Which Needles Make the Grade?

Where are consumer reports comparing products from cars to computers. Now the pork industry has one for needles. A National Pork Board study looked at needle design, particularly the sharpness, strength and detectability.

While it's true that a needle making its way into a pork product is extremely rare, it is an event the industry can't afford. That's the focus behind NPB's "One is Too Many" campaign to prevent and detect broken needles in hog carcasses.

Strength: More than Just a Strong Hub
To determine needle strength NPB researchers used a mechanical pig to simulate natural movement. In that test, aluminum-hub needles bent but did not break, while plastic-hub needles broke every time.

"The most important thing to emphasize is if a producer bends a needle, he should throw it away," says Paul Sundberg NPB's assistant vice president of veterinary issues. "Needles don't break unless they are bent, straightened and then reused."

Researchers also performed static tests where constant pressure was applied during the injection, with no animal movement. In those tests not one needle broke when loaded and used a single time. The lesson here is that restraining animals to give injections is crucial to preventing broken needles.

"We're trying to tell people that even if you have a strong hub, it's not necessarily the best needle," says Steve Hoff, associate professor of agricultural and biosystems engineering, Iowa State University.

 "There's more to the story."

Sharpness: Which Needle Scores the Point?
Dull needles require more force to provide an injection, which could lead to bending and breaking more often than sharp needles.

Researchers tested sharpness retention by using a machine to inject a needle 1 mm beyond the needle's furthest cut-point. This was done into two layers of chamois over a 1-inch piece of high-density, rigid insulation board.

Measurements cited the distance that the needle had to travel to imbed it to a point 1 mm beyond the needle's furthest cut-point. The test used computer software to control needle motion and provide consistency in this travel distance. Each needle punctured the medium in a new location for 30 repetitions.

In most cases, sharpness-retention results showed a clear trend of increasing puncture force with repeated use. This was true up to 10 to 15 repetitions, but after 15 punctures that trend leveled off.

The higher the needle's gauge – that is the smaller the needle's diameter – the less puncture force required. This is especially evident in comparing 22-gauge needles to 16-gauge needles, says Hoff.

Also, there are significant differences in the puncture force required between manufacturers, he adds. The bevel design between manufacturers studied resulted in vastly different puncture forces. The manufacturer with the highest puncture force throughout had a clear trend of increasing force with increasing punctures.

Detectability: Finding a Needle in a Pork Stack
Even the best needles will break occasionally, so it's important that packers are able to detect a needle, should it remain in a hog carcass or meat cut.

The study looked at the delectability of 1-inch and 1/2-inch needle fragments imbedded in meat. Researchers used pork shoulder roasts weighing 3.48 to 3.73 pounds. Needle fragments were imbedded horizontally toward the back of the cut, horizontally in the side of the roast (parallel to the long axis of the detector) and vertically in the roast's center. Each needle was tested for 15 passes through the detector in each of the three positions.

Needles imbedded horizontally in the back of the roast were detected 1.5 times to 10 times more frequently than the other two positions.

Air-Tite and PDN were the most easily detected needles by a significant margin. The PDN needle fragments were actually detected 100 percent of the time, says Hoff.

In most cases, when the needle fragment was placed horizontally in the cut's side (parallel to the long axis of the detector) or vertically in the roast's center, detectability fell off sharply. If you remove the PDN results, the other fragments were detected between 0 percent and 32 percent of the time.

Add up detection rates of all the needles, placed in all locations and the study shows detectability ranges from 6.7 percent to 100 percent. Hoff points out that for needles most predominantly used today, the detection rate was between 6.7 percent and 26.2 percent, averaging 14.9 percent. However, if all of the needles commonly used today entered the detector either vertically or horizontally (and parallel with the detector axis), the average falls to 7.2 percent detected.

These detection rates illustrate how important it is for you to avoid broken needles. At the very least, you need to mark any hog that might be carrying a broken needle, and notify your packer upon delivery, to assist him in the process of removing the needle.

Looking at the big picture, Sundberg says the best needle will depend on what you need. "A needle with ideal characteristics bends at the hub if it needs to bend. Plastic hubs can shatter more easily," says Sundberg. "Stainless-steel alloys are strong, but they aren't as sensitive to metal detectors at the packing plant. Many of the needles used today have stainless steel as the primary metal in their alloy."

Sundberg isn't sure which alloy is the most detectable for machines in packing plants.

Another point to remember is that there's a threshold between research and the real world. For example, there may be needles with different strength scores but they may be equal in terms of on-farm use, even though some scored higher in the study, says Sundberg.

"The cost information also needs to be considered, so producers can determine, which needle provides the best benefits for their dollar," he notes. "We didn't include cost information because it varies so much by companies and the volume that you buy."

The point of this research is to provide information that you can use to make decisions. For a more detailed consumer report on the needles call (515) 223-2600 and ask for Paul Sundberg or look for the full report an NPB's Web site: www.porkboard.org.  



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