Consider vaccination to cut overall sheep costs
March lambing flocks are now entering the period when pre-lambing vaccinations should be considered. In many commercial flocks, vaccinating, to prevent sudden deaths caused by clostridial disease and pasturella pneumonia, is a common practice.
The correct use of vaccines can result in the treated animals receiving high levels of immunity. However, it is important to remember that, unlike drenches, vaccines are very sensitive and can easily become ineffective. Given that vaccination can account for 15-20pc of total vet costs on sheep farms, it is essential that this expenditure results in high levels of immunity being conferred to the animals treated.
The aim of the vaccine is to act as an insurance policy. The vaccine gives the sheep a mild form of the disease or may simulate a disease challenge within the animal. This challenge forces the sheep to produce antibodies to the disease-causing organism within the vaccine. It is these antibodies that are stored in the body, so when an actual disease outbreak occurs, the sheep will already have the antibodies available to fend it off. However, for the vaccine to provide protection, it requires adequate time to allow the sheep to develop antibodies. Therefore, the vaccination should occur well in advance of a predicted disease outbreak.
In pre-lambing ewes, the vaccine has a two-fold purpose. The first one is to give the ewe her annual booster so that she has protection for the following 12 months. The second purpose of the pre-lambing booster injection is to produce antibodies that will be available to the newborn lambs when they receive the ewe's colostrum shortly after birth.
The immunity that is passed to the lamb in the ewe's colostrum is, however, just passive and only lasts for a few months. Therefore, in time, the lambs will need to be vaccinated so they can develop their own active immunity.
In general, vaccines can be divided into two different groups. Live vaccines (examples are scabivax -- orf vaccine -- and toxovac -- toxoplasmosis vaccine) are the most sensitive group and often have a very short shelf life. The key point to remember with these vaccines is that they actually give the sheep a mild form of the disease. The second group consists of the dead vaccines that contain dead or deactivated forms of diseases, which do not cause disease but still stimulate an immune response from the animal. In Ireland, clostridial vaccines generally fall into this category; these are more stable and generally have a longer shelf life.
For vaccinations to work correctly and achieve the desired immunity, it is important that the manufacturers' recommendations are followed exactly. Below, I have listed some general guidelines that should be considered when planning your vaccination programme:
- Virtually all vaccines should be stored in a fridge. Because they are temperature sensitive, it is important that the vaccine is kept cool at all times prior to use;
- Be aware of the shelf live. Do not use it if it has passed the use-by date;
- Always read the manufacturers' recommendation on how and when the vaccine should be administered;
- Because most vaccines do not have antimicrobial agents or preservatives, it is important to avoid contamination of the vaccine when filling the syringe. Ideally an automatic syringe should be used;
- Do not vaccinate sheep that are suffering stress/disease as their immune system may not be able to respond as expected;
- Ensure that, where the initial vaccination course requires two shots, a set period, set apart from the second shot, is given within the required time frame;
- For antibodies to be passed from the ewe to the lamb, it is important that the lamb receives adequate colostrum within the first 12 hours after birth;
- It is important to remember that not all animals will achieve full immunity -- no vaccine will result in 100pc immunity in all of the sheep.
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