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Oldowan sites in primary geological context are rare in the archaeological record. Here we describe the depositional environment of Oldowan occurrences at Kanjera South, Kenya, based on field descriptions and granulometric analysis. Excavations have recovered a large Oldowan artefact sample as well as the oldest substantial sample of archaeological fauna. The deposits at Kanjera South consist of 30 m of fluvial, colluvial and lacustrine sediments. Magneto- and biostratigraphy indicate the Kanjera South Member of the Kanjera Formation was deposited during 2.3–1.92 Ma, with 2.0 Ma being a likely age for the archaeological occurrences. Oldowan artefacts and associated fauna were deposited in the colluvial and alluvial silts and sands of beds KS1–3, in the margins of a lake basin. Field descriptions and granulometric analysis of the sediment fine fraction indicate that sediments from within the main archaeological horizon were emplaced as a combination of tractional and hyperconcentrated flows with limited evidence of debris-flow deposition. This style of deposition is unlikely to significantly erode or disturb the underlying surface, and therefore promotes preservation of surface archaeological accumulations. Hominins were repeatedly attracted to the site locale, and rapid sedimentation, minimal bone weathering and an absence of bone or artefact rounding further indicate that fossils and artefacts were quickly buried.
In reproducing ewes, a periparturient breakdown of immunity is often observed to result in increased fecal egg excretion, making them the main source of infection for their immunologically naive lambs. In this study, we expanded a simulation model previously developed for growing lambs to explore the impact of the genotype (performance and resistance traits) and host nutrition on the performance and parasitism of both growing lambs and reproducing ewes naturally infected with Teladorsagia circumcincta. Our model accounted for nutrient-demanding phases, such as gestation and lactation, and included a supplementary module to manage the age structure of the ewe flock. The model was validated by comparison with published data. Because model parameters were unknown or poorly estimated, detailed sensitivity analysis of the model was performed for the sheep mortality and the level of infection, following a preliminary screening step. The parameters with the greatest effect on parasite-related outputs were those driving animal growth and milk yield. Our model enables different parasite-control strategies (host nutrition, breeding for resistance and anthelmintic treatments) to be assessed on the long term in a sheep flock. To optimize in silico exploration, the parameters highlighted by the sensitivity analysis should be refined with real data.
The incidence of recreational water-associated outbreaks in the United States has significantly increased, driven, at least in part, by outbreaks both caused by Cryptosporidium and associated with treated recreational water venues. Because of the parasite's extreme chlorine tolerance, transmission can occur even in well-maintained treated recreational water venues (e.g. pools) and a focal cryptosporidiosis outbreak can evolve into a community-wide outbreak associated with multiple recreational water venues and settings (e.g. childcare facilities). In August 2004 in Auglaize County, Ohio, multiple cryptosporidiosis cases were identified and anecdotally linked to pool A. Within 5 days of the first case being reported, pool A was hyperchlorinated to achieve 99·9% Cryptosporidium inactivition. A case-control study was launched to epidemiologically ascertain the outbreak source 11 days later. A total of 150 confirmed and probable cases were identified; the temporal distribution of illness onset was peaked, indicating a point-source exposure. Cryptosporidiosis was significantly associated with swimming in pool A (matched odds ratio 121·7, 95% confidence interval 27·4–∞) but not with another venue or setting. The findings of this investigation suggest that proactive implementation of control measures, when increased Cryptosporidium transmission is detected but before an outbreak source is epidemiologically ascertained, might prevent a focal cryptosporidiosis outbreak from evolving into a community-wide outbreak.
