Nancy Jasrotia1, Nagaraj Gulagi2, Anju Kujur3
1,3- PhD Scholar, Animal Reproduction Division ICAR-IVRI, Izatnagar, U.P
2- Veterinary Officer, Government of Karnataka, Dist- Shahapur, Karnataka

Pigs are an important form of livestock that adapt greatly to any system and their production is mainly undertaken on larger farms. Efficient management of the animals of all age groups in such extensive setup holds the key to economic profitability. A fundamental key in swine production is the pregnant sow. Good management of the pregnant sows ensures better reproductive performance. One of the management aspects apart from the components of nutrition, heat detection and pregnancy diagnosis is the management of farrowing. Pregnancy in sows is maintained by high levels of progesterone produced by the corpora lutea which remain the only source of progesterone throughout the entire gestation. A normal gestation length in sows takes 114 to 116 days, with 10% farrowing resulting before 114 days and 25% after 116 days of gestation. The farrowing process lasts 3 to 5 hours with a piglet being born every 15 to 30 minutes.

Induction of parturition is a common practice in modern sow herds which results in the synchronization of farrowing.  In sow herds where insemination time differs, the time of farrowing will also differ resulting in difficulty in supervision during farrowing. With the induction of parturition, this variation can be narrowed to allow better supervision. Induced farrowing is a tool in parturition management of sow herds that is much beneficial at farm level. A synchronized farrowing process performed under supervision will ensure better health status of the sows and piglets.

Benefits of induced farrowing:

It is practiced in order to reduce the variability of gestation length and directing parturition towards normal daytime working hours. It will ensure timely intervention for any requirement during the farrowing process. Close supervision during the farrowing process facilitates care of dam and newborn which results in lowered neonatal piglet mortality and stillbirth rates, both of which are known to be caused by asphyxia during parturition. Further, induced farrowing allows transfer of piglets of same age group from one sow to another (cross fostering) and to apply other management interventions, such as iron injection, teeth and tail clipping, castration and weaning of piglets. It also allows better sow batch-management systems.

Optimal time to induce farrowing:

It may vary from farm to farm. Before the induction therapy, the normal gestation length of the farm should be established (may vary from 112 to 117 days). It is important that the induction is not given too early in gestation. However, it is recommended that induction of parturition should not be performed more than two days before the average gestation length of the sows of a farm. Earlier induction will result in low birth weight piglets with potentially compromised lung development. This will increase the rates of neonatal mortality and stillbirth. Further, farrowing induction before day 112 of gestation is reported to be associated with a lower percentage of fat, protein and globulin in colostrum which is detrimental to the growth of piglets.

Different protocols for induction of farrowing

  1. Single dose of prostaglandin: Routes of application can be intramuscular, intra- and perivulvar injection, topical application at the vulvar mucosa and injection in the peri-anal region. Mostly, intramuscular injection in the neck region and injection in the vulvar region are employed. In the latter, half the dose is sufficient to obtain the same results as the full dose used intramuscularly. The reason for the efficacy of the lower PGF2α dose administered intravulvally possibly involves a higher local ovarian PGF2α concentration, since the venous drainage of the reproductive tract is greatly interconnected.
  2. Split dose prostaglandin: Two doses of prostaglandin are applied with an interval of 6-8 hours. Some sows do not respond to a single injection of PGF2α due to incomplete luteolysis. Some of the corpora lutea recover and pregnancy is maintained. Hence, split dose technique can be used. It can be used either by intramuscular injection of PGF2α (full dose) or intravulvally (half dose).
  3. Combination of prostaglandin and oxytocin: Combining an injection of Cloprostenol with an injection of oxytocin 20-24 hours later increased the percentage of sows farrowing. After the administration of prostaglandins, the time of cervix relaxation varies between sows. Oxytocin can only be used after the complete relaxation of cervix. Thus, timing and dosage of oxytocin administration are critical factors which require further research. The administration of high doses of oxytocin may induce hard pressure upon the piglets and their umbilical cord, leading to hypoxia but the literature is ambiguous. It may also lead to uterine fatigue and a decreased reaction on physiological concentrations of oxytocin. Oxytocin can be employed for slow deliveries and/or after delivery of the 6th or 7th pig to ensure a prompt completion of farrowing.
  4. Use of other products in combination with prostaglandin:Administration of relaxin 24h prior to injection of PGF2α enhances the synchrony of the onset of parturition. Suggested hypotheses are the well-known effects of relaxin on cervical dilatation and sensitization of the uterus to the withdrawal of progesterone.
  • β-adrenergic blocking agent, e.g. Carazolol, 20 hours after PGF2α results in the prompt onset of labor, similar to the effects of oxytocin but without negative effects on the piglets. Its binding to the myometrial adrenergic receptors inhibit the tocolytic effects of adrenaline released in response to stress of farrowing.
  • α-2 agonists, e.g. Xylazine, 20 hours after PGF2α results in onset of farrowing process. It induces the contraction of the myometrium as oxytocin. But, xylazine causes sedation and vomiting, hence is not desirable in sows around parturition.
  • Corticosteroids are important for visceral maturation and parturition and their incorporation in an induction regime may prove beneficial under conditions where compromised lung maturity is the issue.

The dosage used with reference to the literature available: PGF2α: full dose = 10mg, half dose = 5mg; Cloprostenol: full dose = 175µg, half dose = 87.5µg; Oxytocin: 10-30 IU

Conclusion: Induced farrowing is an important herd management tool but if not practiced properly, it may affect the piglets and sow negatively. It might result in premature delivery of piglets which have lower birth weight and a lower growth rate. The goals of induced farrowing may differ between herds. The three main protocols used to induce parturition in sows are a single injection of prostaglandins, the split-dose technique and a combination of prostaglandin with the administration of oxytocin 20-24 hours later. The most ideal and preferable induction protocol is generally herd specific and hence the interventions must be monitored accordingly.