by Sally Colby
The time spent planning for the ideal heifer calf to add to the milking string may be wasted if she isn’t properly immunized. The act of vaccinating an animal doesn’t guarantee she’s immunized or protected from disease. Good immunization is the result of proper vaccine handling from the time products arrive on the farm until they’re administered.
Dr. Joel Franks of Zoetis said some cases of illness that appear to be vaccine failure are actually host factors: animals are nutritionally deprived or experienced stressors that dampened the immune response, leaving the animal unable to respond properly to the vaccine. Human factors should be also considered if vaccine failure is suspected, and that’s what a vaccine audit can reveal.
The first audit consideration is vaccine protocol – a game plan that outlines when and where vaccines will be given. It includes the age range of the animals to be vaccinated (newborn or weanling, pre-breeding heifer or a heifer coming back from the calf grower as a springer). The other factor is careful consideration of which diseases are most likely to affect the growing heifer. Franks said dairy farms should have a core vaccine protocol as well as risk-based vaccines to be used as needed.
To prevent vaccine failure, it’s important to understand vaccine categories and how vaccines work. Killed vaccines are killed (or inactivated) and cannot cause disease in an animal. “It’s the viral particles, or antibodies, that are required for the animal to respond and mount an immune response,” said Franks. “Because it isn’t quite natural and has a weaker initial response, it’s important to boost killed vaccines according to product label. A single injection of a killed vaccine will not result in long-term protective immunity.”
One advantage of killed vaccines is that they’re safe for use on pregnant animals. If pregnancy status or vaccination history of a group of animals is unknown, using a killed vaccine is the best option for protecting the heifer and the calf she’s carrying.
Modified live vaccines are live vaccines that have been attenuated (or altered) so they cannot cause disease. “It’s closer to a natural infection but won’t cause disease,” said Franks. “The animal will respond to it as it would natural disease and mount antibodies against it, and there’s also a process called cell-mediated immunity. Those together offer more robust protection from disease and longer herd protection.” If pregnancy status or vaccination history of animals is unknown, Franks recommended producers work with their herd veterinarian to determine whether modified live vaccines are appropriate.
Good vaccination protocol includes proper storage from the time vaccines are in farmers’ hands. If vaccines are picked up from the vet’s office, they should be packed in ice. Shipped vaccines should arrive in an insulated cooler with frozen packs and refrigerated immediately.
Vaccines should be stored in a dedicated refrigerator maintained at a temperature between 35º and 46º. The ideal refrigerator for storing vaccines has a glass front that allows personnel to check contents and locate what is needed before opening the door.
Refrigerators used to store vaccines should not be used for any other purpose, including human consumables (lunches, drinks), milk samples or colostrum.
Storing colostrum in the same refrigerator as vaccines sets the vaccines up for less-than-ideal performance or failure.
When warm colostrum is placed in same refrigerator as vaccines, the temperature rises significantly. If a refrigerator door is opened for colostrum storage, it can take up to half a day to reach the proper temperature.
The only way to accurately determine temperature is with thermometers, and since temperatures vary throughout a refrigerator, thermometers should be placed in the upper, middle and lower sections. Vaccines should be kept away from the sidewalls of the fridge to avoid temperature fluctuations. If possible, glass shelves should be replaced with grates to enhance airflow.
It’s good practice to record product lot numbers, date of administration and withdrawal date as vaccines are placed in a refrigerator. Vaccines should be rotated to ensure expired products aren’t being used. Any reconstituted vaccines should be used within an hour or two.
Although unused vaccine bottles are fairly well protected from contamination, it’s important to keep the fridge clean to avoid contamination. A dirty refrigerator used to store vaccine bottles with needles sticking out of the tops is a perfect scenario for contamination.
Vaccines should not be removed from the fridge until the animals are gathered and confined. In warm weather, chute-side practice should include storing vaccines in a cooler with frozen packs to ensure all products remain at the proper temperature until use and not exposed to UV light. Vaccines should also be kept in a cooler in winter to prevent freezing.
If an auto syringe is used, be sure it’s properly calibrated prior to vaccinating animals. Auto syringes should be kept in a covered cooler between groups to ensure any product remaining in the syringe doesn’t become too warm or cold. Keeping syringes in a cooler will also help prevent contamination from manure and other debris when switching animal groups.
After use, auto syringes should be completely disassembled, thoroughly cleaned with warm water and air-dried. Soap or disinfectants can leave residue that affects the efficacy of vaccines and should not be used on auto syringes.
For modified live vaccines that require mixing, keep all materials clean and free from dust and debris. Vaccines should be mixed gently, not shaken. If the needle is mistakenly inserted in the caked vial first, there’s no need to discard it – pull the transfer needle out and use a clean syringe and needle to draw the diluent. Add it to the caked vial and mix gently.
Be sure to read label instructions to determine how to administer vaccines. For intramuscular (IM) injections, Franks recommended an 18-gauge, 1.5-inch needle. Subcutaneous injections can be administered with a 16-gauge, 5/8- to one-inch needle. Consider the age of the animal and the product when determining needle size.
The Beef Quality Assurance program recommends giving injections in the triangle of the neck. Franks suggested changing needles every 10 to 15 animals, but if the needle is bent or burred, it should be changed immediately. Keep a sharps container nearby to ensure used needles are disposed of properly.
For optimal vaccine results and to achieve disease prevention, care for vaccines properly from the time they’re received to the time they’re administered. Store vaccines in a clean, dedicated refrigerator at the correct temperature and maintain good vaccine hygiene throughout the vaccination process.
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