Breeding Mare

The Breeding Mare. The breeding season is here! Mares are on tour! This year’s foals are hardly dry and across the country, studs are now busy getting their mothers ready for next years crop. In this issue, we will look at the mare and how she gets through this demanding period.Mare nursing new born foal.

Firstly, there are a number of factors to consider in the period before the breeding season commences.



This is of vital importance; the mare should be in good body condition generally on a rising plane of nutrition. If the mare is pregnant a correct diet is particularly important in the last three to four months of pregnancy as a lot of fetal growth occurs in this period. Mineral requirements should be met at all stages during the pregnancy and particular attention should be made to the protein, calcium and phosphorous levels which should be gradually increased in the last four months to help the developing foal. Copper levels in the diet should be adequate for the local area as considerable regional variations in requirements occur. Additionally, in barren mares supplementation with Vitamin E has been shown to improve fertility rates.

Start of normal cycling activity

The breeding season typically begins in the spring and ends in the early autumn. The mare is a long day breeder, in that day length is the primary factor controlling ovarian activity. In the early spring with increasing daylight hours the ovarian activity is stimulated and later in the autumn when the daylight hours are of reducing the length the ovaries return to a state of dormancy. In thoroughbred breeding use of artificial lighting is frequently employed to trick the mare’s body into believing the days have got longer earlier. Two to four weeks before the shortest day of the year the mare’s stable is illuminated to give 16 hours light to 8 hours darkness. This is continued until the mare is cycling, which may take two to three months. This procedure is generally done on barren or maiden mares, but it may also be done on pregnant mares to ensure early cycling activity post foaling. This procedure is more important in the early breeding season.

If increasing this period of light does not induce early ovarian activity then use is often made of hormonal manipulation using various hormone drugs. Use of these drugs is also frequently employed solely to manipulate the cycle.

Covering the mare

All foaling mares should be examined 7 days after delivery. They should have endometrial swabs taken to determine if any womb infection is present. Even if the mare is not being bred on the foal heat, it is important that she is thoroughly checked out so that she will be ready for covering at the next heat. Your vet will check for vaginal and vulval injuries, cervical damage or bruising, presence of urine pooling and if the uterine infection is present appropriate antibiotic therapy will be commenced. Some studs will also look for specific tests on your mare, for example, CEM, EVA.

Using manual and ultrasound examination of the ovaries your vet will decide the optimum time of mating to ensure the mares best chance of conceiving. In the non-thoroughbred, a choice of artificial insemination is increasingly available to the mare owner. This is of benefit in that the mare does not have to visit the stud and it is possible for the stallion to cover more mares in the season.

Examination of the mare.

Checking for pregnancy

This can be performed using ultrasound examination from 14 to 16 days. At this stage, twins are most easily monitored and squeezing can eliminate one. Twins, if allowed to develop, are a disaster, as they rarely carry to full term and if they do can be an obstetrical emergency, and may be born dead. Repeat ultrasound examination is advised at 27 to 28 days. More frequent scans may be necessary if the mare has multiple uterine cysts or if she has a history of early embryonic loss. Once the mare is confirmed pregnant at this stage, in most cases they carry to full term, which is approximately an 11 months gestation period.

Case Study

In the case of this issue focus I will look at the problem of the repeat breeder, the mare that despite everything will not go in foal. Chronic or repeated endometritis (womb lining infection) is one of the most common reasons for this problem. A typical history of mares that are susceptible to endometritis is that they have the infection cleared by therapy only to show up signs of endometritis post-breeding on the next heat. It is thought that the uterine defense mechanism in these mares can be depressed. Covering, AI, diagnostic procedures and pneumovagina can cause the bacterial contamination of the womb. Normally mares readily eliminate contaminants from the uterus, whereas susceptible mares are unable to eliminate these contaminants, which results in endometritis.

What can we do to help?

The importance of stud hygiene at covering is very important. Endometrial swabbing is very important to identify the organisms causing the infection. These can be bacterial or fungal and sensitivity testing should be done to identify the correct antibiotic or drug that will eliminate them. On ultrasound examination in the days after covering the presence of fluid should be noted. This can be eliminated using the appropriate anti-microbial therapy in combination with other drugs. Sometimes in the very resistant case to aid the local defenses in the womb an infusion of the mares own plasma is used to boost the local immunity. If the mare has poor conformation, an operation called the Caslicks procedure is carried out after covering which prevents pneumovagina. These are some of the most common methods of dealing with these cases.

Also something that I have found of tremendous benefit in recent years for these mares is the complimentary use of herbal supplements. Anifertil from the Animal Herb Company is the supplement that I have used and in the last few years, it has helped get several difficult cases in foal, sometimes mares that were barren for two to three years. Why exactly herbs help is maybe not completely understood but one simple understanding is that they are supplying vital nutrients that the mare’s diet maybe deficient in. With the overuse of pasture fertilizers and lack of proper management, paddocks may have become deficient in vital nutrients that the mare would naturally seek out for herself. By providing appropriate herbal supplements we can supply these vital nutrients. It’s natural and can only be of benefit. The poor breeder is a challenge and can be very frustrating for owners but with intensive treatment and management, many cases can have a successful outcome.

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