Sheep Health Research Articles

The effect of annual shearing time on wool production by a spring-lambing Merino flock in south-eastern Australia

Time of shearing affects many aspects of wool production and sheep health but no study has examined these factors concurrently in a spring-lambing, self-replacing Merino flock in southern Australia. A 5-year field experiment compared wool production in spring-lambing Merino ewes and their progeny shorn at different times and managed under commercial conditions in south-eastern Australia. Groups of 200 adult ewes were shorn in December, March or May, and their progeny were shorn in December or October, March or June, or May or July, respectively. There was no consistent association between time of shearing and the staple strength of wool (P = 0.73). December-shorn ewes produced significantly lighter and finer fleeces (average 19.1 μm, 3.0 kg clean weight) than did March-shorn ewes (19.4 μm, 3.1 kg). Fleeces from ewes shorn in May were of similar weight to those from March-shorn ewes (3.1 kg), but they were of significantly broader diameter (19.7 μm). In young sheep, desirable changes in some wool characteristics for each shearing group were offset by undesirable changes in others. On the basis of median historical (1991–2006) wool prices, shearing ewes in March and their progeny first in June produced the greatest total value of wool over a sheep’s lifetime ($161/head). The wool values per head for other shearing times were as follows: March (weaners)–March (ewes): $158; October–December: $157; December–December: $153; July–May: $151; and May–May: $148. Thus, December and March shearing were appropriate alternatives for maximising wool value produced from a self-replacing Merino flock in south-eastern Australia, whereas May was a less preferable shearing time because it always produced wool of lesser value.

Seroprevalence of Peste des Petits Ruminants (PPR) virus antibodies in goats and sheep in north-eastern Uganda

Peste des petits ruminants (PPR) is a contagious viral disease of small ruminants in Africa and Asia. PPR outbreak in Uganda was reported in Karamoja region in July, 2007, but the disease epidemiology has not been fully explored. This study was undertaken to determine the seroprevalence and the extent of distribution of PPR antibodies in goats and sheep within the districts surrounding Karamoja so as to guide future control efforts. Serum samples were purposively collected from eleven districts including Soroti, Kumi, Kapchorwa, Katakwi, Sironko, Bukedea, Bukwa, Kaberamaido, Lira, Pader, and Kitgum based on the history of poor goat and sheep health. Seroprevalence of PPR virus antibodies was determined using competitive enzyme linked immunosorbent assay (c-ELISA). The overall seroprevalence of PPR virus antibodies in sheep and goats in the districts surrounding Karamoja region was 9.4 % (CI=95%, 7.6-11.2). No PPR virus antibodies were detected in sera from Kaberamaido and Soroti districts while Kitgum district recorded the highest seroprevalence of 21.3% (CI=95% 16.6- 25.8). This study shows that PPR antibodies were distributed beyond the initially confirmed Karamoja region. There is need for further research on the epidemiology and risk factors of PPR in Uganda. Key-words: Peste des petits ruminants (PPR), seroprevalence, goats and sheep, Uganda.

Olfaction in the female sheep botfly

The nasal botfly Oestrus ovis (Diptera, Cyclorrhapha: Oestridae) is a myiasis-causing insect species, which affects the health of sheep, goats and humans. Gravid females are viviparous and larviposit into the animal's nostrils. Host-searching and larvipositing flies are visually guided and influenced by climatic conditions, whereas olfaction seemed to play no role in this process. However, here, we show that the antennae of adult O. ovis female flies are relatively small but well developed and inhabited by several types of olfactory sensilla. Further, we show that the antennal lobes of this species receive input from antennal afferents and consist of a clearly defined glomerular organisation. We also give the first evidence of the fly's ability to detect several synthetic odour compounds. Our findings provide a morpho-functional basis for future investigations on olfactory-mediated behaviour of this insect pest.

