Date Full Report Received11/25/2019
Date Abstract Report Received11/25/2019
Funded ByNational Pork Board
Each year approximately 133 million piglets in the United States undergo processing procedures such as tail docking, castration and teeth clipping. Pain associated with piglet processing is an emerging animal welfare concern. We proposed that delivery of a non-steroidal anti-inflammatory drug, firocoxib, from the sow, through the milk, to nursing piglets would reduce pain associated with processing in piglets. The first study compared the drug concentrations, effectiveness, safety and tissue drug concentrations of four doses of firocoxib (0.5, 1.0, 1.5, or 2.0 mg/kg) when administered to sows and delivered to nursing piglets prior to processing. Sixteen sows, 5±2 d postpartum, were randomly assigned to one of four treatment groups. On d 0 sows received a single intramuscular dose of firocoxib at 7±1 h before piglet surgical castration, tail docking, and teeth clipping (males) or sham handling (females). Firocoxib, cortisol and prostaglandin E2 (PGE2) concentrations were determined from selected samples collected from sows and three piglets/litter (two barrows and one gilt) at 0, 2, 4, 6, 8, 12, 24, 48, 72, 96, and 120 h after drug administration. On d 21, piglets were weighed and all animals were euthanized and necropsied. Tissues were collected from 3 piglets/litter for histological examination and drug residue analysis. Firocoxib concentration were maintained in sows and piglets for a long time with the time taken for plasma drug concentrations to decrease by half ranging from 26 to 31 h in sows and 30 to 48 h in piglets. Barrows nursing sows that received 2.0 mg/kg firocoxib had a lower circulating concentrations of the stress hormone, cortisol, at 1±1 h after processing compared to barrows nursing sows that received 1.0 mg/kg (P=0.0416) and 0.5 mg/kg of firocoxib (P=0.0397). From processing to weaning, litters of sows receiving 2.0 mg/kg firocoxib gained more weight than litters of sows that received 0.5 mg/kg (P=0.008) or 1.0 mg/kg (P=0.005). No signs of toxicity were observed on examination of the kidney, liver, stomach and small intestine and concentrations of firocoxib were below the limit of detection (0.01 µg/g) in all tissues examined from sows and piglets. These findings indicate that maternal delivery of firocoxib to suckling piglets before tail docking and castration may safely reduce processing-induced stress and enhance production by increasing weaning weights. In a second study, we evaluated changes in the temperature of the skin and the eye, using infrared thermography (IRT), and changes in gait, assessed using a pressure mat, as potential biomarkers of pain in piglets after delivery of firocoxib in the milk before processing. Eight sows (n=2 sows per replicate for 4 replicates), nursing approximately eight piglets per litter (male and female; 5 days old; minimum BW = 1.8 kg) were enrolled in the study. Replicates were conducted in January, February, July and August 2019. Sows were randomly assigned to 1 of 2 treatment groups (n = 4 sows (32 piglets)/ group). Group 1 received 1.5 mg/kg Firocoxib intramuscularly (IM) in the right side of the neck at the time of study commencement. Group 2 served as a control and received a placebo injection consisting of physiological saline at a similar injection volume as sows in the firocoxib group. Treatments were administered at 6±1 h before piglet surgical castration, tail docking, and ear notching (males) or tail docking and ear nothing (females). IRT images were captured at 1 h, 2 h, 4 h, 7 h, 24 h, 30 h, 36 h and 48 h after processing. The effect of castration on piglet gait was assessed by briefly removing piglets from their pen and allowing them to walk across a pressure mat at 0.5, 7 h, 24 h, 36 h and 48 h post-processing. Female piglets had significantly greater skin temperatures compared to male piglets (P=0.0473). Skin temperature of the head was also significantly lower in piglets that were nursing sows that received firocoxib compared to control piglets at 2 h (P=0.0108) and 4 h (P=0.0316). However, skin temperatures of the head of piglets that were nursing sows that received firocoxib were higher than piglets nursing placebo-treated sows at 36h (P=0.0086) and 48h (P=0.0375) after processing. It is noteworthy that skin temperatures of piglets nursing the firocoxib-treated sows were higher than the control piglets in January and February but this effect was less evident in July and August. Eye temperatures in piglets that were nursing sows that received firocoxib were higher than piglets nursing placebo-treated sows at 1h (P=0.0207), 30h (P=0.0011) and 36 h (P=0.0024) after processing. Eye temperatures of piglets nursing the firocoxib-treated sows were also higher than the control piglets in August (P<0.0018). These observations suggest that season should be considered when infrared thermography is used to assess changes in eye and skin temperature after processing. Furthermore, compared to the skin temperature of the head, eye temperature assessment may be more robust for assessing pain in summer compared to winter. Piglets nursing sows in the control group demonstrated a significantly greater increase in the force applied to the front limbs at 7 h after processing compared to piglets nursing sows medicated with firocoxib (P=0.0127). We hypothesize that pain associated with castration results in a shift in force from the hind limbs to the front limbs of piglets to distribute weight away from the surgical site. In conclusion, these studies demonstrated the feasibility and safety of administering firocoxib in the milk to piglets before processing. Furthermore, the results of these experiments showed that at the higher doses tested, firocoxib delivered in the milk to piglets reduced markers of pain after processing. This was illustrated by a reduction in stress hormone concentrations, an increase in head and eye temperatures at later time points after processing and a reduction in processing-induced changes in weight distribution of the limbs in treated compared to control piglets. These findings address current animal welfare concerns related to pain associated with processing in piglets and will have an immediate and significant impact on the sustainability of U.S. swine production systems. The results of this study support the use of transmammary firocoxib to mitigate pain associated with processing and thus help to maintain consumer confidence in pork production practices and keep American agriculture competitive as pain management expectations evolve.