Intramuscular vs. Intradermic Needle-Free Vaccination in Piglets: Relevance for Animal Welfare Based on an Aversion Learning Test and Vocalizations.

The aim of the present study was to compare intramuscular injection with a needle and intradermic needle-free vaccinations against porcine reproductive and respiratory syndrome (PRRS) in piglets at 28 days old by studying behavioral and physiological reactions. A total of 72 piglets divided into 2 sex-balanced batches were assessed. Within each batch, the piglets were divided into three treatments, which were Hipradermic (0.2 ml of UNISTRAIN® PRRS vaccine administered with an intradermic needle-free device), Intramuscular (IM, 2.0 ml of vaccine), and Control (not vaccinated). Before the vaccination, the piglets were trained to cross a 4-m-long raceway to perform an aversion learning test. The day of vaccination, the time taken to cross the raceway was registered for each piglet at different times: prior to the vaccination and 10 min, 2, 24, 48, and 72 h after the vaccination, to measure variations in these times as signs of aversion to the vaccination process. Vocalizations, as potential signs of pain, were recorded as well at the end of this raceway to analyze their frequency (Hz), duration, and level of pressure (dB) at the moment of vaccination. Salivary cortisol, as a sign of the HPA-axis activity, was assessed 10 min after the vaccination. In addition, activity budgets, local reaction to the vaccine, and serological titer were also considered in the study. Ten minutes after the vaccination, the IM piglets took longer (

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Copyright © 2021 Dalmau, Sánchez-Matamoros, Molina, Xercavins, Varvaró-Porter, Muñoz, Moles, Baulida, Fàbrega, Velarde, Pallisera, Puigredon and Contreras-Jodar.

Déclaration de conflit d'intérêts

AS-M, JM, and AP are employees of the Laboratorios HIPRA SLU. AS-M and JM were involved in the conception and design of the study. This means that they asked to the IRTA researchers what they wanted to study and IRTA researchers proposed how and when. They did as well some amendments to the firsts drafts of the protocol according to the best practices of laboratory and IRTA researchers considered those that were improving the methodology. The case of AP was different because she was responsible of training AX and AV-P in vaccinating the animals properly, to provide the vials for vaccination, and to check for the company that the day of the vaccination everything was done according to the protocol. None of these three persons had access to the animals for any of the parameters assessed neither to the data. This paper comes from the report that IRTA sent to this company at the end of the study. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.