In my last two columns, I focused on choosing the right implant for your operation and on options for re-implanting cattle over the course of a production cycle. While these are important aspects of any implant program, equally important is ensuring the proper placement of the implant in the animal’s ear. While this may seem like a simple step, failure to do so in a proper fashion can render the implant ineffective and result in a loss of productivity. With this, the last column in this series, I will focus on proper management of the implant program.
First, let’s consider basic anatomy of the bovine ear. With respect to proper placement of implants, there are three important landmarks. The first is the cartilaginous ring at the base of the ear — do not place the implant here. The second and third are the two cartilage ribs that run horizontally along the ear. Ideal placement is in the middle third of the backside of the ear between these cartilaginous ribs. The goal is to place the implant between the skin and the cartilage, thereby avoiding major blood vessels. Such placement ensures proper absorption of the hormonal payload over the life of the implant.
While the above refers to the ideal, there are situations where you will be faced with less than ideal ears for implanting. These include frozen ears, multiple tag sites or previous implants. Obviously, these situations will rely on your judgement as to where to place the implant. It might be as simple as switching ears, or in the case of frozen ears, skipping the implant if it cannot be done in a safe and effective manner.
Once you have decided on the implant site, the next step is to ensure the ear is properly cleaned and/or sanitized. Implanting cattle with dirty ears can lead to inflammation and ultimately abscesses, which seal off the implant and by their nature, impede absorption. Proper sanitization procedures (i.e. which disinfectant to use, strength, etc.) should be discussed with your veterinarian. But suffice it to say, mud- or manure-covered ears should be scrubbed with a brush soaked in disinfectant prior to implanting.
A proper disinfectant protocol also includes ensuring that the needle of the gun is disinfected between animals. This is accomplished using a sponge and a disinfectant tray. The needle is cleaned by swiping it across the face of the disinfectant-soaked sponge. It is also possible to purchase implants that contain an antibiotic pellet. Such implants are designed to reduce the inflammatory response at the implant site and thereby reduce issues with abscesses. These implants are not, however, a substitute for a proper sanitization program.
The next point to consider is proper implanting technique, which in many cases varies with the specifics of the gun used. Each company has a unique gun(s) for its line of implants. These guns typically fall into two types: those with a fixed needle or those with a retractable needle. Guns with a fixed needle lay down a row of pellets once the needle is inserted and the trigger of the gun is pulled. It is critical that the needle is fully inserted under the skin at the proper site before you pull the trigger. The trick to successfully implanting with this type of gun is to slowly remove the needle as the trigger is pulled. This creates space for the pellets to be deposited in a straight row.
The second type of gun differs in that once the trigger is pulled, the pellets are laid in a row as the needle automatically retracts. There is no need to manually withdraw the needle. Following removal of the needle (fixed or retractable), one should be able to see and palpate the straight row of pellets. Following palpation, the implant site can be closed by pressing on the injection site, although this is not always standard practice as it is a potential source of contamination. With experience, operators can be equally effective with either type of gun and often the choice of which gun to use will come down to which implant line you choose.
There are a number of issues that can result from improper implanting technique. The first is abscess development and walled off implants as already discussed. Other issues include bunching or crushing of pellets or “missing” pellets. Bunching of pellets can result from failure to withdraw a fixed needle as the trigger is pulled. In this case, there is no room for the pellets and they deposit in a cluster, as opposed to a straight line. Absorption of the hormonal payload is subsequently reduced.
Similarly injecting pellets into the cartilage can reduce absorption. Crushed implants can also result from failure to withdraw a fixed needle once the trigger is pulled, or injecting into cartilage. In this case, crushed implants have an increased rate of hormone release, which can shorten the payout period and more importantly result in behavioural issues such as excessive riding.
Missing implants result from withdrawing the needle too quickly or inserting the needle such that it goes through the ear and the pellets are deposited on the floor. All of these issues reduce the expected productivity gains from your implant program.