Dag Score Research Articles

Correlation of Faecal Egg Counts with Clinical Parameters and Agreement between Different Raters Assessing FAMACHA©, BCS and Dag Score in Austrian Dairy Sheep.

Gastrointestinal nematodes, most notably trichostrongylids, are known to cause significant losses in sheep production. Previous studies have shown that monitoring parameters (e.g., FAMACHA©, BCS, dag score) change with increasing egg excretion. These parameters are well known and frequently used for targeted selective treatment. Based on the willingness to participate in this study (based on a previous questionnaire distribution among sheep farmers in Austria) we investigated the associations between faecal egg counts and the FAMACHA©, BCS, and dag scores of 1195 dairy ewes. Faecal samples were analysed using the Mini-FLOTAC technique I and larval culture. Three raters assessed the FAMACHA©, BCS, and dag scores in sheep to calculate the inter-rater agreement and intraclass correlation coefficient. The responses to the questionnaire of 23 farms were used for the evaluation, of which 16 farms were visited. Trichostrongylid eggs were detected in 95% of the faecal samples. The BCS was negatively correlated with the eggs per gram of faeces (EpG) (r = -0.156; p < 0.001) and the FAMACHA© score was slightly positively correlated with EpG (r = 0.196; p < 0.001). A small proportion of sheep (25%) shed the majority of eggs (47% to 84%). A moderate to good agreement for the parameters was found between the raters. In conclusion, the clinical parameters showed only weak correlations with faecal egg counts, and we confirmed that a minority of the flock is responsible for the majority of the pasture contamination with trichostrongylid eggs. Clinical raters should be trained before a study to increase the agreement between them.

The DeCAMFounder: nonlinear causal discovery in the presence of hidden variables

Abstract Many real-world decision-making tasks require learning causal relationships between a set of variables. Traditional causal discovery methods, however, require that all variables are observed, which is often not feasible in practical scenarios. Without additional assumptions about the unobserved variables, it is not possible to recover any causal relationships from observational data. Fortunately, in many applied settings, additional structure among the confounders can be expected. In particular, pervasive confounding is commonly encountered and has been utilised for consistent causal estimation in linear causal models. In this article, we present a provably consistent method to estimate causal relationships in the nonlinear, pervasive confounding setting. The core of our procedure relies on the ability to estimate the confounding variation through a simple spectral decomposition of the observed data matrix. We derive a DAG score function based on this insight, prove its consistency in recovering a correct ordering of the DAG, and empirically compare it to previous approaches. We demonstrate improved performance on both simulated and real datasets by explicitly accounting for both confounders and nonlinear effects.

Association between the prion protein genotype and animal performance traits in a large multibreed sheep population

Genetic susceptibility to scrapie, a fatal disease of sheep and goats, is modulated by polymorphisms in the prion protein (PrP). Neither the frequency of the PrP genotypes nor their association with animal performance has been investigated in a large multibreed Irish sheep population. Scrapie genotypes were available on 16 416 animals; the breeds represented included purebred Belclare (733), Charollais (333), Suffolk (739), Texel (1 857), Vendeen (191), and crossbreds (12 563). Performance data on lambing, lamb and ewe performance as well as health traits were available. The association between alternative approaches of describing the PrP genotype (i.e. 15 individually called PrP genotypes, five genotype classes representing susceptibility to scrapie, or number of ARR haplotypes) and animal performance were quantified using animal linear mixed models. All 15 of the possible scrapie genotypes were detected, although the frequency differed by breed. The frequency of the five PrP haplotypes in the entire population were 0.70 (ARR), 0.15 (ARQ), 0.11 (ARH), 0.02 (AHQ) and 0.01 (VRQ); the most susceptible haplotype (VRQ) was only detected in purebred Texels and crossbreds. No association was detected between the PrP genotype of either the animal or dam and any of the lambing traits (i.e. lambing difficulty score, perinatal mortality and birth weight). With the exception of ultrasound muscle depth, no association between the PrP genotype and any of the lamb performance traits (i.e. lamb BW and carcass) was observed. Lambs carrying the category four PrP genotype (i.e. ARR/VRQ) had 1.20 (SE = 0.45) mm, 1.38 (SE = 0.12) mm, 1.47 (S = 0.25) mm shallower ultrasound muscle depth relative to lambs of the less susceptible scrapie categories of 1, 2, 3, respectively (P < 0.05). Nonetheless, no association between PrP genotype and lamb carcass conformation, the ultimate end goal of producers, was detected. Ewe litter size, body condition score or lameness did not differ by PrP genotype of the ewe (P > 0.05). For ewe mature BW, ARH/VRQ ewes differed from most other ewe PrP genotypes and were, on average, 3.79 (SE = 1.66) kg heavier than ARR/ARR genotype ewes. Lamb dag score differed by dam PrP genotype (P < 0.05), although the differences were small. Results from this study show that scrapie is segregating within the Irish sheep population, but the PrP genotype was not associated with most traits investigated and, where associations were detected, the biological significance was minimal. This suggests minimal impact of selection on PrP genotype on performance, at least for the traits investigated in the present study.

