By Alexa Gormley, Ki Beom Jang, Yesid Garavito-Duarte, Zixiao Deng and Sung Woo Kim

The last several decades have brought immense changes to the productivity of modern sows due to improvements in genetics[1]. Among these improvements, litter size has increased at a rate of approximately 0.20 pigs per year over the last 20 years, which leads to an increased need for milk production in response. As such, there are concerns that the nutrient demands on the sow may be much greater than in the past, therefore, current feeding programs may be limiting in certain nutrients, specifically amino acids [2].

Considering that the most recent publication of the Nutrient Requirements of Swine (NRC) [3] was published in 2012, it can be assumed that those recommendations are below the actual requirements of modern sows. If highly prolific modern sows are not properly supported through the dietary composition, the sow will utilize her own maternal body stores to support the growth of her litter [4], which could cause negative physiological effects that can impact the health and growth of the litter [5], and limit future reproductive performance and longevity of the sow [6]. As such, the objective of this review was to investigate the amino acid requirements of the highly prolific modern sows and identify physiological challenges that could potentially be mitigated using select dietary interventions.

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As litter size and piglet birthweight increase, amino acid requirements during gestation will simultaneously increase. The amino acid needs of a sow during late gestation are primarily required for fetal growth, mammary tissue growth and colostrum production, with the rest going towards sow maintenance and uterine development [7]. Kim et al. [8] determined the deposition of amino acids in fetal and mammary tissue throughout different timepoints of gestation. To estimate the change in amino acids during gestation related to increased litter size and birthweight, data from this paper were used to estimate the change in amino acid requirements since publication of the most recent NRC [3]. In 2022, the Pig Improvement Company (PIC) reported that piglet birthweight on their elite farms had increased by approximately 0.22 kg per piglet from 2012 to 2022 [9]. This increase in birthweight combined with the previously discussed litter size data from PigCHAMP [10], was used to estimate the increase in amino acid requirements per day, in early and late gestation.

Two estimates were created (Figures 1 and 2), using the maintenance values for lysine provided by Kim et al. [8] for all estimates. Using data related to the average lysine gain per day per fetus [11], a ratio was generated to account for the increased litter size and individual piglet weight, by year. The Kim-based estimate utilized the analyzed values provided in the literature [8], whereas the NRC-based estimate utilized the recommendations generated based on the review of cited literature [3]. Two different estimates were created to account for the difference in the initial amino acid recommendations from both sources. The result reveals an estimated 31% (NRC-based estimates) and 26% (Kim-based estimates) increase in grams per day of lysine during early gestation (0 to 70 days gestation), and an estimated 33% (NRC-based estimates) and 29% (Kim-based estimates) increase in grams per day of lysine during late gestation (70 days gestation to farrowing), when compared with the current NRC feeding program, respectively.

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The physical challenges faced by modern sows due to their increased reproductive performance can cause adverse physiological effects like oxidative stress and general inflammation, increase incidence of prolapse and lameness, and decrease the quantity and/or quality of sow colostrum and milk [6]. To manage some of these physiological effects that may be unavoidable due to the burden of increased reproductive performance, the use of select dietary interventions have been investigated with success in improving sow and piglet outcomes. Some of the dietary interventions include but are not limited to, enzymes, organic minerals, single-cell organisms, and plant oils and extracts. A summary of the adverse physiological effects brought on by increased reproductive performance and the related research regarding opportunities for the use of select dietary interventions can be found in the full publication.

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The rapid genetic improvements to reproductive performance in modern sows have led to nutritional challenges. In particular, the increased nutrient requirements of modern sows may not be reflected in current feeding programs, indicating that sows may utilize their own body stores to support the growth of the litter and colostrum and milk production. Similarly, the use of select dietary interventions can possibly improve reproductive performance and enhance the growth and health of suckling piglets. The use of additional mineral supplementation, enzymes, algae and yeast-based derivatives, and fiber sources and probiotics all have the potential to reduce the impact of adverse physiological effects caused by increased reproductive performance. In conclusion, thoughtful nutritional management strategies are crucial to address these concerns and ensure the well-being and performance of both sows and piglets.

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