Pre- and postweaning performance of pigs injected with dexamethasone at birth

A trial was conducted to determine pre- and postweaning performance of pigs injected with dexamethasone either 1 or 24 h after birth. In Exp. 1, 225 pigs (Triumph4 x PIC Camborough 22) were assigned according to birth weight and sex to three treatments. Treatments included either saline (Control), Dex1 (2 mg/kg BW i.m. injection of dexamethasone within 1 h of birth), or Dex24 (2 mg/kg BW i.m. injection of dexamethasone within 24 h after birth). Birth weights (1.56 +/- 0.06 kg) did not differ among treatments (P > 0.10) or between sexes (P > 0.10). There was a treatment x sex interaction on BW at weaning (15 d; P < 0.05) with Dex1 and Dex24 males 10% heavier than Control males (4.77 and 4.78 vs. 4.34 kg, respectively), and no significant differences in BW among the females (P > 0.05). In Exp. 2, 180 pigs from Exp. 1 were transported to a segregated early weaning nursery facility where each sex was assigned to 10 pens per treatment (60 pens total). Pigs were fed fortified corn-soybean meal diets in a three-phase feeding program. At the end of Exp. 2 (49-d period), there was a treatment x sex interaction (P < 0.01) for BW with Dex1 and Dex24 barrows being on average 8% heavier than the Control barrows (30.1 and 29.8 vs. 27.7 kg, respectively), and no significant difference in BW (P > 0.10) among the gilts. No treatment differences in feed efficiency (gain:feed) were observed during the nursery period (P > 0.10). In Exp. 3, pigs from the nursery were moved to a finishing facility where each sex was assigned to 4 pens per treatment (24 pens total). All pigs were fed fortified corn-soybean meal diets in a four-phase feeding program with sexes fed separately. Real-time ultrasound was used to measure 10th rib backfat depth and longissimus muscle area. At the end of Exp. 3 (83-d period), there was a treatment x sex interaction (P < 0.05) for final BW with Dex1 and Dex24 barrows being on average 5.45 kg heavier than Control barrows (119.6 and 120.7 vs. 114.4 kg, respectively), and no difference (P > 0.05) in BW among the gilts. No treatment differences (P > 0.10) were observed for backfat depth, longissimus muscle area or gain:feed. These studies demonstrate that dexamethasone (2 mg/kg BW) given within 24 h of birth significantly improves both pre- and postweaning performance of barrows with no beneficial effects on gilts.