in the mare BSE may not identify the cause of subfertility. Consequently, other examinations may be indicated (Table 1.1).
Additional Comments
Interpretation of the results of a mare BSE should take into account the mare’s age, reproductive history, breed, stallion, breeding management, and other factors. Ultimately the goals are to determine the potential for fertility and detect abnormalities that may be associated with reduced fertility. Management and therapeutic options may be outlined to help optimize a successful outcome. It is important to emphasize that a mare BSE is only an evaluation of potential fertility and that the true assessment of fertility is the ability of the mare to conceive and carry a foal to term.
Table 1.1 Diagnostic tests that may be performed in addition to the standard tests in a mare breeding soundness evaluation.
| Test | Indication |
|---|---|
| Chromosome analysis (karyotype) | Evaluate numeric or structural changes in chromosomes |
| Hormone analysis | Evaluate pituitary and/or ovarian endocrine function. Most commonly used to evaluate corpus luteum function and in the detection of an ovarian granulosa cell tumor |
| Hysteroscopy | Direct visualization of the interior of the uterus to detect intrauterine adhesions and other localized lesions, as well as inflammation and fibrosis |
| Laparoscopy | Direct visualization of the serosal surface of the ovary, oviduct, uterus, and abdominal cavity. Also used in ovarian biopsy, evaluation of oviductal patency, and the application of prostaglandin E2 (PGE2) to the oviductal surface |
| Low volume lavage | Collection of uterine samples for culture, cytology, and other evaluations (e.g., polymerase chain reaction). The effluent fluid may also be evaluated for clarity and pH |
| Oviductal flush | Performed by laparotomy, laparoscopy, or via videoendoscopy; used both diagnostically and therapeutically in suspected cases of oviductal blockage |
| Oviductal patency test | Deposition of fluorescent microbeads or starch granules onto the surface of the ovary or possibly within the infundibulum of the oviduct and subsequent examination of the uterine lumen for passage of the test material is used diagnostically to evaluate oviductal patency |
| Oviductal PGE2 application | Direct application of PGE2 can be used diagnostically and therapeutically in suspected cases of oviductal blockage |
| Ovarian biopsy | Laparoscopic collection of ovarian tissue for histologic evaluation may be used in the diagnosis of ovarian pathology |
| Test breed | Breeding to a highly fertile stallion can be used diagnostically to help determine if the mare is a cause of subfertility or infertility |
Further Reading
1 LeBlanc MM, Lopate C, Knottenbelt D, Pascoe R. 2003. The Mare. Equine Stud Farm Medicine and Surgery. London: Elsevier, pp. 113–213.
2 McCue PM. 2008. The problem mare: management philosophy, diagnostic procedures, and therapeutic options. J Eq Vet Sci 28: 619–26.
2 Teasing
Patrick M. McCue
Equine Reproduction Laboratory, Colorado State University, USA
Introduction
The 21‐day equine estrous cycle can be divided into two phases: estrus and diestrus, based on sexual receptivity to a stallion. Estrus is the period during which a mare is sexually receptive to the advances of a stallion. Behavioral estrus is stimulated by increasing levels of estradiol produced by the developing dominant follicle in the absence of progesterone. The average length of estrus has been reported to be 6.5 days, with a range of 4.5–8.9 days. Ovulation typically occurs 24–48 hours before the end of estrus. An increase in progesterone from the developing corpus luteum is responsible for the cessation of behavioral estrus. Behavioral diestrus largely overlaps the physiological luteal phase associated with high levels of progesterone produced by the corpus luteum.
Equipment and Supplies
Stallion, mare, lead shank, helmet, facilities (teasing rail, fence, chute, stall).
Technique
A mare should be teased with a stallion that exhibits good libido in order to successfully evaluate estrous cycle stage.
Adequate time should be taken to allow shy or nervous mares to express behavioral estrus.
Knowledge of the mare’s previous behavioral patterns may be helpful.
In addition, observation of the mare’s behavior with other horses in a pasture or paddock may indicate when a mare is in estrus.
Individual Teasing
An individual mare should be exposed to a stallion for an interval of time that is long enough for her to show estrus or diestrus types of behavior. It is preferable to have both the mare and stallion restrained for individual teasing; however, if only one handler is present, it is better to have the stallion restrained with the mare loose so that abnormal behaviors in the stallion may be corrected. Mares that remain indifferent may need to be teased longer, teased with a different stallion, or may just show more subtle signs. Mares may be reluctant initially and yet later show frank estrus behavior (i.e., “break down”). Sometimes full behavioral estrus is only expressed within a few hours of ovulation. It is also not unusual for a mare to fail to show signs of estrus while being directly teased to a stallion, and then break down as the stallion leaves. Mares may also display estrus at the mere sound or sight of a stallion. Mares with a foal by their side may be reluctant to display estrus behavior readily as they are concerned for their foal’s safety.
Group Teasing
A stallion may be used to tease more than one mare concurrently if he is brought to the edge of a pen or turned out adjacent to a group of mares. Mares are allowed to approach the stallion at will in such a teasing program. However, some mares will not approach the stallion and will not express estrus when teased as part of a group. It may be necessary to tease such mares individually.
It is often not very efficient to tease mares as a group, since often the only mares that come to the fence or tease rail are assertive mares in heat or mares that want to attack the stallion. One may not be able to determine the heat status of mares that remain a distance from the stallion. It is generally more effective, but certainly more time consuming, to tease mares individually. Mares that
