Flush feeding gilts

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Flush feeding is a nutritional strategy to improve the rate and quality of ovulation of sows & gilts. It is achieved by increasing the amount or source of energy to stimulate reproductive hormones and ovary activity.

Flush feeding was first studied and recommended around 30 years ago but there has been very little research since. However, there have been two recent studies in Brazil (Mallmann et al., 2020) and one from SEGES in Denmark (Bruun et al., 2021).

The Mallmann study looked at 102 gilts that included PIC terminal lines and PIC Camborough. They were fed ad lib (average 3.5 kg/d) in the rearing phase and then 2.1 kg/d for 10 days before first heat stimulation. After first heat, the animals received altronegest (e.g. Regumate) for 14 days – first cycle. The second cycle was between 2nd to 3rd heat. Gilts were fed a 2x2 combination of 2.1 or 3.6 kg/d in cycle 1 & 2. The ration was a 0.54 % SID-Lysine ration, similar to a gilt or late gestation ration.

Feeding 3.6 kg/d of the gilt gestation in cycle 1 (1st to 2nd heat) gave a higher ovulation rate (82.2 vs 73.9, P = 0.343). There were also more follicles with less variation in follicle size (P = 0.074 & 0.062). Feeding 3.6 kg/d in cycle 2 (2nd to 3rd heat) did, however, increase early-stage embryo mortality. Gilts fed 3.6 kg/d in cycle 1 met their breeding weight targets (143 kg) at 2nd heat whilst animals fed 3.6 kg/d in cycle 2 added 1.7 mm of P2 and 19.5 kg of BW.

The SEGES study (Bruun et al., 2021) used DanBred gilts fed ad lib during the gilt rearing period and then high, 3.3 kg/d, or low, 2.33 kg/d, feeding level in a 2 x 2 combination whilst on altrenogest (d 0 – 18) and the second period (d 18 – 25). The ration was 0.61 % SID-Lysine and 9.0 MJ/kg NE, and so similar to a low energy gilt rearing ration for animals 90 – 100 kg and over. Faccin et al. (2022) reviewd the Bruun paper and summarised:

  • They observed that the weight of gilts influenced total litter size. Gilts with low back fat tended to respond more positively to a longer flushing period than heavier gilts with more back fat. Flush feeding during the follicular phase (7 d) provided the greatest benefit in total born without increasing back fat.

Flush feeding gilts with higher levels (3.3 – 3.5 vs 2.1 – 2.3 kg/d) of gilt gestation or gilt rearer was shown to improve ovulation rate, follicle size, follicle variation and total born. The response in one study was, however, linked to gilt condition as low back fat animals responded more positively. Gilts in the other study and on high-level feeding added an extra 10 kg and 1 mm P2 between 1st & 2nd heat. 

Feeding higher levels of gilt ration pre-service has performance benefits, but producers should avoid over-feeding and excessive weight and back fat gain which will reduce gilt and sow lifetime productivity – it's not easy! 


Bruun, T., Bache, J., Amdi, C., 2021, The effects of long- or short-term increased feed allowance prior to first service on litter size in gilts. Translational Animal Science, 5:1-12. https://doi.org/10.1093/tas/txab005 

Faccin, J., Tokach, M., Goodband, R., DeRouchey, J., Woodworth, J., Gebhardt, J., 2022, Gilt development to improve offspring performance and survivability. Journal of Animal Science, 100, 1-10

Mallmann A., Arend, L., Oliveira, G., Mellagi A., Ulguim, R., Bernardi, M., Bortolozzo, F., Knox, R., 2020, Effects of flush feeding strategy before breeding on reproductive performance of modern replacement gilts: impacts on ovulation rare and litter traits. Journal of Animal Science, 98, 6, 1-10, https://doi.org/10.1093/jas/skaa186