Pre-lambing ewe flock health
With scanning of March lambing flocks well underway Damian Costello, Sheep Specialist, Teagasc Athenry looks at some of the main health issues to be addressed between scanning and lambing. As with many conditions affecting the ewe flock, prevention is generally better than cure.
Clostridial/ pasteurella diseases remain a major cause of mortality in sheep despite the presence of relatively cheap and highly effective vaccines. Vaccination is essential to reducing losses due to these conditions as generally the first noticeable clinical symptom is death which leaves little option for treatment.
- In all cases farmers need to follow manufactures instructions carefully in terms of product storage and correct administration.
- Most products are administered by subcutaneous injection with the loose skin on the upper side of the neck being a suitable site.
- Cleanliness is essential throughout the process including regular replacement of the needle.
- It is generally not recommended to conduct vaccinations on sheep with wet fleeces as it can result in contamination of the needle and abscess formation.
Primary vaccination course: Each animal must complete a full primary course of vaccination. This requires two doses given four to six weeks apart (read manufactures instructions). It is important to note that if changing from say one of the 8 in 1 products to a 10 in 1 that the two shot primary course is required to achieve full cover. Onset of immunity will not occur until two weeks after the primary vaccination has been completed. Active immunity in animals that have received the full course is reported to last up to 12 months. Remember a single shot is not sufficient.
Annual booster: Once the primary vaccination course has been completed an annual booster needs to be administered within to the 12 month period to facilitate re-vaccination. In the case where retained ewe lambs are not mated and have received their primary vaccination at say 10 weeks and 14 – 16 weeks of age, it’s a good idea to administer a booster to these animals when treating the breeding flock pre lambing so that they are lined up with the flock for their annual booster in subsequent years.
In addition to the ewe flock it is important not to forget to give the rams their annual booster to afford them protection as they are often overlooked. Where farmers operate split lambing flocks they may need to consider vaccinating these batches on separate dates to ensure they fall within he recommended vaccination window.
Passive immunity is the transfer of maternal immunity to new-born offspring that occurs via colostrum provided that the ewe has been vaccinated four to six weeks pre lambing. Remember sufficient amounts of good quality colostrum must be consumed by lambs within the first 24 hours of life. The duration of passive immunity is variable and as passive immunity declines lambs will need to be enrolled on a vaccination programme to provide cover. It is advisable to seek veterinary advice as to when vaccination of lambs should be carried out if this is a particular issue on your farm.
In the case of liver fluke, aim to treat immature and mature stages at this time of year. If housing sheep, delaying treatment for 6 weeks post housing means flukicides containing closantel, nitroxynil or rafoxinide should be effective to remove all fluke present. Do not use a combined fluke and worm product on mature ewes as adult ewes have good immunity to stomach worms and do not require routine treatment. There is no performance benefit in treating the mature healthy ewe for stomach worms and it speeds up the development of resistance to anthelminthics. Lactating yearling ewes are one exception and may warrant a worm drench.
Investigating an abortion outbreak
A higher than normal barren rate at scanning, greater than 2% ewes aborting in the weeks preceding lambing and lambs being stillborn or weak lambs at birth are all indicators that infectious abortion may be an issue in the flock. It is not possible to diagnose the cause of abortion visually.
In order to plan a strategic approach to tackling the issue the following steps can provide an accurate diagnosis of the cause:
- Assume the worst and hope for the best in all cases of ovine abortion – promptly isolate affected ewe to avoid potential spread of infection to rest of the flock and clearly identify the ewe in case follow up blood tests are required
- Collect aborted foetus/lamb and afterbirth in a clean plastic sack and contact your vet providing relevant flock information that may assist in the diagnosis and also to organise submission of the sample to the regional veterinary laboratory (RVL)
- Clean out bedding from pen where aborted material was collected and thoroughly disinfect the area
- Sending a number of clean fresh samples to RVL for analysis increases the chances of getting a diagnosis
- Discuss the next steps with your veterinary surgeon
These include Pregnancy Toxaemia (Twin Lamb Disease) caused by inadequate nutrition in late pregnancy and Hypocalcaemia (Milk Fever) caused by inadequate calcium in the diet. In both cases diagnosis and treatment needs to be prompt to avoid mortality. In terms of prevention appropriate nutrition and good feeding management including adequate feed space are key. Treat any condition that depresses feed intake – for example separating and treating any lame ewes as well as penning weak/thin ewes separately for extra feeding. Also avoid any sudden changes in diet and keep a constant calcium level in the diet (milk fever).
Treatment on an individual ewe basis involves prompt disinfection and careful replacement along with fitting a retainer or harness. For more persistent or difficult cases veterinary intervention will be necessary to suture as well as administering pain relief and possibly long acting antibiotic. An epidural anaesthetic will help minimise ewe straining in severe cases. All cases should be permanently identified/marked for culling as they are likely to reoffend. Where more than 1% of ewes in the flock prolapse it merits further investigation. Examine in particular the amount of feed space per ewe in each pen. Other issues include ensuring constant access to quality forage and implementing good feeding management practices.
If you liked this article you might also like the Teagasc Sheep Newsletter - January 2022
The Teagasc Sheep Specialists and Teagasc Advisors issue an article on a topic of interest to sheep farmers on Tuesdays here on Teagasc Daily. Find more on Teagasc Sheep here Teagasc provides a Local Advisory and Education service to farmers. Find your local Teagasc office here