How long should a pig needle be and where is it better to do an intramuscular injection

The answer to this question was given by German researchers who studied 730 magnetic resonance images of 136 pigs.

A team of researchers (Maren Bernau, Ulrike Gerster, Armin Manfred Scholz) from Animal Breeding Center Oberschleissheim, Faculty of Veterinary Medicine, Ludwig-Maximilian University of Munich and Faculty of Agriculture, Economics and Management, Nürtingen-Geislingen University of Applied Sciences published the results of their work on the topic of veterinary medicine in pig production in the journal Animals 2022 on the MDPI portal.

“Injections always cause local reactions. To minimize them, the optimal location as well as the optimal depth of injection should be considered.

Each intramuscular injection leads to a change and destruction of tissues with painful consequences. Unlike laboratory animals, for farm animals there is no clear information about the type of injection, the volume and size of the needle.

Several articles have compared, for example, injection sites in pigs.

For intramuscular injections in pigs, the neck tissue behind the base of the ear was found to be the best point. In pigs, the muscles in the neck are smaller and surrounded by looser connective tissue compared to the lumbar or gluteal region.

Thus, it is recommended as a preferred injection site for pigs weighing more than 10 kg to determine a point one finger width located caudal (along the longitudinal axis to the tail) from the base of the ear. Piglets are injected into the tissue of the neck.

In addition to the injection site, needle length and diameter play an important role in both drug delivery and associated pain. It is well known that thin and short needles cause less irritation. Human studies have shown a strong correlation between injection pain and needle thickness, with a smaller needle diameter resulting in less pain upon insertion.

Thus, the length of the needle is an important parameter to guarantee the least harmful injection for each size of the animal in order to avoid painful injuries.

The aim of this study was to evaluate magnetic resonance images of porcine neck tissue to provide useful information for predicting the optimal/suitable injection depth for intramuscular injections in pigs of different ages and weights injected at the recommended site.

This study is entirely anatomical in nature and did not include measurements of needle tip position, nor evaluation of parameters that affect the distribution efficiency of the injectable material in pigs.

A total of 730 magnetic resonance images of the neck were evaluated to determine depth from the skin to the proposed optimal muscle injection site and depth to the spine at two locations at the base of the ear.

Four age groups were formed for observation:

<29 (age range (from-to days) 5-26; weight range (from-to in kg) 3.5-11.5)

29–70 (age range 31–70; weight range 6.0–31.5)

71–117 (age range 71–117; weight range 12.5–54.5)

>170 (age range 171–195; weight range 58–124).

The pigs were purebred German Landrace (26% of animals) or hybrids of Pietrain sires and German Landrace sows (74% of animals). Males (uncastrated; 54% of animals) and females (46% of animals) were included (age group >171 days for females only).

Based on the results of the study, the following recommendations were made.

For fattening pigs (71–117 days of age), a needle length of 20 mm is recommended in this study.

For young pigs (up to 70 days old) the optimal needle length is 12 to 14 mm.

For older pigs (over 170 days old) a needle length of 30 mm is recommended.

However, further research is needed, especially in the youngest (MILK pigs) and oldest (sows) age groups, since these are the groups that are mostly injected/vaccinated. In addition, age and weight should be studied in more detail as compared to neck fat distribution, genetics and sex of the animal.”