Christine Pelland from South West Ontario Veterinary Services, Using Oxytocin Judiciously: Too Much Of A Good Thing Can Be A Problem

Oxytocin is a hormone produced in the brain of the gilt or sow. The production of oxytocin is stimulated by the suckling process. Oxytocin causes the smooth muscle in the udder to contract and is responsible for the “milk let down” reflex . Oxytocin is also important in the natural farrowing process. Here again, oxytocin causes contraction of smooth muscle in the uterus and this helps to maintain gentle rhythmic uterine contractions and muscle tone. Oxytocin injectable is one of several “uterotonic” drugs that help to stimulate contraction of uterine muscle. When the farrowing process slows down, Oxytocin injectable can be administered to the farrowing gilt or sow in order to stimulate uterine contractions. The use of the proper dose of Oxytocin will quite predictably result in a reduction of farrowing duration. When used properly it can be an important aid in the farrowing process. As with most things in life there can be too much of a good thing. Excessive use of oxytocin can lead to piglet hypoxia as a consequence of interference with normal blood flow in the umbilical cord. Hypoxia can result in struggling of the piglet in the birth canal and this struggling often increases the amount of meconium (fetal pig poop) that is visible during the farrowing process. Hypoxia can lead to increased stillborns or piglets that are weak at birth. Hypoxic piglets are prone to having reduced intake of colostrum and this can result in disease problems. An oxytocin dosage that is intended to work as an intramuscular dose in the neck can be quite excessive if that same dose is given subcutaneously beside the vulva. The devil is in the details.

Oxytocin is a prescription drug and is used in consultation with your herd veterinarian. The dosages and protocols for oxytocin in the literature and lay press are numerous and quite variable. Even the label directions can be a problem in some situations. The following are common veterinary recommendations that can help guide the judicious use of  oxytocin on your farm:

  • Administer oxytocin only after you have internally checked the gilt or sow to assure there is nothing blocking the reproductive tract (ie. A stuck piglet that just needs to be shifted).
  • Limit usage in gilt litters. Gilts tend to be less predictable than sows in their response to oxytocin.
  • For a normally farrowing sow, it is not ideal to  use oxytocin until a minimum of  approximately 6 pigs have been born.
  • Use oxytocin when a sow has not had a piglet for over 30 minutes
  • Only use a maximum of 2 doses per sow (either given in the muscle OR perivulvar).

The increased numbers of total born in today’s hyperprolific sows has had a tendency to increase farrowing duration. These Brazilian and US researchers wanted to revisit the effects of oxytocin on farrowing duration, birth interval, farrowing assistance, stillbirth rate, and piglet viability traits by performing a systematic review and a meta-analysis. The search for studies was performed during January 2020 using the PubMed, ISI Web of Science, Science Direct, and Scopus databases. The literature search was conducted using the key words: oxytocin, pig, farrowing, stillbirth, piglet, and dose. Studies which evaluated the effects of oxytocin on farrowing duration, birth interval, stillbirth rate, and farrowing assistance were included in the review. Of 1215 articles, 23 (1.9%) were selected for fulfilling the criteria for inclusion in the present study. A high variety of oxytocin doses was observed among studies.

The researchers found the following when oxytocin was used as a standard injection even if there was no apparent farrowing problem:

  • Oxytocin increased (30%; P < 0.05) the stillborn proportion in the litters compared to control sows that received no oxytocin.
  • Oxytocin increased the need of farrowing assistance by 137% (P < 0.01) compared to control.
  • Oxytocin reduced the farrowing duration by 18% and the birth interval by 17% ( as predicted)

Take Home Messages

  • When used judiciously, oxytocin is a valuable tool that can be used to shorten farrowing duration of hyperprolific sows and as an aid in resolving farrowing difficulties .
  • If used as a standard injection, oxytocin will cause more harm than good by increasing the incidence of hypoxia and stillbirths in females that otherwise were not having any farrowing difficulties. Therefore, the criteria to use these drugs should be based on individual cases.
  • If you have any questions about oxytocin use you should contact your herd veterinarian.

Ref: Bruno B D Muro , Rafaella F Carnevale , Ines Andretta , Diego F Leal , Matheus S Monteiro , André P Poor , Glen W Almond , Cesar A P Garbossa  Effects of uterotonics on farrowing traits and piglet vitality: A systematic review and meta-analysis   Theriogenology . 2021 Feb;161:151-160. doi: 10.1016/j.theriogenology.2020.12.003. Epub 2020 Dec 9.