Composites of 8 mol% yttria-stabilized zirconia (YSZ) and titanium nitride (TiN) were obtained by mechanical mixing of commercial powders. High-density samples of (1-x) YSZ / x TiN, with x = 0, 25, 50, and 75 wt.%, were obtained by spark plasma sintering (SPS) at 1450 °C for 5 min. Surface contamination with carbon from the SPS was eliminated by diamond sawing of parallel surfaces. X-rays diffraction analyses showed that samples are composed by a mixture of the initial phases, without appreciable reaction as inferred from calculated lattice parameters. dc 4-probe electrical measurements in the 100-850°C under showed that samples have a metallic behavior, indicating that the percolation threshold was attained for the sample with the lowest content of the TiN (x=25 wt.%), which corresponds to ∼27 vol.%.
TM-QTL is a quantitative trait locus (QTL) on ovine chromosome 18 (OAR18) known to affect loin muscling in Texel sheep. Previous work suggested that its mode of inheritance is consistent with paternal polar overdominance, but this has yet to be formally demonstrated. This study used purebred Texel sheep segregating for TM-QTL to confirm its presence in the chromosomal region in which it was first reported and to determine its pattern of inheritance. To do so, this study used the first available data from a Texel flock, which included homozygote TM-QTL carriers (TM/TM; n=34) in addition to homozygote non-carriers (+/+; n=40 and, heterozygote TM-QTL-carriers inheriting TM-QTL from their sire (TM/+; n=53) or their dam (+/TM; n=17). Phenotypes included a wide range of loin muscling, carcass composition and tissue distribution traits. The presence of a QTL affecting ultrasound muscle depth on OAR18 was confirmed with a paternal QTL effect ranging from +0.54 to +2.82 mm UMD (s.e. 0.37 to 0.57 mm) across the sires segregating for TM-QTL. Loin muscle width, depth and area, loin muscle volume and dissected M. longissimus lumborum weight were significantly greater for TM/+ than +/+ lambs (+2.9% to +7.9%; P<0.05). There was significant evidence that the effect of TM-QTL on the various loin muscling traits measured was paternally polar overdominant (P<0.05). In contrast, there was an additive effect of TM-QTL on both live weight at 20 weeks and carcass weight; TM/TM animals were significantly (P<0.05) heavier than +/+ (+11.1% and +7.3%, respectively) and +/TM animals (+11.9% and +11.7%, respectively), with TM/+ intermediate. Weights of the leg, saddle and shoulder region (corrected for carcass weight) were similar in the genotypic groups. There was a tendency for lambs inheriting TM-QTL from their sire to be less fat with slightly more muscle than non-carriers. For example, carcass muscle weight measured by live animal CT-scanning was 2.8% higher in TM/TM than +/+ lambs (P<0.05), carcass muscle weight measured by carcass CT-scanning was 1.36% higher in TM/+ than +/+ lambs (P<0.05), and weight of fat trimmed from the carcass cuts was significantly lower for TM/+ than +/+ lambs (−11.2%; P<0.05). No negative effects of TM-QTL on carcass traits were found. Optimal commercial use of TM-QTL within the sheep industry would require some consideration, due to the apparently different mode of action of the two main effects of TM-QTL (on growth and muscling).
Genomic prediction utilizes single nucleotide polymorphism (SNP) chip data to predict animal genetic merit. It has the advantage of potentially capturing the effects of the majority of loci that contribute to genetic variation in a trait, even when the effects of the individual loci are very small. To implement genomic prediction, marker effects are estimated with a training set, including individuals with marker genotypes and trait phenotypes; subsequently, genomic estimated breeding values (GEBV) for any genotyped individual in the population can be calculated using the estimated marker effects. In this study, we aimed to: (i) evaluate the potential of genomic prediction to predict GEBV for nematode resistance traits and BW in sheep, within and across populations; (ii) evaluate the accuracy of these predictions through within-population cross-validation; and (iii) explore the impact of population structure on the accuracy of prediction. Four data sets comprising 752 lambs from a Scottish Blackface population, 2371 from a Sarda×Lacaune backcross population, 1000 from a Martinik Black-Belly×Romane backcross population and 64 from a British Texel population were used in this study. Traits available for the analysis were faecal egg count for Nematodirus and Strongyles and BW at different ages or as average effect, depending on the population. Moreover, immunoglobulin A was also available for the Scottish Blackface population. Results show that GEBV had moderate to good within-population predictive accuracy, whereas across-population predictions had accuracies close to zero. This can be explained by our finding that in most cases the accuracy estimates were mostly because of additive genetic relatedness between animals, rather than linkage disequilibrium between SNP and quantitative trait loci. Therefore, our results suggest that genomic prediction for nematode resistance and BW may be of value in closely related animals, but that with the current SNP chip genomic predictions are unlikely to work across breeds.
