Getting your mare ready for the breeding season

Last Updated on March 15, 2022 by Allison Price

It is easier to think of warm tea and log fires in winter than it is about getting your horses ready for breeding season. Now is the right time!

We can start early to manage nutrition and identify reproductive problems before we begin breeding. Dr. Nerida Richards, Nutritionist, and Dr. Jen Clulow (Veterinary Reproduction Specialist) discuss how to maximize reproductive efficiency in your Mare or Stallion so that they can perform at their best when it comes time.

Dry mares need to be fed

We aim to have a dry, healthy mare that is not pregnant. We see an increase in:

  • Insulin resistance
  • Laminitis
  • An increase in bone and joint wear and tear
  • Inability to move;
  • Heat stress

These problems can all lead to poor reproductive performance. Low mobility can lead to poor uterine clearance mechanisms, and mares with equine metabolism syndrome may be more susceptible to uterine infections.

Forage is a good thing.

Your mare will get many calories from forage (hay, pasture, and chaff) in winter. Forage is also a great way to keep your horse warm during winter. The bacteria ferments the fibrous parts of the forage in horse’s stomach. The ‘by-product’ of fermentation is heat. This heat is what helps horses stay warm in winter.

To control horse weight, adjust your horse’s diet

Condition scoring your mare will help you determine if she is losing, maintaining or gaining weight. You will be able to determine what your mare needs and adjust her diet accordingly. You may have to increase the calories in your diet if your mare is losing weight you don’t want. This can be done by:

Breeding Season

1. You can feed your animals more hay, and lucerne hay if you don’t already.

2. You can add high-energy feeds such as sweetfeeds, pellets, oil, or high-energy fibres like copra meal, sugarbeet pulp, or copra meal to your horse’s diet. You should only use the highest quality feeds possible. If you are using sweetfeeds, make sure it contains extruded and micronized grains. These are easier to digest for horses.

Eat a balanced diet

Unbalanced diets won’t provide your mare with the energy, protein, vitamins, and minerals she needs. Your mare may experience a deficiency, which can lead to her not being as healthy as she should. A lack of nutrients can cause:

  • Weight loss
  • Delayed cyclicity
  • Immune system suppression
  • Muscle wastage
  • Increased susceptibility for diseases such as greasy heal and respiratory disease
  • Dry, dull skin and hair
  • Slow growing hooves that are brittle

Traditional methods of determining if your horse is getting the right food were difficult. However, the FeedXL Nutrition Calculator makes it easy to determine if your horse is getting the right feed.

and finally

All the rules for good horse husbandry are applicable in winter. It’s a good time to check her health, get a dental exam and spring faecal egg counts. Also, make sure she has all the necessary vaccinations.

Preparing the mare for breeding

After we have taken care of her nutritional needs, we can now focus on breeding. It is a good idea to breed early in the season, especially if there are any problems.

Light therapy

The mare is a long-day breeder. The mare will cycle when the daylength increases. By artificially increasing daylength, mares can be placed under lights to extend their breeding season. Your mare’s breeding season can be extended to increase the chances of having foals early. It also allows you more time for management if there are any issues. You can light-treat your mare by placing an Equilume(tm), or placing a Marescaping(tm) mask, on the 1st of July 2020. This will allow you to increase vernal transition and “spring heat” in the mare. Your mare should be able to cycle normally by September after this preparation.

Early breeding

The first season’s cycle is called vernal transition, or “spring heat”. Priming the cycle with oestrogen is necessary to make it work properly. The effects can be very unpredictable with mares who teasingly teasing the stallion may have follicles that grow and regress without ever ovulating. Many breeders choose to breed on the second cycle because it is more predictable. The mare’s oestrous period lasts 21 days. If your mare is teasing a gelding, or stallion, it’s likely that she is still in transition to a normal breeding cycle. We can now start breeding her, hopefully with her nutritional issues taken care of.

Pre breeding evaluation: Identifying and addressing problems

It is important to get the mare ready as soon as possible so that any problems can be addressed before she is bred. Ask yourself why the mare is so dry. Is it possible that she has just weaned a foal. If this is the case, and you have decided to not breed her last year, that’s great! Your veterinarian will be able to determine if she is cycling normal (not transitioning), and if there are any abnormalities. Some studs will require pre-breeding cultures of the uterus or the clitoris. These cultures should be taken while the mare is in oestrus and can help you identify any issues your mare may have before you bring her to the stallion.


It is possible to save money and time by identifying abnormalities early in the season. This pre breeding check is essential if your mare is not pregnant or is suffering from dryness. These problems can make the difference between a live foal or an empty mare.

Breeding options

Live Cover

Breeds like Thoroughbreds have a limited number of mares that can be used as live cover. Mares must be in standing oestrus and be open to receiving the stallion’s attention. This breeding strategy can injure both mare and stallion. It is important to ensure that everyone is safe.

Artificial Insemination: Cooled Sperm

All over Australia, you can find cooled semen. There are some disadvantages to cooled semen, such as unreliable courier services and intensively managed mare preparation. Not all stallions can be used for cooled-semen insemination. Cooled semen has the advantage of giving you a chance to have a cycle of pregnancy with a rate similar to live cover (60-70%), provided that your mare is properly managed. With adequate fertility, stallion spermatozoa may be cooled for as long as 48 hours. Ideal cooled sperm can be inseminated within 24 hour of collection. The mare will ovulate within 12 hours. This is a complex process that requires intensive management from your veterinarian. Sometimes, long-range forecasts are required to ensure the semen arrives at the insemination center at the correct time. Before using this method, it is important to know how cool semen is shipped across Australia and what the costs are. If your mare is suitable, frozen semen may be more reliable if you live in remote areas.

Artificial Insemination: Frozen Sperm

The use of frozen spermatozoa opens a number of genetic possibilities for breeders here in Australia.Spermatozoa can be sourced from local stallions with a busy competition career, deceased stallions and stallions living abroad.It is important to ensure that your mare is a suitable candidate for frozen breeding as results can be disappointing.Internationally, pregnancy rates with frozen spermatozoa range between 30-70% with an average of around 50% per cycle conception rates with good quality frozen spermatozoa.Unfortunately, there are no international standards for frozen spermatozoa so different numbers of spermatozoa and different numbers of straws make up a “dose” and post thaw motility rates can be highly variable.Frozen spermatozoa are also often sold as “doses” or “straws” rather than “pregnancies” so make sure you read your breeding contract carefully.Foal heat is usually avoided, and aged mares are often not suitable candidates for various reasons.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!