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The treatment of infectious ovine keratoconjunctivitis in pre-export feedlot sheep in Western Australia

Murdoch, Fraser (2016) The treatment of infectious ovine keratoconjunctivitis in pre-export feedlot sheep in Western Australia. PhD thesis, Murdoch University.

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Approximately two million sheep are exported from Australia annually, worth in excess of $170 million to the Australian economy. With the live export industry facing increasing scrutiny it is essential that the industry take steps to optimise the welfare of those animals involved.

Infectious ovine keratoconjunctivitis (IOK) is a significant, infectious eye disease of sheep and is the reason for the rejection of many sheep from the live export chain. Establishing a practical and effective treatment protocol has the potential to reduce economic losses associated with rejected stock and to improve the welfare of those animals presenting with clinical disease.

Injectable oxytetracycline (OTC) has been used as a treatment worldwide and has been shown to be effective. However, in pre-embarkation feedlots the number of animals is so large that such individual treatment is not feasible. This research investigated the clinical efficacy and impact on animal health of OTC given in-feed or in-water.

Oxytetracycline is absorbed from the gastro-intestinal tract following oral administration in feed or water. This research showed that oral administration of OTC results in changes to the rumen microflora population.

Although the change in rumen microflora corresponded with reduced feed intakes, feed intakes returned to normal following cessation of treatment, indicating that any changes to the ruminal microbiome are transient. Oxytetracycline given in-feed for five days results in a significant clinical improvement in IOK.

In-water OTC caused a persistent decrease in feed and water intake rendering it an unsuitable treatment.

Mild cases of IOK can be successfully treated with in-feed OTC for a five-day period at a dose of 20 mg/kg bodyweight. Sheep with more severe IOK can be successfully treated with two intramuscular injections of OTC at 20 mg/kg bodyweight four days apart.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Laurence, Michael and Robertson, Ian
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