4,503
edits
Changes
Pregnancy and Parturition - Horse Anatomy (view source)
Revision as of 18:01, 26 November 2012
, 18:01, 26 November 2012→Stages of Parturition
*Stage 2: The expulsive stage, characterised by the onset of abdominal contractions which together with uterine contractions lead to foetal expulsion. This takes 12-30 minutes.
*Stage 2: The expulsive stage, characterised by the onset of abdominal contractions which together with uterine contractions lead to foetal expulsion. This takes 12-30 minutes.
*Stage 3: Separation and expulsion of the foetal membranes. This takes 1 hour.
*Stage 3: Separation and expulsion of the foetal membranes. This takes 1 hour.
====Stage 1====
This stage begins with mammary hypertrophy, waxing of the teats and possible escape of milk from the glands. Patchy sweating may be noted behind the elbows and around the flanks. It commences ~4 hours before the birth of the foal and increases as the stage progresses.The mare usually yawns frequently and shows no indication of pain. Food is taken readily. Respirations are normal and the pulse is ~60. Body temperature may become slightly subnormal (36.5-37◦C). The mare becomes restless and wanders aimlessly, she may swish the tail or slap it against the anus. The tail is frequently raised or held to one side. Towards the end of this stage, the mare may kick the abdomen, crouch, straddle the hindlimbs, go down on the knees or sternum before rising again, glance at the flank. This stage terminates with
rupture of the allantochorionic membrane and the escape of allantoic fluid from the vulva. There is no visible straining during this period.
====Stage 2====
This stage is abrupt in onset and lasts an average of 17 minutes. It begins with the appearance of the amnion or commencement of forceful straining. There is not much delay between contractions,they often coincide. Soon after straining begins, the mare goes down and lies on her side with the limbs extended. She generally remains in this position until the foal is born.A transperent blue/white 'water bag' (amnion) visible at the vulva, quickly followed by the appearance in it of a digit. Straining should be at regular intervals. Each comprises 3/4 powerful expulsive efforts followed by a period of rest. Expulsive efforts are generally 3 minutes long. One forelimb procedes the other by 7-8cm. One elbow passes through the pelvic inlet before the other preventing minimal obstruction. The head is usually in the oblique position, but may be transverse with the cheek lying on the limbs. The greates and longest effort is with birth of the head. After expulsion of the foal, the mare may remain on her side exhausted for up to 30 minutes. The umbillical cord is intact when the foal is born. It subsequently ruptures 5-8cm below the belly due to movement of the mare or foal. The foal is usually born within the amnion, which is ruptured by movements of the forelegs. Lower portions of the hindlimbs often remain within the vagina for minutes after the rest of the foal is born.
====Stage 3====
Membranes are expelled quickly after the birth of the foal, usually within 3 hours. The duration of this stage is ~30 minutes. The afterbirth is expelled by myometrial contractions with no straining.
===Placental Changes===
===Placental Changes===
During the last 5 days of gestation, there are changes in the placenta.
During the last 5 days of gestation, there are changes in the placenta.