Improving Reproductive Efficiency in the Wet Mare

This article is from the November 2019 Horse Deals magazine.

Dr. Jen Clulow

BScAgr, BVMS, PhD, DACT
Jen is a Veterinarian with a PhD and is a Registered Specialist in Veterinary Reproduction. Jen has worked in both Australia and the USA but now resides in Scone NSW working for the Scone Equine Group. Jen’s interests are in all forms of equine assisted reproduction.

Dr. Nerida Richards

B.Rur.Sc (Hon1) PhD RAnNutr
Nerida is a graduate from the University of New England with a degree in Rural Science and PhD in Equine Nutrition. Nerida has nearly two decades of experience as a professional Equine Nutritionist both in Australia and Internationally.

The Normal Post Foaling Mare

In the days following delivery of the foal, you may notice several changes with your mare. We need to remember the mare has just delivered a foal, and right up until the time she delivered the foal, she was carrying an average-sized foal of 50kg and up to 20L of fluid. There are some remarkable changes that need to happen to the mare’s uterus to get her ready for another pregnancy.

In addition to a huge reduction in size, the uterus also needs to repair its lining or endometrium as well as clear any placental debris and fluid known as “lochia”. Normal lochia discharge is red/brown in colour and can be of a sticky consistency. This process takes approximately 14 days to complete in the normal mare. Mares that have difficulty foaling, retained foetal membranes, heavy contamination following foaling, a history of placentitis or a prolonged uterine discharge usually take longer for this process to complete.

If you are concerned your mare is producing a large volume of abnormal or malodourous fluid, contact your veterinarian. Your mare may have retained foetal membranes or a uterine infection called “Metritis”, both of which can be life threatening conditions.

The “foal heat” or first oestrous cycle usually occurs between 7-14 days post foaling. Decisions to breed on the foal heat cycle are usually made following a normal birth. Mares that ovulate after day 10 post foaling usually have the best pregnancy result if you choose to breed on this cycle. This allows complete repair of the uterine lining or endometrium before the embryo reaches the uterus. Because of the lower pregnancy rates and early embryonic loss associated with foal heat breeding, this cycle is often skipped. Ultrasound examination of the mare at 10-12 days post foaling may identify whether your mare is a suitable candidate for foal heat breeding but may also identify other issues that may cause breeding failure in subsequent cycles. Foal heat breeding with frozen semen is not usually recommended.

Rather than breeding on the foal heat cycle, most breeders elect to breed on the second oestrous cycle following foaling. This cycle usually occurs around 30 days following foaling following full uterine involution and is therefore often referred to as the “30-day heat”. If you are planning on breeding your mare on this cycle, ultrasound examinations around 25 days will allow your veterinarian to assist in achieving your breeding outcomes on this cycle. In the interests of time, this cycle can be shortened or manipulated to allow for complete restoration of the uterus before making a breeding attempt. Breeding on the 30-day heat will allow your mare to produce another foal at roughly the same time of the year each year.
The foaling mare realistically is the ideal candidate for future breeding if she has a normal foaling and can be maintained in a positive energy balance. During this time your mare will need to increase her milk production as her foal starts to grow and increase its nutritional demands. Remember that at this stage the foal relies completely on the mare for all its nutritional requirements. As such it is important we meet the mare’s nutritional requirements to allow her to also provide for the foal.

Feeding Your Mare & Foal

Getting a lactating mare’s feeding right is critical to ensure she can provide milk for her foal, go back in foal and provide the required nutrients for a foetus when she is pregnant again.
When it comes to rebreeding, your mare’s body needs to be comfortable that it is in the right ‘environment’ to allow another pregnancy. So, she needs to be well-nourished to allow natural cycling to begin again. To achieve this, your mare’s requirement for energy (calories), protein, vitamins and minerals must be met. These nutrients and the role they play in a lactating mare’s diet are looked at below.

