Distribution of leucocyte antigens in Icelandic horses affected with summer eczema compared to non-affected horses

Three hundred and three horses, exported from Iceland to Norway, Sweden, Denmark, Switzerland or Germany were tested for their distribution of leucocyte antigens. One hundred and thirty-six horses were affected with summer eczema. The panel of sera recognised the internationally accepted ELA-specificities A 1 to A10, and the nine work shop specificities W 11 to W 15 and W 18 to W 21. Also, some local specificities, characterised in Switzerland (Be I, Be III, Be 8, Be 25, Be 26, Be 27), and two non major histocompatibility complex (MHC)-linked antigens (Ely 1:1, Ely 2) were included. Only one antigen, Be 8, gave a statistically significant difference in distribution between the two populations: Relative risk = 2.5, x2 = 10.11, corrected P less than 0.01.     

Owner survey of tarsocrural effusion (bog spavin) in Clydesdale horses

A postal survey of the owners of Clydesdale horses in the UK and USA was conducted to obtain information on tarsocrural effusion ('bog spavin') as an indicator of osteochondrosis from 935 horses. Additional information requested included details of how this condition was investigated and treated. The reported tarsocrural effusion incidence was 10 per cent. The majority of respondents believed the condition to be of concern to Clydesdale owners, but only a minority were aware of the implications of tarsocrural effusion, suggesting that owner education would be of benefit.     

Nutritional value of timothy haylage in Icelandic horses

Four mature Icelandic geldings were used in a balance trial to investigate the effect of stage of maturity of timothy (Pleum pratence L.) haylage fed at maintenance level on coefficients of total tract apparent digestibility (CTTAD), and nitrogen and energy metabolism in a 4 × 4 change-over arrangement of treatments. The content of fibre increased and crude protein content decreased with advancing stage of maturity. Very high CTTAD values were found for DM, OM, CP, CF, NDF and ADF in the first two cuts. Overall, there was a negative relationship between stage of maturity (p < 0.05) and the CTTAD of all measured dietary components. Nitrogen (N) intake, N losses in urine and N balance were affected (p < 0.05) by stage of maturity, while the N losses in the faeces were unaffected. There was a strong correlation (r² = 0.95) between N balance and water intake. Gross energy intake and losses in urine (as % of digestible energy intake) were unaffected by stage of maturity, while the energy balance was affected (p < 0.05). The digestible energy content of the timothy haylage studied ranged from 14.1 to 9.0 MJ/kg DM.

In conclusion, early-cut timothy haylage (stem elongation to flowering) has the energy content required to form the basis of diets for high-performing horses. Late-cut timothy haylage (seeding to late seeding), on the other hand, can be used to fulfil the energy and protein needs of maintenance-fed Icelandic horses.     

Genetic analysis of competition data on Icelandic horses

In a study of the possibility of using competition data in the genetic evaluation of Icelandic horses, data from competitions held in Iceland between 1999 and 2004 and in Sweden between 1998 and 2004 were analyzed to estimate the genetic parameters of competition performance traits. The data-sets from both countries included 18 982 records of 3790 horses in 379 different events. Two types of competition were included: sport competitions and gæðinga competitions performed on oval tracks and on a straight track. Each type of competition involves several disciplines in which the horses are ridden in the various gaits. The traits analyzed were two different measures of four-gait, five-gait and tölt, and one pace trait. In both the four-gait and five-gait tests the gaits walk, trot, tölt and gallop are exhibited. In the five-gait test, pace is also exhibited. The traits tölt and pace are performances of these single gaits. Highly correlated and similar traits were combined, and three new traits relating to tölt, four-gait and five-gait were formed. No large differences in means or standard deviations of traits were found between countries. All traits were approximately normally distributed. Genetic parameters were estimated using linear animal models including the fixed effects of sex, age and event for all traits, and the level of discipline was included for some traits. Random permanent environmental effects were also included. Estimated heritabilities were moderate to high, ranging from 0.18 to 0.21 for sport-competition traits, from 0.33 to 0.35 for gæðinga-competition traits and from 0.19 to 0.22 for combined traits. Estimated genetic correlations between different sport-competition traits varied from 0.63 to 0.96, and between the two gæðinga-competition traits it was estimated at 0.43. Genetic correlations between sport- and gæðinga-competition traits ranged from − 0.42 to 1.00. It was concluded that competition traits are suitable to include in genetic evaluations.     