Targeting improved resilience in Merino sheep – Correlations between immune competence and health and fitness traits

Resilience can be defined as the ability of an animal to remain productive in the face of diverse environmental challenges. Several factors contribute to an animal’s resilience including its ability to resist disease, cope with climatic extremes and respond to stressors. Immune competence, a proxy trait for general disease resistance, is expected to contribute to an animal’s resilience. This research aimed to develop a practical method to assess immune competence in Merino sheep which would not restrict the future sale of tested animals, and to estimate genetic parameters associated with the novel trait. We also aimed to explore associations between immune competence and other industry-relevant disease resistance and fitness-related traits and to assess the ability of immune competence phenotypes to predict health outcomes. Here, the ability of Merino wethers (n = 1 339) to mount both an antibody-mediated and cell-mediated immune response was used to define their immune competence phenotype. For that purpose, antigens in a commercial vaccine were administered at the commencement of weaning and their responses were assessed. Univariate sire models were used to estimate variance components and heritabilities for immune competence and its component traits. Bivariate sire models were used to estimate genetic correlations between immune competence and a range of disease resistance and fitness-related traits. The heritability of immune competence and its component traits, antibody-mediated immune response and cell-mediated immune response were estimated at 0.49 ± 0.14, 0.52 ± 0.14 and 0.36 ± 0.11, respectively. Immune competence was favourably genetically correlated with breech flystrike incidence (−0.44 ± 0.39), worm egg count (−0.19 ± 0.23), dag score (−0.26 ± 0.31) and fitness compromise (−0.35 ± 0.24) but not fleece rot (0.17 ± 0.23). Results suggest that selection for immune competence has the potential to improve the resilience of Merino sheep; however, due to the large standard errors associated with correlation estimates reported here, further studies will be required in larger populations to validate associations between immune competence and disease resistance and fitness traits in Australian Merino sheep.

How does maternal genetic merit and country of origin impact lamb performance pre- and post-weaning?

The objective of this study was to investigate the impact of ewe maternal genetic merit and country of origin (New Zealand or Ireland) on lamb growth and performance pre- and post-weaning. The study was conducted from 2016 to 2019, inclusive, and consisted of three genetic merit groups: New Zealand ewes of high maternal genetic merit (NZ), Irish ewes of high maternal genetic merit (High Irish) and Irish ewes of low maternal genetic merit (Low Irish) ewes and their lambs. Each of the genetic merit groups contained 30 Suffolk and 30 Texel ewes, selected based on the respective national maternal genetic indexes; i.e. either the New Zealand Maternal Worth (NZ group) or the Irish €uro-star Replacement Index (Irish groups). The impact of maternal genetic merit on lamb live-weight, average daily gains, age at drafting, ultrasound scanning, and health traits were analysed using linear mixed models. New Zealand lambs were heavier than High Irish lambs at six weeks post-partum (P < 0.05), Low Irish lambs at weaning (P < 0.001) and than both Irish genetic merit groups at ultrasound scanning (P < 0.001) and at drafting (P < 0.05). New Zealand lambs had greater average daily gains at most time points both pre- and post-weaning compared to High Irish and Low Irish lambs. High Irish lambs had greater average daily gains than Low Irish lambs from birth to drafting and from weaning to drafting (P < 0.001). New Zealand lambs had greater muscle depths (P < 0.001), firmer faecal consistency (P < 0.001) and lower dag scores (P < 0.001) in comparison to both Irish genetic merit groups who did not differ from each other (P> 0.05). High Irish lambs had a higher Nematodirus count (P < 0.001) and lamb quality score (P < 0.05) compared to Low Irish lambs. New Zealand lambs were more likely to be drafted from the system by 1st October compared to lambs in the Low Irish genetic merit group (P < 0.001). Lamb mortality from birth to drafting did not differ between any of the three genetic merit groups (P> 0.05). Overall, few differences are reported between the genetic merit groups pre-weaning. However, differences emerged post-weaning between lambs born from ewes of high and low maternal genetic merit and between animals of NZ and Irish origin, demonstrating the potential benefit of their strategic use in the future.

Animal-Based Indicators for On-Farm Welfare Assessment in Sheep.

