Sheep vaccinations
While most may have finished preparing for breeding, it is worthwhile thinking ahead to next year about vaccination management strategies you may wish to implement. What follows is a brief reminder about Toxovax, Campylovexin/ Campyvax-4, Androvax and Ovastim.
Toxovax
Toxoplasmosis in sheep has a seasonal pattern of infection which peaks in April/May/June. It makes good sense to vaccinate ewes/hoggets well in advance of this peak to ensure that maximum protection from the vaccine is achieved at the time it is needed. There is no benefit in leaving vaccination closer to tupping and it may in fact compromise the results.
One injection will protect the ewe for life. This will almost certainly apply to ewes that receive their first vaccination as a 2-tooth. If however hoggets are vaccinated for toxo then many things such as worm burden, pneumonia, footrot, puberty, struggling to make mating weight etc can affect their ability to mount a good immune response following vaccination. For this reason it is worth considering vaccinating such animals again as 2-tooths rather than relying on one shot for life if you feel that they were in any way compromised as hoggets.
Vaccinate ewes and hoggets at least 1 month before the teaser rams join. We recommend not vaccinating hoggets until the end of January at the earliest but any time after this should be OK.
Minimise other stressors such as worms at the time of vaccination. The vaccine is very fragile and once mixed, needs to be used almost immediately. Do not use methylated spirits to clean or soak your needles prior to use, as this will inactivate the vaccine.
Toxovax is an intramuscular injection and therefore must not be given under the skin. Inappropriate handling or incorrect administration of this vaccine can result in failure of protection in the face of a toxoplasmosis challenge. Do not vaccinate rams with this product. Due to the fact that Toxovax is a live vaccine, it has a very short half-life. We therefore do not carry it in stock, but order it in specifically by request. It needs to be ordered 4 weeks before delivery to the Clinic, so remember to contact us well ahead of the planned date of administration.
Campylovexin/Campyvax 4
The vaccines named above are marketed by Virbac and Intervet respectively. They are very similar except that the Intervet vaccine contains an additional strain of Campylobacter - C. jejuni - which has been linked to some cases of abortion.
Campylobacter is the most commonly dignosed cause of sheep abortions. Apart from the abortions that we see, it can also be responsible for lambs born alive but weak and dying after a few days and evidence is now mounting that it can be responsible for losses seen as abnormal foetuses at scanning. Classically Campylobacter causes an abortion storm; however, in some parts of the country up to a 9% increase in docking percentage has been consistently reported following vaccination. On some of these farms, Campylobacter induced abortion had never been detected but the response to vaccination showed that the disease must have been present.
Vaccination scenarios differ depending on the flock history. In summary:
Two vaccinations 4-8 weeks apart are required in the first year. The second one should be given prior to or at ram joining.
If the first shot is received as a hogget then a subsequent booster as a 2-tooth prior to tupping may be advisable. This will vary depending of farm history and is worth discussing with Totally Vets. There is some evidence that there is a return on investment when all the flock is boosted each year.
Where vaccination has never been used before, the entire flock should receive 2 shots in the first year, thereafter only the first-time-to-the-ram-females get two innoculations.
Androvax or Ovastim?
The decision on whether or not to use Androvax (Intervet) or Ovastim (Virbac) is a complicated one and needs careful consideration. There are many factors to be taken into account and these justify a whole article in itself but below are a few reminders.
Androvax and Ovastim are vaccines that cause the production of antibodies which act on the ewes' ovaries resulting in the release of more mature eggs. The average increase in lambs docked from vaccinated ewes is 20% (range 10-40%).
Timing of vaccination is critical. With Androvax the first year requires a sensitiser and a booster 4 weeks apart with the first dose given 8-10 weeks prior to ram joining. Giving the booster closer to mating than 4 weeks or further back from mating than 8 weeks will have a negative effect.
With Ovastim, the first dose should be given 6-9 weeks prior to ram joining with the booster 3 weeks later. Once again too close to or too far back from mating will have a negative effect.
More eggs produced in response to vaccination means that more sperm are required. That means ram numbers need to be addressed. The actual ratios will vary from farm to farm. Scanning of treated ewes is a prerequisite. It is essential that ewes carrying twins/triplets can be identified and fed appropriately in order to achieve maximum survival of the lamb crop. Adequate feed levels with respect to both quality and quantity are necessary and require planning for.
In summary, very important decisions need to be made in relation to managing increased numbers of lambs, the effect on the ewes of carrying multiple lambs, the effect on lambs of being a twin and the effect on feed requirements. In short, good management strategies need to be put in place prior to the use of Androvax or Ovastim.
