluster and Neighbor-joining analyses, the Black Welsh Mountain sheep were identified as being the outlier group, and the remaining groups could be categorized into five distinct sub-populations, which reflects the geographical separation seen between these populations.

Understanding the concept of a reflective surface: can sheep improve navigational ability through the use of a mirror?

Mirror image-induced stimulation and the ability to use the mirror to improve navigational ability for the purpose of object location are considered measures of animal cognitive ability. The purpose of this study was to assess these cognitive abilities in sheep (Ovis aries) as part of a larger programme profiling the cognitive ability of this animal species. Three separate groups of sheep [(n=29); 10 Welsh Mountain, 8 Norfolk Horned and 11 Borderdale] were trained (≥80% criterion) to locate a salient object (yellow bucket containing cereal-based food) in one of two possible positions, from one of two possible starting points. Each group of sheep was then divided into two sub-groups. One sub-group was exposed to a mirror over a period of 15days (mirror exposed), whilst the other group remained mirror naïve. All animals were then retested within the choice maze using the mirror, where two out of the possible four bucket positions were now 'apparent' (as reflections in the mirror), in order to assess whether mirror-exposed animals had a more accurate representation of the real bucket position. Sheep exhibited two out of the three archetypal stages of mirror-induced behaviour, namely social/exploratory and contingency behaviour, with differences existing between breeds. Welsh Mountain sheep spent significantly more time fixating on the self-image and touching the self-image with their muzzle than the other two breeds. During the test phase, no overall differences in performance were observed between the mirror-exposed and mirror-naïve groups. However, Welsh Mountain sheep did perform significantly more correct responses overall, compared to the other two breeds. Although the data did not convincingly demonstrate that sheep could use a reflective surface to improve their navigational ability, the observed differences between groups suggests that some breeds of sheep may demonstrate better navigational ability as well as having a greater engagement with the self-image than others.

218 Action Potential Alternans in the Ageing Ovine Atria

BackgroundThe incidence of atrial fibrillation (AF) has a steep relationship with age. AF prevalence in persons aged over 85 exceeds 15% in European cohorts. The basis for the exaggerated vulnerability...

Collagen fibre implant for tendon and ligament biological augmentation. In vivo study in an ovine model

Although most in vitro studies indicate that collagen is a suitable biomaterial for tendon and ligament tissue engineering, in vivo studies of implanted collagen for regeneration of these tissues are still lacking. The objectives of this study were the following: (1) to investigate the regeneration of the central third of the ovine patellar tendon using implants made of an open array of collagen fibres (reconstituted, extruded bovine collagen); and (2) to compare two collagen crosslinking chemistries: carbodiimide and carbodiimide associated with ethyleneglycoldiglycidylether. Forty-eight Welsh Mountain sheep were operated on their right hind leg. The central third of patellar tendon was removed and substituted with carbodiimide (n=16) and carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants (n=16). In the control group the defect was left empty (n=16). The central third of contralateral unoperated tendons was used as positive controls. Half of the sheep in each group were killed at 3- and 6-month time points. After proper dissection, tendon sub-units (medial, central and lateral) were tested to failure (n=6 for each group), whilst 2 non-dissected samples were used for histology. Both the implants had significantly lower stress to failure and modulus with respect to native tendon at both 3- and at 6-month time points. The implants did not statistically differ in stress to failure, whilst carbodiimide-crosslinked implants had significantly higher modulus than carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants both at 3 and at 6months. Histology showed carbodiimide-crosslinked implants to have a better integration with the native tendon than carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants. Carbodiimide-crosslinked implants appeared partially resorbed and showed increased tissue ingrowth with respect to carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants. To deliver collagen implants as an open array of fibres allows optimal tendon-implant integration and good ingrowth of regenerated tissue. In the present study the resorption rate of both the examined implants was too low due to the high level of crosslinking. This led to only minor substitution of the implant with regenerated tissue, which in turn produced a low-strength implanted region. Further studies are needed to find the right balance between strength and resorption rate of collagen fibres.

Impact on sward composition and stock performance of grazing Molinia-dominant grassland

A comparative experiment was conducted to test the extent to which grazing of rank Molinia caerulea-dominated grassland increases botanical diversity and improves animal performance. The study was carried out on an area of under-grazed Molinia-dominant pasture that had not been stocked for 20 years. Three treatments were compared from 2001 until 2008: (1) no grazing, (2) grazing by Welsh Mountain sheep and (3) grazing by Welsh Black heifers. Patterns of change in sward surface composition across the grazing season were consistent with greater consumption of Molinia by the cattle, but there was little evidence of management regime influencing changes in sward composition year-on-year. There was a significant effect of year on animal performance ( P < 0.001). Although the growth rates of the heifers improved over the course of the first three years of the experiment, this performance was not sustained. In contrast, any weight changes for the sheep were positive. The results highlight the slow pace of change within upland swards, and the need to develop site-specific grazing guidelines.