Intradermal skin testing in Icelandic horses in Austria

Icelandic horses in Austria are commonly affected by an allergic inflammatory skin disease recurring during the summer seasons, which shares characteristic features with Culicoides hypersensitivity. However, the causative agents have not yet been identified. Therefore, intradermal skin testing (IDST) with a standardised extract of Culicoides variipennis and 21 other allergens relevant within Austria was performed in 81 Icelandic horses. All horses included into the study were treated regularly with ivermectin and had no history of administration of anti-inflammatory drugs. Forty-three of these horses were affected by summer seasonal recurrent dermatitis (SSRD). No history or signs of any other disease were evident in any horse. Pruritic dermatitis due to ectoparasites, bacteria and dermatophytes were ruled out by means of fungal culture, skin scraping and biopsy. Culicoides variipennis antigens evoked a positive cutaneous reaction in 1 of 38 normal and 3 of 43 SSRD horses at the proposed dilution of 1:50,000 or 1:25,000, and in 24 of 38 normal and 13 of 43 SSRD horses at a dilution of 1:10,000. Furthermore, no significant differences in onset or intensity of skin reactions to the 21 other allergens, including pollens, moulds, mites and insects, except deerfly and horsefly, were obvious between the 2 groups. Efficiency (percentage of correct results) for the used antigens in the skin test was 0.47-0.60. Maximal sensitivity was 0.51. Altogether, 38 of 43 SSRD horses and 28 of 38 normal horses were positive 4 h after allergen administration. The divergence between IDST results and manifestation of clinical signs found in this study underlines the difficulties associated with establishing a skin test protocol in horses within a geographic area. Whether the outcome of this study would have been influenced significantly by using Culicoides spp. present in Austria has to be clarified in future research.     

Nutritional value of mixed grass haylage in Icelandic horses

The influence of cutting time of mixed grass haylages on energy and nitrogen (N) metabolism, and the coefficients of total tract apparent digestibility (CTTAD) were studied in four mature Icelandic geldings by performing total collection of faeces and urine. The experiment was arranged as 4 × 4 balanced Latin square. The four haylages used were harvested at different times and were considered to be representative in botanical composition for mixed grass haylages in Iceland.     

Risk factors for faecal sand excretion in Icelandic horses

REASONS FOR PERFORMING STUDY: Sandy soil is often mentioned as a risk factor in the development of sand-related gastrointestinal disease (SGID) in the horse. There are other variables, but few studies confirm any of these. OBJECTIVE: To investigate soil type, pasture quality, feeding practice in the paddock, age, sex and body condition score as risk factors for sand intake in the horse. METHODS: Faeces were collected from 211 Icelandic horses on 19 different studs in Denmark together with soil samples and other potential risk factors. Sand content in faeces determined by a sand sedimentation test was interpreted as evidence of sand intake. Soil types were identified by soil analysis and significance of the data was tested using logistic analysis. RESULTS: Of horses included in the study, 56.4% showed sand in the faeces and 5.7% had more than 5 mm sand as quantified by the rectal sleeve sedimentation test. Soil type had no significant effect when tested as main effect, but there was interaction between soil type and pasture quality. Significant interactions were also found between paddock feeding practice and pasture quality. CONCLUSION: To evaluate the risk of sand intake it is important to consider 3 variables: soil type, pasture quality and feeding practice. Pasture quality was identified as a risk factor of both short and long grass in combination with sandy soil, while clay soil had the lowest risk in these combinations. Feeding practice in the paddock revealed feeding directly on the ground to be a risk factor when there was short (1-5 cm) or no grass. Also, no feeding outdoors increased the risk on pastures with short grass, while this had no effect in paddocks with no grass. More than 50% of all horses investigated in this study had sand in the faeces. POTENTIAL RELEVANCE: The identification of risk factors is an important step towards prevention of SGID. Further research is necessary to determine why some horses exhibit more than 5 mm sand in the sedimentation test and whether this is correlated with geophagic behaviour.     

Genetic analysis of 'breeding field test status' in Icelandic horses

Genetic evaluation of Icelandic horses is currently based on results from breeding field tests where riding ability and conformation of the horses are evaluated over the course of 1-2 days. Only a small part of registered horses attend these field tests, and it can be assumed that these are not a random sample of the population. In this study, the trait test status was introduced, describing whether a horse was assessed in a breeding field test. This trait was analysed to find out whether it has a genetic variation and how it correlates genetically to other traits in the breeding goal. Breeding field test data included 39,443 mares born in Iceland in 1990-2001, of which 7431 were assessed in the period 1994-2007. The trait was defined in relation to age, gender and stud of horses. Variance and covariance components were estimated using the Markov Chain Monte Carlo method by applying the Gibbs sampler procedure in the DMU program. Three multivariate analyses were performed where the test status trait was analysed with breeding field test traits. Animal models and sire models were applied. Based on estimated heritabilities (0.51-0.67) and genetic correlations (0.00-0.87), the test status trait showed significant genetic variation and was strongly correlated to some traits. The test status trait reflects preselection in the breeding field test traits and should be included in the genetic evaluation to enhance the procedure, reduce selection bias and increase accuracy of the estimation.     

