Submitted to: Midwestern Section of the American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: November 27, 2006
Publication Date: July 20, 2007
Citation: Vallet, J.L., Nienaber, J.A., Brown-Brandl, T.M., Miles, J.R. 2007. Seasonal, litter size, and birth order effects on farrowing intervals and stillbirth rate in swine [abstract]. Journal of Animal Science. 85 (Supplement 2):118. (Abstract #236) Technical Abstract: The number of piglets weaned is affected by the farrowing process through its impact primarily on stillbirth rate (SR). The effects of season and birth order on the farrowing process and SR are not well characterized. To examine these relationships, farrowing was recorded in first parity gilts of our USMARC BX population in May (68 gilts) and July (59 gilts), 2006, using video cameras. The time of birth of each piglet and whether the piglet was born alive, stillborn, or a mummy was assessed. For each piglet, the time interval from the birth of the previous piglet was calculated. Assisted births and mummies were excluded. There was no significant effect of birth order in the litter on farrowing interval (FI). However, when birth order was converted to a proportion of the litter farrowed, FI and SR were significantly greater (P < 0.01) for the last tenth of the litter. Finally, FI and SR for the last, next-to-last and second-to-last piglets in each litter were examined. The last piglet in the litter had a significantly greater (P < 0.01) FI and SR (52 ± 4 min and 15 ± 4%, respectively) than the next-to-last (21 ± 4 min and 2 ± 1%) and second-to-last (19 ± 5 min and 6 ± 2%) piglet. Seasonal and(or) litter size effects on FI and SR were analyzed by heterogeneity of regression analysis on within gilt averages. No seasonal or litter size effects on average SR were detected. The relationship between litter size and average FI was third order, and differed (P < 0.05) between May and July. The prediction equations for each season indicated that average FI were greater in July for litter sizes less than 5. These results indicate that FI and SR are greatest for the last piglet born in the litter compared to piglets born earlier in the order and suggest that season affects the farrowing process, especially for small litter sizes. Taken together, results suggest that conceptuses remaining in the uterus affect farrowing intervals.