Genetics of swine functional teats

The number of functional teats can be estimated prior to farrowing or quantified at farrowing.

By Audrey Earnhardt and Mark Knauer, North Carolina State University
Piglet survival is of great importance for swine producers throughout the world due to its relationship with animal well-being and farm profitability. Recent data in the United States indicate piglet survival has perhaps decreased as litter size has increased (Figure 1). Yet production systems and geneticists alike are working fervently to reduce this trend.

North Carolina State UniversityFigure 1: U.S. trends for total number born, number weaned and piglet survival.

Figure 1: U.S. trends for total number born, number weaned and piglet survival.

 

Availability and accessibility of functional teats on a sow is essential for enhancing piglet livability. Yet this has been known for some time. In 1961, Enfield and Rempel reported an increase in one functional teat improved number weaned by 0.27 piglets per litter and litter weaning weight by 11.7 pounds per litter.

Building upon these results, North Carolina State University partnered with Smithfield Premium Genetics to evaluate the genetics and importance of functional teats in a modern genetic line. Teats from over 3,000 sows were classified as functional or non-functional. Total teats, functional teats and non-functional teats at farrowing for the population were 14.93, 13.90 and 1.03, respectively. Similar to Enfield and Rempel (1961), our results showed each additional functional teat at farrowing increased number weaned by 0.27 piglets per litter.

Heritability estimates the proportion of a trait that is explained by genetics. For example, if the heritability of a trait is 0.25 then genetics are thought to explain 25% of the variation in that trait with the remaining 75% being explained by environmental factors. Generally, heritability estimates for litter size in swine are low (~0.10), growth rate is moderate (~0.20) and age at puberty high (~0.30). The greater the heritability, the faster genetic progress can be obtained.

In our current study, estimates of heritability for total teats, functional teats and non-functional teats at farrowing were 0.26, 0.22 and 0.12, respectively. Hence functional teat number was moderately heritable.

Summary

  • Results suggest
    • It is possible to increase the number of functional teats on a sow at farrowing.
    • Increasing the number of functional teats at farrowing will enhance piglet survival.
  • We recommend cross-fostering based on the number of functional teats a sow has. The number of functional teats can be estimated prior to farrowing or quantified at farrowing and written on the sow to aid workers when cross-fostering.

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