Survey of mange mite infesting sheep in Riyadh region,Saudi Arabia

The study was performed to survey the Sarcoptic mange in sheep and the effect of infection on the local strains during a specific period in different regions of Riyadh, Saudi Arabia. A total of 1745 sheep were examined clinically and were selected from the suspected cases for laboratory investigation of skin scrapings for disease diagnosis. The examined animals included (509) Naimi, (396) Najdi, (518) Hurri, and (322) Rufidi native sheep.The results showed that the infestation rate was (12.77%) in all sheep. The highest strain was recorded (17.2%, 14.3%, 9.6%, and 8.6%), respectively. The infestation was highest in sheep over two years of age (15.2%) while it was lowest in sheep under two years of age (11.2 %). In addition, the infection rate in females was higher than in males. The prevalence of mange mites in females was (14%) compared to (11.2%) in males. The highest percentage of infestation was recorded in the head region at 67.2%, followed by that in the neck (4.4%), back (16.5%), tail (11.6%), and legs (0%).The presence of mange mites was discovered by microscopic examination of deep skin scrapings of infected animals that were identified morphologically. The infection was assured by histological investigations. This study revealed that mange mite is one of the most significant sheep health constraints in Riyadh. Therefore, proper prevention measures must be implemented to take into consideration other non-host-related risk factors.     

The importance of feet examination in sheep health management

Lameness is still the biggest welfare issue present on sheep farms. In order to prevent and control lameness outbreaks on sheep farms, a good set-up is required, as well as a systematic approach to examining the foot and limb. The cause of lameness cannot be assumed to be foot-rot, but instead there are a whole host of conditions. These may be of a microbial aetiology, such as scald or contagious ovine digital dermatitis, or of non-microbial aetiology, such as white-line lesions or toe granulomas. The consequences of lameness can be far reaching, not only affecting the number of lambs born, but also the size of the lamb and whether they manage to get in lamb the following year. It can result in the difference between making a profit or a loss in the financial year.     

Development of a new piosphere in arid chenopod shruhland grazed by sheep. 1. Changes to the soil surface

Piospheres, that is, zones of attenuating stocking impact extending out from watering places, are a feature of arid pastoral regions. The present authors studied, for the first time, the initial development of a piosphere in respect of a number of variables of the soil surface. The site was near-pristine chenopod shrubland, part of a paddock of 1340 ha near Whyalla, South Australia, stocked with ca. 200 sheep on a new watering point. Soil features monitored over the first 2.5 years were dung deposition, sheep track development and surface erosion, the soil lichen crust, compaction of the soil surface and dustfall, using fenced plots of at least 550 m² as controls. Piosphere patterns (i.e. patterns reflecting the concentricity of stocking pressure around water) were manifest within the first 3 months for sheep dung deposition, sheep track development, and lichen cover. Soil compaction, which was confined to sheep tracks and then largely to the surface 5 cm, displayed a piosphere pattern when it was first recorded 6 months after stocking. Bulk density of this layer was elevated by up to 20%. There was only a weak piosphere pattern in dustfall. The piosphere patterns in sheep track development and destruction of the lichen crust became more pronounced in time. Track direction was near radial. After 2 years the limit of the piosphere pattern ranged from ca. 10 m from the trough for infiltration into dry soil after an abrupt rainstorm, to greater than 800 m for sheep track intensity. These changes occurred at stocking levels amongst the lowest in Australian arid zone pastoral situations. After the first 9 months of sheep stocking there was no discernible effect of grazing on the density of the short-lived grasses or on the pattern of kangaroo arid rabbit activity as judged by the pattern of their dung deposition. No discernible erosion of the soil surface other than in sheep tracks occurred during the first 2 years.     

Fourier analysis of trunk displacements: a method to identify the lame limb in trotting horses

The aim of this paper is to present a method allowing the identification of the lame limb in trotting horses. Using a 3-D kinematic analysis system, 13 sound and 25 lame horses fitted with 4 skin markers placed on the dorsal midline of their trunk were recorded while trotting on a track in the conditions of the routine lameness examination. The vertical displacements of the trunk markers underwent Fourier analysis. Results indicated that these displacements could be represented using only the first and second harmonics. From these two harmonics, indices were then developed. The sensitivity of these indices to the different types of experimental errors was also studied. Results showed that the values of the indices of the lame horses were relatively unaffected by the experimental errors. In lame horses, these indices allowed the quantification of the degree of the lameness, the identification of lame limb with a reliability > 95% and the characterisation of the type of trunk movements. These indices could be easily implemented in a computer program to provide objective information to the clinician or to be used as a first step in the development of an expert system. Moreover, these clinical tools may also be extended to other quadrupedal or bipedal locomotions.     

