Risks with Rebuilding Flocks

Wednesday, July 15, 2020

Planning for rebuilding your flock numbers, when conditions improve, is important to ensure all options are considered. While buying in sheep is one strategy, the biosecurity risks associated with introducing any stock must be considered.

Changes to the management of Ovine Johne’s Disease (OJD) introduced on 1 July 2019 have seen movement restrictions relating to OJD for sheep entering SA removed.

Removal of these restrictions will provide an opportunity for producers to potentially source stock outside of SA for restocking.

The safest sheep to purchase are those that are vendor bred and come from flocks that have conducted regular pooled faecal tests for OJD, with no disease detected.

Many of these flocks participate in the Market Assurance Program (MAP) for OJD.

Some flocks have also submitted adult sheep to abattoir surveillance testing, which whilst is not as definitive at faecal culture testing, does provide some level of assurance of freedom from OJD. 

To minimise the risk introduced animals may pose it is recommended that all sheep entering SA be vaccinated for Johne's Disease, either before entry or upon arrival. 

Completed National Vendor Declarations (NVD) and National Sheep Health Declarations (NSHD) remain mandatory for all sheep entering and moving within SA. Details on testing for OJD that has occurred in sheep flocks will be summarised on the NSHD.

OJD is a chronic, infectious and incurable wasting disease that occurs in sheep and cattle. Clinical signs may include a distinct ‘poor’ tail end of a mob, ‘poor’ sheep within the ‘tail end’ may start dying, weight loss and ill thrift due to thickening of the intestine, and occasionally scouring (while not a classical clinical sign of OJD, it may occur). OJD can also spread from sheep to other species including cattle and goats.

As many of these signs may be confused with nutritional diseases or internal parasites, it is important to have it checked out, if in doubt.

It is also important to note that OJD in Australia has been detected at greater flock prevalence in areas of higher rainfall and higher stocking densities. In general terms, areas of above 400mm average annual rainfall have a higher flock prevalence than those below 400mm.

Johne's disease in sheep remains a notifiable disease in SA, so must be reported to PIRSA Animal Health. Without movement restrictions there is an increased ability for producers with OJD-infected flocks to trade sheep. Check the status of animals before purchasing – check the NVD and NSHD. 

With introducing stock there are other risks such as footrot, lice and/or drench resistant worms to consider. From a footrot perspective it is important to keep in mind that the disease may not show at certain times of the year. Producers should keep introduced sheep isolated for as long as practically possible and ideally through a spread period (i.e. when conditions warm and moist). You must inspect sheep for lameness and seek advice if uncertain.

With sheep lice, keep stock isolated if possible. Regular inspections are needed, keeping in mind it may take up to five or six months before an infestation is visibly detectable. Seek advice on treatment.

Assume that purchased sheep are carrying worms with some degree of drench resistance to one or more drench groups.

Quarantine drench all sheep new to the property using a combination of no less than four unrelated drench actives. Hold the sheep in quarantine in yards (small mobs) or a secure paddock (larger mobs) for at least three days to allow worm eggs present at the time of drenching to pass out of the gut. For further details refer to the Wormboss website,

Further details are available by viewing the webinar on the SheepConnect SA YouTube channel or by contacting your local Primary Industries and Regions SA Animal Health Officer, .