Cortisol agonist improves growth performance and subsides systemic inflammation in newly weaned pigs

Abstract Text: Segregated early weaning (SEW) is one of the most stressful periods that results in intestinal inflammation and reduced productivity of pigs. Anti-inflammatory effects of glucocorticoids have been well documented. Dexamethasone (DEX), a cortisol agonist (CA), is a pharmaceutical compound prescribed in veterinary medicine as anti-inflammatory agents and has the potential to subside the negative effect of systemic inflammation. Our objective was to evaluate the effect of CA on growth performance, intestinal histomorphology, and measures of immune function in weaning pigs. Eighteen gilts of commercially relevant genetics (BW 5.6 ± 0.85 kg) were assigned to three treatments: (i) unweaned (UWS), (ii) SEW plus CA (WCA; 0.2 mg DEX/kg BW), and (iii) SEW plus saline (WS). Pigs were weaned at 23 ±2 d of age and received their treatments via intramuscular injections at day -1 and 3 post-weaning. Serial blood samples were taken via jugular puncture on day 0, 1, 4, and 5 post-weaning and assayed for interleukin-1β (IL-1β), antioxidant levels, and haptoglobin. Pigs in WCA and WS had free access to a conventional corn-soy based diet (14.2 MJ/kg ME and 9 g/kg SID Lysine) after weaning. Pigs were euthanized by intravenous injection of sodium pentobarbital 5 d after weaning and segment of jejunum was removed for histomorphology examination. Body weight of the animals was monitored on a daily basis. Treatment with CA did not affect villus architecture and feed intake (P > 0.10). Weaning reduced the villus height by 30% (709  SE 62.6 μm in UWS; P < 0.03), but had no effect on crypt depth. Relative to WS and UWS, WCA pigs had a higher plasma antioxidant levels (1.14, 1.04, and 1.05 SE 0.032 mM, for WCA, UWS, and WS, respectively; P < 0.02).  Treatment with CA reduced plasma levels of haptoglobin (from 0.74 to 0.39 SE 0.164 g/ml) and IL-1β (from 17.0 to 2.6 SE 5.84 pg/ml) in weaned pigs (P < 0.04). Body weight (kg) was higher in WCA (6.4 SE 0.05) than SW (6.2 SE 0.05), but lower than UWS pigs (6.8 SE 0.08; P < 0.04). Relative to WS, gain-to-feed ratio was higher among WCA pigs (0.56 vs. 0.90 SE 0.070; P < 0.01). Collectively, these results suggest that treatment with CA can partially mitigate the negative effect of weaning stress on growth performance of piglets by subsiding systemic inflammation.

Keywords: cortisol agonist, Dexamethasone, weaning pig