Simple SummaryAs we keep and use sheep, we need to be able to assess their welfare and deal with welfare problems as they arise. To assess welfare, a comprehensive protocol based on valid and feasible indicators is needed. The aim of this study was to review the scientific literature and identify protocols and indicators for assessing the welfare of sheep. We identified promising protocols, well-known and established indicators, such as lameness or body condition score, as well as novel indicators that still need to be evaluated to prove their validity, such as pruritic behaviour or resting time. This review provides a starting point for the development of valid and feasible on-farm protocols using animal-based indicators to assess sheep welfare.The value society assigns to animal welfare in agricultural productions is increasing, resulting in ever-enhancing methods to assess the well-being of farm animals. The aim of this study was to review the scientific literature to obtain an overview of the current knowledge on welfare assessments for sheep and to extract animal-based welfare indicators as well as welfare protocols with animal-based indicators. By title and abstract screening, we identified five protocols and 53 potential indicators from 55 references. Three out of the five protocols include animal-based as well as resource-based indicators. All of them were assessed as being practicable on-farm but lacking reliability. Some of the single indicators are endorsed by the literature and widely used in the field like assessment of behaviour, lameness or body condition score. Others (e.g., Faffa Malan Chart FAMACHA©, dag score or pain assessment) are regularly mentioned in the literature, but their reliability and usefulness are still subject of discussion. Several indicators, such as pruritic behaviour, eye condition, lying time or tooth loss are relatively new in the literature and still lack evidence for their validity and usefulness. This literature review serves as a starting point for the development of valid and practicable welfare protocols for sheep.

357 Effect of Energy Supplementation on Growth, Health, and Carcass Traits of Pasture-raised Lambs

Abstract Energy is often the most limiting nutrient in pasture diets. The effect of energy supplementation on the growth, health, and carcass traits of pasture-raised lambs was investigated. Seventy-nine Katahdin ram lambs were delivered to the Western Maryland Research &amp; Education Center on June 15. After an 11-d acclimation period, lambs were allocated to two treatment groups based on age, weight, birth type, and FEC. Lambs in the PASTURE group (n = 40) rotationally grazed 2 ha of high quality, mixed pasture for 102 d. Lambs in the SUPPL group (n = 39) grazed similar pastures and were hand-fed a daily energy supplement (450 g of whole barley). The groups were handled bi-weekly to determine body weights, FAMACHA©, BCS, and dag scores. Individual fecal samples were collected upon arrival and at two additional time points. Lambs were ultrasound scanned on Sept 25 to determine carcass traits. Data were analyzed using the MIXED procedure of SAS, with statistical significance set at P ≤ 0.05. ADG varied considerably among weigh periods. Standard deviations were typically quite large, indicating wide variation in individual performance. Overall, the SUPPL lambs had higher ADG (P &amp;lt; 0.01), more backfat (P &amp;lt; 0.03), and higher BCS (P &amp;lt; 0.01) than the PASTURE lambs. There were no statistical differences in starting weight, ending weight, and loin depth. While internal parasites were not a problem during the study (only one lamb had a FAMACHA© score &amp;gt;4), PASTURE lambs had lower FEC (P &amp;lt; 0.05) on August 17 (240 ± 81 vs. 468 ± 80 epg). The value of additional gain (0.9 kg) would not have covered the cost of feed; however, four lambs were removed from the PASTURE group (due to death or failure to thrive) whereas only two lambs were removed from the SUPPL group. The study will be repeated in 2021 with similar lambs and protocol.

Gastrointestinal nematode control practices in ewes: Identification of factors associated with application of control methods known to influence anthelmintic resistance development.

Gastrointestinal nematodes (GIN) negatively impact productivity and welfare in sheep globally and are estimated to cost the European sheep industry €157-477 million annually. GIN are mainly controlled by anthelmintic treatment, however, as anthelmintic resistance becomes prominent, the routine treatment of ewes against GIN has been questioned. A questionnaire survey of 383 sheep farmers in Great Britain was conducted to identify strategies currently used to control GIN infections in ewes. Ordinal and binary regression analysis were used to identify factors associated with use of practices known to influence anthelmintic resistance development, including number and timing of ewe GIN anthelmintic treatment, targeted selective treatment (TST) of ewes, drench and move of ewes and long-acting moxidectin treatment of periparturient ewes. Participating farmers treated their ewes against GIN 1.68 times per year on average, with 42.3% and 32.1% of participating farmers worming their ewes once or twice a year on average, respectively. 17.2% of participating farmers wormed their ewes more than twice a year, and 8.4% never worm their ewes. Participating farmers who devised GIN control strategies based on SCOPS guidelines treated their ewes significantly less per year (P<0.001), whilst those determining treatment timing based on ewe DAG scores or the time of year treated their ewes significantly more frequently (P<0.001). Farmers who devised GIN control strategies in conjunction with their vet had greater odds of using TST (P<0.001), as well as farmers who determined flock treatment timing based on ewe condition (P=0.027). The use of narrow spectrum flukicides was significantly associated with reduced number of annual ewe GIN anthelmintic treatments (P<0.001), TST of ewes against GIN (P<0.001) and the avoidance of moving ewes to clean pastures following GIN treatment (P<0.001). The presence of sheep scab on a farm or in the area was significantly associated with increased annual GIN treatments for ewes (P=0.002), not using TST strategies to control GIN in ewes (P<0.001) and moving ewes to clean pasture after anthelmintic treatment, whilst using macrocyclic lactones treatments to prevent sheep scab was significantly associated with the treatment of periparturient ewes with long-acting moxidectin (P=0.001). This research suggests that by encouraging the application of evidence based targeted or targeted selective treatment strategies, further interaction between farmers and veterinarians/SCOPS guidance, and the uptake of best practices for controlling liver fluke and sheep scab on farms, sustainable GIN control strategies can become the common practice in ewes.

