Lumeij JT †, Eysker M †, Kessels BGF, van den Ingh TSGAM†,
Oosterbaan J, Pieterse M, Peterson K, Houwers D †, Vellema P
† Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
A wasting disease was observed in a regulated mouflon population from the 5400 hectare ‘National Park De Hoge Veluwe’ in The Netherlands. A gradual decline in the eviscerated body weights of shot ewes, rams and lambs had been observed over the past few years, and the number of lambs surviving the first season had declined. Differential diagnostically a parasitic or deficiency disease was considered most likely. To enable comparison between environmental influences in consecutive years, 6-month-old lambs, rather than adult mouflons were sampled. Differential gastrointestinal worm counts were performed and the cobalt, copper and selenium status were established from five lambs shot in August 2002. In addition twelve other lambs were shot between June 2002 and January 2003 and only weighed. Based on reference values from domestic sheep, a cobalt deficiency was diagnosed, while the copper and selenium status were considered marginal and good, respectively. Furthermore, Haemonchus contortus burdens were moderate to high. Based on these findings, it was decided to use top-dressing of a total of 10 ha with cobalt salt at 200 kg/ha and place 15 licking blocks containing 60 mg/kg cobalt at sites which were frequented by the mouflons.
In August 2003, eight mouflon lambs were shot and sampled to evaluate the effects of the intervention, in addition to twenty-two other lambs which were shot between June 2003 and February 2004 and only weighed. In contrast to the previous year, the lambs were in good to very good condition, while the cobalt concentration in the liver showed a significant increase to levels within the reference range. Worm numbers were very low. Although it has been shown in comparative studies with twin lambs from domestic sheep that cobalt deficiency increases the degree of parasitism, the extreme dry summer of 2003 was considered an important contributing factor to the low worm numbers. The supplemented mouflon lambs showed a cubic polynomial growth curve, similar to domestic lambs, in contrast to the unsupplemented animals a year previously, which failed to thrive.
Cobalt deficiency in domestic sheep is well known in cobalt deficient areas worldwide, but was demonstrated for the first time in wild mouflons in the present study. Meanwhile, cobalt deficiency has also been diagnosed in wild moose (Alces alces) in Eastern North America and forms an explanation for the elusive ‘Nova Scotia moose mystery’ which has been investigated since 1910. It is likely that cobalt deficiency can also occur in other wild ruminants. Cobalt is essential in the formation of cobalamin (vitamin B12). Cobalamin is of importance for the gluconeogenesis from propionic acid in the rumen. A deficiency causes the paradoxical situation of an energy deficiency while the animals have plenty of food available.
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