Embedded microcomputer-based force plate system validation when evaluating lameness severity differentiation under an induced synovitis model in lactating dairy cattle

Bovine lameness has relatively large negative economic and welfare implications on the U.S. dairy industry. Due to the ramifications, early lameness detection will aid in assisting dairy producers to mitigate downstream effects through early treatment. The objective of this study was to determine the minimum standing time required among 2-, 3-, 4-, 5-, and 10 min time intervals to obtain an accurate weight distribution estimate for each leg when attempting to detect lameness. An embedded microcomputer-based force plate system was developed to measure vertical forces from individual cow limb weight distribution to detect bovine lameness when utilizing an induced synovitis lameness model. The force plate has four quadrants, with each load cell quadrant measuring the force placed on it from a single limb. The force plate recorded weight (kg) every second from each load cell quadrant, after which, a 60 s moving average for weight distribution was calculated. A sequential study design was employed to evaluate non-lame and induced lameness to ensure time requirements were consistent. Prior to induction, the force plate system was used to measure weight distribution every second for 15 min. After lameness induction, additional 15 min increments were recorded every 24 h for seven days. Lameness was induced by injecting the left hind distal interphalangeal joint in three cows with amphotericin B, 12 h prior to the start of the study. Data were analyzed using a linear mixed effect that included the fixed effects of day relative to lameness induction, time period, foot and injected foot. Cow within replicate was included as a random effect. Cumulative minutes were assessed up to 15 min by comparing the least square rolling 60 s cumulative means expressed as a percentage of each animal’s BW percentage placed on each leg for 2-, 3-, 4-, 5-, and 10 min intervals. Results indicate that the minimum time needed for accurate lameness detection in cows was 2 min.     

Epidemiological and histomorphic studies in sheep infected with hydatid cyst in Taif area

Hydatidosis is a zoonotic disease caused by Echinococcus granulosus larvae, which affects sheep worldwide, especially in rural communities. This study aims to determine the prevalence and structure of hydatid cyst in sheep. A total number of 1,198 sheep in different age groups G1 (<1 year), G2 (1–2 years) and G3 (>2 years) were slaughtered at Taif abattoirs, then examined for the presence of hydatid cysts in lung, liver, and mesentery. Prevalence of hydatid cyst infection in imported sheep (13.0%) was higher than of local sheep (10.2%). Particularly, as per gender, prevalence of imported females (71.9%) was higher than those of local females (28.1%), while that of imported males (66.3%) was higher than those of local males (33.7%). Large sizes of hydatid cysts and fertility recorded in G3 were higher in both local and imported sheep than those of G1 and G2. Morphometric analysis of pathological lesions in liver of all infected sheep showed a significant increase compared to non-infected healthy sheep (have no lesions) (P < 0.001). In addition, for all infected sheep, histochemical investigation with Masson’s trichrome stain showed collagen fibers inside the hydatid cyst capsules and in pericystic region. The collagen fibers content and the cellular laminated membranes took the green color, while immunohistochemical evaluation detected a positive reaction for CD3.     

Head and pelvic vertical displacement in dogs with induced swinging limb lameness: an experimental study

Background

Swinging limb lameness is defined as a motion disturbance ascribed to a limb in swing phase. Little is known about its biomechanics in dogs, particularly about the body motions that accompany it, such as vertical head and pelvic motion asymmetry. The aim of this study was to describe the changes in vertical head and pelvic motion asymmetry in dogs with induced swinging limb motion disturbance, mimicking a swinging limb lameness. Fore- and hind-limb lameness was induced in ten sound dogs by placing a weight (200 g) proximal to the carpus or tarsus, respectively. Marker-based motion capture by eight infrared light emitting video cameras recorded the dogs when trotting on a treadmill. Body symmetry parameters were calculated, including differences between the two highest positions of the head (HDmax) and pelvis (PDmax) and between the two lowest positions of the head (HDmin) and pelvis (PDmin), with a value of zero indicating perfect symmetry.