Genetic parameters of breech strike, neck wrinkles, dags and breech cover over the lifetime of crutched Merino ewes in a Mediterranean environment

Aims This study was undertaken to estimate the genetic parameters of breech strike and its indicator traits over the lifetime of crutched Merino ewes in a Mediterranean environment. Methods Breech strike records were collected on 3993 ewes over their lifetime where they were annually crutched. The ewes were scored at different times of the year for neck wrinkle, dag score and breech cover over their lifetime. A total of 13 577 breech strike records from birth up to 5 years of age were generated between 2006 and 2017. Face cover was only scored mid-year. Mixed model methodologies were used to estimate the genetic parameters of the different traits at different ages. Key results Breech strike was heritable (h2) and repeatable (t) on the observed scale (h2 = 0.07 ± 0.01; t = 0.13 ± 0.01), and as a binary trait on a logistic scale (h2 = 0.51 ± 0.10; t = 0.68 ± 0.10). Breech strike was genetically positively correlated across ages. Positive genetic correlations were found between breech strike and the indicator traits of neck wrinkle, face cover, breech cover and dags. Neck wrinkle and face cover, as well as breech cover and dag scored at different times of the year, were heritable and repeatable. Although high genetic correlations were found between different ages for neck wrinkle and post-shearing breech cover, these traits are not genetically the same traits at different ages. However, breech cover scored mid-year, before shearing and after shearing are genetically the same trait. The genetic relationship between dag at different ages is unclear as a moderate positive genetic correlation (rg = 0.25 ± 0.12) was found between hoggets and 2-year-old ewes, whereas a moderate negative correlation (rg = –0.30 ± 0.14) was found between 3- and 4-year-old ewes. The genetic correlations amongst the dag traits in older age groups were not significantly different from zero. Conclusions Breech strike and its indicator traits (i.e. neck wrinkle, breech cover, face cover and dags) were all heritable. Breech strike appears to be genetically strongly correlated across ages, however, the correlations had large standard errors. It was positively correlated with the indicator traits. Moderate to strong genetic correlations were found between ages for neck wrinkle and for breech cover. Dags, however, were poorly correlated across ages, indicating that dags are not genetically the same trait in mature ewes at different ages. Implications This study shows that selecting ewes for low breech strike, and for reduced neck wrinkle, lower breech cover and less dags will reduce breech strike in mature Merino ewes in future generations. However, as the phenotypic correlations were relatively low, culling ewes on these indicator traits will result in little gain in the current generation. It appears that dags at different ages is not genetically the same trait. Thus the benefit of selecting or culling ewes on dags will not be carried over to subsequent ages.

Quebracho tannins aid in the control of Eimeria spp. and gastrointestinal nematodes in lambs and goat kids

The objective was to examine the effects of supplementary quebracho on control of coccidiosis and gastrointestinal nematodes in lambs and kids. In Exp. 1, naturally infected lambs weaned (87.8 ± 0.4 days of age; day 0) in January (winter) were blocked by sex and randomly assigned (n = 10/treatment) to receive supplement with or without 100 g/lamb of quebracho for 28 days. In Exp. 2, single or twin rearing ewes were randomly assigned into two groups, and naturally infected lambs were fed control (n = 28) or quebracho (100 g/lamb of quebracho tannins in feed; n = 27) between -28 and 21 days (weaning = day 0; 70.8 ± 0.1 days of age). In Exp. 3, weaned doe kids (57.6 ± 2.0 days of age) were randomly assigned to receive alfalfa (Medicago sativa) supplement with (n = 9) or without (n = 8) 50 g/kid quebracho or sericea lespedeza (Lespedeza cuneata) with quebracho (n = 8) for 21 days. Fecal oocyst count (FOC), nematode egg counts (FEC), fecal score, dag score (soiling around rear quarters), and blood packed cell volume (PCV) were determined every 7 days. Data were analyzed as repeated measures using mixed models. In Exp. 1, FOC decreased in quebracho-fed lambs (diet × time, P < 0.001) but FEC was similar between treatments during the feeding period (P = 0.19). Packed cell volume (P = 0.19) and fecal score (P = 0.42) were similar between groups. Quebracho-fed lambs had a greater dag score initially (diet × time, P = 0.02), but were similar by day 42 (P = 0.72). In Exp. 2, FOC remained low (P = 0.02), PCV tended to decrease (P = 0.06), but FEC increased on days 14 and 21 (diet × time; P < 0.001) in quebracho compared with control-fed lambs. Quebracho-fed lambs had lower fecal score (diet × time; P = 0.005) but higher dag score (diet × time; P < 0.001). In Exp. 3, FOC of kids fed quebracho (alfalfa or sericea lespedeza supplement) was lower than control (P < 0.001). Fecal score of kids fed sericea lespedeza compared with alfalfa were lower regardless of quebracho (P = 0.01). There were no differences among treatments for dag, FEC, PCV, or body weight (P> 0.10). Quebracho was effective in reducing FOC but not clinical signs of coccidiosis in both lambs and kids, and may not be highly digestible in lambs as it caused loose stools.

