LITMIR.BIZ

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

      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 are less dominant mares or further away from the fence or tease rail should still be observed for estrus behavior.

      Behavioral Responses

Common behavioral responses of mares in estrus and diestrus are listed in Boxes 2.1 and 2.2 and shown in Figures 2.1 and 2.2.

Box 2.1 Common Behavioral Characteristics of Mares in Estrus

Box 2.2 Common Behavioral Characteristics of Mares in Diestrus

Figure 2.1 Mare in estrus (i.e., teasing in heat). Note the base‐wide stance, raised tail, and urination.

Figure 2.2 Mare in diestrus (i.e., out of heat) on far side of teasing wall. Note the ears and aggressive stance.

      It should be noted that expression of estrus does not always indicate that a mare is in the follicular phase of the estrous cycle. Seasonally anovulatory mares, ovariectomized mares, and pregnant mares have all been reported to occasionally show signs of estrus when teased with a stallion. This may be due to submissive behavior or a lack of progesterone.

      Records

Maintaining an accurate record of teasing behavior will be helpful when monitoring the estrous cycle of a mare. Notations can be made as to whether or not the mare exhibits overt, subtle, or no signs of estrus throughout a cycle (Table 2.1).

Table 2.1 Abbreviations

Скачать книгу