Glucocorticoid receptor agonist (GRA): an alternative to in-feed antibiotics (ANT) for newly weaned pigs

Previously we found that GRA reduces systemic inflammation in newly weaned pigs. Therefore, we evaluated the effects of GRA on growth performance and blood chemistry in newly weaned pigs, since inflammation impacts growth. A total of 209 pigs (BW 7.4 ±1.27 kg) were weaned at 26 ±1.5-d of age and assigned to a factorial CRD, with sex and treatment as main effects. Treatments included control (CON), GRA, ANT, and ANT+GRA (ANGA). Dexamethasone (0.2 mg/ kg BW; i.m. injections) and Tylan 40 (0.12% of diet) were used as GRA and ANT, respectively. Pigs had free access to conventional corn-soybean diets according to a phase-feeding program. Feed intake, BW, ADG, measures of blood chemistry and hematocrit were determined over the 28-d post-weaning period. The repeated measures ANOVA (PROC MIXED) in SAS was used for statistical analysis. Interaction effects of sex and treatments were observed on BW and ADG (P = 0.03), but not on the gain-to-feed ratio (G:F). BW (kg) was higher in GRA gilts (10 ±0.08) than ANT gilts (9.7 ±0.06) and barrows (9.6 ±0.05), and CON barrows (9.4 ±0.09; P = 0.01). GRA gilts tended to be heavier than CON gilts (9.8 ±0.10; P = 0.06). ADG (kg) was higher in GRA gilts (0.40 ±0.014) than ANT gilts (0.34 ±0.019), CON barrows (0.29 ±0.016) and ANT barrows (0.36 ±0.012; P = 0.05). Overall G:F was higher in GRA pigs than CON pigs (0.63 vs. 0.56 ±0.020; P = 0.01) and tended to be higher than ANT pigs (P = 0.09). Creatinine levels tended to be lower in GRA pigs than ANT pigs (1.18 vs. 1.30 ±0.046 mg/dl; P = 0.07). Treatments had no effects on other measures of blood chemistry. Collectively, treatment with GRA effectively improves the growth performance of nursery pigs, especially gilts, during the nursery phase. GRA can be considered as an alternative to in-feed antibiotics for mitigating the adverse effects of weaning stress. USDA-NIFA-2017-68008-26304.