Influence of subclinical pulmonary findings on cardiac parameters in Icelandic horses

In the present study we examined, if in Icelandic horses an increase in heart and/ or breathing rate is physiological and breed dependend or a sign of a pulmonary or cardiac disease. Therefore we examined 37 Icelandic horses with the prereport of being healthy. During clinical lung examination four horses showed symptoms of a pulmonary disease like increased breathing rate and enforced breathing at rest. These horses were excluded from the study. The other 33 horses were clinically normal. 17 of these horses were unridden (untrained) and 16 horses were regularly worked (trained). After clinical examination in all horses analysis of arterial blood gas, endoscopy with tracheo- bronchial secret analysis and radiographic examination of the lung were carried out. Additionally electro- and echocardiographic examinations and standardised exercise tests with determination of heart and breathing rate as well as plasma lactate values were performed in all horses. During electro- and echocardiographic examination no pathological findings were observed. In total 22 of the 33 horses showed abnormal lung findings. Seven horses had mild signs of RAO and 15 horses had mild signs of interstitial bronchitis. Three horses had additional pulmonary haemorrhage. Eleven out of the 33 horses showed no abnormal lung findings. The breathing rate at rest differed not significantly between horses with (21 +/- 1/min) or without (23 +/- 2/min) pulmonary findings. The heart rate also did not differ significantly between horses with (39 +/- 1/min) or without (42 +/- 1/min) pulmonary findings. In contrast to this the trained Icelandic horses with abnormal pulmonary findings had significantly higher heart rates (p = 0.01) and significantly lower breathing rates (p = 0.009) compared to those without abnormal pulmonary findings. During echocardiography Icelandic horses with abnormal pulmonary findings had significantly larger left atrial diameter (without abnormal pulmonary findings: 82 +/- 7 mm, with abnormal pulmonary findings: 90 +/- 8 mm, p = 0.02). Compared to the untrained Icelandic horses (5.4 +/- 2 mmol/l) the trained horses showed significantly lower plasma lactate values (3.1 +/- 2 mmol/l, p = 0.001) immediately after exercise. After exercise the icelandic horses with abnormal pulmonary findings had significantly higher breathing rates (p < 0.05) and longer recovery periods (30 minutes) than horses without abnormal respiratory findings (15 minutes). Recovery of heart rate after exercise showed no differences between groups.     

An epidemiological study of summer eczema in Icelandic horses in Norway

A survey of summer eczema was conducted on 391 Icelandic horses in Norway. The study showed a prevalence of summer eczema of 17.6 per cent in the horses investigated. Icelandic horses born in Norway where shown to be less affected with summer eczema than imported horses, 8.2 per cent and 26.9 per cent respectively (P less than 0.001). There was no difference in the prevalence of summer eczema relative to gender or colour of the horse. The number of horses affected with summer eczema rose with increasing age and the number of years which had elapsed since importation. On average, Icelandic horses born in Norway developed summer eczema at the age of 5.3 years. The onset of disease for imported horses was, on average, 4.1 years after importation. The study also revealed that a significantly greater number of horses imported from Iceland to Norway during the period October to April, which has a minimal or low activity of insects (32.3 per cent), had developed summer eczema, compared with horses imported during the period May to September, when insects are more active (16.7 per cent), (P = 0.044). Horses with summer eczema were shown to be significantly more affected by respiratory disease than non-affected horses (P = 0.0086). The most common sites and clinical signs of summer eczema are also described.     

Reference values for echocardiographic parameters of trained and untrained Icelandic horses

The aim of this study was to establish echocardiographic reference values for healthy Icelandic horses. For this purpose cardiologic examinations were performed on 44 healthy trained and untrained Icelandic horses without known cardiologic or pulmonary disease. The atrial diameter of the trained horses were significantly greater than in the untrained horses and the left ventricular free wall diameter was also higher in the trained than in the untrained horses. These findings confirm that the changes of the heart caused by training which have previously been described by other authors in warmbloods, thoroughbreds, dogs and humans are present in Icelandic horses as well. However, in contrast to the findings in race horses, no enlargement of the left ventricle was found in trained Icelandic horses, which may indicate that training conditions of Icelandic horses are not comparable to those of race- or jumping-horses in high level training. The reference values established in this study will serve as basis for the current interpretation of the results of echocardiographic examinations in Icelandic horses. This should enable cardiologists to perform a more detailed and precise examination similar to cardiological examinations in warmbloods and race horses.     

