Maternal Lines Genetic Trends

Maternal Lines


A genetic audit of Hermitage’s maternal and terminal line populations is carried out by consultant geneticist Dr. John Mabry, Professor of Swine genetics at Iowa State University in the United States, each year.

This audit is carried out four times per year to evaluate the progress being made in Hermitage’s nucleus herds. The audit serves as an evaluation of Hermitage’s breeding programmes and to ensure that continued progress is being made in the traits of economic importance.

Hermitage estimates the genetic merit for both the reproductive traits and the growth traits using the BLUP process to get estimated Breeding Values for each trait. In determining the merit of each animal in the maternal lines (LR and LW) we must then consider the traits that influence the profitability of these maternal lines.  Each LR or LW female is expected to have a large litter of high birth weight pigs, provide the milk during lactation to wean a heavy litter.  Also, the maternal line sow provides ½ the genes that influence the growth, feed conversion and lean content of the slaughter pig.  So all these traits must be included in the MLI (Maternal Line Index). Therefore, the MLI is comprised of BV’s for all of the above traits.

However, not all pig producers want the exact same emphasis on each trait.  Some farms want to focus on improving litter size as a first priority, while other farms are more concerned with the weaning weight of the litter and already have a high litter size.

Because of these different needs by different pig farms, Hermitage offers the customer two different MLI’s that can be used in their genetic improvement program.

For those pig farms that still want the most emphasis on litter size, the use of MLI 1 is recommended.

MLI 1 – Born Alive MLI selection is focused on increasing numbers Born Alive above 1kg.

MLI1 Pie chart





For those pig farms that would prefer more emphasis on litter weaning weight, the use of MLI 2 is recommended.

MLI 2 – Weaning Weight MLI selection is focused on litter weight at weaning as a means of selecting for high milk yield (heritable trait) and subsequent improved growth rate.


MLI2 Pie Chart


(Targeting 100kg litter weight average at 25 day weaning) 


Litter Weight at Weaning

Litter weaning Weight is now a significant contributor to the Maternal Line Index 2 as it indirectly selects for milking ability in breeding animals resulting in heavier weaning weights and subsequent improved growth rates of progeny. Progeny with higher weaning weights reach slaughter quicker and consequently cost less to produce. The new Hermitage Maternal Line Indexes will assist customers by influencing and improving the traits of key financial importance in their herds in a fast and efficient way.

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