Evaluation of exogenous glucocorticoid injection on preweaning growth performance of neonatal pigs under commercial conditions.

Three commercial trials were conducted to evaluate the use of dexamethasone (Dex) and/ or isoflupredone (Predef) in improving preweaning growth performance of neonatal pigs. The objectives of the commercial trials were threefold: 1) to evaluate Predef in comparison with Dex; 2) to address the sexual dimorphic growth response observed in a previous commercial trial; and 3) to determine whether there is any benefit of providing Dex treatment to pigs being fed supplemental milk. In Exp. 1, 276 pigs (Triumph 4 x PIC Camborough 22) were assigned according to birth weight and sex to three treatments. Treatments included saline (Control), Dex (2 mg/kg BW i.m. injection of Dex), or Predef (2 mg/kg BW i.m. injection of Predef 2X) within 24 h after birth. A treatment effect was observed for BW at weaning (P < 0.001), with pigs injected with Predef being 0.51 kg lighter than Control and Dex-treated pigs. The lower BW of Predef-treated pigs at weaning were a result of a lower ADG (P < 0.001) during the preweaning period compared with Control and Dex pigs. In Exp. 2, 703 pigs (Triumph 4 x PIC Camborough 22) were assigned according to birth weight and sex to three treatments. Treatments included either an i.m. injection of saline (Control), Dexl (1 mg/kg BW of Dex), or Dex2 (2 mg/kg BW of Dex) within 24 h after birth. No treatment effects were observed for BW at weaning (P = 0.24) or ADG (P = 0.19). In Exp. 3, 342 pigs (Genetiporc) were assigned according to birth weight and sex to two treatments. Treatments included either an i.m. injection of saline or Dex (2 mg/kg BW) within 24 h after birth. All pigs were provided supplemental milk from the time of treatment until weaning age. No treatment effects were observed for BW at weaning (P = 0.13) or ADG (P = 0.11). The negative response to Predef was similar to the growth-suppressive effects observed by others using chronic glucocorticoid treatment. In contrast to our previous findings, Dex did not improve preweaning growth performance regardless of dose or supplemental milk.