Energy

A lactating mare’s requirement for energy is DOUBLE that needed by a mature idle horse. She will eat a lot! Not feeding a lactating mare enough energy means she will lose weight. If she is losing weight, or if she has fallen below a condition score of 5 (on the Henneke 1 to 9 scale), it may make it difficult to get her back in foal and could also reduce the amount of milk she produces for her foal. This may result in stunted growth. If she exceeds a condition score of 7 her milk production may fall and it also puts unnecessary pressure on her joints and hooves which can cause pain and lameness for the mare. Therefore, you need to aim for maintenance of a body condition score of 5-7.

The basis of a mare’s energy intake should be provided by pasture and/or hay. If pasture and/or hay is not enough to maintain body condition, high energy feeds like commercial complete feeds, cooked cereal grains, legumes like lupins, high energy fibres and oils can be added to the diet.

To manage energy intake, you should condition score your lactating mares regularly and adjust their energy intake up if they are losing weight and down if they are gaining weight. This is particularly important in the first few weeks to a month post foaling to ensure she doesn’t suddenly lose a lot of weight.

Protein and Amino Acids

Lactating mares need high-quality protein with plenty of essential amino acids to enable them to provide milk for the foal and to maintain their own muscle mass. Not enough high-quality protein in a lactating mare’s diet will cause milk production to fall and the mare will begin to lose muscle. This will be most visible initially over her rump and topline. Watch for any signs of muscle loss. If you notice her losing muscle, her diet needs adjusting!

The majority of protein in the mare’s diet should come from the forage the diet is based on. When there is not enough protein in the pasture/hay to meet a mare’s requirements, good quality protein sources that are rich in essential amino acids such as soybean, lupins, faba bean, canola meal and lucerne or feeds based on these ingredients should be used to meet requirements. Poor quality sources of protein such as unnamed ‘vegetable protein meals’ and cottonseed meal should always be avoided in lactating mare diets.

I find a great way to help with meeting essential amino acid requirements for lactating mares is to first add some lucerne hay to the diet to replace some of the pasture or lower quality forage she is eating. Then add a feed that contains high-quality protein, with my first choice being feeds based on soybean meal. Soybean is known to have the highest quality plant protein available, making it perfect to support the protein and amino acid requirements of wet mares.

Vitamins and Minerals

Vitamins are extremely important in the lactating mare’s diet and have an impact on the mare’s health and fertility as well as the foal’s growth, muscle development and immune function. Mares with access to green pasture will have most of their vitamin requirements met by the pasture alone. Mares with no access to pasture will generally need to be supplemented with vitamins.

A lactating mare has massive requirements for minerals, and particularly for the macro-minerals calcium and phosphorous, which are secreted in large quantities within milk. It is also important to meet her requirements for trace minerals as they are required to ensure the structural soundness of her future foals.

Not meeting the lactating mare’s requirements for minerals will mean her body reserves are depleted, leaving her susceptible to disease and lameness. Mineral deficiency can also reduce her milk production and fertility and can affect the soundness of future foals.

A lactating mare’s mineral requirements will be partially met by the pasture/hay in her diet. However, it is unlikely a mare’s full mineral requirements will be met, so some supplementation will almost certainly be necessary.

Vitamins and minerals can be supplemented in the form of a concentrated vitamin/mineral supplement or in the form of a complete feed, depending on your preference for style of feeding and how much feed your mare needs to maintain body condition.

If your mare is an easy keeper, using a concentrated vitamin/mineral supplement or balancer pellet will allow you to provide the vitamins and minerals she needs without providing additional calories that could make her gain unneeded weight. Well formulated balancer pellets are particularly useful for these mares. On the other hand, if your mare is a hard keeper, it would be easiest to use a complete feed that provides the mare with additional calories and protein as well as providing the vitamins and minerals she needs.

Which Is the Best Feed for Your Mare?

When choosing the right feed and developing a feeding program for your lactating mare you need to consider the following:
1 Do you have pasture available?
2 What sort of pasture do you have and what is its quality like?
3 Will your mare maintain bodyweight on pasture alone, or do you need to feed additional feed for her to maintain bodyweight?
4 What hay do you have available and what is its quality like?
5 Is your mare an easy or hard keeper?
6 Does she need to gain, maintain or lose weight?
7 What stage of lactation is she in?
8 Do you prefer to feed a complete feed or mix your own feeds using supplements?

