28 February 2025

Meeting the energy requirements of lactating sows in 2025

With litter sizes on Irish pig farms growing, Peadar Lawlor highlights the need for optimal sow nutrition during lactation. Balancing high feed intake and nutrient density is essential to rearing healthy litters while maintaining sow condition.

Born alive on Irish pig farms has increased by approximately 4 pigs/litter in the last 20 years and by 2.2 pigs/litter in the past 10 years, alone.  It’s not surprising then that optimising nutrition during lactation has become even more essential than ever.  The physical intake of our sows must be high and there is also a case for increasing the nutrient density in lactation diets to help rear these large litters to respectable weaning weights while at the same time avoiding excessive weight loss in sows during lactation with all its negative implications.

What are the energy requirements of a sow during lactation?

The energy and nutrient requirements of lactating sows are calculated from the body weight of the sow (Maintenance component), milk yield (Production), loss in body weight (mobilisation of body tissue) during lactation.

Maintenance

Maintenance requirement is quite modest. For a sow with an empty weight of 220kg this is 28.1 MJ DE per day.

Milk production

The big determinant of the energy and nutrient requirement of lactating sows is milk production. Milk production is estimated indirectly from the weight gain of the litter during lactation. This in turn is influenced by the number of pigs weaned by the sow and their average weaning weight. Lactation length will also influence the energy and nutrient requirement of a sow on a daily basis during lactation.

As a rule of thumb, every 0.5 kg change in the average pig weight at weaning increases the sow’s energy requirement for milk production by ~ 7 to 8 MJ DE/day (increases with higher litter size per sow).  Likewise, every extra pig weaned per litter increases the energy requirement for milk production by ~6 to 8 MJ DE/day (increases with higher average piglet weaning weight). 

Loss in body weight

Each 1 kg of body weight loss during lactation contributes 12.5 MJ DE to the energy requirements of the sow over an entire lactation. Therefore, for every 10 kg weight loss in a sow during lactation there is reduction in the sow feed energy requirement of ~4.5 MJ DE/day.  Although, an important source of energy for the sow during lactation, it is important that weight loss during lactation should not be greater than 5% (~10 kg) for first parity sows and 10% (~22 kg) for older parities if early returns to oestrus, high farrowing rate and a high subsequent litter size are to be achieved. 

Total lactation Energy Requirement = Maintenance + Milk production – Loss in body weight

Table 1 shows the total average daily energy requirement (MJ DE / day) of sows for a 28 day lactation and how it changes with increasing average piglet weaning weight and increasing number of pigs weaned per litter.

Table 1. Daily Energy Requirement (MJ DE / day) of sows during a 28 day Lactation depending on number of pigs weaned per sow and average piglet weaning weight

* Every 10 kg weight loss in a sow during lactation reduces the sow’s feed energy requirement of ~4.5 MJ DE/day.  But sow weight loss during lactation should not exceed 10% for sows and 5% for gilts.

By way of example using Table 1 above, a sow weaning 14 piglets at an average weight of 8.0kg has a  daily energy requirement during a 28 day Lactation of 128.4 MJ DE / day.  However, allowing this sow to lose 10% (22kg) from its empty weight during lactation will contribute 9.9 MJ DE / day to the sow’s energy demand.  Therefore, the average daily energy provided from feed must be 118.5 MJ DE/day (128.4 – 9.9).  If feeding a standard diet containing 14.2 MJ DE/kg then this sow would need to have an average daily feed intake of >8.3kg.  However, if feeding a higher energy diet of 15 MJ DE/kg then an average daily feed intake of 7.9kg will achieve the same energy intake from feed. Failure to achieve these feed intakes means that sows will lose excessive weight during lactation and/or milk yield will be depressed.  The follow-on from this is reduced reproductive performance in sows for the next parity and/or reduced piglet weaning weight.

In Moorepark we have been feeding a lactation diet containing ~15MJ DE/kg for the past ~8 years now. Our lactation feeding curve provides a potential average daily feed intake of 8.8kg (133 MJ DE) /day during a 28 day lactation. The average weaning weight of pigs on the unit is currently 8.6kg.  What’s more, our average piglet birth weight is >1.4kg which we believe is also be a result of the high energy intakes being achieved during lactation. Had we still been feeding a 14.2 MJ DE/kg lactation diet then an average daily lactation feed intake of 9.3kg would have been necessary, whereas because we feed a 15.0 MJ DE/kg lactation diet less physical intake (8.8kg/day) is necessary to achieve the same energy intake.  It is also important to note that weight loss in sows during lactation is minimal currently in Moorepark meaning that sows are weaned in exceptionally good condition.

Feeding a 15MJ DE/kg lactation diet means that you can achieve a target energy intake with ~ 0.5kg/day less physical intake of feed.  This certainly helps in achieving high target daily energy intakes during lactation, however, achieving high physical feed intakes of feed during lactation is always a must. In the next issue we will explore how we can promote high physical lactation feed intake in sows.