Examination of teeth in sheep health management

Effectively functioning teeth are essential for sheep health and optimum production. Examination of the teeth of sheep is an important part of any clinical investigation and can be used to estimate age up to four years and to identify dental disorders. Examination of the incisor teeth is straightforward; however, a thorough evaluation of the pre-molar and molar teeth is difficult and may result in abnormalities of these teeth going unnoticed. Dental abnormalities often result in decreased production and can be important on both an individual sheep and a flock basis. Associated clinical signs include abnormal appearance of the incisors, weight loss, cud-staining and swelling or malocclusion of the jaw. The aetiology of many dental abnormalities is not well understood, which can make prevention difficult.

Bacteriological examinations in sheep health management

Pathogenic bacteria adversely affect the health and productivity of sheep in a variety of production systems. This paper provides a guide to the major bacterial diseases of sheep, outlines best practice for collection and transport of appropriate samples to a diagnostic laboratory and summarises laboratory techniques used to identify the pathogens.

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.

Haematological tests in sheep health management

The evaluation of sheep complete blood cell count (CBC) can be of significant aid to clinical examination. Accurate assessment of haematologic data depends on the proper collection, preparation and transportation of blood samples. Blood should be drawn from animals at rest, calm and well restrained at the time of sampling, in order to avoid artifactual changes, such as a stress leucogram caused by endogenous steroid or epinephrine release or haemolysis from traumatic collection. Proper venipuncture is important to avoid contamination by tissue thromboplastin, which encourages clot formation and invalidates haemostatic function tests. Tubes must be filled to capacity to ensure the proper blood–anticoagulant ratio. When haemostasis tests are indicated, blood should be carefully transferred to vials containing anticoagulant, in order to prevent haemolysis, which precludes the use of evacuated tubes. Blood samples for haematologic studies are best processed as soon as possible after collection, but if a delay is expected they should be refrigerated at 4 °C and for a maximum period of 24 h (with the exception of platelet counts which should be performed within 4–6 h after sample collection), while air-dried blood smears must be prepared immediately after sampling to be stained with Wright or any modified Romanovsky stain. Complete blood counts can be performed either manually or with the aid of sophisticated instrumentation. Automated haematology instruments provide rapid cell counts of blood, haemoglobin calculation, potentially useful erythrocyte indices, but they cannot detect morphologic abnormalities and haemoparasites. Red blood cell counting and morphological changes are useful when evaluating anaemia. The differential white blood cell count is more important than the total white blood cell count, because increases and decreases in individual cell types may occur simultaneously, leaving total count unchanged. Overall, CBC can provide valuable information to the sheep clinician. Moreover, evaluation of a well-prepared blood film is an essential adjunct to interpretation of all cell counts, allowing detection of significant morphologic abnormalities or presence of haemoparasites.

Clinical evaluation of reproductive ability of rams

Clinical evaluation of reproductive ability of rams is an integral part of sheep health management programs. The majority of problems adversely affecting the reproductive ability of rams can be easily detected with clinical evaluation. The procedure is easy to perform, has a small cost and does not require specialized support from a veterinary laboratory. As a management procedure, the method should be applied two months before the breeding season, in order to detect problems, which would adversely affect the reproductive ability of rams. It should also be performed when selecting ram-lambs as replacement sires in a flock; their first evaluation should be performed at weaning, followed by another two examinations: two to four months later and before the first mating season of these rams. The method should also be performed before the purchase of any ram as sire in a flock. Regular monitoring of reproductive ability of rams in a flock contributes to early diagnosis of disorders. As a diagnostic procedure, the method should be performed during the investigation of reproductive problems within a flock. During the evaluation of reproductive ability of rams, various clinical findings can be detected and their importance can vary. In general, rams should be in good condition and have healthy genitalia, normal libido and the ability to mate the ewes. Clinical evaluation of rams is performed in the following stages: (a) history-taking, (b) evaluation of the ratio “ewe:ram” in the flock, (c) general clinical examination, (d) clinical examination of the genitalia, (e) ultrasonographic examination of the genitalia and (f) evaluation of libido. Veterinary advice is important, in order to incorporate the clinical evaluation of reproductive ability of rams into the health management of sheep flocks.

