Magnetic Resonance Imaging Used to Define the Optimum Needle Length in Pigs of Different Ages

Abstract

Intramuscular injections result in tissue destruction and alteration. Therefore, it is necessary to evaluate the optimum injection point for intramuscular injections. As animals—especially pigs—vary in size and explicit information about injection depth is not available. To determine the predicted optimum injection depth, magnetic resonance imaging was used in pigs of different ages and weight groups. In total, 730 magnetic resonance images of 136 pigs were used to calculate the optimum injection depth for intramuscular injections. Four age groups were evaluated: <29 days of age, 29−70 days of age, 71−117 days of age and >170 days of age. For fattening pigs (71−117 days of age), the present study recommends a needle length of 20 mm (range: 40−58 mm). For younger pigs (<70 days of age), a needle length of 12 to 14 mm (range: 10−18 mm), and for older pigs (>170 days of age), a needle length of 30 mm (range: 25−37 mm) is recommended. However, more data are needed. Therefore, further studies are necessary, especially in the youngest (suckling pigs) and oldest (sows) age groups, as these are the groups mainly injected/vaccinated. Additionally, age and weight should be examined in more detail compared to fat distribution in the neck, genetics and the sex of the animal.

Keywords: animal welfare; injection depth; magnetic resonance imaging; pigs.

Figure 1

Demonstration of the measurements performed at the ear-base level. (a) Definition of the coronary image at the ear-base level (pig 1668; 23.5 kg, 94 days of age). (b) Defining the first injection point (OI_1), 10.55 mm behind the base of the ear. (c) Measuring the optimum injection point at 10.55 mm distance (OI_1) from the base of the ear (here: 19.77 mm). (d) Measuring the distance to the middle of the neck at 10.55 mm distance (MN_1) from the base of the ear (here: 44.03 mm). (e) Defining the second injection point (OI_2), 20.39 mm behind the base of the ear. (f) Measuring the optimum injection point at 20.39 mm distance (OI_2) from the base of the ear (here: 22.46 mm). (g) Measuring the distance to the middle of the neck at 20.39 mm distance (MN_2) from the base of the ear (here: 45.82 mm).