Sow longevity begins during gilt rearing
Sow mortality has increased worldwide, highlighting the need to optimise management and nutrition strategies from the early rearing stages in order to improve reproductive longevity. Over the past decade, there have been relevant improvements in sow reproductive performance, which has created the need for more precise nutrition that adequately meets maintenance, growth, gestation and mammary development requirements. At the same time, genetic progress in maternal lines has led to higher body weights (BW) at the same breeding age. Considering a fixed age of 210 days at first insemination, estimated BW was 144 kg in 2014, whereas in 2025 the estimated average BW reaches 159 kg. Consequently, the proportion of sows inseminated above the recommended threshold of 160 kg has increased from 10.5% to more than 50% (Figure 1).
Body weight at first breeding and culling risk
Various studies have identified BW during rearing as a determining factor in reproductive longevity. Patterson et al. (2020) indicated that young sows weighing more than 160 kg at first insemination show a higher replacement rate, and a recent SEGES study showed that a weight above 164 kg increases the risk of culling or mortality by 1.39 times compared with lighter sows. Lameness is one of the main causes of culling in these cases, which supports the recommendation to avoid BW above 160 kg at first breeding. In addition, sows inseminated at a heavier weight tend to remain heavier in later parities, increasing their maintenance energy requirements and, therefore, feed intake. Although individual weighing may be impractical under commercial conditions, it is essential to monitor average batch weight at first insemination, for which predictive models based on flank-to-flank measurements may be used. Knowing BW and age at first breeding, lifetime average daily gain (ADG, g/day) during gilt rearing can be estimated, and this should be between 600 and 800 g/day. If weight at insemination is high but ADG is appropriate, reducing age at first breeding could be considered as an adjustment to the growth program.
Nutritional strategies to regulate growth
Two recent studies evaluated growth control during gilt rearing through diet manipulation and its impact on longevity after following sows through to farrowing 4 (Tsai et al., 2023; Leiva et al., 2025). In both studies, sows fed diets with lower nutritional density (lower energy, higher NDF, lower amino acid levels and lower Trp:Lys ratio) showed lower ADG and poorer feed conversion during the first rearing phase, up to the point of selection. However, these sows tended to show compensatory growth when given a common diet until first breeding, reaching similar BW without achieving effective control of final weight at first insemination or differences in later reproductive performance. However, sows fed lower nutritional density diets during the first stage of rearing increased their retention through to farrowing 4 by 8%, which could represent an interesting strategy to maximise herd longevity (Leiva et al., 2025).
Feed intake control as a management tool
Another line of research is the control of feed intake during rearing in order to modulate growth. In a trial with Duroc line boars, one group was fed ad libitum and another received restricted intake to achieve an ADG of 500 g/day between 20 and 28 weeks of age. Boars with controlled growth showed a lower incidence of lameness and greater retention in insemination centres, without affecting semen quality (Lu et al., 2022), which may indicate that modulating growth through intake control could be a strategy of interest to improve longevity and reproductive performance in sows.
Skeletal development and physical feed characteristics
In this context, another key nutritional consideration is to ensure adequate skeletal development during rearing. In this regard, it may be advisable to increase phosphorus levels in young sow diets by approximately 8% above those used in grow-finish feeds, with the aim of maximising bone mineralisation. Optimising structural integrity at this stage is essential to reduce the risk of lameness and improve longevity throughout productive life. Likewise, the physical characteristics of the feed should also be considered. In this regard, a particle size between 750 and 900 µm is associated with a lower incidence of gastric ulcers, which helps improve digestive health and long-term productivity.
The role of management and environment in future productivity
However, nutrition alone is not enough, and management and environmental conditions play a fundamental role. Birth weight, colostrum intake and pre-weaning growth are positively associated with reproductive performance in adulthood and with sow longevity (Flower et al., 2025). During rearing, it is essential to ensure appropriate stocking density, a floor type that minimises injuries, adequate feeder space and number of drinkers, correct group management and continuous health control in order to support the development and reproductive maturity of the future breeding female. In addition, recording oestrous cycles and delaying breeding until the second heat (or the third if target weight has not been reached) are associated with greater reproductive longevity (Patterson et al., 2020; 2025). (Table 1)
Gilt development: a critical phase for long-term success
In general, inadequate conditions during the rearing stage can compromise future productivity relatively easily. These sows are not finishing animals, but breeding females of high genetic and economic value, so management errors at this stage have long-term production consequences.
Conclusion
In conclusion, a holistic approach integrating nutritional strategies, skeletal development, reproductive management and optimised environmental conditions during rearing through to first breeding is essential to improve sow reproductive longevity and productive efficiency in modern production systems.