Substantial genetic gains in reducing breech flystrike and in improving productivity traits are achievable in Merino sheep by using index selection

Context The availability of effective indirect rather than direct selection criteria for genetically reducing breech flystrike is crucial for the Australian wool industry, as expression of breech flystrike is routinely suppressed by management interventions to minimise the risks to sheep health, welfare and productivity. Understanding how much genetic gain can be made in reducing breech strike, while also selecting for other key traits is important in choosing breeding objectives, particularly for Merino genetic improvement programs. Aims We predicted genetic gains from within-flock selection to reduce breech flystrike incidence (FS) and improve productivity under a range of scenarios that all used indirect selection criteria in the genetic evaluation of FS. Methods Three breeding objectives were modelled, by adding FS as a trait to the breeding objective for the Dual Purpose Plus (DP+), Fibre Production Plus (FP+) and Merino Production Plus (MP+) indexes available from MERINOSELECT. A large range of economic values were examined for FS, from 0 to –$240/strike.sheep per year in $20 increments. For all scenarios, full records of productivity traits and pedigree information were assumed to be available for use as selection criteria, as well as records of breech wrinkle, dag and breech cover scores. Predictions were conducted for scenarios assuming (a) moderate heritability for FS (b) low heritability for FS, and (c) low heritability for FS, but higher heritability for dag score than assumed for scenarios (a) and (b). Key results After 10 years of selection, under assumption (a) predicted genetic gains in FS ranged from 0, up to maximum reductions of 0.19, 0.21, and 0.20/strike.sheep per year from use of the FP+FS, MP+FS and DP+FS indexes, respectively. Under assumption (b) predictions of genetic gain for FS were considerably lower and ranged from 0 to maximum reductions of 0.04, 0.06 and 0.06/strike.sheep per year based on use of FP+FS, MP+FS and DP+FS indexes, respectively. Under assumption (c), predicted genetic gains in FS were very similar to those under assumption (b). When 70% of the maximum gains in FS studied were targeted, from 70% to 93% of genetic gains in the overall index (excluding FS) were predicted to be retained when FS had moderate heritability, and from 85% to 95% when FS had low heritability. Conclusions and implications There is a practical range of economic values for FS (from –$60 to –$80/strike.sheep per year for MP+FS and DP+FS indexes and –$60 to –$140/strike.sheep per year for a FP+FS index when the heritability of FS is moderate and –$100 to –$200/strike.sheep per year for a MP+FS index and –$140 to –$240/strike.sheep per year for FP+FS and DP+FS indexes when the heritability of FS is low), that could be used in breeding programs to genetically reduce FS, while retaining competitive levels of genetic gains for other important traits. Reduction of FS is achievable to low levels, after 10–20 years of index selection, similar to levels achieved by mulesing (0.01/strike.sheep per year in average seasonal conditions).

To dock or not to dock? Faecal soiling measurement in sheep

AbstractFaecal soiling is one of the welfare indicators in the AWIN welfare assessment protocol for sheep (Ovis aries) and is measured by dag scores. Studies on dag scoring for ewes with docked and undocked tails have given rise to contradictory results. The aim of this study was to compare faecal soiling between ewes with docked and undocked tails and evaluate inter-rater reliability for faecal soiling of ewes. This study was conducted on a farm in Southern Brazil and included 66 undocked and 94 docked ewes. Dag score was recorded by three assessors on a scale of 1 to 5. There was no significant difference on faecal soiling for docked compared to undocked ewes and the median dag score was 3 (1-5). Repeatability amongst assessors by intra-class correlation coefficient of dag scores on docked and undocked ewes was 0.49 and 0.40, respectively; however, these repeatabilities showed no significant differences. The modest repeatability between three assessors on dag scoring indicates caution as regards the use of faecal soiling as an indicator and suggests a need for further studies. The best field results may be obtained by increasing the assessment sample to at least 160 ewes or by raising the number of assessors to five to promote better inter-observer repeatability. Results suggest that taildocking did not promote cleanliness on the breech area. Considering the negative impact on welfare, it seems reasonable to reverse the burden of proof and desist from recommending tail-docking in the absence of clear scientific evidence of any benefit.