Refugia-based treatment strategies aim to prolong anthelmintic efficacy by maintaining a parasite population unexposed to anthelmintics. Targeted selective treatment (TST) achieves this by treating only animals that will benefit most from treatment, using a determinant criterion (DC). We developed a mathematical model to compare various traits proposed as DC, and investigate impacts of TST and drenching frequency on sheep performance and anthelmintic resistance. Short term, decreasing the proportion of animals drenched reduced benefits of anthelmintic treatment, assessed by empty body weight (EBW), but decreased the rate of anthelmintic resistance development; each consecutive drenching had a reduced impact on average EBW and an increased impact on the rate of anthelmintic resistance emergences. The optimal DC was fecal egg count, maintaining the highest average EBW when reducing the proportion of animals drenched. Long-term, reducing the proportion of animals drenched had little impact on total weight gain benefits, across animals and years, whilst reducing drenching frequency increased it. Decreasing the frequency and proportion of animals drenched were both predicted to increase the duration of anthelmintic efficacy but reduce the total number of drenches administered before resistance was observed. TST and frequency of drenching may lead to different benefits in the short versus long term.
High temperature multi-source co-evaporation has been the most successful approach to fabricate record efficiency Cu(InGa)Se2 devices, yet many groups have been unable to replicate this success when transferring these methods to the Cu2ZnSnSe4 system. The difficulties stem from the dramatic differences in the thermochemical properties which result in decomposition and loss of volatile species, such as Zn and SnSe, at temperatures needed for growth. In co-evaporation, decomposition and element loss must be managed throughout the entire growth process, from the back contact interface to the final terminating surface of the film. The beginning and ending phases of deposition encompass different kinetic regimes suggesting a phased approach to growth may be helpful. A series of depositions with different effusion profiles were used to demonstrate the effects of decomposition during different stages of growth. Secondary phase detection can be challenging in CZTSe, but a combination of SEM imaging and thin cross-section depth profile by EDS were found to best identify and locate the secondary phases that occur during different phases of growth for co-evaporated Cu2ZnSnSe4 films.
Deposition with a uniform incident flux followed by shuttered vacuum cool-down yielded films with a ZnSe phase at the absorber/Mo interface and Cu-rich composition at the surface of the exposed film. Devices from these absorber layers never exceeded conversion efficiencies of 1%. Decomposition at the surface could be prevented by continuing effusion of Se and Sn during the cool-down of the substrate. Resulting films demonstrated more faceted grains as well as significantly improved device performance. Secondary phases that traditionally form at the back contact during the beginning of growth were minimized by decreasing the substrate temperature to 300°C during the initial stages of deposition which reduced the ZnSe formed at the Mo interface. The thermochemical origin of the secondary phases will be discussed and the performance of representative devices will be presented.