Epidemiological information in sheep health management

We use epidemiology whenever we consider the management of sheep health. To measure a disease, we need a precise and unique case definition and we often use diagnostic tests to assist in defining a disease. Diagnostic tests are not always accurate. Thus, it is necessary to consider the decisions that will be taken, based on the result of testing, in order to decide the most useful approach to interpret a test based on its test sensitivity and specificity and the prevalence of the disease in a flock. This is particularly important when decisions on culling or selection of sheep to attain, e.g. freedom from disease, are made on the basis of test results. Infectious diseases spread within and between flocks in a variety of ways; brought-in sheep are the most likely source for introduction of a new pathogen or strain of a pathogen. When a pathogen enters a naïve flock, it spreads through susceptible sheep and persists in the flock, whilst there are susceptible sheep that can be infected. Pathogens use a variety of techniques to persist, including changes in the pathogen itself, alterations in infected hosts enabling them to remain infectious for prolonged periods or to be re-infected, persistence in other host species or in the environment. We need to consider these strategies to decide whether elimination or control of a particular pathogen is more likely to be effective. Whatever the flock control strategy, treatment of diseased individuals is essential for their welfare and can also protect the rest of the flock, if treatment reduces the infectious period. Decisions on management of disease are based on our knowledge of the flock and its management and the evidence base for various control strategies. There are now formal techniques for evaluating the evidence base that can assist in evaluating evidence. One area where we need to evaluate evidence is on cause. It is not possible to prove anything, but we can use the weight of evidence to evaluate likely cause. There are nine aspects of association with which we can evaluate a piece of evidence; these are: strength, consistency, specificity, temporality, dose–response, plausibility, coherence, experiment and analogy.

Parasitological examinations in sheep health management

Sheep are parasitised by a diverse range of internal and external parasites. The majority of adult helminths and many of the ectoparasites affecting sheep, are grossly visible to the naked eye due to their size. With internal parasites, however, observation and detection of adult stages is generally only possible on post-mortem examination of the appropriate organs and viscera. More often, the presence of parasites in the gastrointestinal tract, lungs and liver can be detected by parasitological examinations of appropriate samples, usually faeces, for the presence of their eggs, cysts or larval stages. This review focuses on the clinical and laboratory diagnostic approaches to a number of important parasitic diseases of sheep, in particular, parasitic gastroenteritis and the detection of species showing the presence of anthelmintic resistance, as well as other diseases, such as liver fluke and coccidiosis. The diagnosis of ectoparasite infections is generally much more straightforward, because of their size and location on the skin. However, misidentification can occur without appropriate experience in parasite identification. Accurate and correct diagnosis is fundamental to good parasite control, otherwise inappropriate or consequential, apparent treatment failures may occur.

The implementation and value of diagnostic procedures in sheep health management

Good sheep flock health management is a prerequisite for economically sustainable, efficient productivity. Veterinary flock health planning involves disease investigations, monitoring and biosecurity, each of which is underpinned by the implementation of diagnostic techniques. While a large array of diagnostic techniques is available, it is important that the most appropriate tests are chosen and that the results are interpreted rationally, within the context of the problem being investigated or monitored. This paper uses examples of common production-limiting problems to illustrate the implementation and value of diagnostic techniques in sheep flock health management.

Phenotypic and genetic relationships between udder morphology and udder health in dairy ewes

