Data was collected on 1866 sows at a 3600 sow commercial farm in eastern North Carolina. Sows were randomly assigned to one of four treatments from day 108 of gestation until farrowing (Control, supplemented with .5 or 1 pounds soy oil daily, supplemented with .5 pounds coconut oil daily). Sows were randomly allocated to treatments based on parity and location within the farrowing room. Oil sources were top dressed daily with 4.5 pounds of lactation diet. After farrowing, sows had ad libitum access to the lactation diet. Sows supplemented with soy oil tended (P=.10) to have fewer stillborn piglets than sows not supplemented with soy oil. However, the difference was only 0.06 piglets. No differences (p>.05) were detected between dietary treatments for number of piglets weaned or piglet survival. Of the sows that conceived by day 7 after weaning, control sows tended (p=.06) to have a longer wean-to-conception interval than sows supplemented with 1 lb of soy oil prefarrow (4.5 vs. 4.4 days). While .1 of day is not of great economic importance itself, a lower wean-to-conception interval would tend to be associated with greater subsequent farrowing rate and litter size. Sows supplemented with oil prefarrow had larger (p<.05) subsequent total number born and tended (p=.07) to have greater subsequent number born alive than control sows. Accordingly, sows supplemented with soy oil tended (p=.08) to have more subsequent total number born and tended (p=.09) to have greater subsequent number born alive than control fed sows. The difference in subsequent number born alive between sows supplemented with soy oil and control fed sows was .35 piglets. No differences (p>.05) in lactation body condition loss between dietary treatments were observed. Given there were no differences in number weaned, litter weaning weight or body condition loss in lactation, perhaps this suggests that supplementing oil prefarrow had no impact on sow lactation feed intake.
The improvement in subsequent litter size from feeding oil prefarrow appears very real. As the industry starts to calculate an ROI on feeding a transition diet or prefarrow diet, feeding soybean oil prefarrow was found to have a very favorable ROI.