The answers to these questions will determine whether a complete feed or a supplement is best for your mare and will also help you determine what amount of feed your mare needs. If your mare is a hard keeper or if you have very little or only poor quality pasture available, a complete feed will most likely be needed. If you have good quality pasture and/or your mare is an easy keeper you may find a vitamin/mineral supplement or balancer pellet is all that is required.

Regardless of what you choose to feed, ensure your lactating mare always has free access to forage in the form of pasture or hay, a salt lick and very clean, freshwater.

FeedXL It!

The nutrition calculator FeedXL.com will help you put together a balanced diet that meets the energy, protein, lysine, mineral and vitamin needs of your lactating mare to ensure that she remains healthy and productive during this phase of her reproductive cycle. This will have the flow-on effects for going back into foal and maintaining her new pregnancy for you.

And just as importantly, FeedXL will allow you to accurately create diets for your growing foal. A growing horse’s requirements are constantly changing, and the future soundness and health of your foal really depends on you getting nutrition right in the formative years of its life. So, don’t guess at what you should be feeding (please). Investing a little time now on a good diet for your mare and growing horse can save you a lot of time, frustration and heartache in the future.

Common Problems That Compromise Fertility

As mentioned in our previous instalment, a 24-hour foal examination is recommended. Your veterinarian can not only perform a clinical examination of your foal and check whether there has been adequate passive transfer of immunity from the mare’s colostrum but can also, importantly, check your mare. Foaling accidents do occur and can certainly impact on the future breeding prospects of your mare. Early identification of these problems can allow swift management and treatment where required. Foaling accidents may include vaginal lacerations, cervical tears, damage to the perineal body, haematomas on the outside and the inside and damage to the urinary tract. Some of these trauma-related problems will need to be addressed surgically before breeding, while others may require additional healing time.

One of the most common problems in the post foaling period is retained foetal membranes. Foetal membranes are usually passed within three hours post foaling. If you can’t find the membranes – it is best to get your veterinarian to check they are not retained. Although scavenging by wildlife is common in Australia, membrane remnants can be retained completely inside the mare giving the impression they have been passed. If you find the membranes in the paddock, check for completeness and gather them for your veterinarian to double-check during the foal examination.

If your mare does retain her foetal membranes this is a potential medical emergency. In just five hours, the mare may start to become systemically ill showing signs of sepsis including an elevated rectal temperature, mild colic signs, general dullness and other signs of endotoxaemia including laminitis. If untreated, this condition can be fatal. Small doses of oxytocin may assist in the release of membranes but if the membranes are still present five hours post foaling, please contact your veterinarian immediately. Mares may require anti-microbials and uterine lavage to help alleviate the bacterial overload and remove the membranes. It is not recommended to attach weights or pull on the membranes as tearing of the intricate attachment between the membranes and the uterus can leave behind small pieces of tissue which can also result in severe illness of your mare. If in doubt, call your veterinarian.

Delayed uterine involution is another common issue that may affect fertility following foaling. A reduction in normal uterine clearance may be due to limited movement e.g. boxed mares, heavy contamination following foaling, retained foetal membranes, trauma during foaling, placentitis or urine accumulation. These mares may require additional assistance with hormones such as oxytocin and/or uterine lavage to ensure gross contamination is removed from the mare’s uterus. A prolonged or malodourous discharge may require further investigation. It is recommended that these mares have a uterine culture performed prior to breeding to identify any bacterial infection that may prevent pregnancy.

The mare with a foal at foot is usually our ideal breeding candidate. There is often an expectation that all mares will go in foal on the first breed, but just remember that fertilisation and the maintenance of pregnancy is multifactorial. Age-related changes happen to all of us. Any problems in the post foaling period or inadequate nutrition has the potential to impact negatively on her fertility. We already know she is capable of producing a foal to term and, provided we look after her and identify any problems early, she should be able to do it all over again. Happy breeding!

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