How Litter Phenotype Can Improve Efficiency

Interactions between the genetic potential (G) of the terminal line sow and boar to produce a good litter, and the “sow environment” (E) in which the litter develops, produce different “birth-litter phenotypes” leading to increased variation in litter average birth weight as sows mature. Although some higher parity sows produce litters of 10 to 16 pigs over successive parities with acceptable (1.5 to 1.7 kg) to outstanding (more than 2.0 kg in some cases) birth weights, an equal number of litters will have a lower litter average birth weight (1.0 to 1.5 kg).

Selection for lifetime productivity of the commercial sow has included longevity, breeding success, and initially the total pigs born per litter, balanced against selection for the sow’s contribution to grow-finish performance of the progeny. Selection for the total born has generally been replaced by selection for pigs born live and for litter survival and quality, thus increasing indirect selection for more “optimal” uterine capacity. This might be defined as the birth of good numbers (more than 25 pigs weaned /sow/year) of high quality (minimum of 1.4 kg litter average birth weight) offspring.  However, for the present, we need to consider the implications of litter phenotype for production efficiency.

If a low birth weight phenotype in mature sows has an epigenetic component (the G x E interaction), this pre-programs these low birth weight litters to have relatively poor postnatal growth performance. This has implications for both sow and litter management. The key message is that managing differences between, rather than within, litters may offer the greatest potential for cost savings in the immediate future. There are real opportunities to first, target nutritional interventions at specific sub-populations of mature sows as a means of improving litter quality at birth and at weaning; second, to optimize the cost of nursery and grow-finish diets to reflect the growth potential and expected carcass value of different litter (sow) phenotypes. Ongoing collaborations involving the University of Alberta, PIC Technical Services and JBS-United are establishing the repeatability of epigenetic effects on litter phenotype. They are also exploring cost effective nutritional strategies that recognize these phenotypic differences in commercial sow populations.

Contact – george.foxcroft@ales.ualberta.ca