Results

Induction of swinging forelimb lameness showed significant changes in HDmax (median and range: sound 1.3 mm [??4.7 to 3.1], in the left side ??28.5 mm [??61.2 to ??17.9] and in the right side 20.1 mm [??4.4 to 47.5]) and, induction of swinging hind limb lameness showed significant changes in PDmax (sound 2.7 mm [??7.4 to 7.2], in the left side ??10.9 mm [??22.4 to 0.5] and in the right side 8.6 mm [??3 to 30]), as well as an increased hip movement asymmetry (sound 1.6 mm [??8.6 to 19.9], in the left side ??18.1 mm [??36.7 to 5.4] and in the right side 15 mm [??20.7 to 32.1]) (P?<?0.05).

Conclusions

Induced swinging fore- and hind limb lameness resulted in significant increased asymmetry of the maximal vertical displacement movement of the head and pelvis, due to decreased lifting of the head in forelimb lameness and of the pelvis in hind limb lameness. The results suggest that asymmetry of the maximal vertical displacement of the head and pelvis (i.e. lifting) is a key lameness sign to evaluate during examination of swinging limb lameness.

     

Culling Rate of Icelandic Horses due to Bone Spavin

A survival analysis was used to compare the culling rate of Icelandic horses due to the presence of radiographic and clinical signs of bone spavin. A follow-up study of 508 horses from a survey five years earlier was performed. In the original survey 46% of the horses had radiographic signs of bone spavin (RS) and/or lameness after flexion test of the tarsus. The horse owners were interviewed by telephone. The owners were asked if the horses were still used for riding and if not, they were regarded as culled. The owners were then asked when and why the horses were culled. During the 5 years, 98 horses had been culled, 151 had been withdrawn (sold or selected for breeding) and 259 were still used for riding. Hind limb lameness (HLL) was the most common reason for culling (n = 42). The rate of culling was low up to the age of 11 years, when it rose to 0.05 for horses with RS. The risk ratio for culling was twice as high for horses with RS compared with horses without RS and 5.5 times higher for culling because of HLL. The risk of culling (prognostic value) was highest for the combination of RS with lameness after flexion test, next highest for RS and lowest for lameness after flexion test as the only finding.     

Recognition of lameness and decisions to catch for inspection among sheep farmers and specialists in GB

Background

Epidemiological studies have used farmer estimates of the prevalence of lameness in their flocks. This assumes that farmers can identify lame sheep. Eight movie clips of sheep with locomotion from sound to moderately lame were used to investigate the ability of farmers and sheep specialists to recognise lame sheep. Each participant was asked to complete a form and indicate, for each movie clip, whether they thought the sheep was lame and whether they would catch it if it was the only lame sheep or if 2 – 5, 6 – 10 or > 10 sheep were equally lame. The farmers' responses were compared with their estimates of flock lameness prevalence and the interval between observing a lame sheep and catching it.

Results

178 farmers and 54 sheep specialists participated. Participants could identify even mildly lame sheep but made a separate decision on whether to catch them. This decision was dependent on the severity of lameness and the number of sheep lame in a group. Those who said they would catch the first lame sheep in a group were significantly more likely to catch mildly lame sheep (farmer-reported median prevalence of lameness 5% (IQR: 2%–6%)). In contrast, farmers who waited for several sheep to be lame indicated that they would only catch more severely lame sheep (farmer reported median flock lameness 11% (IQR: 9%–15%)). Approximately 15% of farmers did not catch individual lame sheep (farmer reported median flock lameness 15% (IQR: 10%–15%)). The flock prevalence of lameness increased as time to treatment increased and time to treatment was positively correlated with only catching more severely lame sheep.

Conclusion

If movie-clips are similar to the flock situation, farmers and specialists can recognise even mildly lame sheep but vary in their management from prompt treatment of the first lame sheep in a group to no individual sheep treatments. The former practices would be appropriate to minimise transmission of footrot, a common, infectious cause of lameness and so reduce its incidence. The analysis also suggests that farmers estimate lameness prevalence relatively accurately because farmers who treated the first mildly lame sheep in a group also reported the lowest prevalence of lameness in their flock.

