Needle-free intradermal vaccination, an opportunity to improve commercial pig welfare.

In-farm livestock production vaccinations are commonly delivered intramuscularly using needles. While there are alternative strategies these have been subject to little attention and limited commercialisation. One such alternative is needle-free vaccines and studies have focused on the immune response few have addressed the welfare implications. This study aims to compare the impact of intradermal needle-free vaccination and intramuscular injection in terms of the welfare of the piglets. A total of 179 piglets were divided into two treatments: intradermal needle-free delivery and intramuscular delivery of a vaccine. Measures of health and welfare included, vocalisations, behavioural observations, papule formation, and weight. Piglets vaccinated via the needle-free intradermal route vocalised less and displayed no significant behavioural differences but showed increased weight compared to piglets vaccinated intramuscularly. The use of a needle-free device to deliver a vaccine through an intradermal route revealed no adverse effects on piglet welfare and supports the use of alternative strategies to vaccinate livestock.