During the off season and leading into the breeding season the focus is usually on wet mares however management of dry mares is also important to ensure they start the season in optimum condition, ready to cycle and get in foal early.
The New Zealand Thoroughbred breeding industry is unique in comparison to most other major breeding countries in that horses are maintained outside all-year-round on a predominantly pasture-only diet with minimal supplements fed.
In New Zealand we have a comparatively short breeding season (around 105 days) which means there is added pressure to get mares cycling early.
Factors that most influenced reproductive performance in a New Zealand study looking at reproductive performance of mares in the Waikato included: The stud farm, mare age, mare reproductive status (dry vs wet) and stallion effects.
Dry mares performed better reproductively than wet mares. This is most likely due to the fact that most of the “dry” mares were either maidens or as a result of voluntary “rest” rather than poor fertility. With our low-cost pasture-based system, short breeding season and industry push for well grown early foals, we are more willing to carry mares over rather than breed late in the season. That being said mares are not selected for reproductive performance like other livestock industries, resulting in high value mares with fertility challenges being kept in the broodmare band. It is important to get these mares cycling early so they have as many opportunities as possible during the season to get in foal.
The highest in-foal rates were in young mares and dry mares exposed to an artificial lighting regime prior to the onset of the breeding season.
The New Zealand study showed light exposure significantly increased the odds of dry mares conceiving by the end of the season. This occurred due to a combination of an increased first cycle pregnancy rate and increased number of service opportunities in a season. The start of mating to conception interval was also shorter in dry mares under lights.
Our pasture based grazing system makes implementing artificial lighting regimes more complicated, mares need to be housed or yarded overnight which can be labor intensive or light masks used.
Mares should be kept warm (covered and or shelter) especially those mares under lights as it stimulates early shedding of the coat. Mares should also be optimally fed a nutritionally balanced diet. Mares in good body condition begin cycling on average a month earlier than mares in poorer condition. Similarly, an increasing plane of nutrition or grazing green pasture is associated with earlier returns to cycling. Younger mares cycle earlier than older mares and ambient temperature is also a factor. (See handout on Mares under lights for more information).
Maiden mares and poor doers may need to be separated and managed preferentially to ensure they are doing well. Mares coming off the track should be managed to reduce stress by buddying up, and slowly transitioning them to the broodmare paddock.
Grazing animals require good dentition and feet. Dental and farrier maintenance and treatment becomes very important in the day to day management of broodmares in New Zealand. This is not a place to cut corners! Dry mares should have their teeth fully examined annually and more often if there are dental issues. This should be done by a qualified person with a dental gag, light, mirror and sedation. Early detection and treatment of dental conditions can have a marked effect on mare health, nutrition and longevity. (See dental issues in broodmares handout for more information)
A good experienced farrier that works alongside your vet when needed, to maintain and resolve foot issues is imperative.
Relevant vaccinations should be done to reduce the circulating viral or bacterial load on a property and to maintain vaccination protocols, don’t skip dry mares because they are not pregnant. A good worming program is also necessary.
Teasing mares is key to any broodmare operation. Good teaser pony’s along with experienced personal are essential. Teasing records should be kept for all mares being bred. Some mares are shy breeders, others don’t show with a foal at foot, some may only break down and show the day they need to be served, however most show with consistent signs for the stage of their cycle (see teasing mares handout for more information).Mares should be paddock teased daily, then if showing interest, they should be brought up so they can be yard and hand teased more intensively.
Maidens and fractious mares may need to spend time alongside the teaser before being served by the stallion. Well teased mares will reduce the risk of damage or danger to the stallion, the mare and handlers!
Accurate teasing can save valuable time and money during the season, it may reduce the number of times that a vet needs to scan a mare. However not all mares read the book, so if in doubt get her checked.
Mares showing signs of oestrus are then palpated by the vet. Rectal palpation and ultrasonography of the ovaries, uterus and cervix, will help define her reproductive status. Follicles on the ovaries are measured and graded along with uterine folds and cervical tone.
Palpation to determine timing of ovulation is important especially where stallions are heavily booked and the number of covers on individual mares needs to be kept to a minimum.
Early in the season many mares may show signs of oestrous but are still transitional. These mares have multiple small follicles on their ovaries. This means they are still progressing from being anestrus (not in season) to being in oestrous (in-season). It is not until one follicle is selected to mature that the mare ovulates, and a normal cycle is initiated. These “transitional mares” can be frustrating as many tease well and may require frequent scans by the vet. Hormonal treatment may hasten them to start cycling.
Estrous cycles can be manipulated with the use of exogenous hormones. The most commonly used include progesterone, prostaglandin and human chorionic gonadotrophin.
Some common reproductive issues found in mares includes endometritis, post mating metritis, urine pooling, uterine cysts, an incompetent cervix and retained endometrial cups these are generally diagnosed when a vet examines them ultrasonographically.
(See mare reproduction handout for more details).
In summary, dry mares should not be overlooked. Good management is important to keep them in optimal health and condition leading into the season to give them every opportunity to cycle and be served early. Our year-round grazing system requires a greater emphasis be placed on maintenance and treatment of our mare’s teeth and feet.
Exposing dry mares to lights significantly increases the odds of a dry mare conceiving, and conceiving earlier, by the end of the season.
Effective teasing is a key part of any broodmare operation and can save time, money and reduce danger to the horses and handlers. Combined with veterinary palpation and treatment where indicated resulting in timely service of mares.