     

Genetic parameters for lameness,mastitis and dagginess in a multi-breed sheep population

The objective of the present study was to quantify the extent of genetic variation in three health-related traits namely dagginess, lameness and mastitis, in an Irish sheep population. Each of the health traits investigated pose substantial welfare implications as well as considerable economic costs to producers. Data were also available on four body-related traits, namely body condition score (BCS), live weight, muscle depth and fat depth. Animals were categorised as lambs (<365 days old) or ewes (⩾365 days old) and were analysed both separately and combined. After edits, 39 315 records from 264 flocks between the years 2009 and 2015 inclusive were analysed. Variance components were estimated using animal linear mixed models. Fixed effects included contemporary group, represented as a three-way interaction between flock, date of inspection and animal type (i.e. lamb, yearling ewe (i.e. females ⩾365 days but <730 days old that have not yet had a recorded lambing) or ewe), animal breed proportion, coefficients of heterosis and recombination, animal gender (lambs only), animal parity (ewes only; lambs were assigned a separate ‘parity’) and the difference in age of the animal from the median of the respective parity/age group. An additive genetic effect and residual effect were both fitted as random terms with maternal genetic and non-genetic components also considered for traits of the lambs. The direct heritability of dagginess was similar across age groups (0.14 to 0.15), whereas the direct heritability of lameness ranged from 0.06 (ewes) to 0.12 (lambs). The direct heritability of mastitis was 0.04. For dagginess, 13% of the phenotypic variation was explained by dam litter, whereas the maternal heritability of dagginess was 0.05. The genetic correlation between ewe and lamb dagginess was 0.38; the correlation between ewe and lamb lameness was close to zero but was associated with a large standard error. Direct genetic correlations were evident between dagginess and BCS in ewes and between lameness and BCS in lambs. The present study has demonstrated that ample genetic variation exists for all three health traits investigated indicating that genetic improvement is indeed possible.     

Competition between red kangaroos (Macropus rufus) and sheep (Ovis aries) in the arid rangelands of Australia

Abstract Competition between red kangaroos and sheep in the more arid areas of Australia was examined by means of a large-scale manipulative experiment incorporating two replicates of each of three treatments: sheep-only, kangaroo-only and a sheepAangaroo mixture. The study was conducted over two years during which time pasture conditions varied markedly. Competition was intermittent, occurring only during a period of climatically related food depletion (semi-drought). At this time there was a large increase in kangaroo densities due to an influx of kangaroos from neighbouring areas. Competition reduced live-weight in sheep but had no significant impact on wool production. This effect was linked to diet selection. Competition caused red kangaroos to favour paddocks destocked of sheep but had no detectable effect on the condition of kangaroos.     

The signature of scrapie: differences in the PrP genotype profile of scrapie-affected and scrapie-free UK sheep flocks.

The amino-acid sequence of the PrP protein plays an important role in determining whether sheep are susceptible to scrapie. Although the genetics of scrapie susceptibility are now well understood, there have been few studies of the PrP gene at the population level, especially in commercially farmed sheep. Here we describe the PrP genetic profiles of the breeding stock of four UK sheep flocks, comprising nearly 650 animals in total. Two flocks had been scrapie affected for about eight years and two were scrapie free. Scrapie-resistant PrP genotypes predominated in all flocks but highly susceptible genotypes were present in each case. The distribution of PrP genotypes was similar in the scrapie-affected and scrapie-free flocks. The former, however, showed a slight but significant skew towards more susceptible genotypes despite their previous losses of susceptible sheep. Surprisingly, this skew was apparent in younger, but not older, sheep. We suggest that these patterns may occur if sheep flocks destined to become scrapie affected are predisposed by a genetic profile skewed towards susceptibility. The age structure of the scrapie-affected flocks suggests that the number of losses attributable directly or indirectly to scrapie considerably exceeds that recognized by the farmers, and also that significant losses may occur even in sheep of a moderately susceptible genotype. Similar patterns were not detected in the scrapie-free flocks, indicating that these losses are associated with scrapie infection as well as genotype.     

