Therapeutic effects of mitoquinol during an acute heat stress challenge in growing barrows.

Study objectives were to determine the effects of mitoquinol (MitoQ, a mitochondrial-targeted antioxidant) on biomarkers of metabolism and inflammation during acute heat stress (HS). Crossbred barrows [n=32; 59.0±5.6 kg body weight (BW)] were blocked by BW and randomly assigned to 1 of 4 environmental-therapeutic treatments: 1) thermoneutral (TN) control (n=8; TNCon), 2) TN and MitoQ (n=8; TNMitoQ), 3) HS control (n=8; HSCon), or 4) HS and MitoQ (n=8; HSMitoQ). Pigs were acclimated for 6 d to individual pens before study initiation. The trial consisted of two experimental periods (P). During P1 (2 d), pigs were fed ad libitum and housed in TN conditions (20.6±0.8°C). During P2 (24 h), HSCon and HSMitoQ pigs were exposed to continuous HS (35.2±0.2°C), while TNCon and TNMitoQ remained in TN conditions. MitoQ (40 mg/d) was orally administered twice daily (0700 and 1800 h) during P1 and P2. Pigs exposed to HS had increased rectal temperature, skin temperature, and respiration rate (+1.5°C, +6.8°C, and +101 breaths/min, respectively; P<0.01) compared to their TN counterparts. Acute HS markedly decreased feed intake (FI; 67%; P<0.01); however, FI tended to be increased in HSMitoQ relative to HSCon pigs (1.5 vs. 0.9 kg, respectively; P=0.08). Heat-stressed pigs lost BW compared to their TN counterparts (-4.7 vs. +1.6 kg, respectively; P<0.01); however, the reduction in BW was attenuated in HSMitoQ compared to HSCon pigs (-3.9 vs. -5.5 kg, respectively; P<0.01). Total gastrointestinal tract weight (empty tissue and luminal contents) was decreased in HS pigs relative to their TN counterparts (6.2 vs. 8.6 kg, respectively; P<0.01). Blood glucose increased in HSMitoQ relative to HSCon pigs (15%; P=0.04). Circulating non-esterified fatty acids (NEFA) increased in HS compared to TN pigs (P<0.01), although this difference was disproportionately influenced by elevated NEFA in HSCon relative to HSMitoQ pigs (251 vs. 142 μEq/L; P<0.01). Heat-stressed pigs had decreased circulating insulin relative to their TN counterparts (47%; P=0.04); however, the insulin:feed intake ratio tended to increase in HS relative to TN pigs (P=0.09). Overall, circulating leukocytes were similar across treatments (P>0.10). Plasma C-reactive protein remained similar among treatments; however, haptoglobin increased in HS relative to TN pigs (48%; P=0.03). In conclusion, acute HS exposure negatively altered animal performance, inflammation, and metabolism, which were partially ameliorated by MitoQ.