There was a time when genetic selection for feed efficiency and average daily gain was primarily focused on terminal sire lines. As profit margins tighten and farm overhead costs continue to increase the relentless search for additional genetic improvement in growth and feed efficiency has resulted in more selection within maternal lines for these traits. As the selection pressure for growth and feed efficiency increases within maternal lines it is important that reproductive efficiency does not suffer. Don’t throw the baby out with the bath water! Residual Feed Intake (RFI) is one of a number of methods of measuring feed efficiency. Residual feed intake is defined as the difference between a pigs observed and expected feed intake. Expected feed intake is determined for each pig, based on its growth rate and backfat thickness. Pigs that consume less feed than expected have a lower RFI, are more feed efficient, and they are therefore economically better for lean production compared to pigs with high RFI. US researchers wanted to evaluate the relationship between sow reproductive performance and lactation feed efficiency to selection for residual feed intake (RFI) during the grow/finish phase of production (RFI) in 2 selection lines of pigs developed at Iowa State University (Ames, IA) and to estimate heritabilities of these traits. One LRFI line was selected over 7 generations for decreased RFIG/F (low RFI [LRFI] line) and the other line was randomly selected for 5 generations and then selected for increased RFIG/F (high RFI [HRFI] line).
After 7 generations of selection, LRFI sows had 1.0 more piglets farrowed ( = 0.11) compared with HRFI sows, 1.3 more pigs born alive ( < 0.05), similar farrowing survival, 0.4 fewer mummies ( < 0.01), and more piglets weaned, both by litter (1.6 more; < 0.01) and by sow (1.1 more; < 0.01). Interestingly, the LRFI sows consumed 25 kg less feed and lost 9.8 kg more of Body Weight (BW), 7.0 kg more fat mass, and 3.1 mm more backfat than HRFI sows ( < 0.001) during lactation. Although LRFI sows had a greater negative energy balance (-19.8 vs. -8.0 MJ ME/d; < 0.001), they had better RFI during lactation (-28.6 vs. 8.2 kg; < 0.0001), and the trend was for LRFI sows to have better lactation efficiency (61.3 vs. 57.8%; = 0.47) than HRFI sows. This study demonstrates that selection for decreased RFI has favorably affected piglet performance and lactation efficiency but has unfavorably affected sow body condition loss and energy balance during lactation.
Ref: Young JM, Bergsma R, Knol EF, Patience JF, Dekkers JC. Effect of selection for residual feed intake during the grow/finish phase of production on sow reproductive performance and lactation efficiency J Anim Sci. 2016 Oct;94(10):4120-4132. doi: 10.2527/jas.2015-0130.
Take Home Message:
Selection for LRFI in maternal lines can result in pigs with increased efficiency during grow-finish as well as improved ability to direct body resources where they are needed during pregnancy and lactation.
We don’t have to throw the baby out with the bath water but we do need to be very focused on the challenge of minimizing weight loss during lactation
Submitted by Brent Jones, DVM