Heritability can be defined as the proportion of variation within a trait that can be attributed to inherited genetic factors (Falconer and Mackay, 1996). A heritability estimate ranges between 0 and 1 where an estimate of < 0.10 may be considered low and a heritability of > 0.30 might be considered high. Genetic correlations range from -1 to 1 with zero indicating no genetic association between two traits and a genetic correlation close to -1 or 1 meaning two traits are very similar.

Survival

Compared to piglet survival, industry wean-to-finish survival is relatively higher averaging 92 to 93% (Knauer and Hostetler, 2013). Yet on an individual pig level, a mortality in late finishing is substantially more costly than a piglet mortality in lactation or in the nursery period. As pigs grow, they acquire feed cost, housing costs and labor costs. Hence maximizing wean-to-finish survival is essential towards proper animal well-being and farmer profit.

Survival during the wean-to-finish period, or segments of the wean-to-finish period, are reported to be heritable. Gorssen et al. (2021) and Putz et al. (2019) both reported a heritability estimate of 0.13 for finishing survival and wean-to-finish survival, respectively. Yet neither study included a common litter effect in their model.

Leite et al. (2021) found heritability estimates for nursery survival, finishing survival, and wean-to-finishing survival of 0.08, 0.04, and 0.06, respectively. Similarly, Su et al. (2022) reported the heritability estimate for survival from 5 days of age until harvest was 0.02. Harper et al. (2019) showed heritability estimates for survival from weaning to 70 days of age of 0.02 to 0.03.

By comparison, Leite et al. (2021) and Su et al. (2022) reported common litter effects for post-weaning survival traits were 0.09 to 0.16 and 0.05 to 0.07, respectively. In other words, the litter a pig was reared in had a relatively greater influence on its post-weaning survival than an individual pig’s genetics. While genetic selection for wean-to-finish survival appears feasible, albeit slow, a better understanding of litter characteristics that influence post-weaning survival are warranted. 

Full-value

Full-value pigs are those sold at an appropriate weight to a farmer’s primary market (Fix et al., 2010). Hence pigs that die or light weight pigs sold to a secondary market would not be considered full-value. 

Lenoir et al. (2022) reported heritability estimates for full-value at 150 days of age of 0.03 to 0.06. Genetic correlations between full-value with growth rate, feed:gain ratio, backfat and muscling ranged from 0.22 to 0.31, 0.21 to 0.21, 0.21 to 0.35, and 0.14 to 0.42, respectively. In other words, full-value pigs had genetically favorable associations with growth rate and muscling and unfavorable associations with feed conversion and backfat.

Dufrasne et al. (2014) found heritability estimates for discounted pigs at the end of the nursery period and the end of the finishing period of 0.14 and 0.10, respectively. Similar to Lenoir et al. (2022), Dufrasne et al. (2014) reported a decrease in discounted pigs at finishing was genetically associated with greater carcass weight (r_g = -0.34). Collectively, these results suggest selection for increased growth rate would enhance the percentage of full-value pigs marketed.

References

Dufrasne, M., I. Misztal, S. Tsuruta, N. Gengler, and K. A. Gray. 2014. Genetic analysis of pig survival up to commercial weight in a crossbred population. Livest. Sci. 167:19-24.

Falconer, D. S., and T. F. C. Mackay. 1996. Introduction to Quantitative Genetics, Ed 4. Longmans Green, Harlow, Essex, UK.

Fix, J. S., J. P. Cassady, J. W. Holl, W. O. Herring, M. S. Culbertson, and M. T. See. 2010. Effect of piglet birth weight on survival and quality of commercial market swine. Livest. Sci. 132:98-106.

Gorssen, W., D. Maes, R. Meyermans, J. Depuydt, S. Janssens, and N. Buys. 2021. High heritabilities for antibiotic usage show potential to breed for disease resistance in finishing pigs. Antibiot. 10:829.

Harper, J., K. L. Bunter, and S. Hermesch. 2019. Genetic parameter estimates for pre-and post-weaning piglet mortality. Proc. 23rd Assoc. Advmt. Anim. Breed. Genet. Armidale, NSW. 23:159-162.

Knauer, M. T., and C. E. Hostetler. 2013. US swine industry productivity analysis, 2005 to 2010. J. Swine Health Prod. 21:248–252.

Leite, N. G., E. F. Knol, A. L. S. Garcia, M. S. Lopes, L. Zak, S. Tsuruta, F. F. Silva., and D. Lourenco. 2021. Investigating pig survival in different production phases using genomic models. J. Anim. Sci. 99(8), skab217.

Lenoir, G., L. Flatres-Grall, N. C. Friggens, and I. David. 2022. Robustness scores in fattening pigs based on routinely collected phenotypes: determination and genetic parameters. J. Anim. Sci. 100(5), skac157.

Putz, A. M., J. C. Harding, M. K. Dyck, F. Fortin, G. S. Plastow, J. C. M. Dekkers, and PigGen Canada. 2019. Novel resilience phenotypes using feed intake data from a natural disease challenge model in wean-to-finish pigs. Front. Genet. 9:660.

Su, G., T. Liu, O. F. Christensen, M. S. Lund, and B. Nielsen. 2022. Feasibility of reducing mortality of pigs from birth to slaughter by genetic selection. Proc. 12th WCGALP, pp. 3204-3207. Wageningen Academic Publishers.