Scientific Abstract

Piglets raised in commercial production systems in the U.S. undergo painful management procedures without analgesia or anesthesia provision. This is a significant animal welfare issue, affecting millions of piglets each year. The objectives of this study were to assess the efficacy of firocoxib, administered to the sow and delivered transmammary to her piglets, and a vapocoolant spray (ethyl chloride), to reduce pain associated with piglet processing procedures. This study also sought to determine if cortisol could be quantified from the hair and saliva of pre-weaned pigs, to provide a more welfare-friendly option to assess piglets’ physiological stress response. One hundred and twenty-eight Yorkshire x Landrace piglets (5 days old) across 16 litters were used. The study was split into a winter cohort and a summer cohort, with an equal number of piglets represented in each group. Seven hours prior to processing piglets, half of the sows received an intramuscular injection of 2.0mg/kg firocoxib (for transmammary-delivery to piglets). Piglets were assigned to one of four treatment groups: transmammary-delivered firocoxib + ethyl chloride spray, transmammary-delivered firocoxib only, ethyl chloride spray only, or control/no treatment. The ethyl chloride spray was applied to the tail and scrotum of the piglets immediately before tail docking and surgical castration, respectively. The outcome variables included assessment of blood-drug concentration, behavior, cranial and eye temperature (using infrared thermography), plasma, hair, and salivary cortisol concentration, facial grimacing, gait, vocalization, and weight. Piglet pain measures were taken at baseline (the day before processing) and out to 48h post-castration and tail docking. The addition of the ethyl chloride spray did not lead to significance for any of the outcome measures; therefore, treatments were collapsed into two groups: FIROpiglets who received transmammary-firocoxib prior to processing and CON piglets who were processed without analgesic drug provision. At the time of processing, FIRO piglets emitted calls of lower amplitude than CON piglets (P<.0001). FIRO piglets engaged in significantly less agonistic behavior and significantly more play behavior across the observation period compared to CON piglets (P=0.04 and P=0.002, respectively). There was no significant difference in pain behavior or stress outcome measures in piglets associated with transmammary-delivered firocoxib. The greatest concentration of firocoxib was found in piglets ~30h post-administration to the sow (P<0.0001). This suggests that sows may need to be administered the analgesic drug more than 24h prior to processing piglets, to ensure an adequate blood-drug concentration at the level of the piglet is achieved. Additionally, piglets in the winter cohort had3 significantly higher levels of firocoxib in their blood compared to piglets in the summer cohort (P=0.0008). Seasonal differences in farrowing room temperature also impacted other stress outcome measures, such as plasma cortisol concentration, cranial and eye temperature, average daily gain, vocalization, and gait (P<0.05). Future work will need to account for seasonal differences to determine optimal drug doses and treatment regimens. Cortisol was successfully extracted and quantified from the saliva and hair of pre-weaned pigs, which may provide new, less invasive options to monitor acute and chronic stress in the swine industry. Overall, transmammary-delivery of firocoxib may have provided some benefit to piglets in this study; however, the concentration of analgesic at the level of the piglet was not sufficient to significantly reduce pain.