How to reduce disease risks in rapidly expanding flock
SHEEP TECH
In previous articles Clifford Richardson outlined his plans to expand his sheep flock from 80 ewes lambing in 2016 to 200 ewes and 40 ewe lambs going to the ram in 2017. The initial plan was to operate a closed flock with replacements bred from within the flock. The relatively low stocking rate has made grassland management difficult and the removal of paddocks with high covers has been a necessity to allow lambs to graze at ideal grass heights to maximise performance.
Clifford is considering buying in pedigree Lleyn hogget ewes from England to accelerate his expansion. Purchasing in stock either within Ireland or from other countries poses considerable flock health risks. Clifford will analyse all the risks and then take the appropriate steps to reduce the likelihood of introducing a new disease into what is currently a healthy flock.
When purchasing in sheep Clifford is potentially exposing his flock to all the major sheep diseases that can be carried by sheep from farm to farm and, more importantly, from sheep to sheep. The first step is to establish a disease history of the flock of origin. This is easier said than done and more often than not you are relying on the honesty of the seller.
It is also important to examine the sheep individually prior to purchase. The next step will be to quarantine all incoming animals for 30 days after purchase. On arrival, the sheep should be treated for scab and internal parasites. Clifford will house the sheep on clean concrete, and dose them with either Startect or Zolvix and give moxidectin 1pc injection for scab.
It is important that the moxidectin injection is only used on sheep that have not been previously vaccinated for footrot and that the Startect or Zolvix is ordered from the local vet well in advance of the sheep landing on the farm, since the availability of both products can be limited. The sheep should also be treated for fluke at this stage with a product that kills immature and adult fluke. Clifford will use a closantel dose as this will also kill the Barber’s pole worm (heamonchus contortortus) which is common in sheep imported from the UK.
The sheep should remain indoors for 48 hours before being let out to an isolated section of the farm where they will remain in isolation from the main flock for 30 days. The shed should then be cleaned out and the faeces either placed in a manure pit or slurry tank were the potential surviving resistant worms will be killed. The quarantine period will allow Clifford to monitor the imported sheep closely and allow enough time for the sheep to show symptoms of diseases they may be carrying. At this stage they can be either culled or treated.
CODD (contagious ovine digital dermatitis) causes severe lameness in sheep and is often associated with boughtin sheep. It can spread from sheep to sheep very quickly. It is likely to develop during the quarantine period and can be dealt with by seeking veter-
inary advice. Scaring on the lips may be evidence of orf, but Clifford is currently vaccinated for orf so this should not pose a problem for him.
Enzootic abortion causes major losses and stress to the farmer when introduced to a flock for the first time. There are no visual signs of the disease, so it can’t be detected during the quarantine period. Purchasing stock from flocks that have never been exposed to the disease would be the ideal. However, like all other diseases, Clifford must assume there is a potential risk that the incoming hoggets may have been exposed to the disease and may spread the disease to home-bred animals if they come in contact with the lambing fluids and placenta around lambing time.
Clifford has a number of
options to prevent a potential abortion storm. He can vaccinate the entire flock, but this is an option he does not want to take at this point.
He can also keep the purchased stock isolated from other stock on the farm for the first breeding and lambing season. However, this would involve a change of overalls and wellingtons every time he moves from one shed to the other during lambing and no cross-fostering of lambs between lambing groups.
The third option would be house all stock in the same shed but in different pens where they have no direct contact with the home flock. He can also ensure that the purchased sheep lamb one week after the main flock has finished lambing and is out at grass. This will eliminate
the risk for the home flock. Again the hoggets should be blood sampled six weeks after lambing. We have focused on the most commonly bought in diseases that in my experience have been an issue for farmers in the Sligo and Leitrim area. Enzootic abortion, CODD, resistant internal parasites, orf and scab can all lead to poor productive performance and financial losses when introduced. There are numerous other potential diseases associated with purchasing stock. Farmers should be aware that when purchasing in stock they must assume that the animals are carrying disease and take the necessary precautions to reduce the risk to their flocks.
Tom Coll is a Teagasc drystock and business advisor based in Mohill, Co Leitrim