Producing and raising a litter is an energetically demanding process for sows, involving significant physiological changes during gestation and lactation. The energy demands during this period are influenced by factors such as litter size, body condition and environmental conditions. Accurate understanding of these energy requirements is essential for optimizing sow health, reproductive efficiency and piglet growth.

Energy requirements during gestation

The energy requirements for gestation include maintenance energy for the sow’s basic metabolic functions and additional energy for fetal growth, uterine and placental development, and maternal weight gain. Metabolizable energy for maintenance (ME_m) could be calculated according to Samuel et al. (2024) using the metabolic body weight formula:

Similarly, net energy for maintenance (NE_m) could be calculated according to Li et al. (2024):

For a 205 kg sow, maintenance energy is approximately 6550 kcal ME/day or 5309 kcal NE/day. As gestation progresses, energy requirements increase due to fetal growth, with an additional 120–190 kcal/day per fetus (Quiniou et al., 2001). For a sow carrying a litter of 13.5 piglets, this amounts to an additional 1620–2565 kcal/day during late gestation. Consequently, total energy requirements during late gestation range from 8170–9115 kcal/day. For comparison, NRC (2012) suggests 6450 kcal/day effective ME intake up to day 90 of gestation and 7650 kcal/day effective ME intake from day 90 onwards for a parity 4+ sow expected to deliver 13.5 piglets after gaining 40 kg over gestation. Therefore, over the 115-day gestation period, the cumulative energy requirement is estimated at 795–820 Mcal.

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Energy requirements during lactation

Lactation imposes the highest energy demands on the sow due to milk production, which is critical for piglet growth and survival. Milk yield typically ranges from 8–12 kg/day, with an energy cost of production of 8–10 MJ/kg (Noblet & Etienne, 1989). For a sow producing 12 kg of milk per day:

In addition to milk production, maintenance energy for the sow remains at approximately 6550 kcal/day. Thus, total energy requirements during lactation can reach 29.5 Mcal/day for high-yielding sows. Over a typical 21-day lactation period, the total energy requirement is approximately 620 Mcal.

Total energy investment for a litter

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Combining the energy needs for gestation and lactation, the total energy investment for producing and nursing a litter is approximately the sum of gestation (795–820 Mcal) and lactation (620 Mcal). The total energy required is therefore 1415–1440 kcal, depending on factors such as litter size, milk yield, and maternal weight.

Assuming typical feed intake of a parity 3 sow in gestation [4 lbs feed/day * 1500 kcal/lb = 6000 kcal/day] and lactation [18 lbs feed/day * 1500 kcal/lb = 27 Mcal/day] would suggest that at current common industry feeding practices, sows are not receiving the necessary energy to fully support the investment for a litter.

Implications for feeding strategies

Meeting these energy demands is critical for maintaining sow health and optimizing reproductive performance. Underfeeding during gestation can lead to low birth weight piglets and poor sow body condition, while insufficient energy intake during lactation can result in excessive weight loss, reduced milk production and delayed return to estrus (Dourmad et al., 1998). Feeding programs must account for:

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Precision feeding strategies that adjust energy intake based on the sow’s stage of production and individual needs are essential for optimizing outcomes.

Producing a litter represents a substantial energy investment for sows, with the majority of energy consumed during lactation due to milk production. Accurate estimation of energy requirements (including for maintenance) is essential for developing effective feeding strategies that support sow health, litter growth and overall productivity. Advances in nutrition and management practices, such as precision feeding, can help producers meet these demands efficiently while ensuring animal welfare.

References

Dourmad, J. Y., Noblet, J., & Etienne, M. 1998. Effect of energy and protein intake of sows on their reproductive performance. Livestock Production Science, 56, 105-113.

Li, Z., Gao, W., Shi, H., Xu, S., Zeng, Z., Wang, F., Lai, C., & Zhang, S. 2024. Evaluating the Net Energy Requirements for Maintenance Based on Indirect Calorimetry and Heart Rate Monitoring in Gestating Sows. Animals, 14(19), 2907.

National Research Council (NRC). 2012. Nutrient Requirements of Swine (11th Revised Edition). National Academies Press.

Noblet, J., & Etienne, M. 1989. Estimation of sow milk nutrient output. Journal of Animal Science, 67(12), 3352-3359.

Samuel, R.S., Moehn, S. and Ball, R.O. 2024. Energy expenditure and maintenance requirements in non-pregnant first-parity sows. Animals, 14, 3276.

Quiniou, N., Dourmad, J. Y., & Noblet, J. 2001. Effect of energy intake on the performance of different types of sows during lactation. Animal Science, 73, 261-270.