Modelling of breech strike risk and protective efficacy of mulesing in adult Merino sheep

Context Mulesing provides a high degree of protection against beech strike, but wool producers need to be able to predict the level of risk of flystrike if they cease mulesing. Aims To use data from trials of mulesed and unmulesed sheep to estimate the distribution of adult breech scores (wrinkle, breech cover and dag) from mean flock values, and use those scores to estimate the risk of breech strike in Merino sheep flocks. Methods Breech scores and breech strike from flocks with comparable mulesed and unmulesed sheep were examined using logistic functions to relate breech scores in mulesed sheep to those in unmulesed sheep, and to estimate the risk of breech strike in sheep for any given combination of breech scores. Key results Functions are given to estimate whole flock adult breech wrinkle and breech cover using combinations of the breech traits that are available. Unmulesed Merino sheep have a 6-fold increased risk of breech strike compared with mulesed sheep under the same conditions. There were increased relative risks of breech strike of 2.0 for each unit increase in dag score, 2.2 for each unit increase in breech wrinkle score and 1.7 for each unit increase in breech cover score. Mulesing reduced each of these risk factors, but had an additional 3.2-fold benefit independent of these factors. Adult breech wrinkle was most reliably estimated from neck wrinkle or from marking breech wrinkle (before mulesing). Breech cover was estimated from face cover, or from marking breech cover. The risk of breech strike if adult sheep were to be left unmulesed in a commercial flock was predicted using a centred log ratio transformation to estimate the distribution of dag scores in the unmulesed sheep, given the actual distribution in the mulesed flock. If the distribution was not known, then the mean dag score of the mulesed sheep could be used to estimate the distribution of dag scores in unmulesed sheep using a 2/3 power function to transform the mean dag score. Conclusions A flock of unmulesed sheep would need to lower breech wrinkle, breech cover and dag scores by 0.5 for each score to achieve a comparable level of risk of breech strike in mulesed sheep. Implications The use of the model will allow wool producers to selectively breed for sheep with lower risk of breech strike, while continuing to mules the sheep as long as it is necessary to do so. They will be able to estimate what the risk of strike would be if they cease mulesing, due to the proportion of sheep with potentially high wrinkle score, high breech cover or high dag scores at any stage of their breeding program.

Deriving economic values for national sheep breeding objectives using a bio-economic model

The economic value of a trait in a breeding objective can be defined as the value of a unit change in an individual trait, while keeping all other traits constant and are widely used in the development of breeding objectives internationally. The objective of this study was to provide a description of the development of economic values for the pertinent traits included in the Irish national sheep breeding objectives using a whole farm system bio-economic model. A total of fourteen traits of economic importance representing maternal, lambing, production and health characteristics were calculated within a whole farm bio-economic model. The model was parameterised to represent an average Irish flock of 107 ewes with a mean lambing date in early March, stocked at 7.5 ewes per hectare and weaning 1.5 lambs per ewe joined to the ram. The economic values (units in parenthesis) calculated for maternal traits were: €39.76 for number of lambs born (per lamb), €0.12 for ewe mature weight cull value (per kg), −€0.57 for ewe mature weight maintenance value (per kg), −€0.09 for ewe mature weight replacement value (per kg) and −€0.84 for ewe replacement rate (per%). The economic values calculated for lambing traits were: €54.84 for lamb surviving at birth (per lamb), −€0.27 and −€0.30 for direct lambing difficulty in single and multiple-bearing ewes, respectively (per%); the corresponding values for maternal single and multiple lambing difficulty (per%) were −€0.25 and −€0.27, respectively. The calculated economic values for production traits were: −€0.25 for days to slaughter (per day), €3.70 for carcass Conformation (per EUROP grade) and −€0.84 for carcass fat (per fat score). The economic values for health traits were: −€0.24 for ewe lameness (per%), −€0.08 for lamb lameness (per%), −€0.25 for mastitis (per%), −€0.34 for dag score (per dag score) and −€0.08 for faecal egg count (per 50 eggs/g). Within the two Irish breeding objectives, the terminal and replacement breeding objective, the greatest emphasis was placed on production traits across both the terminal (62.56%) and replacement (41.65%) breeding objectives. The maternal and lambing traits accounted for the 34.19% and 23.45% of the emphasis within the replacement breeding objective, respectively. Results from this study will enable the implementation of new economic values within the national terminal and replacement Irish sheep breeding objectives which highlights the traits of importance for increasing overall farm profitability.

Live weight as a basis for targeted selective treatment of lambs post-weaning

Targeted selective treatment (TST) has been proposed as a sustainable method of gastrointestinal nematode control that reduces the number of anthelmintic treatments administered, thereby preserving a susceptible nematode population in refugia. In order to minimise the impact of withholding treatment on animal performance, animals that would benefit most should be selected for treatment. However, the most suitable criteria for selecting which animals to treat remain a subject of research. The impact of implementing a TST strategy based on lamb live weight was investigated, and whether heavy lambs were more resilient than light lambs if left untreated. The study was conducted using weaned lambs on 3 sheep farms, and over 2 years. On each farm lambs were weighed and divided into heavy, medium and light weight classes. Within the heavy (n = 225) and light (n = 218) weight classes lambs were randomly allocated to two treatments; anthelmintic treatment or no anthelmintic treatment. All lambs in the medium weight class were treated. Animal performance and parasitological parameters were assessed over a 28-day period. Anthelmintic treatment had a significant effect (P < 0.01) on faecal egg count, average daily weight gain, body condition score and dag score; there was no treatment by weight class interaction. Anthelmintic treatment had no effect on plasma pepsinogen concentration or on blood leukocyte numbers. Withholding anthelmintic treatment from lambs therefore had a negative effect on worm egg count and animal performance with no evidence that heavy lambs were more resilient than light lambs when left untreated.