The aim of this paper was studying the phenotypic and genetic relationships between udder morphology traits and udder health in dairy sheep. From 2000 to 2008 udder traits, somatic cell count (SCC) and clinical mastitis cases were recorded in an experimental flock consisting each year of around 900 ewes. A logistic regression was performed to evaluate the risk for a ewe of showing either a mastitis or at least 2 daily SCC records greater than 1 × 10 6 cells/ml in one of its lactations as function of udder traits scored in 1st lactation. 1587 individual udder scores and 39,950 SCC daily records were used for the analysis. Secondly, genetic correlation between lactation mean of somatic cell score and udder traits were estimated by a REML method applied to four bi-trait animal models, using data from 2251 primiparous ewes. Logistic regression results indicated that the risk of mastitis or high SCC values during the productive life increased as the cistern height increased and the degree of udder suspension and udder depth decreased. This suggests that the appraisal of the udder is a useful tool for culling decision aimed at increasing the sanitary status of the flock. The genetic correlation between lactation SCS and udder traits were favourable for udder depth (−0.50 ± 0.12), teat placement (0.39 ± 0.011) and degree of udder suspension (−0.42 ± 0.011) and closed to zero for the degree of separation of the two halves. Thus selection for udder morphology, already implemented in some dairy sheep breeds with the aim of improving machine milkability, will lead to a favourable correlated genetic response on SCC.

Foot health in sheep – prevalence of hoof lesions in UK and Irish sheep

Foot health in sheep – prevalence of hoof lesions in UK and Irish sheep

Teladorsagia circumcincta in the sheep abomasum: defining the role of dendritic cells in T cell regulation and protective immunity

Parasitic nematodes of the small-ruminant gastrointestinal tract pose a problem worldwide. The impact of these pathogens is worsened by the emergence of anthelmintic resistance to all three available classes of drugs. In addition to causing considerable economic loss, these parasites are detrimental to the health and welfare of sheep and goats. Vaccination offers an alternative approach to drug-based control and a great deal of investment has gone into the investigation of protective antigens for some of these nematode species. However, attempts at vaccination are hindered by a lack of understanding of how best to promote protective immunity to nematode species, such as Teladorsagia circumcincta, which inhabits the abomasum of sheep. This situation contrasts with that in murine models of gastrointestinal nematode infection, where the basis of protective immunity is increasingly well understood. In this review, we discuss the current knowledge of the immune effector mechanisms elicited by T. circumcincta and consider the probable role of dendritic cells in the initiation of both effector and regulatory responses in the abomasum.

Current management of farms and internal parasites by conventional and organic meat sheep French farmers and acceptance of targeted selective treatments

Sheep meat production in France is characterized by large flocks and a limited supply of labour. Digestive-tract strongyles are considered as one of the main health problems and control relies mostly on the use of anthelminthics, although resistance to at least the benzimidazoles is increasing. We conducted interviews on nine conventional and seven organic farms regarding whether an anthelmintic targeted selective treatment program could fit within the operations of the farms. In addition, necropsies of lambs were performed on three organic farms, and faecal egg counts and small lungworm counts were performed on all farms in autumn in ewes. Each interview consisted of an open discussion on sheep health and was terminated with comments on digestive-tract helminth infection as detected in parallel with the interview. Factors likely to affect the adoption of the targeted selective treatment approach were subjected to cluster analysis. Conventional farms were mostly advised by veterinarians and relied on systematic planning of anthelmintic treatments. The frequency of treatments was up to once a month for lambs and two to three times a year for ewes. The concept of selecting animals to be treated according to a scheme of targeted selective treatments based on phenotypic markers (e.g., anaemia, diarrhoea, weight gains) was not seen as feasible by these farmers. Conversely, organic farmers, with greater use of advisors and a restricted range of anthelmintic treatments were more susceptible to integrating phenotypic markers into their practices for controlling digestive-tract strongyles.

Sheep responses to grazing ryegrass with AR37 endophyte

Over 10 years the health and production of sheep grazing ryegrass with AR37 fungal endophyte was compared to those grazing Standard and AR1 endophytes, and endophyte-free, under four different trial protocols, including short and long term grazing, cultivar effects and seasonal differences. Sheep developed some ryegrass staggers on AR37 treatments but it was less frequent and usually less severe than on Standard.