Gastrointestinal nematode parasitism is the most important disease affecting livestock production systems in developing countries, particularly small ruminant production systems. Of particular importance are infections with the strongyle Haemonchus contortus. Integrated disease control strategies are required, including improved management, nutrition and wise use of anthelmintic chemicals. Increasingly, selection of sheep or goats for improved nematode resistance is viewed as a valuable option to complement other control measures. Breeding for resistance is possible because of the existence of extensive genetic variation in resistance, both within and between breeds of sheep and goats. Such breeding schemes are most likely to be based on choice of appropriate breeds adapted to the local environmental conditions, followed by phenotypic selection for resistance. Goal and selection objective traits are likely to include performance (e.g. growth rate) under conditions of parasite challenge, faecal egg count (FEC) and measures of anaemia. With current technologies, genetic markers are likely to be too expensive and logistically difficult to incorporate into breeding schemes in tropical or developing countries. Genotype by environment interactions may be expected, particularly when comparing animals in environments that differ in the extent of parasite challenge or differ in the quality of available nutrition. However, there is no reason to expect antagonistic genetic relationships between performance and resistance, and selection indices should be readily constructed that improve both performance and resistance. If FEC is decreased, then pasture contamination should also decrease, leading to additional benefits for all sheep grazing the same pasture. Finally, breeding for nematode resistance should lead to lasting and sustained improvements in resistance or tolerance. There is no empirical evidence to suggest that nematodes will evolve rapidly in response to resistant hosts, and mathematical models based on genetic and biological principles also suggest that resistance should be sustainable.
A model was used to investigate two mechanisms describing reductions in food intake (anorexia) observed during gastrointestinal parasitism in lambs, and to explore relationships between anorexia and food composition. The mechanisms were either a reduction in intrinsic growth rate, leading to a consequent reduction in food intake (mechanism 1; M1), or a direct reduction in food intake (mechanism 2; M2). For both mechanisms, lambs growing from 2 to 6 months of age were modelled, with one of three levels of trickle challenge with Teladorsagia circumcincta. Scenarios were simulated for feeds varying in either protein or energy content, or both. Major differences were found between the predictions resulting from M1 and M2 on low-energy foods that constrained the intake of uninfected lambs through bulk. With M1, food intake was governed by the first operating constraint, whereas with M2 an additivity of constraints was observed. On the other foods, the duration of anorexia increased with increasing energy content of feed for M1, whilst the duration of anorexia decreased with increasing protein content of feed for M2.For foods that did not have an impact upon lambs' gastrointestinal tract capacity, published data were consistent with predictions of M2. Due to an absence of experimental data, no conclusions could be drawn for relationships between anorexia and food composition in the presence of other limiting constraints, such as bulk for low-energy foods. In conclusion, available experimental data and model predictions were consistent with anorexia having an impact directly on food intake, and with impacts of anorexia increasing with decreasing protein content.
Sheep internal parasites (nematodes) remain a major health challenge and are costly for pasture-based production systems. Most current breeding programmes for nematode resistance are based on indicator traits such as faecal egg counts (FEC), which are costly and laborious to collect. Hence, genetic markers for resistance would be advantageous. However, although some quantitative trait loci (QTL) have been identified, these QTL are often not consistent across breeds and few breeding strategies for nematode resistance in sheep are currently using molecular information. In this study, QTL for nematode resistance on ovine chromosomes (OAR) 3 and 14, previously identified in the Blackface breed, were explored using commercial Suffolk (n = 336) and Texel lambs (n = 879) sampled from terminal sire breeder flocks in the United Kingdom. FEC were used as the indicator trait for nematode resistance, and these were counted separately for Nematodirus and Strongyles genera. Microsatellite markers were used to map the QTL and the data were analysed using interval mapping regression techniques and variance component analysis. QTL for Nematodirus and Strongyles FEC were found to be segregating on OAR3 at 5% chromosome region-wide significance threshold in both Suffolk and Texel sheep, and Nematodirus FEC QTL were segregating on OAR14 in both breeds. In addition, QTL for growth traits were also found to be segregating at 5% chromosome region-wide on OAR3 and OAR14. The confirmation that FEC QTL segregate in the same position in three widely used breeds widens their potential applicability to purebred Blackface, Suffolk and Texel sheep, with benefits likely to be observed in their commercial crossbred progeny.