Using Longitudinal Assessment on Extensively Managed Ewes to Quantify Welfare Compromise and Risks.

Simple SummarySheep managed extensively can be exposed to several welfare challenges during the year, and the risk of some diseases can increase in warmer and wetter seasons. In this study, the welfare of Merino ewes was examined over a calendar year. The welfare of these animals, kept on a single farm with consistent management, varied substantially. Overall, the largest number of ewes experienced compromise and risk to welfare at weaning, indicating that this was the most vulnerable time. The main welfare issues identified were under and over feeding, ewe mortality, lameness, ecto-parasites (flystrike) and mastitis, all of which could be improved by modifying management practices, such as improved nutritional management and monitoring and better tail docking procedures. Future research must consider that significant variation in the on-farm welfare of ewes occurs during a calendar year, which needs to be accounted for when conducting on-farm assessments.This study examined variation in the welfare of extensively managed ewes and potential welfare risks. A total of 100 Merino ewes (aged 2–4 years) were individually identified and examined at three key stages: pregnancy, lactation and weaning. Eight animal-based welfare measures were used to assess welfare: flight distance, body condition score (BCS), fleece condition, skin lesions, tail length, dag score, lameness and mastitis. Data were analysed by ANOVA and McNemar’s statistics. Overall, the average BCS of the group was in agreement with industry recommendations. However, a number of animals were classified with inadequate condition (either too thin or too fat) across the three observation periods. The presence of heavy dags was greatest at mid-lactation (87%, P < 0.0001), lameness was greatest at weaning (14%, P = 0.01), clinical mastitis was 1% annually, and five ewes were lost from the study. Ewes had better health at mid-pregnancy compared to mid-lactation and weaning. The main welfare issues identified were under and over feeding, ewe mortality, lameness, ecto-parasites (flystrike) and mastitis, all of which have the potential to be reduced with improved management practices. Future welfare assessment programs must consider that significant variation in on-farm welfare will occur in extensively managed systems and this needs to be accounted for when evaluating farms.

Animal-Based Measures to Assess the Welfare of Extensively Managed Ewes.

Simple SummaryThe aim of this study was to assess the reliability and practicality of 10 animal-based welfare measures for extensively managed ewes, which were derived from the scientific literature, previous welfare protocols and through consultation with veterinarians and animal welfare scientists. Measures were examined on 100 Merino ewes, which were individually identified and repeatedly examined at mid-pregnancy, mid-lactation and weaning. Body condition score, fleece condition, skin lesions, tail length, dag score and lameness are proposed for on-farm use in welfare assessments of extensive sheep production systems. These six welfare measures, which address the main welfare concerns for extensively managed ewes, can be reliably and feasibly measured in the field.The reliability and feasibility of 10 animal-based measures of ewe welfare were examined for use in extensive sheep production systems. Measures were: Body condition score (BCS), rumen fill, fleece cleanliness, fleece condition, skin lesions, tail length, dag score, foot-wall integrity, hoof overgrowth and lameness, and all were examined on 100 Merino ewes (aged 2–4 years) during mid-pregnancy, mid-lactation and weaning by a pool of nine trained observers. The measures of BCS, fleece condition, skin lesions, tail length, dag score and lameness were deemed to be reliable and feasible. All had good observer agreement, as determined by the percentage of agreement, Kendall’s coefficient of concordance (W) and Kappa (k) values. When combined, these nutritional and health measures provide a snapshot of the current welfare status of ewes, as well as evidencing previous or potential welfare issues.

A comparison of two different anthelmintic treatment regimens against natural gastrointestinal nematode infections on two Lithuanian sheep farms

