Farrowing induction is a production tool that’s been used for years in the swine industry. The basic concept is simple: Give an injection to reduce variation in timing of the birthing process such that it is most convenient for staff to attend farrowings.

In practice it is somewhat more complicated.  Ask yourself: What exactly is your objective? What compound(s) do you use to induce farrowing? When do you treat sows? What other considerations are there? If you cannot answer each of those questions honestly the program is destined to fail.

The first step is to define your objective. Sows bred on the same day will farrow anywhere from 111 to 118 days later. That variation results in sows moving to farrowing rooms several days before farrowing, and it can result in weaning-age variation that complicates all-in/all-out, phase feeding and other management practices. Therefore, producers are often interested in reducing the number of days over which a group of sows farrow. 

Also, sows farrow at any time of day or night, and research shows that you can save 0.25 to 0.75 more piglets per litter by attending farrowings so that you can remove placental membranes, warm the pigs, assure colostral intake and such. To facilitate supervision of farrowing, many producers want to increase the proportion of litters born during the daytime. 

So, the induction protocol that best fits your farm will depend on which of these objectives you most want to address.

The normal birthing process includes a series of hormonal events involving both fetal and maternal components. 

Farrowing induction protocols are all based first on regressing the sow's corpus luteum, which produces progesterone and maintains pregnancy.  This is typically practiced with a single intramuscular injection of prostaglandin-F2α. Product labels indicate that the injection should be given no more than 72 hours prior to the anticipated farrowing and that farrowing can be expected 30 hours later. This approach does not concentrate farrowing to daytime hours, and farms with that objective typically administer oxytocin to sows 24 hours after the prostaglandin injection to initiate uterine contractions. If oxytocin is added to the protocol and farrowings are not supervised, however, stillborn rates are higher than for non-induced litters.

What are the challenges to the protocols for inducing farrowing?

You must know breeding dates and natural gestation length with certainty. Prostaglandins can regress CL as early as day 108 of gestation, but fetal survival unlikely. While textbooks say that gestation length in sows is 114 days, most sows do not read the books, and commercial farms have average non-induced gestation lengths of 115 to 117 days. Inducing farrowings on the 112th or 113th day of gestation in these herds would be expected to result in poor piglet viability. Inducing farrowings within 24 to 48 hours prior to your herd’s “natural” farrowing date will likely result in the most satisfactory results in terms of piglet viability and survival.

Our research team has evaluated the impacts of the day of induction during July and August on a commercial farm. The sows were randomly assigned to be induced on either the 113th, 114th or 116th day of gestation. As expected, most (83.8 percent) of the 116-day sows farrowed spontaneously prior to treatment and had an average gestation length of 115.27 days. That’s compared to 114 days (gestation) for sows treated on day 113, 92.5 percent of whom farrowed in response to treatment.  More of the 116-day sows farrowed during unsupervised hours, and this group tended to have a higher number of stillborns. 

Within this experiment there were no differences in the number of pigs born alive, preweaning growth or survival, or postweaning estrus among treatment groups. It is possible that the farm did not capitalize on the fact that more 113-day sows farrowed when the staff was available to supervise or that the summertime weather equalized performance. There were some interesting differences between first- and second-parity sows, suggesting that parity-specific protocols for induction should be investigated.

In a separate analysis, sows that farrowed spontaneously were compared to those that were induced, regardless of their assigned day of treatment. That analysis determined that the number of pigs born alive was slightly higher for sows farrowing spontaneously (12.2±0.24 vs 11.6±0.20). Of course, that would be expected since they farrowed prior to induction, and we know that larger litters tend to be born sooner. 

There were no differences in the number of stillborn pigs or mummies, or the piglets’ daily gain during lactation. Early-farrowing-induction research alluded to the fact that induced sows tended to recycle sooner after weaning, and in this analysis we found 65.1 percent of induced sows showed heat within seven days after weaning. Meanwhile, only 34.9 percent of spontaneously farrowing sows did so.

One of the issues associated with prostaglandin use is that it’s an oil and can be absorbed through the skin.   The action in people is similar to that in pigs — CL regression in women and bronchiole constriction. 

A recent paper (Straw et al., 2005) sought to investigate whether that property could be capitalized on in a pork production setting. The researchers administered Lutalyse once or twice daily into the sow’s vaginal lumen (using a syringe without a needle). While once-daily topical application led to a farrowing response similar to non-induced controls, a twice-daily topical application resulted in synchronous induced farrowing. 

As with any deviation from a product’s label use, a producer must consult with his or her veterinarian before attempting this application in a production setting.

So what are the take home messages? 

  • Review your reasons for inducing farrowing and select an appropriate protocol for your herd.
  • If you choose to add oxytocin to the protocol be prepared to supervise all farrowings.
  • Treat the tool as that — a tool that may assist you in achieving goals of greater farrowing supervision and piglet survival or reduced number of days over which farrowing occurs.
  • Be sure breeding dates and gestation length are known. 
  • Be aware of new research on this   tool, whether that has to do with  application methods or seasonal/parity-specific protocols.  
  • Finally, never stop learning.