372 - Impact of Sow Transition Diet and Genetic Line on Sow Reproduction Under Heat Stress Conditions

The objective was to evaluate a sow transition diet and genetic line for farrowing duration and sow lactation characteristics. One batch of second parity sows (n = 78) were farrowed at the NCDA Tidewater Research Station in July. Sows consisted of two genetic lines, one selected since 2012 for young age at puberty and the other selected for old age at puberty. From day 109 of gestation until day 3 of lactation, sows were fed either 2.73 kg of a corn-soy lactation diet (3322 Kcal ME/kg, 0.99% SID lysine) once per day or 1.36 kg twice per day of a transition diet (3489 Kcal/kg, 0.71 SID lysine). The transition diet contained 45% wheat middlings, 8% added soybean oil, 3000 FTU/kg of phytase and 500 ppm zinc sulfate. Continuous traits and categorical traits were analyzed in SAS using linear models and chi-square tests, respectively. Results showed sows fed the transition diet farrowed numerically faster (P = 0.18) than those receiving the lactation diet (3:04 vs. 3:47). Transition diet fed sows tended (P = 0.10) to have a shorter wean-to-estrus interval than sows fed the lactation diet (5.27 vs. 5.69 days). Sows from the young puberty genetic line tended (P = 0.07) to have a greater average daily feed intake during lactation when compared to old puberty line females (4.92 vs. 4.71 kg). Young puberty sows also had a greater (P = 0.03) percentage of females exhibiting estrus by day 7 after weaning when compared to the old puberty genetic line (80 vs. 57%). No differences (P = 0.39 to 0.87) were detected between diets or genetic lines for stillborn piglet percentage, average piglet birth weight, average piglet weaning weight or litter size at weaning. Results suggest young puberty sows are more likely to return to estrus under the conditions of this study.