50
EQUINE VETERINARY EDUCATION / AE / JANUARY 2020
with RFM that did not undergo manual removal. Intrauterine treatments were in the form of an antibiotic infusion post- breeding. This paper acknowledged that due to a lack of blinding, there may have been bias towards mares that underwent manual removal in selecting animals to receive these interventions and that this may have positively influenced fertility outcomes. Sevinga et al. (2002) measured an array of fertility
parameters (for example pregnancy rate per cycle, pregnancy losses) and concluded that there were no significant differences in the outcomes between mares with RFM that were removed manually and those with RFM that expelled the FM spontaneously or following medical intervention. Cuervo-Arango and Newcombe (2009) measured the accumulation of free intrauterine fluid, as well as pregnancy rate at first service and pregnancy rate at the end of the season. These authors’ also found no significant differences between mares that had early manual removal of FM and those that passed FM naturally. They concluded that early manual removal of FM has no detrimental effects on subsequent fertility of the mare.
Clinical implications
Manual removal of FM may be performed without negatively affecting fertility of the mare; however, the evidence is insufficient to recommend manual removal in all cases. All data that are currently available relate primarily to
heavy breed horses that are known to have a higher incidence of RFM than light horse breeds. The application of results from heavy breeds directly to other breeds may not be appropriate as there is potential for varied responses to manual removal between breeds. Equine clinicians should consider manual removal as a
valid treatment option in heavy breed horses and also in high risk cases that have failed to respond to conservative therapy and repeated oxytocin administration. This approach of implementing manual intervention following oxytocin treatment is in agreement with the conclusions of Vandeplassche et al. (1971), despite this paper regularly being cited to describe the risks of manual removal of FM. The advantages of manual removal of FM are likely to
exceed the risks to mare health and fertility; however, mares which undergo the procedure may require closer monitoring and concurrent intrauterine treatments to facilitate rebreeding. Prolonged placental retention time is shown to have greater negative influence on pregnancy rates in Thoroughbred mares compared to heavy draught mares (Ishii et al. 2013), further supporting the need for timely removal of RFM in these mares. The underlying aetiology of retention of FM may influence
the effects of manual removal and thus future fertility outcomes. For example, it is possible that the response to
manual removal will be different in mares with RFM due to fibrotic adhesion of the allantochorion to the endometrium compared to mares with RFM due to secondary uterine atony. Mares experiencing secondary uterine atony have decreased oxytocin receptor expression in the endometrium and allantochorion, reducing the likelihood of successful expulsion of FM with oxytocin therapy alone (Rapacz-Leonard et al. 2015). This increases the indication for manual removal of FM in cases of secondary uterine atony, as oxytocin therapy is less likely to be successful.
© 2019 EVJ Ltd
Conclusion
Manual removal of RFM has previously been discouraged based primarily on anecdotal and observational evidence. The three recent publications on the effects of manual removal of FM on mare fertility that have been discussed in this article, do not support these long-held beliefs. Further investigations, especially in light horse breeds, are warranted. Evaluation of FM removal techniques and time of removal relative to parturition would be essential if manual removal is to be considered in a routine treatment protocol for RFM in the mare. However, the manual removal of RFM should be considered in relation to substantially proven and successful techniques, such as those described by Burns et al. (1977) and Meijer et al. (2015).
Author’s declaration of interests No conflicts of interest have been declared.
Ethical animal research
Ethical review not applicable for this critically appraised topic.
Source of funding None.
Acknowledgements
We thank Lee-Anne McInerney for her valuable assistance with database searches and referencing.
Authorship M. Platt and A. Walker made a major contribution to study design, search execution, analysis and interpretation of results and preparation of the manuscript. A. Gunn contributed to study design, analysis and interpretation of results, editing of the manuscript. All authors gave their approval of the final manuscript.
References
Brinsko, S.P. (2007) Common procedures in broodmare practice: what is the evidence? Vet. Clin. North Am. Equine Pract. 23, 385-402.
Burns, S.J., Judge, N.G., Martin, J.E. and Adams, L.G. (1977) Management of retained placenta in mares. Proc. Am. Ass. Equine Practnrs. 12, 381-390.
Cuervo-Arango, J. and Newcombe, J.R. (2009) The effect of manual removal of placenta immediately after foaling on subsequent fertility parameters in the mare. J. Equine. Vet. Sci. 29, 771-774.
Ishii, M., Jitsukawa, T., Shimamura, T., Utsumi, A., Endo, M. and Yamanoi, T. (1999) Effect of placental retention time and associated treatments on reproductive performance in heavy draft horses. J. Anim. Sci. 19, 117-121.
Ishii, M., Aoki, T., Yamakawa, K., Magata, F., Gojo, C., Ito, K., Kayano, M. and Nambo, Y. (2013) Relationship between placental retention time and the reproductive performance at the foal heat in thoroughbred and a comparison with heavy draft. J. Equine Sci. 24, 25-29.
Continued on page 53
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76
