Accurate use of vaccine programmes is helping control flock disease levels, believes contract shepherd Justin Horson, who manages 220 ewes on behalf of farm co-operative Cotswold Organic Lamb.
Replacements are vaccinated on arrival at the Gloucestershire-based enterprise, irrespective of where they have come from, says Mr Horson. “We treat bought-in ewes as if they haven’t been on a vaccination programme, as there is no way of knowing what precautions have been taken in the past.”
And to ensure the vaccine confers immunity, all animals are given the second jab four to six weeks later. “In addition, we ensure they are given a booster four to six weeks before lambing to ensure maximum immunity levels are sustained, not only for ewes, but to ensure lambs have a level of protection when they are born.”
To avoid multi-handling, injections can be given at the same time as worming. However, injections must be given within the four- to six-week period, says Mr Horson.
Make sure vaccines are kept refrigerated, he advises, as solutions do not contain preservatives and are volatile to bacterial contamination. “We try to ensure all preparation work is done, such as getting sheep in position and handling systems set up for quick throughput, before taking the vaccine out of the fridge.
“We avoid administering injections in prime cut areas, to prevent abcesses and bruising. Injections should ideally be administered at the base of the neck, under the skin, but not in the muscle. We use disposable needles which are changed at the end of each race, which is about 20 sheep,” explains Mr Horson.
The flock is currently in organic conversion and at different stages throughout the process. This doesn’t detract from the vaccination programme, however, as targeted diseases can be vaccinated against, according to Mr Horson. “The farm uses targeted vaccines for pasteurella and clostridial diseases, which we have identified as key diseases to manage. However, a Soil Association derogation should be sought beforehand.”
Lambs are given the primary vaccine at six weeks which, when the flock was conventional, would have coincided with worming, he explains. “The second vaccine will now be given four to six weeks after the first, or when lambs require worming under organic stipulations.”
Points to consider
There are some basic points to consider when aiming to comply with vaccination protocols, explains Intervet‘s Rosemary Booth. The vaccination process simulates a natural challenge in sheep without the risk associated with exposure to the actual disease-causing organisms.
“For previously non-vaccinated ewes to develop an active immunity two doses are required,” advises Ms Booth. “The first stimulates the immune system to respond to the disease challenge. However, it is the second, crucial, dose which raises immunity to a protective level.”
There should be four- to six-week interval between the two 2ml injections, and to maintain optimum immunity, a booster should be given before a 12-month period has elapsed (see graph).
Lambs should be injected from the age of three weeks if possible, she advises. “Although this is not always viable, the sooner lambs are vaccinated the sooner immunity will build up, allowing the vaccine optimum chance for success. The critical period for lambs to be fully covered is at the end of summer, when clostridial diseases are at their most virile.”
To ensure rapid throughput of ewes and lambs, adequate handling systems need to be in place to avoid stock going through without being injected. “In addition to vaccines requiring refrigeration before use, bottles should be opened and used within 10 hours. So, where possible, the amount needed should be calculated beforehand to minimise wastage,” adds Ms Booth.