Science page: Troubleshooting poor litter size using the National Swine Reproduction Guide

First, we would like wish you the happiest of holidays from all of us at the University of Minnesota, College of Veterinary Medicine.

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week we are sharing how to troubleshoot poor litter size within a production system using the National Swine Reproduction Guide, a report by Sarah Bloomer at North Carolina State University.

Key points:

  • The National Swine Reproduction Guide (NSRG; U.S. Pork Center of Excellence, Des Moines, IA) is a valuable tool to help producers utilize data analysis to troubleshoot reproductive problems in a herd or farm.
  • Analysis of farrow-to-wean farms within a North Carolina production system revealed extended wean-to-service interval of first-parity sows and poor performance of second-parity sows. NSRG recommendations include reviewing lactation diet composition and first-parity sow lactation feed intake.

Reproductive data from nine farms within one production system from 2011 to 2015 were obtained. Average Total Number Born (TNB) for the production system was 12.4 piglets born per litter, yet litter size was lowest in second-parity sows. Greater than 24% of second-parity sows failed to achieve the decision boundary criteria of 11.5 TNB. Within first-parity sows, 73% of the contemporary groups had greater than 10% of their sows failing to return to estrus within 10 days of weaning.

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The following recommendations to improve TNB and reduce Weaning-to-Service Interval  (WSI) were created following consultation of the NSRG:

  1. Limit cross-fostering onto first-parity sows
  2. Review lactation diet composition, particularly amino acid content;
  3. Identify methods to promote first-parity sow lactation feed intake. If economically
    feasible, farms may also consider breeding sows displaying estrus 7 and 8 days post-weaning on their next cycle.


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