This litter is 2 days old. The number farrowed cannot be estimated because herdsmen foster piglets when there are more piglets than teats and when there are >10 or 11 piglets per litter.
Farrowing is another name for parturition , or giving birth. After a normal gestation, initiation of parturition is via fetal pituitary ACTH release with subsequent cortisol release (similar to the cow). Cortisol stimulates both maternal prolactin release and fetal placental estrogen production and also release of PGF-2a with luteolysis, and release of relaxin. Relaxin release from luteal cells causes cervical relaxation.
Progesterone levels drop beginning 24 hours prepartum, and myometrial activity begins to increase. Oxytocin receptors have been increasing in the uterus under increasing estrogen levels.
Behaviorally, the sow shows increased restlessness and inappetance with nesting behavior. The mammary glands become distended with milk during the last 24 hours prepartum. The vulva lips may enlarge during the last week of pregnancy.
Myometrial activity increases through the beginning of farrowing to engage the first piglet into the cervix, causing release of oxytocin and a dramatic increase in myometrial contractions. Dystocia occurs in less than 1% of all farrowings. Fetuses should be delivered in 10 to 15 minutes.
Consecutive piglets being born! In the first image, the white banded black piglet is emerging. In the second, the banded piglet is searching for the "milk bar" while a littermate is born hind feet first. (This is a normal position for swine.) The banded piglet is still searching for a teat when a spotted littermate appears.
Placental expulsion occurs at 2 to 3 intervals during farrowing, as many allantochorions are fused. Most are expelled after the last piglet is born. Umbilical stalks should be counted to be sure all placentas have passed, but retained placenta is uncommon in sows.
An expelled placenta.
Farrowing takes place in separate facilities than gestation, particularly because newborn piglets will be in the environment. Not only must the sows be prevented from accidentally crushing a piglet, the environment must be warmer and cleaner than the environment of a gestational sow. Sows are grouped at servicing so that they farrow in groups and at the time when personnel are available. For even tighter grouping, parturition can be induced via injection of prostaglandins at day 112 of gestation. This practice is very common and complications are rare.
Directly following farrowing, it is very important to ensure that the piglets receive adequate colostrum. Failure of passive transfer accounts for much production lost.
These newborns are searching for their first drink of colostrum. (Notice the umbilical cord going into the sow's vulva.)
Copyright ©1997 by the University of Pennsylvania School of Veterinary Medicine
Faculty: Dr. Paul Pitcher
Student: Sandra Springer,'99