Effects of perfluorooctanoic acid exposure and heat stress on performance and liver health biomarkers in post-pubertal gilts

Objectives were to evaluate how dietary perfluorooctanoic acid (PFOA) and heat stress (HS) affect growth performance and liver health biomarkers in pigs. Crossbred post-pubertal gilts (n = 48; 164.0 ± 11.6 kg body weight [BW]) were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial design: 1) thermoneutral (TN) control (n = 12; TN-CON), 2) TN and PFOA (n = 12; TN-PFOA), 3) HS control (n = 12; HS-CON), or 4) HS and PFOA (n = 12; HS-PFOA), and enrolled in 3 experimental periods (P). During P1 (3 d), pigs were housed in TN conditions (20.3 ± 0.1 °C) and baseline data were collected. During P2 (15 d), HS-CON and HS-PFOA pigs were exposed to cyclical HS (29.3 ± 0.1 to 31.9 ± 0.8 °C), while TN-CON and TN-PFOA remained in TN conditions. Altrenogest was administered once daily (0800 h) during P2 to synchronize estrus. In P3 (4 d), Altrenogest was withdrawn to induce estrus, while experimental treatments remained the same. PFOA (70 ng/kg BW) was orally administered once daily (0800 h) during P2 and P3, and all pigs were euthanized at the end of P3. HS increased rectal temperature, skin temperature, and respiration rate compared to TN counterparts during P2 (0.34 °C, 5.67 °C, and 22 bpm, respectively; P < 0.01) and P3 (0.26 °C, 6.96 °C, and 22 bpm, respectively; P < 0.01), and these were only marginally influenced by PFOA. During P2 and P3, HS markedly decreased feed intake (FI) and average daily gain (ADG), and PFOA tended to decrease FI and ADG; an effect most pronounced in TN conditions (410 g/d; P ≤ 0.08 and 320 g/d; P ≤ 0.09, respectively) during P2 and P3. HS decreased circulating alkaline phosphatase and alanine aminotransferase in P2 and P3 (P ≤ 0.01), and increased gamma-glutamyl transferase in P2 (P < 0.01), but these enzymes were unaffected by PFOA. There was little to no dietary treatment or environmental effects on other liver health biomarkers. HS decreased absolute and relative liver, lung, and kidney weights, and PFOA decreased absolute lung weight (11%; P < 0.05) and relative lung weight (0.06%; P = 0.09). In summary, PFOA and HS independently compromised appetite and growth, but the effects of PFOA and HS do not appear to be additive.