Redox modulation of the fetal cardiovascular defence to hypoxaemia

Episodes of hypoxia in utero present a potentially serious challenge to the fetus, but are counteracted by defence responses including marked redistribution of blood flow from peripheral circulations to the brain. Here, we report the novel observation that the oxidant tone is an important modulator of this cardiovascular defence. Using pregnant Welsh Mountain sheep surgically prepared for long-term recording, we investigated in vivo the effects on the fetal cardiovascular defence to acute hypoxaemia of fetal treatment with the antioxidant vitamin C. The mechanisms via which vitamin C may affect the vascular oxidant tone were investigated by monitoring fetal plasma concentrations of nitrates and nitrites, by determining changes in the activity of superoxide dismutase (SOD) in fetal plasma, and by investigating the effect of vitamin C treatment on the fetal cardiovascular defence to hypoxaemia following nitric oxide (NO) synthase blockade. Fetal treatment with vitamin C markedly depressed the normal femoral constrictor response to acute hypoxaemia in the fetus (5.2 ± 1.0 vs. 1.1 ± 0.3 mmHg (ml min(-1))(-1), mean ± s.e.m.; P < 0.05) an effect which was completely restored following NO synthase blockade (6.2 ± 1.3 mmHg (ml min(-1))(-1)). Compared to saline infusion, fetal treatment with vitamin C during acute hypoxaemia also significantly increased fetal plasma SOD activity from normoxic baseline (-8.9 ± 6.5 vs. 15.0 ± 6.6% inhibition, P < 0.05) and decreased the plasma concentration ratio of nitrate:nitrite from normoxic baseline (ΔNO3(-):NO2(-); 0.15 ± 0.30 vs. -0.29 ± 0.11, P < 0.05). The data provide in vivo evidence of redox modulation of redistribution of blood flow in the fetus, part of the fetal brain sparing during acute hypoxaemic stress.

Performance of crossbred Welsh Mountain ewes in the hill environment

The Welsh Mountain sheep is a numerically important breed in the UK, but its lambs are characterised by low slaughter weights and poor carcass conformation. The reduction in stocking rates that is often associated with environmental conservation schemes, offers the potential for the use of larger ewes. Crossbreeding allows more rapid genetic change to be undertaken than would be possible from selection within breeds, and affords the potential to utilise heterosis and improve the quality of subsequent crosses with the Bluefaced Leicester. This work compared the survival and productivity of purebred Welsh Mountain ewes with a range of crossbred ewe types maintained in a hill environment.

Scrapie-resistant sheep show certain coat colour characteristics.

Susceptibility to scrapie is known to be associated with polymorphisms at the prion protein (PrP) gene, and this association is the basis of current selective programmes implemented to control scrapie in many countries. However, these programmes might have unintended consequences for other traits that might be associated with PrP genotype. The objective of this study was to investigate the relationship between PrP genotype and coat colour characteristics in two UK native sheep breeds valued for their distinctive coat colour patterns. Coat colour pattern, darkness and spotting and PrP genotype records were available for 11 674 Badgerfaced Welsh Mountain and 2338 Shetland sheep. The data were analysed with a log-linear model using maximum likelihood. Results showed a strong significant association of PrP genotype with coat colour pattern in Badgerfaced Welsh Mountain and Shetland sheep and with the presence of white spotting in Shetland sheep. Animals with the ARR/ARR genotype (the most scrapie resistant) had higher odds of having a light dorsum and a dark abdomen than the reverse pattern. The implication of these associations is that selection to increase resistance to scrapie based only on PrP genotype could result in change in morphological diversity and affect other associated traits such as fitness.

Exploration of cytoplasmic inheritance as a contributor to maternal effects in Welsh Mountain sheep

Cytoplasmic effects were investigated using a dataset comprising three breeding groups of Welsh Mountain sheep. The influences of cytoplasmic effects were investigated by comparing animal models with and without a random term representing cytoplasmic effects. The models were applied to the eight-week weight, scan weight (mean 152 days) and ultrasonically scanned muscle and fat depth. The animal model included the random effects of animals and the maternal additive genetic, maternal permanent environmental and maternal common environmental effects. In total there were 24 569, 10 509, 8389, 8369 records for the eight-week weight, scan weight, muscle depth and fat depth respectively. Four subsets were further analysed containing maternal lines with at least five, ten, fifteen and twenty animals/line. There was no evidence of cytoplasmic effects on eight-week weight and muscle depth. Cytoplasmic effects contributed 1–2% of phenotypic variance for scan-weight and fat depth, but the effect was generally non-significant (P > 0.05). As the number of animals per maternal line increased, the magnitude of cytoplasmic effects also increased for these traits. Direct heritability estimates for the eight-week weight, scan weight, muscle depth and fat depth using the full dataset were 0.18, 0.25, 0.24, and 0.21 respectively.

Exploration of cytoplasmic inheritance as a contributor to maternal effects in Welsh Mountain sheep

Exploration of cytoplasmic inheritance as a contributor to maternal effects in Welsh Mountain sheep

Analysis of data from the passive surveillance of scrapie in Great Britain between 1993 and 2002

Reports of clinical scrapie in Great Britain between January 1, 1993 and December 31, 2002 were reviewed. Scrapie was confirmed in 4142 sheep on 1099 holdings. The cumulative case and...