Mare Mastitis
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Mastitis (inflammation of the udder) is a relatively uncommon problem in mares. Some of the likely reasons that mares develop mastitis much less commonly than other animals (such as cows) is that they have comparatively small teats, and the udder, even when engorged, remains well tucked up between the hind legs. This decreases the risk that the teats will be traumatized or soiled compared to the large, low-hanging teats of a cow. Also, frequent nursing by foals (normally several times an hour) keeps the udder relatively empty and helps prevent build up of bacteria in and around the teat. The fact that people don’t frequently touch a mare’s teats and udder also helps prevent contamination with bacteria from our hands or from other sources that may be transmitted indirectly on dirty hands.
When a mare does develop mastitis, it can cause quite a significant problem, for both the mare and her foal. For one thing, mastitis is usually very painful! Even the most well behaved, tolerant mare will usually object to foal trying to nurse. Usually the mare will simply move away from the foal, but very persistent foals may also get kicked. Beyond this, problems for the foal are two-fold:
- The foal will not receive adequate nutrition and will quickly run down its body’s own meagre reserves, thus making it more prone to infections and other complications.
- If the foal is able to nurse at all from the inflamed part of the udder, it is drinking milk that is often heavily laden with the bacteria causing the infection, which represents an additional challenge to its body’s defenses and immature intestinal flora.
The infection in the mare is usually bacterial in nature, and the culprits tend to be opportunistic bacteria that can be found around any horse, especially Streptococcus zooepidemicus, but also Staphylococcus, Actinobacillus, Pseudomonas, Klebsiella and Escherichia coli. In mild cases the infection will be limited to the udder. In severe cases, and especially with Gram-negative infections, mares can develop systemic illness due to endotoxemia or septicemia, which can lead to complications like colitis and laminitis (founder). Mastitis may occur in only one half (gland) of the udder, or in both parts of the udder at the same time.
Mastitis is diagnosed by culturing bacteria from the milk. It’s very important to take a culture sample before beginning treatment in case the bacteria involved aren’t sensitive to the initial antibiotic treatment. Mares are usually also treated with an anti-inflammatory to help keep them more comfortable. However, the most important component of therapy is stripping the udder (i.e. milking the mare out) as often as possible to remove the bacteria and all the inflammatory debris. Hot packing the udder helps to promote drainage, and hand walking helps decrease edema and swelling around the udder.
Most mares recover from mastitis in 5-7 days with proper treatment, but it’s important to initiate treatment as early as possible, before the infection becomes severe. Signs to look for that may indicate a lactating mare is developing mastitis include:
- The mare being persistently reluctant to allow the foal to nurse
- Abnormal swelling of the udder, particularly if it is hot and painful on palpation
- Abnormal-looking milk (often watery with white flecks/chunckies) from one or both teats
- Sudden development of ventral edema around the udder
- Reluctance to walk or abnormal gait in the hind limbs
- Non-specific signs like fever, lack of appetite, and depression
If you suspect your mare may be developing mastitis, she should be examined by a veterinarian as soon as possible. It is also very important to monitor the foal in these situations – if the foal is not able to get sufficient milk from the mare, it may need to be supplemented by bottle or bucket feeding until the mare recovers.
- Avoid touching the teats and udder of normal mares whenever possible in order to decrease the risk of contaminating the teats with bacteria from your hands.
- If you need to touch/check the udder, wash your hand thoroughly first with soap and water (preferably warm water - most mares appreciate that!).