Availability of gastro-intestinal nematode larvae to sheep following winter contamination of pasture with six nematode species on the Northern Tablelands of New South Wales

This experiment was designed to determine the infective consequences of winter pasture contamination by sheep infected with 6 species of trichostrongylid gastro-intestinal nematode (GIN) at Armidale in the New England region of NSW. Ten helminthologically inert pasture plots were contaminated using ‘donor’ sheep harbouring artificial infections of Haemonchus contortus, Trichostrongylus colubriformis, Trichostrongylus vitrinus, Trichostrongylus axei, Nematodirus spathiger and Teladorsagia circumcincta. A single plot was contaminated in March to serve as a positive control and three plots in each of the winter months of June, July or August of 2007. Weekly assessments of 24 h faecal output and worm egg count of all donor sheep, combined with differentiation of larval cultures enabled calculation of total egg deposition per plot for each GIN species for each month of contamination. All plots were provided with supplemental spray irrigation sufficient to remove desiccation as a cause of non-development. The infective consequence of each monthly contamination was assessed by grazing each plot with two tracer sheep for the last 14 days of each month following contamination until a final grazing in November. Translation for each GIN species was expressed as the percentage of eggs deposited translating to worms counted in tracer sheep. The GIN parasites fell into two distinct groups differing greatly in translational success. Translation of egg to establishment in the tracer host was ineffective for H. contortus, T. axei and T. colubriformis but effective for T. vitrinus, T. circumcincta and N. spathiger. Overall mean total translation for each of these species throughout the experiment was respectively 0.00%, 0.00%, 0.00%, 0.34%, 0.45% and 0.48%. We conclude that winter contamination of pastures in this region with eggs of the latter 3 species is capable of impacting on the health of sheep subsequently grazing these pastures. Where H. contortus and T. colubriformis predominate, paddocks selected for spring lambing may be grazed safely over the winter months without contributing significantly to pasture contamination. These findings are particularly relevant to the preparation of clean spring lambing paddocks in this region using grazing management.

The role of the companion animal veterinary surgeon in behavioural husbandry

An American Veterinary Medical Association mission statement regarding the human-animal bond reads, veterinary surgeon's role in the human-animal bond is to maximise the potential of this relationship between people and animals. To fulfil this aim and implicit obligations, as well as enhancing the welfare of both human and animal companion, it is impossible to ignore the emotional and behavioural aspects of this relationship in favour of purely physiological illness and disease. Rather than only addressing defects in the dog-human relationship which have already occurred – the client complains about destruction in the home, urinating indoors or being snappy towards the children for example – the onus is now on all veterinary surgeons to be rather more pro-active in their approach. It must be appreciated that a relationship does not exist merely between a particular pet and members of their family, but also between that animal and all the humans it may happen to come into contact with elsewhere, including those inhabiting veterinary surgeries. The dog which becomes progressively harder to handle in the surgery over time, although frequently labelled as 'difficult', 'aggressive' or simply 'vicious', is in reality simply one whose behavioural needs and emotional welfare have been inadvertently damaged in the process of maintaining physical health or attending to physical disease. On the other hand, a dog who is genuinely pleased to enter a veterinary surgery, and whose behaviour and emotions have been nurtured in the same way as its physical needs, is a tribute to the attending veterinary surgeon as well as its owner. At present, lack of adequate and appropriate behavioural management is routinely compromising much of the treatment vets try to deliver to their patients, both medical and surgical. In the UK, the new Animal Welfare Act (2007) stipulates that all those in contact with an animal have a 'duty of care' towards it, which encompasses both physical and mental needs, health and well being. It is therefore a legal, if not also moral, obligation of veterinary surgeons in the UK to ensure that necessary, effective and humane behavioural management is in place, bearing in mind these requirements. It would however often seem that farm animals have the better deal in this regard. Management systems and environment are routinely considered to have a bearing on the cow, sheep or pig's physical health and the development of disease, and are therefore automatically included in the large animal veterinary surgeon's remit. Not so for the domestic dog, which may be skidding uncomfortably on a fashionable laminate floor, subjected to the impact of noise from a multitude of household gadgets, or contained and punished with electric shock, and yet its small animal veterinary surgeon be completely unaware of its plight. How can we truly say such animals are 'under our care' if this is the case? This poster presentation will summarise some of the very simple means whereby not only appropriate behaviour, but also accompanying emotions, can be generated and maintained in dogs in all veterinary contexts. Using basic knowledge of learning theory and its practical application, the behavioural repertoire of a dog can be manipulated and cared for in such a way as to ensure emotional welfare and maximum success of medical and surgical veterinary interventions. Not only will such care have benefits within the context of the surgery, as a dog's need to become aggressive will be diminished, but veterinary surgeons and nurses will be presented as 'role models' to be emulated by their clients in all aspects of the animal's life. It will help prevent iatrogenic behavioural damage, allow 'best practice' in terms of clinical care, and result in much improved client loyalty and compliance. Above all, the field of behaviour must not be viewed as time-consuming and financially inefficient, only to be tackled on a 'case-by-case' basis. Instead, it must become second nature for any veterinary surgeon to consider both external behaviour and underlying emotions as part of his or her daily clinical repertoire and demonstrate routine care for them. This is the basis of 'behavioural husbandry'.

