Inducing Kiddin in Goats
William Braun, Jr., DVM
|Dr Braun is currently an associate professor of veterinary medicine in the College of Veterinary Medicine, University of Missouri. He previously taught at the School of Veterinary Medicine, Louisiana State University. He is a board certified theriogenologist, a recognized specialist in animal reproduction. In the past he has been an associate and contributing editor and author for the Dairy Goat Journal. Dr. Braun just finished as section editor and author for the section on goat reproduction to be published this year (1996).
The elective induction of parturition (kidding) is easily accomplished in the goat. A functional corpus luteum (CL, or yellow body) is the sole source of progesterone needed to maintain pregnancy in the goat. Unlike many other species, the caprine placenta produces little or no progesterone. Anything that interferes with the function of the CL during gestation will result in the termination of that pregnancy either as induced abortion or induced parturition.
The main benefit of induced parturition is being able to accurately predict the time of kidding in the goat. Predicting the time of kidding allows the owner to prepare in advance for the event and be present when the kids are born. Attended kiddings are important to dairy goat producers who are interested in disease control and to some Pygmy breeders who wish to assist in potential cases of dystocia (difficult birth). Diseases, like CAE and mycoplasmosis that are primarily transmitted through colostrum or milk, may be controlled by removing the kids at birth and not allowing them to suckle their dams. Other indications for induced parturition would include late term injuries to the doe and impending or early cases of pregnancy toxemia.
The events leading to normal parturition in the goat require the functional maturation of the fetal adrenal cortex, with parturition triggered by the activation of the fetal pituitary-adrenal axis. ACTH (adrenocorticotropic hormone) is released by the fetal pituitary gland that stimulates the release of corticosteroids by the adrenal glands. An increase in fetal corticosteroids stimulates placental estrogen synthesis, which in turn stimulates the synthesis and release of prostaglandin (PGF) from the placenta and endometrium (uterine lining). The cascade continues with PGF causing luteolysis (breakdown of the CL) resulting in a decrease in progesterone. An increase in estrogen and decrease in progesterone stimulates myometrial activity (uterine contractions) which is further enhanced by the effects of PGF, causing a direct effect on the myometrium and stimulating oxytocin release.
Prostaglandin (Lutalyse®) is the drug of choice to induce parturition in the goat. Doses of 2.5 to 20 mg PGF have been used, with the higher doses giving a more predictable time of parturition. Treatment is followed by a dramatic decrease in plasma progesterone concentration 24 hours post injection. Few cases of retained placenta have been reported with PGF-induced parturition.
For the practical induction of parturition, the doe should be at least 144 days into gestation. Care must be exercised to ascertain that no unrecorded breedings or errant bucks have caused a miscalculation in gestation length. If a doe is only 123 days instead of 144 days (i.e., bred the next estrus cycle) the induction will result in abortion or poorly viable kids. The typical induction dose of PGF is 10 mg (2cc Lutalyse) for a dairy type goat and 5 mg (1cc Lutalyse) for a Pygmy type goat. At these doses, kidding may be expected in 30 to 36 hours. In other words, if the goat is treated in the morning, she is expected to kid the afternoon of the next day. It must be remembered that these times are averages, and some goats may take longer to kid.
The induction of parturition at day 144 merely sets forward the timing of kidding. The events that follow the injection of PGF are the same events, in the same order, as natural kidding and as such should put no added burdens on the doe. For those of you that look and feel for the loosening of the pelvic ligaments just prior to kidding, this same event occurs in induced parturition. It is the relative increase in estrogen levels and decrease in progesterone levels that account for this softening. Both events occur whether the kidding is natural or induced.
Induction of parturition will not result in the birth of kids smaller than the breed average. These does are almost at term when they are induced so the kids have done just about all the growing in the uterus that they will accomplish. Some producers have reported a slight decrease in colostrum production in induced goats. [Ed. note: This is a good reason to have good quality frozen colostrum on hand.)] Induction, by itself, will not cause any increase in dystocias. In the Pygmy, where dystocias may be encountered more frequently than in the dairy goat, induced parturition allows the owner to attend kiddings and offer assistance if needed. Any dystocia encountered following induction is due to the size of the Pygmy doe [pelvic capacity] and not to the induction itself.
Lung maturation in the kid is complete well before the time that induced parturition is attempted. During the final weeks in the uterus, and to a certain extent the final days, the kid will produce a surfactant that allows the lungs to stay inflated when they start to breathe following birth. Without this surfactant, the lungs will collapse and not take in air properly. Actually what collapses are the tiny alveoli (air cells) within the lungs. The kid produces this surfactant in response to increased levels of corticosteroids that occur late in gestation. In reality, most kids should survive if they are born even 10 to 14 days early. Of course, the earlier they are born, the more difficulties they will encounter. At day 144, when induction is initiated, the kid is ready to survive ouside the uterus with no problems.
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