BackgroundAccording to targeted treatment (TT), the whole flock is dewormed based on knowledge of the risk, or parameters that quantify the mean level of infection, whereas according to targeted selective treatment (TST), only individual animals within the grazing group are treated, based on parasitological, production and/or morbidity parameters. The aim of this study was to compare two different treatment protocols on sheep farms in Lithuania. The study was conducted from 15 April to 31 October 2014 on three sheep farms. On the TT (the whole flock) and T(S)T (with FECs ≥ 300, respectively) farms all adult animals were treated orally with fenbendazole irrespective of EPG counts before the grazing season. The second treatment was applied with injectable ivermectin on both farms. However, on the TT farm all sheep were also treated on 2nd August regardless of their EPG counts, while on the T(S)T farm only those animals with an EPG ≥ 300 were treated on 1 July using a threshold of ≥ 300 EPG. No treatments were administered on the control farm (n = 1) during the study.ResultsSpring treatment of ewes significantly reduced nematode faecal egg counts (FEC) both on the TT and T(S)T farms, with the benefit of lowering pasture contamination with infective L3 stage larvae at the start of grazing season, while it remained significantly higher on the control farm. The positive effect of the spring treatment of ewes was reflected by increased body weight gains (BWG) in lambs in the first half of the grazing season. Following the second treatment, the weight gains in lambs on the T(S)T farm were higher compared to lambs on the TT farm, while BWG in the control lambs started to decrease. The difference was also substantiated by the body condition scores (BCS) and dag scores (DS) of lambs, which were highest on the T(S)T farm compared with those on the control and TT farms.ConclusionsThe results of this study show that both treatment strategies were useful in reducing clinical effects (BCS and DS) of gastrointestinal nematode parasitism and increasing the performance in lambs. Furthermore, on the T(S)T farm some of animals were left in refugia, helping to slow down the development of anthelmintic resistance (AR) in future.

Multiple-trait QTL mapping and genomic prediction for wool traits in sheep

BackgroundThe application of genomic selection to sheep breeding could lead to substantial increases in profitability of wool production due to the availability of accurate breeding values from single nucleotide polymorphism (SNP) data. Several key traits determine the value of wool and influence a sheep’s susceptibility to fleece rot and fly strike. Our aim was to predict genomic estimated breeding values (GEBV) and to compare three methods of combining information across traits to map polymorphisms that affect these traits.MethodsGEBV for 5726 Merino and Merino crossbred sheep were calculated using BayesR and genomic best linear unbiased prediction (GBLUP) with real and imputed 510,174 SNPs for 22 traits (at yearling and adult ages) including wool production and quality, and breech conformation traits that are associated with susceptibility to fly strike. Accuracies of these GEBV were assessed using fivefold cross-validation. We also devised and compared three approximate multi-trait analyses to map pleiotropic quantitative trait loci (QTL): a multi-trait genome-wide association study and two multi-trait methods that use the output from BayesR analyses. One BayesR method used local GEBV for each trait, while the other used the posterior probabilities that a SNP had an effect on each trait.ResultsBayesR and GBLUP resulted in similar average GEBV accuracies across traits (~0.22). BayesR accuracies were highest for wool yield and fibre diameter (>0.40) and lowest for skin quality and dag score (<0.10). Generally, accuracy was higher for traits with larger reference populations and higher heritability. In total, the three multi-trait analyses identified 206 putative QTL, of which 20 were common to the three analyses. The two BayesR multi-trait approaches mapped QTL in a more defined manner than the multi-trait GWAS. We identified genes with known effects on hair growth (i.e. FGF5, STAT3, KRT86, and ALX4) near SNPs with pleiotropic effects on wool traits.ConclusionsThe mean accuracy of genomic prediction across wool traits was around 0.22. The three multi-trait analyses identified 206 putative QTL across the ovine genome. Detailed phenotypic information helped to identify likely candidate genes.

Factors explaining the incidence of breech strike in a Mediterranean environment in unmulesed and uncrutched Merino sheep

Factors responsible for an increase in breech strike were investigated in an unmulesed Merino flock in a Mediterranean environment that were not crutched in 4 years but were crutched in the subsequent 2 years. No chemical preventative treatments such as dipping or jetting were applied in order to assess the susceptibility of the different progeny groups. The number of breech strikes for each animal was recorded from birth to hogget shearing at 17 months of age. Production traits were measured and a large number of visual wool and body conformational traits were subjectively scored to determine whether they contribute to variation in breech strike. Large differences (P &lt; 0.01) in the incidence of breech strike were found between years. A significant interaction (P &lt; 0.05) was found between year of birth and sex for breech strike to weaning, as rams had a higher strike rate than ewes in 1 year only. Across years ewes generally had a higher strike rate than rams. No consistent pattern in potential indicator traits could be found across years, as many traits each explain a small proportion of the variation in breech strike. Dags and skin wrinkle in the tail and breech area contributed most to the variation in breech strike. In uncrutched sheep, dags scored at yearling age for rams, and before hogget shearing for ewes, explained 16% and 10% of the variation in breech strike, respectively, whereas tail wrinkle scored post-weaner shearing explained 21% of the variation in breech strike in both ewes and rams. In sheep that were crutched at yearling age, about 4 months before the normal fly season, tail wrinkle was the most important indicator trait of breech strike in rams, whereas dags at yearling and dags before hogget shearing were the most important indicator traits in ewes. This research confirms that dags and wrinkles are major predisposing factors to breech strike in a Mediterranean environment and that sheep with higher dag and wrinkle scores were consistently more likely to be struck. A large proportion of variation in the incidence of breech strike remains unexplained in uncrutched and unmulesed sheep.