IgA and IgE activity against Teladorsagia circumcincta was investigated in a flock of Texel lambs following natural, mixed nematode infection among lambs. The distribution of IgA activity was similar to a gamma distribution whereas IgE activity was different. Box-Cox analysis demonstrated that X0·25 was a suitable transformation to normalise IgE responses. The transformed IgE activity was under moderate to strong genetic control. Nine different allergens were identified by proteomic analysis. Tropomyosin was selected for further analysis. IgE activity against tropomyosin was moderately heritable and associated with decreased egg counts and with reduced body weight at the time of sampling.
Sensory traits, such as juiciness and tenderness, are known to be important to the consumer and thus will influence their consumption of meat, specifically beef. These traits are difficult to measure and often require the use of taste panels to assess the complex parameters involved in the eating experience. Such panels are potentially a large source of measurement error, which may reduce the effectiveness of breeding programmes based on the data they generate. The aim of this study was to assess the quality of such taste panel-derived sensory traits as well as calculating genetic parameters and residual correlations for these traits along with a further set of traditional carcass quality traits. The study examined a sample of 443 Aberdeen Angus-cross animals collected from 14 breeder–finisher farms throughout Scotland. To assess the quality of the taste panel measurements, three consistency statistics were calculated: (i) panel-member consistency, i.e. the extent to which an individual panel member varied in their scoring for a given trait over the period of the experiment; (ii) repeatability, i.e. the consistency with which an individual panel member was able to score a trait on repeated samples from the same animal; and (iii) reproducibility, i.e. the extent to which taste panel members agreed with each other when scoring a trait. These consistency statistics were moderately high, particularly for panel-member consistency and reproducibility, with values ranging from 0.48 to 0.81 and 0.43 to 0.73 respectively. Estimated heritabilities were low for most of the sensory taste-panel-evaluated traits where the maximum value was 0.16 for overall liking. Residual correlations were high between many of the closely related sensory traits, although few significant correlations were found between the carcass quality data and meat quality traits.
The Ram Genotyping Scheme was launched in Great Britain in 2001 as part of the National Scrapie Plan and was devised to reduce and eventually eradicate classical scrapie susceptible genotypes from the national pedigree flock. Anecdotal claims from breeders suggest that sheep with more resistant PrP genotypes may have inferior phenotypes. In this study, we test this possibility for lamb production traits in three breeds of lowland sheep: Charollais (22 752 lambs), Poll Dorset (22 589 lambs) and Texel (23 492 lambs). Data were received from 50 breeders and comprised weights at birth, 8 weeks and scanning (from which average daily weight gain was derived), and ultrasonic muscle and fat depths. Animal (direct) genetic effects and up to three maternal effects were fitted in linear mixed models for each trait. Fitting either PrP genotype or number of copies of individual alleles carried as fixed effects allowed potential associations with the PrP gene to be assessed. There were no significant associations seen in the Poll Dorset breed; however, significant associations were found with the number of allele copies carried in the other two breeds included in this study. Charollais lambs carrying one copy of the VRQ allele had significantly (P < 0.01) greater ultrasonic muscle depth (0.58 mm) and fat depth (0.2 mm) than non-carriers. In the Texel breed, lambs with one ARR allele were significantly heavier than those with two or zero ARR alleles; heterozygous ARR lambs were 0.07 kg heavier at birth (P < 0.05), 0.42 kg heavier at 8 weeks (P < 0.01) and 0.17 kg heavier at scan weight (P < 0.01), than non-carriers. After Bonferroni corrections to adjust significance thresholds to account for the large number of independent comparisons made, all significant results remained so at P < 0.05 or greater, except for the ARR allele effect on birth weight in the Texel breed, which was no longer significant. These results compare favourably with others from studies on many continental breeds of sheep, published in recent years, and add credence to the conclusion that selection on PrP genotype is unlikely to have any noticeable impact on the measured growth and carcass traits in sheep.