New types of foreign bodies and the effect of magnets in traumatic reticulitis in cows

TRAUMATIC indigestion is a complex of diseases that occur when sharp or pointed foreign bodies accumulate in the reticulum of cattle and injure the reticular wall, sometimes piercing the wall and penetrating to the peritoneal cavity. From that point, the foreign bodies may proceed further and cause injury to surrounding structures (Poulsen 1990). Cattle do not sort their feed fastidiously, and this shortcoming, associated with the special structure of the forestomachs of ruminants, predisposes them to foreign body lesions (Poulsen 1976). Systems for feeding dairy cows have changed dramatically during the past decade, and new types of foreign bodies that cause trauma may have emerged (Harwood 2004, Monies 2004). There is anecdotal evidence that wires from tyres used to cover silage, and beer cans dropped at roadsides, have been of increasing importance as causes of ‘hardware disease’ in cattle. Varying prevalences of foreign body lesions, from 7 per cent to 21 per cent, have been reported (Fuhrimann 1966, Raahauge 1977, Andersen and Gillund 1980). In 2004, the prevalence of foreign body lesions or chronic peritonitis, which may be related to foreign bodies, recorded at the export slaughterhouses in Denmark was 2 per cent (F. T. Steffensen, personal communication). Studies have documented the finding of fencing wire, nails, screws and mixed pieces of metal as typical foreign bodies (Jagos 1969, Khamis and Fahmy 1976, Raahauge 1977, Stober and Surborg 1978, Neumann 1979, Andersen and Gillund 1980). However, tyre wire has also recently been identified as a cause of foreign body lesions in cows (Harwood 2004, Monies 2004). Previous studies have shown prevalences of foreign body lesions of 5 per cent and 17 per cent in cattle to which prophylactic magnets had been administered (Khamis and others 1976, Andersen and Gillund 1980). One result of the industrialisation of farming is an increased risk of the presence of foreign bodies in cattle feed and in the stable surroundings (Poulsen 1976). As a consequence of the increasing incidence of traumatic reticulitis, and the occurrence of new types of traumatising foreign body in Denmark (Poulsen 1990) and the UK (Harwood 2004, Monies 2004), there is a need to assess whether currently available magnets still have the expected preventive effects on hardware disease in cattle. This short communication describes such a study. The study was carried out at the Danish Crown slaughterhouse in Toender, Denmark. A total of 1491 slaughter cows was examined during a two-week period; 94 per cent of them were milking cows. Each gastrointestinal system was marked with a unique code at the point during the slaughter process where the gastrointestinal system was separated from the body. Each gastrointestinal system was examined and any foreign bodies, foreign body-related lesions and magnets were recorded and collected for further examination. Foreign bodies found within the gastrointestinal tracts were characterised by type, form, surface, cross-section, size, end-shape (sharp or blunt) and whether they were magnetic. Lesions in the forestomachs were characterised macroscopically, and representative cases were examined histologically. The two magnets tested were cylindrical cage magnets with different fields of magnetic force. One magnet (magnet I) (Bovivet Mag I; Kruuse) had a magnetic force of attraction of 110 mT (M. Eberhardt, personal communication). It was constructed of two flat magnets, had a total length of 10 cm, a diameter of 3·5 cm, and weighed 121 g. The distance from the surface of the magnets to the outermost limit of the cage varied from 3 to 12 mm. The other magnet (magnet II) (Bovivet Mag II; Kruuse) had a magnetic force of attraction of 210 mT (M. Eberhardt, personal communication). Five round magnets were included in this magnet, which also had a length of 10 cm and a diameter of 3·5 cm. The weight of magnet II was 137 g and the distance from the surface of the magnets to the limit of the cage was 7 mm. Magnets found in the slaughter cows were recorded with respect to their contents, weight and magnetic force of attraction by the use of SF dynamometers (S. Frederiksen, personal communication). The data were analysed and presented using the procedures FREQ, GLM and LOGISTIC in the statistical package SAS; a significance level of P<0·05 was used. Foreign bodies were found in 16 per cent of the cows, and chronic reticular lesions caused by foreign bodies were present in 10 per cent of them. All the lesions were chronic and localised, and were a result of intravital penetration of foreign bodies. The nature of the lesions varied from localised scars within the reticular wall to massive, adhesive apostematous reticuloperitonitis. Of 286 foreign bodies observed (Fig 1), 11 per cent were tyre wires (Fig 2), 14 per cent were fencing wires, 5 per cent were screws, 9 per cent were nails, 37 per cent were mixed pieces of metal, 2 per cent were copper and 22 per cent were remnants of boluses containing antiparasitic drugs. No parts of beer cans were found. Table 1 shows further details of the foreign bodies, including whether they were found attached to the reticulum. A significant (P<0·0001) association was found between the type of foreign body and the presence of lesions, and a significant (P=0·002) association between the cross-section of the foreign bodies and the presence of lesions was observed. The association between the end-shape of the foreign bodies and the presence of lesions Veterinary Record (2005) 157, 287-289