Diseases of the Reproductive System

Chapter 56 Diseases of the Reproductive System

Of all our domestic animals, it appears that successful reproduction is most difficult in the mare. Even with all the advances in reproductive technologies (artificial insemination, embryo transfer, hormonal manipulation), the mare’s reproductive efficiency remains about 60% to 75%. This is partially due to the mare’s estrous cycle. The mare has a 21-day estrous cycle and is in estrus for 5 to 7 days. Unlike most animals, the mare ovulates 24 to 48 hours before the end of estrus, making timing of insemination more difficult in the mare. Because of the low reproductive efficiency, reproductive disorders can have a large impact on a breeder’s operation.

BACTERIAL ABORTIONS

A wide variety of bacteria can cause abortions, most often as a result of placentitis. Bacterial abortions are more commonly seen in older mares. The most common bacteria isolated are Escherichia coli, Salmonella spp., Klebsiella spp., and Actinobacillus spp.

CLINICAL SIGNS

• Abortion
• Discharge
• Mare returns to estrus
• Premature milk letdown

DIAGNOSIS

• Bacterial culture and sensitivity

TREATMENT

• After a bacterial abortion, the mare’s uterus should be flushed, with antibiotics placed in the final liter of flush.
• Systemic antibiotics may also be administered.

VIRAL ABORTIONS

The most common cause of equine viral abortion is equine herpesvirus type 1 (EHV-1). Abortions usually occur in the last trimester, and more than one mare on the farm is affected. This condition closely resembles bacterial abortions and fungal abortions.

DIAGNOSIS

• Virus isolation from aborted fetus and placenta

TECH ALERT

Wear gloves when handling any aborted fetal materials and the placenta.

INFORMATION FOR CLIENTS

• Pregnant mares should be vaccinated with a killed vaccine at 5, 7, and 9 months gestation to prevent viral abortions.

CONTAGIOUS EQUINE METRITIS

Equine metritis is a highly contagious disease that was first described in England and Ireland (see Color Plate 30). The disease has since been eradicated from the United States. Presenting history is often limited to the animal being infertile. The causative organism is a Gram-negative bacterium, Taylorella equigenitalis. The organism is usually passed from the stallion to the mare during breeding.

CLINICAL SIGNS

• Ten to 14 days after breeding there is a copious mucopurulent discharge from the vulva.
• Discharge usually stops within 2 weeks and mares become inapparent carriers.

DIAGNOSIS

• Bacterial culture and sensitivity—the urethral fossa and diverticulum in the stallion and the clitoral fossa in the mare are often the most rewarding sites from which to collect a sample

TREATMENT

• Antibiotics may not be effective.
• The main goal in treatment is to clear the organism from the uterus and clitoral fossa in the mare and from the sheath, urethral fossa, and urethral diverticulum in the stallion; treatment involves washing the affected areas at least once daily for 1 week with chlorhexidine scrub.

DYSTOCIAS

Dystocia is defined as difficulty during parturition. In mares, the second stage of labor (defined as the time from when the amniotic sac ruptures to the time the foal is delivered) should last NO MORE THAN 20 MINUTES! Dystocias appear to occur more in maiden mares.

There are many possible reasons for difficult parturition in mares. The three most common are:

• Mare/foal size mismatch
• Malpresentation of foal
• Twins

A dystocia is said to occur if the amniotic fluid rushes out and 20 minutes later there is still no foal. It becomes serious if the mare is straining, with no progress in foal delivery.

TREATMENT

• Correct the position of the foal in the birth canal.
• If the foal is determined to be dead on a vaginal examination, a fetotomy can be performed.
• A Cesarean section can be performed as a last resort, preferably at a surgical referral center.
• The procedure can be done on the farm if referral is not an option; at this point the main goal is to save the foal because most mares will not survive an on-farm Cesarean section.

TECH ALERT

The placenta separates from the maternal blood supply early in the foaling process. Most equine foaling occurs within 30 minutes of the start of contractions. Any mare taking longer than this to deliver a foal may need immediate assistance to avoid the loss of the mare, foal, or both.

ENDOMETRITIS

Endometritis is one of the most common reproductive diseases in mares. Endometritis can be classified into four classes. A higher class number indicates a smaller likelihood of the mare becoming pregnant. The condition is more often seen in older mares, both those that have had many offspring and maiden mares. Underlying causes of endometritis include:

• Repeated breedings
At each breeding, semen elicits a mild inflammatory response. A result of this inflammation is a small amount of fibrosis.
After repeated matings, these small pathologic changes start to combine into a larger problem.
• Chronic infections
Infections of the uterus can occur when the mare’s physical barriers to infection are compromised.
Streptococcus zooepidemicus, E. coli, Pseudomonas spp., Klebsiella spp., Staphylococcus spp., yeast, and fungi are common disease-causing organisms.
Mares with poor vulvar conformation are more likely to contract uterine infections.

Related posts:

  1. Hematologic and Immunologic Diseases
  2. Hematologic and Immunologic Diseases
  3. Diseases of the Cardiovascular System
  4. Hematologic Diseases

Stay updated, free articles. Join our Telegram channel
Tags:
Aug 31, 2016 | Posted by in GENERAL | Comments Off on Diseases of the Reproductive System

Full access? Get Clinical Tree
Get Clinical Tree app for offline access