Flushing ewes: what it is, when to do it and how to apply the technique

As breeding season approaches, one of the simplest and best-known tools for increasing the number of lambs born is the flushing technique. It consists of improving the ewes’ nutrition for a short period before and during mating to stimulate a higher ovulation rate. Done well, it can mean more twins and a tighter lambing period; done badly, it is an expense that does not pay off.

In this article we explain what flushing ewes means, how it works, when it makes sense and which mistakes to avoid.

What is flushing in ewes?

Flushing is an increase in the nutritional plane, mainly energy, offered to ewes for a few weeks before the rams are introduced and during the first weeks of mating. The goal is for the ewes to be gaining weight and body condition at the time of ovulation.

This increase can be achieved by moving the flock to better-quality pasture (improved pastures, forage crops or a reserved paddock) or by supplementing with grain or another energy feed.

Why does it work?

The response to flushing is explained by the effect of nutrition on the reproductive system. When a ewe receives more energy, her levels of glucose, insulin and other metabolic hormones change, which favors follicle development in the ovary and increases the chance of two eggs being released instead of one. The expected result is a higher ovulation rate and therefore more multiple births.

Besides the “dynamic” effect (being on a rising plane of nutrition), there is also a “static” effect: ewes that arrive at mating in better weight and body condition tend to ovulate more than those that arrive thin.

When and for how long should you apply it?

Recommendations from extension services generally agree on these guidelines:

• Start about 2 to 4 weeks before the rams are introduced.
• Continue through the first weeks of mating (roughly one estrous cycle, about 17 days).
• Then return to a maintenance nutritional plane, avoiding abrupt changes at the start of pregnancy, since severe undernutrition in the first weeks can affect embryo implantation.

If you use grain supplementation, introduce it gradually, increasing the amount little by little over several days to avoid digestive problems such as acidosis or enterotoxemia. Ask your veterinarian or technical advisor for the right amount for the type of feed and the weight of your ewes.

Which ewes respond best?

Moderate or low body condition

Flushing has a greater effect on ewes with moderate or somewhat low body condition (on a 1 to 5 scale, roughly between 2 and 3). Ewes that are already in very good condition or fat usually respond little, because their ovulation rate is already close to its maximum. Very thin ewes, on the other hand, may not recover in just a few weeks: in that case the work has to start much earlier, from weaning.

Age and breed

Mature ewes usually respond better than ewe lambs. Breed also matters: more prolific breeds have a greater potential to turn the improvement into twins.

Time of year

The response is usually greater at the beginning and end of the breeding season than at its peak, when the natural ovulation rate is already higher.

How to implement it step by step

• Assess body condition of all ewes about 6 to 8 weeks before mating. Separate the thin ones, the ones in good condition and the fat ones.
• Plan your feed resource: reserve a good-quality paddock or decide on the supplement you will use.
• Check health: control of internal parasites (for example with the FAMACHA method and fecal egg counts), hoof condition and teeth. A parasitized ewe does not make use of the feed.
• Start flushing 2 to 4 weeks before the rams go in, with gradual changes.
• Prepare the rams too: clinical check, body condition, and the health of feet and testicles.
• Keep records of dates, groups and results (pregnancy by ultrasound, twins, lambs marked) to evaluate whether the technique paid off.

Common mistakes

• Flushing ewes that are already fat: the cost is not recovered.
• Starting too late or cutting the nutritional plane abruptly at the start of pregnancy.
• Introducing grain all at once, without adaptation.
• Forgetting that more twins mean more demand in late pregnancy and lactation: you need to plan pre-lambing feeding and shelter for lambing.

Does it make sense in your system?

The profitability of flushing depends on feed cost, lamb price, the condition of the flock and your ability to raise more twins with good survival. In extensive systems with lambing in harsh weather, more twins do not always mean more lambs weaned. That is why it is key to measure results year after year.

Measure the result of every mating season with OvinApp

To know whether flushing is working for you, you need data: body condition, mating dates, pregnancy, lambing and lambs per ewe. With OvinApp, the free app for managing sheep and goats, you can keep your flock’s reproductive records on your phone and compare groups and seasons to make better decisions.

Conclusion

Flushing is a simple technique that, applied to the right ewes at the right time, can improve the ovulation rate and the number of lambs born. The key is to assess body condition, plan the forage or supplement, make gradual changes and record the results. Before defining a supplementation plan, consult your veterinarian or technical advisor to adapt it to your system.

Sources

• INTA. Reproductive and nutritional management of the flock. Publications from the Bariloche and Chubut experiment stations. https://www.argentina.gob.ar/inta
• Secretariado Uruguayo de la Lana (SUL). Technical material on sheep reproductive management. https://www.sul.org.uy/
• Sheep 101 / University of Maryland Extension (S. Schoenian). Flushing. https://www.sheep101.info/
• FAO. Resources on small ruminant production and nutrition. https://www.fao.org/