The crude survival of cows which had suffered uterine prolapse in this study was low, 58% were alive 30 days later. This is similar to the study performed by Ishii et al. in Japan (61% crude survival) [13]. However, low compared earlier to studies by Carluccio (82%) [4] and Ødegaard (74%) [1]. In the current study 21% of animals were euthanised or underwent on farm emergency slaughter before treatment commenced, which is higher than the 10% reported by Ødegaard in 1977, and the 13% reported by Ishii et al. [13]. The reason that such a high proportion of the animals suffering from the condition were euthanized may be linked to large distances between farms and veterinary care in Norway. However, the most likely explanation is that there is a functional on farm emergency slaughter system available throughout Norway, meaning that many veterinarians and farmers would choose to ‘cut their losses’ and slaughter a cow to salvage some of her value rather than risking losing all her value by treating her [8, 9]. This opinion is supported by the positive univariate correlation seen in this study between general clinical state and likelihood of treatment.
Beef cows were more likely to be treated than dairy cows. Whilst it is true that dairy cows were more likely to be in a poor clinical state than beef cows, it is likely that the decision to treat beef cows is a multifactorial decision, with the desire to keep the dam alive to suckle perhaps being a motivation. The payment system for cattle undergoing on farm emergency slaughter in Norway is such that a greater proportion of the value of a beef cow, compared to a dairy cow, is lost if it is slaughtered on farm rather than in a slaughterhouse. Statistically there was no difference in hazard of death for beef and dairy cattle after treatment, which perhaps indicates that some more dairy cows could have been treated and recovered. Both recumbent animals and those with an injured and/or oedematous uterus were less likely to be treated than standing animals with an undamaged uterus. Both factors also are likely to have contributed to the overall clinical assessment of the animal. Animals that were recumbent and/or had an injured uterus were probably more likely to be considered in a poor state than those that were standing with no visible complications This is supported by the fact that in the multivariable logistic regression model built to investigate factors associated with treatment both production system and uterine injury remained in the final multivariable model whilst general clinical appearance did not.
Most veterinary surgeons treated uterine prolapse similarly. The overwhelming majority (> 80%) used caudal epidural analgesia, and a prolapse board (or some other aid to lift the uterus prior to its replacement). The vulval lips were held together in some way in all but two of the treated cases. This is interesting as the value of suture placement has long been debated and in fact no evidence base is available to show that this practice is beneficial [2, 10, 11]. Further it is known that placement of sutures can have negative implications for an animal’s health if prolapse recurs [2, 10]. A previous study has shown that a considerable proportion of veterinary surgeons do not feel that sutures have a benefit – but place them if the farmers would like them to be [11]. Whilst this is understandable it does present some ethical dilemma given that the founding stone of medical and veterinary ethics is primum non nocere (“above all, do no harm”) [16]. Therefore, further study into the value of placing potentially harmful sutures should be undertaken.
The immediate, and 30-day, survival rate after treatment in this study was similar but slightly lower than the majority of [1, 3,4,5, 17], but not all, studies [13]. The current study looked at 30-day and 180-day survival, other studies have typically used a two-week period to investigate the immediate survival after prolapsing [3, 5, 13]. The longer time was used in this study to include animals that may have been treated with pharmaceuticals before being slaughtered once medicine withdrawal periods were complete. Longer term survival in a herd is complicated and often linked to reproductive performance and herd management issues. The reproductive performance of these animals was not studied in the current study because the study design did not lend itself to gathering reliable information on these events.
Only two factors were found to significantly influence survival in the first 30 days post treatment. These were general clinical state as assessed by the attending veterinary surgeon and the time taken for a veterinary surgeon to reposition the uterus. If reparation took 20 min or less hazard of death in the first 30 days was lower than if reparation tool more than 20 min. It is important to be aware that the effect described is an association which is not the same as a causal relationship. Ideally prognostic indicators would allow for a veterinary surgeon to decide whether to commence treatment or not. However, knowledge of post-treatment prognosis is important as has been highlighted by Gregory [7], who also found a correlation with survival and rapid uterine reparation. Most practitioners did not use antimicrobial treatment routinely when replacing a uterus, which contrasts with expert opinion on the subject [11]. This may be because they felt this was not necessary or it may be because of a desire to not prohibit the on farm emergency slaughter of animals by treating with medicines that have a meat withdrawal period. It is therefore interesting that the use of local intrauterine antibiotics tended to be associated with a lower hazard of death in the 30 days post treatment in this study. This effect was not seen in the multivariable model. It should be noted that this study was not designed compare treatments and define a gold standard treatment so these findings must be treated with caution.
The value of veterinary opinion regarding general clinical appearance was shown in the current study to be correlated with the hazard of death after treatment up until Day 30 and Day 180 in the univariate survival analysis. This is an important finding as it demonstrates that veterinary clinical opinion is important – and the most accurate prognostic indicator determined by this study. The method used by veterinary surgeons to evaluate clinical state was left ‘open’. In other words, no guidance as to which criteria should be evaluated were included in the questionnaire. Discovering more about how veterinarians evaluated clinical state could be an interesting area for further research.
The strength of the association was such that general clinical appearance also remained in the final multivariable survival model which was built to see which factors impacted on the hazard of death in the first 30 days after treatment. Interestingly the occurrence of vaginal prolapse in the pregnancy prior to the prolapse also tended to be associated with an increased hazard of death in the 30 days following treatment of uterine prolapse. This is the first study reporting this relationship. It makes biological sense, as a cow that has previously suffered from a vaginal prolapse may be more likely to have a pre-existing pathology in the reproductive tract at the time of uterine prolapse which could potentially provide irritation making a recurrence of the prolapse more likely. Damaged vulval or cervical tissue may also be infected by bacteria which could increase the likelihood [2] of infection of the uterus with pathogenic bacteria leading to post-partum uterine infection and increased mortality.
A positive association between the incidence of vaginal prolapse and uterine prolapse has been previously reported in Norway in the 1970’s [1]. However, work performed worldwide after this has not described this relationship [2]. Vaginal prolapse in pregnant cows is a common finding which is generally only reported if the prolapse is severe and confers a problem for the cow. Consequently, it is likely that the true incidence of vaginal prolapse is under-reported. A possible association between vaginal prolapse, uterine prolapse and survival after a uterine prolapse could potentially be linked but under-reporting has meant that this association has been difficult to document in international studies. It could also be that there is a predisposition for this relationship in Norway – where the predominant dairy breed is the Norwegian Red. This article highlights the need for more knowledge in this area.
Unfortunately, the statistical power to identify differences between the explanatory variables in this study is low. Ideally the population size would have been greater. Selection of veterinary surgeons to participate in this study was not random and some data collection was incentivised (blood sampling). Previous researchers have commented that the sporadic nature of uterine prolapse has made the data collection difficult. It is unlikely that the sampling will have biased the results of the study. Not targeting participation would have likely reduced the number of cases reported and reduced the statistical power of the study. Despite having limited statistical power, this study has value as it not only revisits an old problem 30 years after most of the research in the field was published, but also because it allows for other researchers to use these data in combination with reports from other workers to perform a meta-analysis of data to provide a stronger evidence base on which to make clinical decisions. These data are limited in so much as they refer to Norwegian cattle and Norwegian production systems. Those looking to apply the findings of this study elsewhere should consider the presence of a well-functioning on farm emergency slaughter service and the fact that predominant dairy breed in Norway is the Norwegian Red when interpreting data. However, within Norway the study has a high validity and is directly applicable to farm animal practice.
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