Marital fertility in polygynous unions in Nigeria

The effect of polygyny on fertility, by age cohort, was examined in 4 regions of Nigeria through use of data from the 1981-82 Nigerian Fertility Survey. Simple tabulation of numbers of live births by maternal age and type of marriage union indicated that, with the exception of the 30-39-year age group, fertility in polygynous unions tends to be higher than that in monogamous marriages. Overall, such tabulations reveal an average of 3.90 births among polygynous women and 3.47 births among monogamous women. However, when age-specific fertility rates were compared, except for women under 20 and over 40 years of age, rates were higher in monogamous unions (7.286 overall) than for women in polygynous households (7.200 overall). Mean completed fertility, taking into account marriage duration as well, shows a tendency for women in polygynous unions to be more fertile (with the exception of women aged 25-44 years who had been married 10-19 years). The absolute difference in fertility between the 2 types of marital unions ranged from 0.32 children in the northwest to 0.64 in the southeast. With adjustment for independent variables such as education, the absolute mean differences were reduced, from between 0.28 children in the southeast to 0.42 in the northeast, but the direction of high fertility was still in favor of women in polygynous unions. But when the covariates (e.g., age at marriage) were taken into account as well as the independent variables, there was a dramatic reduction in the mean difference between the fertility of these 2 groups of women. These findings suggest that some changes in reproductive behavior are taking place in Nigeria that are restricting the fertility of women in polygynous unions. These changes are hypothesized to reflect the spread of formal education in Nigeria, with the expectation that women will contribute to the costs involved in educating their children.     

Demographic variation in the Australian desert cassia under grazing pressure

Summary Demographic variation was examined in 3 populations of the Australian desert shrub Cassia nemophila which vary in their grazing histories. Age-specific life tables were constructed from 50 years of observations on mortality and recruitment at the Koonamore Vegetation Reserve in South Australia. Population projection matrix models were used to examine population responses to grazing pressure. The predicted population growth rates, reproductive values and stable age distributions are evaluated and compared with observed results. Grazing by sheep or rabbits, in high populations, prevents shrub recruitment and causes local population extinction. However, where protected from sheep and with low rabbit pressure, Cassia populations have increased. Current sheep grazing practices and rabbit population levels if continued will have a drastic affect on Cassia populations and other shrub species, and on the structure and composition of the Australian arid shrublands in general.     

A Two-Year Participatory Intervention Project with Owners to Reduce Lameness and Limb Abnormalities in Working Horses in Jaipur,India

Background

Participatory methods are increasingly used in international human development, but scientific evaluation of their efficacy versus a control group is rare. Working horses support families in impoverished communities. Lameness and limb abnormalities are highly prevalent in these animals and a cause for welfare concern. We aimed to stimulate and evaluate improvements in lameness and limb abnormalities in horses whose owners took part in a 2-year participatory intervention project to reduce lameness (PI) versus a control group (C) in Jaipur, India.

Methodology/Principal Findings

In total, 439 owners of 862 horses participated in the study. PI group owners from 21 communities were encouraged to meet regularly to discuss management and work practices influencing lameness and poor welfare and to track their own progress in improving these. Lameness examinations (41 parameters) were conducted at the start of the study (Baseline), and after 1 year and 2 years. Results were compared with control horses from a further 21 communities outside the intervention. Of the 149 horses assessed on all three occasions, PI horses showed significantly (P<0.05) greater improvement than C horses in 20 parameters, most notably overall lameness score, measures of sole pain and range of movement on limb flexion. Control horses showed slight but significantly greater improvements in four parameters, including frog quality in fore and hindlimbs.

Conclusions/Significance

This participatory intervention succeeded in improving lameness and some limb abnormalities in working horses, by encouraging changes in management and work practices which were feasible within owners’ socioeconomic and environmental constraints. Demonstration of the potentially sustainable improvements achieved here should encourage further development of participatory intervention approaches to benefit humans and animals in other contexts.     

Reproductive performance of the Y'ankasa sheep of Nigeria

The reproductive performance of the Y'ankasa sheep of Nigeria was studied to determine any seasonal effects on their breeding pattern. The study also aimed at documenting the reproductive performance levels of these animals as a basis for evaluating the results of any breeding improvement program in Nigeria using indigenous or exotic breeds of sheep. The study shows that this breed of sheep is a year-round breeder although some months favor lambing more than others. The age at first lambing and the lambing interval for these animals are 15.5 months and 9.7 months respectively. For 1975, the conception and lambing rates were 87.8% and 139% respectively. The rates for 1976 were 91% and 148%. Seventy-seven percent of the lambing were singles and the rest twins. The sex ratio, number of females per 100 lambs, was 49%. Lamb mortality rate up to 3 months of age was 12.0%. The lambs in our study grew very slowly, gaining only 15 kg in a 9-month period. By 10 months of age these lambs wieghed only 20 kg.     

