Getting strong and viable piglets at weaning starts with looking back to where they came from: the sow. Throughout the last few decades, the swine industry has done an outstanding job in terms of management of sows and optimizing numbers of farrowing units. As Lavery et al. (2019) highlights, we currently have hyper-prolific sows that can wean up to 31.3 piglets per year. Although pigs weaned per sow per year has been one of the primary metrics used to evaluate sow farm performance, there are other indicators that are valuable for swine producers, such as sow parity, litter size and the number of pigs successfully marketed per sow (per year). With that in mind, this article discusses the importance of assessing sow productivity on a lifetime basis and how it’s related to progeny performance.

Due to the importance of sow longevity in the swine industry, many studies have been conducted over the last few decades to determine the relationship between sow parity and litter performance. For example, it’s well documented that progeny from gilts (Parity 1) have lower piglet birth weight and weaning weight. On the other hand, as Bergstrom et al. (2011) suggests, sows that are parity 2 through 5 show greater litter size and birth weight when compared to parity 1 and to parity 6 through 9 sows. An analysis conducted by Lavery et al. (2019) - which examined the results of 1058 sows and 13,827 piglets from two farms between 2005 and 2015 - showed that second and third parity sows weaned more piglets than gilts and older sows. However, sows with a parity of 3 and 4 had an increased amount of total born alive and heavier piglet birth weight. In contrast, parity 5 sows presented higher pre-weaning mortality.

Sow longevity also affects the health status and immune system development of their litters. Parity 1 progeny are more susceptible to disease, which can lead to higher mortality rates, greater variation in pig weights, and fewer pigs reaching market age. Miller (2008) also suggests that those piglets are more likely to facilitate the proliferation of farm-endemic pathogens in the herd. Moreover, Carney-Hinkle et al. (2014) demonstrated that serum IgG concentrations were higher and colostral IgA concentrations tended to increase in older parity sows when compared to first parity sows.

Litter size is another critical variable to consider when managing sows. With increased sow reproductive performance during the last two decades, the swine industry has gone from an average litter size of 10 to 13 (born alive). Similar to parity, the number of piglets born also affects progeny performance. Many studies support that an increase in litter size (number of live piglets born) can be associated with more piglets having poor growth and viability (Galiot et al., 2018). This is because litter size is negatively correlated with birth weight and weaning weight (Putz et al., 2015). With an increase in litter size, the mean birth weight decreases and the percentage of animals with a birth weight <1kg increases. Moreover, pre-weaning mortality is positively correlated with litter size, with larger litters frequently having higher mortality rates.

Even though birth weight decreases with larger litter sizes, Bergstrom et al. (2011) indicated that an optimal parity structure in a herd can alleviate some of the negative effects of increased litter size on pig growth, thus improving the number of pigs with potential to successfully be marketed. Considering the average herd parity as an indicator in their system, swine producers can manage their parity structures by creating a good balance between young gilts with improved genetics and sows with a parity of 3 through 5 that are providing high-quality litters, while culling older sows based on their reproductive performance. Following PIC recommendations, working with an average herd parity of 3.5 is critical for achieving higher farm productivity and, consequently, higher profitability.

Bergstrom, J. R., Potter, M. L., Nelssen, J. L., Tokach, M. D., Henry, S. C., Dritz, S. S., ... & DeRouchey, J. M (2011). The association of sow and litter characteristics with piglet birth weight; and the implications for growth, survival, and carcass characteristics of pigs on a commercial farm. Kansas State University.

Carney-Hinkle, E. E., Tran, H., Bundy, J. W., Moreno, R., Miller, P. S., & Burkey, T. E. (2013). Effect of dam parity on litter performance, transfer of passive immunity, and progeny microbial ecology. Journal of Animal Science, 91(6), 2885-2893. doi: https://doi.org/10.2527/jas.2011-4874

Galiot, L., Lachance, I., Laforest, J. P., & Guay, F. (2018). Modelling piglet growth and mortality on commercial hog farms using variables describing individual animals, litters, sows and management factors. Animal reproduction science, 188, 57-65. Doi: https://doi.org/10.1016/j.anireprosci.2017.11.009

Lavery, A., Lawlor, P. G., Magowan, E., Miller, H. M., O’driscoll, K., & Berry, D. P. (2019). An association analysis of sow parity, live-weight and back-fat depth as indicators of sow productivity. animal, 13(3), 622-630. Doi: https://doi.org/10.1017/S1751731118001799

Miller, Y. J., Collins, A. M., Smits, R. J., Emery, D., Begg, D., & Holyoake, P. K. (2008). Improving the performance of the progeny of gilts. Final report. 2D–1010506. The Pork Cooperative Research Centre.

Milligan, B. N., Fraser, D., & Kramer, D. L. (2002). Within-litter birth weight variation in the domestic pig and its relation to pre-weaning survival, weight gain, and variation in weaning weights. Livestock Production Science, 76(1), 181-191. Doi: https://doi.org/10.1016/S0301-6226(02)00012-X

Putz, A. M., Tiezzi, F., Maltecca, C., Gray, K. A., & Knauer, M. T. (2015). Variance component estimates for alternative litter size traits in swine. Journal of Animal Science, 93(11), 5153-5163. Doi: https://doi.org/10.2527/jas.2015-9416