Variations in the concentration of zinc in the blood of Icelandic horses

The effect of factors including the horses' farm environment, their sex and age and whether they suffered from summer seasonal recurrent dermatitis (sweet itch) on the concentrations of zinc in the plasma, whole blood and blood cells of 104 Icelandic horses was investigated. Its concentration in plasma varied significantly between farms (P<0.01), but its concentration in blood and blood cells was not influenced by any of the variables. The concentration of zinc in the blood cells was 10.5 times greater than in plasma, but its concentration in plasma was not correlated with its concentration in whole blood or blood cells owing to the variability in the proportion of whole blood zinc present in plasma (relative plasma zinc), which ranged between 9 and 24 per cent. This variability was significantly influenced by a three-way interaction between farm, sex and sweet itch (P<0.05). Relative plasma zinc was positively correlated with absolute plasma zinc (r=0.78, P<0.001) and negatively correlated with whole blood and blood cellular zinc (r=-0.58, r=-0.71, P<0.001).     

Zinc and copper plasma levels in Icelandic horses with Culicoides hypersensitivity

Zinc concentration has been shown to have a potent immunomodulatory capacity, particularly influencing T helper cell organisation and cytokine secretion. Culicoides hypersensitivity (CHS) in horses resembles the early and late phase of type I hypersensitive reactions in man, characterised by a shift from T helper cell subtype 1 to T helper cell subtype 2 cytokine profile. In this pilot study, zinc and copper levels were measured in the plasma of 48 CHS-affected and 56 healthy Icelandic horses age 4-25 years (mean approximately 11 years) kept on 7 farms. Affected horses were divided into 3 groups according to the severity of disease. Time of blood collection and feeding management was constant. No differences in zinc or copper plasma levels and plasma copper/zinc ratio were determined among CHS horses and controls by univariate analysis of variance. Therefore, the most significant influences on zinc and copper plasma levels were affected by the location of housing. However, Spearman correlation showed a negative coefficient between the plasma zinc concentration and the severity of CHS (r = -0.31). Due to a probability value of P = 0.002 the null hypothesis r = 0 is rejected, although only 9% of the total variation of plasma zinc is presently explained by its relationship to CHS. In contrast, the Spearman correlation coefficient between plasma copper levels and severity of CHS was not significant (r = -0.14; P = 0.16). The minor deviations in plasma zinc concentrations in association with the severity of CHS may be real or due to neurohumoral or cytokine-mediated mechanisms, but appear too minimal to be relevant.     

Investigation of the prevalence of summer eczema in Icelandic horses in northern Germany

An epidemiological study on summer eczema (SE) was performed in 490 Icelandic horses from 24 stud farms located in Lower Saxony and Westphalia. The study revealed a prevalence of summer eczema of 29.8 %. Horses imported from Iceland were affected with a frequency of 71.9 %, whereas horses born in Germany and other countries had a prevalence of 15.6 % and 27.3 %. Mares (33.1 %) and geldings (29.1 %) were more often affected by summer eczema than stallions with 15.5 %. The most common sites of summer eczema were mane and tail. Five to eight years old horses were more severely affected by SE than younger or older horses. Piebald horses showed higher degrees of SE than grey horses. The high prevalence of SE in Icelandic horses kept in Germany was due to imported horses from Iceland particularly horses imported at an age of seven to 15 years were at an extremely high risk to SE (96.4 %). The prevalence of SE significantly increased with higher age. Chestnut and grey horses born in Germany were prone to a lower risk to SE than bay, black or piebald horses. In horses imported from Iceland, a higher inbreeding coefficient was significantly related to a lower prevalence of SE. The most efficient measure recommended for reduction of SE in Germany would be to abandon imports of Icelandic horse from Iceland.     

Colonic obstructions due to enteroliths in four horses.

Four cases of enterolith obstruction in horses aged from six to 14 years are reported. All four cases had symptoms of persistent low grade abdominal pain and anorexia with an absence of defaecation. Examination revealed reduced gut motility and accumulation of gas, but heart and respiratory rates, rectal temperatures and complete blood counts were all within normal limits. Enteroliths of varying sizes were removed from the region of the transverse colon in all four horses.