Further studies on prevalence of hydatidosis in slaughtered animals from North Jordan

Examination of 471 sheep, 118 goats, 157 cattle and 56 camels slaughtered in abattoirs in North Jordan was carried out during March-May 1984. Drought conditions that prevailed during the preceding winter led to slaughtering old female sheep (greater than or equal to 4 years) due to scarcity of food, which allowed us to analyse the prevalence of hydatidosis in various age groups of sheep. An overall infection rate of 27.8, 1.7, 5.8 and 10.7 percent was found in sheep, goats, cattle and camels, respectively. The infection rate was as low as 1.5 percent in male and 1.9 percent in female sheep under 2 years of age. However, the rate of hydatid infection increased with age and reached as high as 63.7 percent in ewes 4 years of age and older. The percentage of animals with fertile cysts was also highest in sheep (68.7 percent of infected animals) and increased with age reaching 100 percent in ewes which were 10 years of age or older. Analysis of all cysts recovered from the livers and lungs of infected ewes from various age groups revealed a sharp increase in the mean total number of cysts in age groups over 8 years of age. The fertility rate of the cysts in the liver was significantly greater in ewes 6 years old or more (64.8--78.6 percent) than in younger age groups (8.7-46.2 percent). In the lung, the fertility rate increased progressively with age reaching as high as 97.9 percent in ewes 10 years old or more. These findings of high infection and fertility rates of hydatid disease in sheep, particularly of older age groups, prompt plans for further epidemiological studies and control programmes.     

Prevalence of hepatitis-B surface antigen among blood donors and human immunodeficiency virus-infected patients in Jos, Nigeria

Information is very scarce on the prevalence of hepatitis-B virus (HBV) infection among blood donors and patients with human immunodeficiency virus (HIV) infection in Nigeria. Hepatitis-B surface antigen (HBsAg) ELISA was used to determined the prevalence of HBsAg among 175 blood donors (aged 20-40 years) and 490 HIV-infected patients (aged 17-60 years) in Jos, Nigeria. Twenty-five (14.3%) of the blood donors and 127 (25.9%) of the HIV-infected individuals were HBsAg seropositive, indicating a higher HBV infection among HIV-infected persons than among healthy blood donors. A slightly higher HBsAg seroprevalence was recorded in the males (14.6%) than females (12.9%) of the blood donors. Among the HIV-infected patients, the males had considerably higher HBsAg seroprevalence than the females (31.8 vs 22.1%) with the highest prevalence of HBsAg occurring in the 51-60 years age group (44%), followed by those of 31-40 years (28.2%). Results confirmed the high endemicity of HBV infection in Jos, Nigeria and the significantly greater prevalence of HBV infection among HIV-infected patients than among blood donors.     

Malaria Endemicity in the Rural Communities of Ebonyi State,Nigeria

Malaria remains a global health threat. Approximately 97% of the population is at risk in sub-Saharan countries, particularly Nigeria. This study compared the performance of 2 diagnostic methods in assessing malaria endemicity in the rural communities of Ebonyi State, Nigeria. A total of 1,140 study participants were screened for malaria parasite using Rapid Diagnostic Test kits (RDT) in the field, while thick and thin films for microscopy were examined in the laboratory. Our result showed that malaria prevalence was 56.8 by RDT and 38.6% by microscopic test. Age group under 10 years had the highest prevalence of 28.9% (RDT) and 23.6% (microscopy), respectively. The highest prevalence of 19.5% by RDT was recorded in Onicha Local Government Area, while the highest prevalence of 13.4% with microscopy was recorded in Ezza North Local Government Area. The sensitivity and specificity of microscopic examination were both 100%, while those of RDT were 95.5% and 75.9%, respectively.     

Syndrome of arachnomelia in Simmental cattle

Background  

Epidemiological studies have used farmer estimates of the prevalence of lameness in their flocks. This assumes that farmers can identify lame sheep. Eight movie clips of sheep with locomotion from sound to moderately lame were used to investigate the ability of farmers and sheep specialists to recognise lame sheep. Each participant was asked to complete a form and indicate, for each movie clip, whether they thought the sheep was lame and whether they would catch it if it was the only lame sheep or if 2 – 5, 6 – 10 or > 10 sheep were equally lame. The farmers' responses were compared with their estimates of flock lameness prevalence and the interval between observing a lame sheep and catching it.