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  • Title: Therapeutic effects of mitoquinol during an acute heat stress challenge in growing gilts.
    Author: Mayorga EJ, Freestone AD, Rudolph TE, Roths M, Abeyta MA, Rodríguez-Jiménez S, Goetz BM, Opgenorth J, Selsby JT, Baumgard LH.
    Journal: J Anim Sci; 2024 Jan 03; 102():. PubMed ID: 39212947.
    Abstract:
    Study objectives were to evaluate the effects of mitoquinol (MitoQ) on production parameters, gastrointestinal tract (GIT; stomach and small and large intestines) weight, and circulating leukocytes during a 24-h acute heat stress (HS) challenge. Crossbred gilts [n = 32; 49.1 ± 2.4 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 moved into individual pens and allowed to acclimate for 6 d. The study consisted of 2 experimental periods (P). During P1 (2 d), all pigs remained in TN conditions (20.6 ± 1.5 °C) and were fed ad libitum. During P2 (24 h), pigs were fed ad libitum and exposed to either TN or constant HS (37.3 ± 1.3 °C). Mitoquinol (40 mg/d) was orally administered twice daily (0700 and 1800 hours) during P1 and P2. As expected, pigs exposed to HS had increased rectal temperature, skin temperature, and respiration rate (+1.5 °C, +8.7 °C, and +86 bpm, respectively; P < 0.01) compared to their TN counterparts. Compared to TN, HS pigs had decreased feed intake (67%; P < 0.01) and significant BW loss (+1.5 vs. -1.9 kg, respectively; P < 0.01). Total GIT weight was decreased in HS relative to TN pigs (P < 0.01), and this was influenced by decreased luminal contents (2.43 vs. 3.26 kg, respectively; P < 0.01) and reduced empty GIT mass (3.21 vs. 3.48 kg, respectively; P = 0.03). Stomach contents remained similar between TN and HS pigs (P > 0.54) but tended to increase in MitoQ relative to CON pigs (0.90 vs. 0.63 kg, respectively; P = 0.08). Stomach content as a percentage of the previous 24 h feed intake was increased in HS compared to the TN controls (93% vs. 31%; P < 0.01). In contrast, small and large intestinal contents were decreased in HS compared to TN pigs (23% and 49%, respectively; P < 0.01). Liver weight decreased in HS relative to TN pigs (1.15 vs. 1.22 kg, respectively; P = 0.02), and was decreased in MitoQ compared to CON pigs (1.13 vs. 1.24 kg; P < 0.01). Circulating lymphocytes tended to be decreased in HS relative to TN pigs (16%; P = 0.07). In summary, acute HS increased all body temperature indices, negatively influenced animal performance, and differentially altered GIT motility as evidenced by decreased gastric emptying and increased intestinal transit. However, MitoQ supplementation did not appear to ameliorate these effects. Heat stress (HS) causes enormous financial losses to animal agriculture due to its adverse effects on animal productivity. While the mechanisms behind HS-induced malaise are multifaceted and intricate, evidence points to intestinal barrier dysfunction and the ensuing immune response as a primary contributor. Presumably, HS induces oxidative stress (OS) within the intestinal epithelium, potentially leading to intestinal hyperpermeability. Mitochondria are the primary source of endogenous reactive oxygen species; thus, administering mitochondria-targeted antioxidants, such as mitoquinol (MitoQ), may be more effective at reducing OS than traditional dietary antioxidants (e.g., vitamin E, selenium). We have previously observed positive effects of MitoQ on growth performance in acutely heat-stressed barrows, which prompted our objective to determine if the results were repeatable with gilts. Herein, HS increased all body temperature indices, reduced feed intake, and caused severe body weight loss. Additionally, HS reduced gastrointestinal tract (GIT) weight and differentially altered GIT luminal contents, suggesting HS disparately affects GIT motility. However, contrary to our expectations, MitoQ did not alleviate these physiological and phenotypic responses to HS. Altogether, the beneficial results from our previous MitoQ experiment in barrows were not repeatable in gilts, and it remains unclear whether supplementing antioxidants during HS is beneficial for animal performance.
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