Oxytocin works well to stimulate the farrowing process, when given at the proper time. However, when improperly or overly used, it can exacerbate farrowing problems.
In short, oxytocin use should be limited to older-parity sows and during the last half of the birth order, explains Steve Dritz, DVM, College of Veterinary Medicine, Kansas State University (KSU).
Dritz presented a review of oxytocin use for sows and gilts at last fall's KSU Swine Day in Manhattan, KS.
The role of oxytocin is to shorten farrowing time and the interval between each pig born. The U.S. Department of Agriculture's 1995 National Animal Health Monitoring System survey revealed that 8.2% of pork producers use oxytocin for all sows farrowed.
Oxytoxin works by stimulating uterine contractions, which in turn decrease the interval between piglet births.
When sows were allowed to farrow normally without intervention, 75% of the stillbirths occurred after the eighth pig was born, in one study presented by Dritz. Stillbirths are fully developed pigs that die during birth and never take a breath.
“In contrast, this same study indicated that 88% of stillbirths were recorded before the fifth pig was born, when sows were administered a single dose of oxytocin after the first pig was born,” he says.
An evaluation of risk factors for stillbirths on two commercial swine farms in Brazil found that the use of oxytocin increased the risk for stillbirth. A total of 101 litters were evaluated on the first farm, and 373 litters on the second farm. The percentage of litters with one or more stillbirths increased on each farm when sows received oxytocin during the birthing process.
As a farrowing tool, oxytocin is used on many farms to reduce stillbirths and as an aid in the farrowing process. As shown in the study illustrated in Figure 1, the use of oxytocin can reduce farrowing time by more than half, and lower the time between pigs farrowed by half.
“But administration of oxytocin before the cervix is fully dilated or before the first pig is born can lead to dystocia or difficult birth,” observes Dritz.
“Improper oxytocin use can also cause an increased number of stillbirths by causing ruptured umbilical cords, which lead to decreased oxygen delivery to the piglet during birth” (Figures 2-3).
Also in that study, severe meconium staining was more prevalent in liveborn and stillborn pigs of oxytocin-treated sows. Meconium staining occurs when waste products accumulate in the intestinal tract before the pig is born.
Explains Dritz: “If a pig is oxygen-deprived during the birth process, it will expel the meconium through its mouth because it is trying to breathe. But because it is still in the placenta, the meconium stains the amniotic fluid and the pig.”
Roy Kirkwood, DVM, swine reproductive specialist at Michigan State University, reports that some recent work and several studies from Mexico confirm that oxytocin use increases stillbirths.
“The data is fairly convincing in that the regular use of oxytocin is not a good idea,” he says. Overuse of oxytocin can produce higher incidences of interrupted farrowings that require manual intervention, which is a risk factor for uterine infections and subsequent infertility.
The use of oxytocin also impacts the pattern of stillbirths, occurring more often when the first four pigs are born, rather than when the last four pigs are born, Kirkwood observes.
While oxytocin has potential negative implications, its use can be beneficial to farrowing by stimulating uterine contractions and preventing stillbirths in older sows, comments Dritz.
Use ½ cc (10 IU) to stimulate uterine contractions. The use of larger dosages should be avoided.
Dritz' other recommendations include:
Administer oxytocin only after the cervix is fully dilated;
Use little or no oxytocin in gilt litters;
For a normal farrowing sow, don't use oxytocin until at least six pigs have been born;
Use oxytocin when a sow has not had a piglet for more than 40 minutes; and
Use a maximum of two doses/sow.
Don't use oxytocin as a substitute for obstetrical assistance when problems are evident, including bloody discharge from the vulva, obvious pain or straining, or a history of stillbirths.