Setting gilts up for a long and productive life.

by Jennifer Patterson and Sergio Canavate

Sow retention is a complex trait that influences sow lifetime productivity -the quality pigs weaned per sow per year - and the efficiency and profitability of a swine operation.

It is also a long process.

A gilt becomes a potential replacement female at birth and should produce at least three litters before being removed from the herd (Stalder et al., 2003, Patterson and Foxcroft, 2019).

There are numerous factors that impact sow retention, including genetics, nutrition, management, housing and environment, health and stockmanship, and there are many time points in a gilts productive life where these factors can positively (or negatively) impact retention (see Figure 1).

Figure 1. Schematic diagram of key timepoints in a replacement gilts productive life from birth until farrowing at parity 3. Figure adapted from Canavate (2023).

Why is sow longevity and retention important?

As reported by Engblom et al. (2016), annual culling rates range between 40-50 percent and many sows are replaced prior to their third parity, of which 15 to 20 percent of culled sows produce only one litter of pigs.

The primary reasons for unplanned culling in early parity sows are for reproduction failure and locomotion problems (Sasaki and Koketsu, 2011) . The early culling of young females is a driver of low sow longevity, productivity and efficiency (Patterson and Foxcroft, 2019) .

In addition to profitability, improved retention results in a better parity structure that positively impacts health stability, better performance (most productive females), grow-finish performance and overall improvements in sustainability and sow welfare.

What does current industry data look like?

Data from nearly 1,100,000 gilts (PigCHAMP North America database) were used to determine retention rate trends across the industry. Gilts were grouped into cohorts by year of entry into the sow farm (2016 – 2020) and represented multiple genetic suppliers, farm sizes and types, management practices, etc.

Retention rate from first service was calculated as the number of females that successfully reached farrowing at the next parity divided by the number of gilts first-served (Tani et al. 2018) . A female was determined to be a sow in a breeding herd if she had at least one mating in her lifetime. Data was included if the sow had enough time to farrow the next parity or was removed from the herd (death or euthanized or culling) at any prior stage.

Reasons for culling were determined by the individual farms, retrospectively classified by removal type (death or euthanized or culling) and then broadly grouped by removal reason.

Retention rate until parity 6 over multiple entry years is shown in Figure 2.

Figure 2. Percent loss of females between parities classified by year of entry into the sow herd. *Data for gilts entered in 2020 were not included because they did not have enough time to reach later parities. Insert illustrates retention from gilt first-service (Srv) to farrowing at sixth parity (P1-P6).

Overall, ~30 percent of females first served remained in the herd after six parities. Approximately eight to 10 percent of these gilts did not farrow their parity 1. Loss between parity 1 and parity 2 ranged from 14.5-19.0 percent and loss in subsequent parities ranged from approximately 10-13 percent.

Figure 3. Breakdown of removal reason between parity 1 and parity 2.

This data illustrates the biggest loss is between parity 1 and parity 2 - so let’s take a closer look.

Overall, approximately 72 percent was due to culling, and 28 percent due to death and euthanasia, and the top three reasons were reproduction (39.1 percent), lameness (15.5 percent) and productivity (9.5 percent).

Although, mortality remains a challenge in our industry, culling for failure to farrow (did not conceive, returns, negative pregnancy checks, abortion and not in pig), no heat after weaning, lameness and productivity are the largest contributors to losses between parity 1 and parity 2

What are the biggest opportunities for improvement?

Gilt management practices from birth have the potential to influence the future reproductive performance of the sow herd. The loss of early parity sows is a driver of low retention.

The importance of the gilt for profitability of an operation means it should have its own focus - creating a Gilt Development Unit (GDU) helps establish its importance to ensure this happens in practice. This involves the development of a specialized labour force and ensuring they have tools to be successful.

Setting gilts up for success is key, there are four critical time points early in a gilt’s life that represent a foundational opportunity for improving sow longevity.

1. Pre-selection 1 - Early selection practices at birth and weaning will impact sow retention. A low birth weight and a low sow birth weight phenotype are a risk for increased pre-weaning mortality, poor growth from birth and lower retention until final selection. If selected and bred, a low birthweight limits sow lifetime productivity. Post-farrowing management (day one care), colostrum intake, cross-fostering and weaning age are critical to improving the retention and performance of replacement gilts (Faccin et al. 2022);
2. Pre-selection 2 - Increase selection intensity by assessing the quality and quantity of gilts prior to entering the final selection phase. Classify gilts as either:
   • Gilts to be culled: Gilts not achieving a growth rate

     of 0.6 kilograms/day (1.323 pounds/day) at ~140 days of age, or those with poor health, inadequate number of teats, any defects or are unthrifty, would not be permitted to enter the final selection or

