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BestBETs for Vets
Oxytocin versus carbetocin administered to cows after uncomplicated calvings and subsequent fertility

Abstract

BestBETs for Vets are generated by the Centre for Evidence-based Veterinary Medicine at the University of Nottingham to help answer specific questions and assist in clinical decision making. Although evidence is often limited, they aim to find, present and draw conclusions from the best available evidence, using a standardised framework. A more detailed description of how BestBETs for Vets are produced was published in VR, April 4, 2015, vol 176, pp 354-356.

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Clinical scenario

During a visit to one of your dairy farm clients, the owner asks for your advice about managing his cows following calving. He currently gives all of his cows an injection of oxytocin after calving to promote uterine involution, and feels it helps get the cows back into calf more quickly. One of his neighbours has recently switched to using carbetocin instead, and he asks whether you think he should do the same. You wonder whether there is any evidence that switching to carbetocin might have a positive impact on fertility in this herd.

The question

In [postparturient cows] does [exogenous oxytocin compared with carbetocin] improve [subsequent fertility]?

Search strategy

The search strategy can be viewed at https://bestbetsforvets.org/bet/27, and it is also available as a supplement to this article on Veterinary Record's website at http://veterinaryrecord.bmj.com/content/179/7/175

Search outcome

▪ 377 papers found in Medline search

▪ 376 papers excluded as they did not meet the question

▪ One total relevant paper from Medline

▪ 493 papers found in CAB search

▪ 489 papers excluded as they did not meet the question

▪ Three papers excluded as they are in a foreign language

▪ One total relevant paper from CAB

▪ One relevant paper from both Medline and CAB Abstracts

Search last performed

March 23, 2016

Comments

An additional paper (Bajcsy and others 2006) was identified which compared oxytocin and carbetocin; however, it focused on measuring outcomes related to uterine contractility. As this outcome was not of direct relevance to the question, the paper was excluded.

Summary of evidence

Paper 1: Effects of the administration of oxytocin or carbetocin to dairy cows at parturition on their subsequent fertility (Barrett and others 2009)

Patient group: Five-hundred-and-one Holstein-Friesian dairy cows on five farms. Cows were allocated into three groups, and for groups receiving a treatment this was administered within six hours of parturition. Group 1 received 25 iu oxytocin, group 2 received 0.35 mg carbetocin and group 3 received no treatment.

Study type: Randomised controlled trial

Outcomes: The occurrence of periparturient hypocalcaemia and retention of fetal membranes beyond 12 hours following calving was observed. An endometritis score between 28 and 42 days after calving was noted. Reproductive performance (ie, median calving to first insemination interval, first insemination pregnancy rate, median calving to pregnancy interval and inseminations per pregnancy) was recorded.

Key results: The median calving to first insemination interval, the first insemination pregnancy rate, the median calving to pregnancy interval and the inseminations per pregnancy were all similar between cows receiving oxytocin compared to those receiving carbetocin.

Study weaknesses: Treatments were not allocated randomly but sequentially in chronological order which may introduce some selection bias. There was limited detail in the methods section about how the farms were recruited and some basic data were missing, particularly in terms of comparability between groups in relation to age, parity and reasons for drop-out. While assessment of endometritis score was blinded, there did not appear to be any other blinding at administration of treatment or assessment of outcome. The sample size was not justified and so the study may have been underpowered. While the methods stated that statistical analyses were conducted to compare the three groups in terms of reproductive performance, P values were not stated for these analyses. The authors did not state whether ethical approval had been obtained to undertake the study.

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Comments

Given that only one study was identified, and that there were various limitations to this study, an adequately powered and randomised controlled trial would need to be conducted to answer this question with greater certainty. However, given that few differences were found between the groups, it may be beneficial to explore the literature examining the use of oxytocin compared with no treatment, or carbetocin compared with no treatment.

Bottom line

The current evidence suggests that there is no difference between oxytocin or carbetocin given after calving in relation to subsequent fertility.

Authors of this BestBET for Vets

Natalie Robinson and Marnie Brennan, University of Nottingham.

BestBETs for Vets are generated by the Centre for Evidence-based Veterinary Medicine (CEVM) at the University of Nottingham. More information and other BestBETs for Vets can be found at https://bestbetsforvets.org/index. BestBETs for Vets are led by Rachel Dean, Kathryn Wareham and Marnie Brennan at the CEVM.

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Disclaimer from the CEVM

The BETs are a summary of the evidence found on a topic and are not clinical guidelines. It is the responsibility of the individual veterinary surgeon to ensure appropriate decisions are made based on the specific circumstances of patients under their care, taking into account other factors such as local licensing regulations. Further terms and conditions are at https://bestbetsforvets.org/disclaimer

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