Clinical profile of sheep fed non-conventional feeds containing phenols and condensed tannins

A study was carried out to investigate the effects of feeding low quality non-conventional feeds (NCF) containing phenols and condensed tannins on the clinical profiles of sheep. Thirty-two Omani sheep were fed one of four diets with two base roughages, urea-treated palm frond (UTPF) and Rhodesgrass hay (RGH) and two concentrates, commercial concentrate (CC) and a by-products concentrate (BC) for 120 days. Haematological, serum biochemical and urine analyses were used to assess sheep health. Non-conventional feeds (urea-treated palm frond and by-products concentrate) contained higher levels of polyphenols and condensed tannins than conventional feeds (Rhodesgrass hay and commercial cubes). Feeds based on urea-treated palm frond had lower dry matter, crude protein, acid detergent fibre, neutral detergent fibre, gross energy ( P < 0.001) and ash ( P < 0.05) digestibility coefficients than those based on Rhodesgrass hay. Animals fed NCF had lower feed intake ( P < 0.001) and lower body gain ( P < 0.001) than those fed conventional ones. They also produced larger volumes of faeces ( P < 0.01) which contained higher levels of nitrogen ( P < 0.001) and had lower viscosity values of intestinal content ( P < 0.001). Rumen liquor of NCF-fed animals had higher pH and lower ammonia–nitrogen levels ( P < 0.01). Animals fed urea-treated palm frond plus by-products concentrate had lower lymphocyte ( P < 0.01), monocyte ( P < 0.05) and eosinophil ( P < 0.05) counts by the end of the trial than those fed Rhodesgrass hay based diets. The urea-treated palm frond and by-products concentrate fed animals had lower blood urea nitrogen (BUN) levels ( P < 0.05), higher ( P < 0.01) alanine aminotransferase (ALT) and lower serum iron ( P < 0.001) than those fed Rhodesgrass hay based diets. There was a trend of increasing blood, leukocytes and specific gravity in the urine of NCF-fed animals. This experiment implies that feeding low quality non-conventional feeds containing antinutritional factors for relatively long periods might produce subtle negative effects on the physiology and chemistry of the digestive system and blood parameters which might negatively affect sheep health and make them more susceptible to diseases.

Veterinary consultancy and health schemes in sheep: Experiences and reflections from a local German outlook

Based on the experiences on veterinary consultancy in numerous small ruminant flocks, a “hygiene guideline” was developed, as a modular standard procedure for establishing flock individual health plans. The hygiene plan can be used in whole or in modules according to the needs, the possibilities and the facilities of the flocks. For small flocks and for hobby shepherds, a health plan calendar has been developed. The current situation in the flocks of the “ Sheep and Goat Flock Health Service-Hannover” is reflected under the light of the hygiene guidelines. These guidelines and the current situation in the health service are discussed with respect to general needs of health plans for small ruminant flocks.