   • “Pre-Select or Prime” gilts: Identify gilts based on their positive phenotypic traits such as structure, conformation and locomotion. Identifying the underlying genetic and phenotypic relationships between different traits represents an opportunity to improve sow retention and productivity. Plan ahead - understand the potential housing and environmental limitations and tailor the gilt flow to meet your needs;
3. Final selection - A purpose-designed GDU program facilitates both the stimulation and detection of early Puberty. An early pubertal response (a measure of sexual precocity) is linked to better sow lifetime productivity and controls weight of gilts bred with at least one heat-no-serve event (HNS). The high growth rate of contemporary gilts is a major risk for gilts being bred overweight with resulting problems for retention. Direct contact with boars is more efficient in triggering early puberty. A consistent supply of mature (older than 10 months), high libido (sexually motivated), size appropriate boars is an essential, and often under recognized, component of the GDU;
4. Gilt eligibility at mating - There are four general recommendations: 1) Early puberty: Start boar stimulation early enough (~170 days). Gilts should have a recorded heat by 195 days. 2) Breed gilts on at least 2nd detected estrus: Delay to 3rd estrus only to meet minimum weight targets. 3) Breed gilts between 140-160 kg (~308.7-352.7 lbs) body weight: Avoid going beyond that. 4) Breed gilts prior to 225 days of age: Older than that, they are likely overweight!

Photo Credit: Igor Sokolov - stock.adobe.com

Retaining young parity sows is vital to improved retention. Start with the end in mind: The goal is to set gilts up right. In addition to improved parity 1 farrowing rate and first litter size, gilts should perform well during their first lactation, wean a productive litter and be successfully rebred and farrow parity 2.

Given the challenges and opportunities described above, important questions come to mind.

Do we need to rethink what we view as gilt management? With changing modern genotypes, should gilt management be extended to include those that wean parity 1, or those that successfully farrow parity 2? Should we establish new key metrics to help improve retention? The data show that doing so will improve productivity, sustainability, profitability and sow welfare.

Additionally, farm records can provide powerful insights if they are useable and used, enabling data-driven decisions that positively affect overall herd performance. In the case of the replacement gilt, the necessary data are often not collected and/or analyzed - but this data is critical to track and monitor reproductive success.

It becomes essential to determine what your retention rate is and to identify sources of early parity loss.

The successful introduction and retention of gilts through their early parities drives lifetime performance of the breeding herd and represents an opportunity to improve and enhance overall sow longevity.

References

Canavate, S. (2023). Sow robustness: Key areas to maximize sow retention. American Association of Swine Veterinarians, Denver, Colorado, March 3-7th.

Engblom, L., Calderón Díaz, J.A., Nikkilä, M., Gray, K., Harms, P., Fix, J., Tsuruta, S., Mabry, J. and Stalder, K. (2016), Genetic analysis of sow longevity and sow lifetime reproductive traits using censored data. J. Anim. Breed. Genet., 133: 138-144. https://doi.org/10.1111/jbg.12177

Faccin, E., Tokach, M., Goodband, R., DeRouchey, J., Woodworth, J., and Gebhardt J. (2022). Gilt development to improve offspring performance and survivability, Journal of Animal Science, Volume 100, Issue 6, skac128, https://doi.org/10.1093/jas/skac128

Patterson, J., Foxcroft, G. (2019). Gilt Management for Fertility and Longevity. Animals, 9(7), 434. https://doi.org/10.3390/ani9070434

Sasaki, Y., Koketsu, Y. (2011). Reproductive profile and lifetime efficiency of female pigs by culling reason in high-performing commercial breeding herds. Journal of Swine Health and Production, 19, 284-291.

Stalder, K. J., Lacy, R. C., Cross, T. L., and Conatser, G.E., 2003. Financial impact of average parity of culled females in a breed-to wean swine operation using replacement gilt net present value analysis. Journal of Swine Health and Production, 11, 69–74

Tani, S., Piñeiro, C. Koketsu, Y. Culling in served females and farrowed sows at consecutive parities in Spanish pig herds. Porc Health Manag 4, 3 (2018). https://doi.org/10.1186/s40813-018-0080-y

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Jennifer Patterson

Jennifer Patterson obtained her MSc in Animal Science and focuses on gilt development working with many industry groups around the world to improve sow lifetime productivity. Jennifer is currently a research associate and the Swine Industry Liaison for Livestock Gentec at the University of Alberta. Gentec focuses on genetics and genomics in swine and beef cattle and provides industry with practical recommendations and tools to help put science into practice.

Sergio Canavate

Sergio Canavate obtained his Veterinarian degree in the University of Murcia and developed his career focused on supporting gilt development and sow herd performance working with many producers across the globe. Since 2010, Sergio has been a part of PIC Technical Service Team, and is currently leading the PIC Global Applied Female Reproduction Team.

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