No one likes to give injections to pigs. Whether vaccinating sows or pigs to prevent disease or administering medications to treat or control disease, proper injections are a routine and necessary task in our production systems.

In recent years, some new developments have made the job easier, reduced the risk of broken needles in pork carcasses, and reduced the risk of injury to people from inadvertent needle sticks or repetitive motion injuries. And even when the old stand-by syringe and needle are used, there are things worth reviewing to make the job more effective and safe.

Since there is no recent data on the adoption of the new injection technologies and the incidence of injection sites in market hogs and cull breeding stock, a Pork Checkoff-funded study was initiated to quantify the injection devices currently being used, the common injection sites on the pig, and the prevalence of injection site lesions.

The first objective was to determine the most common injection methods used on hog farms, as reported by swine veterinarians. During the spring of 2008, a Web-based survey was administered to members of the American Association of Swine Veterinarians (AASV), who had previously self-reported as clinicians. The survey documented farm demographics, injection technology, needle types and sizes, and injection locations for each stage of production and for pharmaceutical classes. Additionally, protocols for handling a broken needle event were recorded. The response rate of the survey was 36.8% (132/359).

Injection Technologies

Within the last 10 years, detectable needles have been developed and needle-free injection systems have been introduced to the swine industry.

Currently, there are several needle-free injection systems on the market, including those made or marketed by Pulse Needle Free Systems, Merial Limited, Genesis Instruments (DCI), Agro-Jet and Acu-Shot. Each has different features that deserve consideration. All have an internal piston that is driven back by gas or electric power. At the time of injection, the dose is delivered by the piston. The initial fluid jet pierces the skin, allowing the dose to be delivered into the dermis, subcutaneous tissues and, depending on the device, orifice size and pressure setting, into the muscle.

Some advantages of needle-free delivery are accurate and precise dose delivery, reduction in repetitive motion injury, elimination of needle stick injury risks to humans and eliminating the risk of broken needles in pork products.

Nonetheless, all needle-free devices are more difficult and costly to implement than conventional needle and syringe, and food safety benefits are not directly realized by producers, except in fully integrated systems. In our study, 28% of swine veterinarians reported needle-free device use by producers in breeding swine, 8% in market swine.

Detectable needles, available for several years, are made of special alloys that are detectable by metal detectors located on packer-processing lines. Most plants have metal detectors on the lines processing the highest-risk products, such as shoulders. Since not all lines have the metal detectors, preventing needles from entering the food chain is not 100% fail-safe. And, since not all pork producers use detectable needles, there is added risk.

In our study, veterinarians reported 40% of producers used detectable needles. Clearly, increasing use of detectable needles would result in less risk of a broken needle finding its way to a consumer's plate.

Avoiding Needle Breakage

Regardless of whether detectable or conventional needles are used, there are several steps you can take to reduce the risk of needle breakage:

  • Never straighten a bent needle. Research and practical experience has shown that needles rarely break the first time they bend. Successive bending commonly results in needle breakage.

  • Restrain the pig appropriately.

  • Use the correct needle gauge for the size of pig you are injecting.

  • Be aware that the shaft of some needles can separate from the hub prematurely. This hub-shaft separation results when the needles are not sufficiently crimped at the manufacturer. If you observe this default, return all the boxes of needles from that lot to your supplier and demand a refund.

  • Provide proper training. Effective employee training programs highlight the importance of proper injection methods.

It is unrealistic to think that a needle will never break, so when it happens, make sure workers know what to do.

The PQA Plus program (www.pork.org/Producers/PQAP.aspx?c=PQAP) recommends that all producers have a broken needle policy that outlines the steps to take if a needle breaks while injecting an animal. The first step is to identify the pig. Many producers have special ear tags specifically made for this purpose, although a temporary mark can be sufficient until the pig can be segregated. If the needle can be removed, do so. If the needle cannot be removed, contact your processor to determine the next step to take.

Our survey of veterinarians found that 87% of pork producers have a broken needle policy, 77% have reported a broken needle to a processor, and 38% have been contacted about a physical hazard or abscess associated with an injection-site lesion.

Location, Location, Location

The study showed the neck was the most common site of injection of breeding stock, except for hormones given to sows, where perivulvar injection was the most common (67%). Thirty-eight percent indicated injections were given in the sows' hips. For growing pigs, the neck was the most common site of injection (>99%).

In order to quantify lesions associated with injection site locations identified in the survey, market hog and cull sow processing facilities were surveyed.

Market Hog Study

The market hog study was a cross-sectional survey of carcass defects detected during harvest at commercial processing plants. Each of three plants was visited three times over a one-year period for a total of nine sample periods. Chi-square analysis — used to compare the prevalence of lesions between plant locations — was used.

Four thousand carcasses were visually observed for presence of defects. Of all market swine carcasses, 97.5% had no lesions; 2.2% had a neck lesion; 0.15% had a hip lesion; and there was a 0.08% prevalence each for shoulder, perivulvar and ham regions. One pig had two lesions in the neck and shoulder. There were no significant differences between market hog plants in the prevalence or distribution of lesions.

These data suggest a very low prevalence of carcass defects in the market hog population studied, as well as a consistency of distribution of defects, suggesting standardization of injection practices among farms. Furthermore, the defects were located in the neck, the most commonly recommended location for injection by the PQA Plus program.

Sow Plant Study

The study design for cull sows was a cross-sectional survey of carcass defects detected during harvest at commercial sow processing plants. Each of three plants was visited three times over a one-year period for a total of nine sample periods. Again, chi-square analysis was used to compare the prevalence of lesions between plants.

A total of 3,200 sow carcasses were visually observed for presence of defects. Of sow carcasses, 84.9% had no lesions, 11.2%, a neck lesion; 2.7%, a lesion on the hip; 0.3%, a ham lesion; 0.6%, a perivulvar lesion; 0.06%, a loin muscle lesion; 0.6%, a shoulder lesion; and 0.5% of sow carcasses had two lesions. There was a significant difference in prevalence of lesions between plants.

For the presence of any lesion, the prevalence was 11.1%, 24.2% and 7.6% for Plants B, D and E, respectively. The plants differed in the prevalence of lesions at different locations on the carcasses. The prevalence of neck lesions was 6.1%, 21% and 4.3% for Plants B, D and E, respectively. The prevalence of hip lesions was 3.7%, 1.8% and 2.4% for Plants B, D and E, respectively. The prevalence of lesions in the perivulvar, ham and shoulder regions were also different between plants.

Veterinarians' Report

Data from the AASV survey indicates that the hip location is being used frequently for injection in sows, and there is a growing use of needle-free injection technologies. Additional study is warranted regarding the impact of these alternate injection technologies and injection sites on the prevalence and economic impacts of cull sow carcass defects.

While the hip is an easy and safe location for workers to give injections to sows, the site is problematic for cull sow processors. Hip injections are not recommended since this location is of higher value, and the total amount of trim is higher when an abscess is present.

C. Scanlon Daniels, DVM, is a co-owner of Circle H Headquarters LLC, a diversified veterinary practice, laboratory and contract research organization in Dalhart, TX (www.circleh.info). Research reported in this article was funded by Pork Checkoff. Julie Funk, DVM, Michigan State University, was co-investigator, and University of Minnesota veterinary students Conrad Spangler and Carissa Odland assisted with the project. Spangler is currently a veterinarian with Circle H Headquarters LLC, and Odland is currently a veterinarian with the Pipestone (MN) Veterinary Clinic.