Can we do a better job feeding reproductive sows?
It doesn’t have to be precision feeding
By Lee-Anne Huber
We are asking sows to develop more fetuses, give birth to more offspring and produce more milk. These increases in productivity should be supported by feeding programs that better match the nutritional needs of the sow. Can it be done with a single diet in gestation and a single diet in lactation? No.
Gestation feeding programsFetal growth and mammary development are the driving forces behind the nutrient requirements of sows beyond day 85 of gestation. Thus, nutrient requirements increase mainly in late gestation. Increasing standardized ileal digestible (SID) lysine (protein) supply by 40% (26 vs 19 g SID lysine per day) via the addition of soybean meal in late-gestating gilt diets, improved the amount of mammary development that occurred by the end of gestation1. The same improvement in mammary development was not observed for multiparous sows in response to soybean meal supplementation in late gestation2. Consequently, females that are developing mammary tissue for the first time seem to be particularly responsive to the late-gestating feeding program.
Developing more mammary tissue by the end of gestation is one thing – but does that mean these females will produce more milk in the ensuing lactation period? Yes.
Increasing SID lysine intake by 15-to-19% above the currently perceived requirements in late gestation (22 to 23 vs 19 g SID lysine per day) via the addition of soybean meal maximized piglet birth weight and milk production in the subsequent lactation period3. Thus, the feeding program employed in late gestation can have long-term consequences for the subsequent lactation period, but it is not necessary to increase SID lysine (protein) intake beyond 23 g/d.
Practically, in the absence of electronic sow feeders with feed blending capabilities and multiple feed lines in dry sow barns, altering the feeding program for late-gestating gilts could be daunting. However, feeding programs can be modified using simple and non-technical approaches.
A possible scenario is outlined in Figure 1. According to the NRC (2012) gestating sow model, the overall average SID lysine requirement is 12.6 g/d for gilts that were bred at 150 kg body weight and are gestating a litter of 17 piglets with an anticipated average birth weight of 1.3 kg. Using a standard, static feeding program (0.56% SID lysine) approximately 12.3 g of SID lysine will be provided per day. We do a great job of meeting the estimated average SID lysine requirement throughout gestation.
Since we formulate to the average SID lysine requirement, it means that we over-supply lysine in early gestation and under supply lysine in late gestation. Indeed, the estimated SID lysine requirement in late gestation (between days 90 and 114), when fetal growth and mammary development are occurring rapidly, is 6 g/d greater than what is provided by the standard, static feeding program (Figure 1). To achieve maximum subsequent milk production, we are undersupply SID lysine by up to 10.7 g/d.
Using a top-dress approach, simply providing 230 g per day (1.5 cups) of soybean meal per gilt in addition to the standard ration after gestation day 90 will better meet the estimated SID lysine requirements, without over-supplying energy and running the risk of over-conditioning the gilts prior to farrowing.
Providing an additional 400 g of soybean meal on-top of the standard ration would achieve sufficient SID lysine intake to maximize subsequent milk production, but at this level, energy supply may be too high, depending on the initial feeding program and body condition of the gilts. Such adaptations of the feeding program should be made under the supervision of a nutritionist and considering each individual farm system.
Lactating sow feeding programs Lactating sows are producing more milk than ever before. Average daily feed intake and body weight of sows throughout the lactation period are both dynamic, meaning that perhaps the feed composition should be dynamic as well. Through a series of experiments, it was shown that yes, the optimal SID lysine-to-net energy (NE) ratio changes in each week of lactation and is different for first- versus multiparous sows4,5.
Using the weekly optimal SID lysine-to-NE ratios for first- and multiparous sows, unique blends of ‘low’ and ‘high’ SID lysine-to-NE ratio diets can be created to better match sow needs as lactation progresses and feed intake increases. Dynamic SID lysine-to-NE feeding programs improved piglet average daily gain (256 vs 246 g) and body weight at weaning (6.4 vs 6.2 kg) for both first- and multiparous sows6.
In the absence of automated feed blending at each feeder in the farrowing room, a top-dressing approach could also be employed, again using soybean meal. In this case, a nutritionist should help to calculate the amount of daily soybean meal required, depending on the parity-specific feed (energy) intakes observed in individual herds.
Altering the supply of protein and energy in gestation and lactation doesn’t necessarily require advanced feeding technologies, but it certainly better supports sows in the endeavor of producing more piglets and more milk in each reproductive cycle. References1. Farmer, C., Palin, M.F., Hovey, R.C., Falt, T.D., Huber, L. 2022. Dietary supplementation with lysine (protein) stimulates mammary development in late pregnant gilts. J. Anim. Sci. 100: skac051. doi:10.1093/jas/skac051.
2. Farmer, C., Gillies, C., Johannsen, J.C., Hovey, R.C., Huber, L. 2023. Dietary supplementation with lysine (protein) in late pregnancy does not enhance mammary development in multiparous sows. J. Anim. Sci. 101: skad385. doi:10.1093/jas/skad385.
3. Kloostra, V., Farmer, C., Huber, L. 2025. Standardized ileal digestible lysine (protein) intake by primiparous sows should be increased in late gestation to maximize whole-body nitrogen retention, piglet birth weight, and subsequent milk yield. J. Anim. Sci. 103: skaf271. doi:10.1093/jas/skaf271.
4. Watzeck, M.C., Huber, L. 2024. The standardized ileal digestible lysine-to-net energy ratio in the diets of sows to optimize milk nitrogen retention is dynamic during lactation. J. Anim. Sci. 102: skae094. doi:10.1093/jas/skae094.
5. Gregory, N., Huber, L. 2025a. The standardized ileal digestible lysine-to-net energy ratio in the diets of lactating primiparous sows to optimize maternal nitrogen retention is dynamic but does not impact piglet performance. J. Anim. Sci. 103: skaf168. doi:10.1093/jas/skaf168.
6. Gregory, N., Huber, L. 2025b. Meeting the estimated daily optimal standardized ileal digestible lysine-to-net energy ratios for first and second parity lactating sows improved piglet growth rates. Transl. Anim. Sci. 9: txaf070. doi:10.1093/tas/txaf070.
Huber is an associate professor in the Department of Animal Biosciences at the University of Guelph.
