Untersuchungen zur Bedeutung und Quantifizierung der Klauenqualität und Moderhinkeresistenz beim Schaf

Abstract

The objectives of the present study were to determine the importance of footrot in Germany, Austria and Switzerland based on information of sheep farmers about prevalence, prophylactic and therapeutic methods. Furthermore, the use of potential selection criteria such as morphological and histological claw parameters as well as unspecific detected blood parameters as an immune response on a commercial footrot vaccination for breeding on footrot resistance were investigated. Therefore, different sheep breeds were examined under consideration of footrot. In total 223 sheep farmers from Germany (51 %), Switzerland (35 %) and Austria (14 %) took part in the survey (Chapter II). The questionnaire was published in national sheep journals and via internet from July until September 2010. Half of all participating sheep farmers (49 %) held 13 ± 8 ewes, 12 ± 10 lambs, 5 ± 4 teggs and 2 ± 4 rams. Footrot was diagnosed in 70 % of all sheep farms, whereas most of the sheep farmers (89%) diagnosed the disease by themselves. The prevalence within the sheep flocks was 36 ± 31 %. Characteristic symptoms were lameness (41 %) as well as typical odour (12 %). A predominant proportion of sheep farmers indicated that ewes are infected most frequently (83 %) and that footrot is present especially in autumn (39 %). Most sheep farmers treated infected sheep with claw trimming (91 %). Foot bathing (83 % vs. 57 %; P < 0.01) and vaccination (44 % vs. 28 %; P < 0.05) are used significantly more frequently by farms with more than 50 ewes when compared to farms with less than 50 ewes. Irrespective of the method footrot treatment was quoted to cost the sheep farmer on average 9.25 per sheep and year. Almost all sheep farmers (91 %) implement prophylactic methods against footrot, whereas routinely claw trimming (87 %) and quarantine of new sheep (44 %) are the favoured prophylactic methods. Investigations of morphological and histological claw parameters were carried out on 240 sheep in different breeds aged from 1 to 8 years. The breeds used were Merinoland (ML) and Rhoen (RH) sheep (Chapter III). The claws of the left bodyside were measured four times (once a month) during the grazing seasons (ML: 2008; RH: 2009). The claw horn samples for examination of the microstructure were collected at the last date. On average RH had a shorter diagonal length and length of the dorsal border, a lower heel height and a flatter dorsal angle when compared to ML. Furthermore, claw horn of RH showed a higher number of horn tubules, a greater diameter of tubules medullary cavity, a thicker tubules cortex as well as greater average and total horn tubules zone per unit area. Footrot was only diagnosed in the ML flock. Sheep with footrot (14 %) had significant larger dorsal angles (P < 0.01), significant higher heel heights of medial claws (P < 0.05) and shorter lengths of the diagonal of medial claws (P = 0.057). Significant relationships between histological parameters and footrot status were not identified. Phenotypic correlations between morphological and histological parameters were low (-0.23 0.17) and mostly not significant. The estimated heritabilities particularly for length of diagonal and heel height as well as for all histological parameters were on a useful level for selective breeding (0.15 0.57). The serologic immune response to a commercial footrot vaccination was investigated in 244 sheep aged from 1 to 8 years in the breeds ML (n = 200), German Blackhead Mutton (BH, n = 30) and Leine (LEI, n = 14) sheep by using serum protein electrophoresis (Chapter IV). For immunization sheep were vaccinated in week 0 and week 6 (booster) and blood samples were taken at both dates (unvaccinated and vaccinated status). Concentration of gamma globulins was significantly higher in vaccinated status when compared to unvaccinated status (P < 0.01). Most of the other serum proteins were also significantly different at the dates of sampling (P < 0.05). Among breeds BH showed a significantly higher relative gamma globulin concentration when compared with LEI. Footrot was only present in the ML flock (63 %). However, a significant relationship between footrot status and blood parameters was not given. The heritabilities of blood parameters were on a high level in the unvaccinated status (0.25 0.62), but low in the vaccinated status (0.09 0.42). Also the heritabilites of the percentage variation between both dates of sampling (0.03 0.28) were on a low level. The morphological claw parameters diagonal length and heel height might be applied as selection breeding criteria for footrot resistance, whereas the histological as well as the serological parameters are not recommended due to missing relations to prevalence of footrot and partly low heritabilities.