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CASE NOTES


Prepartum vaginal prolapse and dystocia in Babydoll Southdown ewes

Lou Baskind, South East Local Land Services, Braidwood

Posted Flock & Herd August 2023

Introduction

This case report details an unusual occurrence of prepartum vaginal prolapse and dystocia in Babydoll Southdown sheep, and a possible association with deficiency of Vitamin D following below average solar exposure.

Signalment and history

The affected stud was a small flock of 'Babydoll-type' Southdown ewes on the Southern Tablelands of NSW. The flock consisted of 14 ewes in total, 11 of them multiparous and three maiden. Two of the ewes were homebred, and neither of these suffered prolapse. All the affected ewes were bred at the same source stud in southern Victoria and had been on this property for a period of between six months and three years. Ages ranged from two to six years. The Victorian-bred sheep had very short-docked tails, notably shorter than the homebred sheep.

Standard routine husbandry was up-to-date and internal parasites well managed with tactical worm control including onsite worm egg counts (WECs). The flock were given a quarterly oral drench with a proprietary Vitamin E liquid.

At joining and during early pregnancy they grazed ample high quality mixed species pasture and nutritional status was high. In the last two months of pregnancy, rainfall far exceeded the annual average. The pasture was then short and green, and it became waterlogged. Pasture growth rates were very slow in these months.

The pasture was so wet that the low dry matter content was thought to be limiting intake and a concentrate supplement was introduced. The ewes were fed a grain-based pellet with protein of 14% and metabolisable energy of 12 Mj/kg. The pellets were gradually introduced and increased to 1kg/head/day by one month prior to lambing.

There was ad lib access to a dry loose lick of equal parts salt, lime and Causmag.

Clinical signs

The ewes were joined to rams in the first week of April 2021. In the last four weeks of gestation, seven ewes (50%) suffered vaginal prolapses. Two of these, and another that did not prolapse, had become recumbent in the previous weeks and responded rapidly to a '4-in-1' metabolic mineral injection consisting of calcium, magnesium, phosphorous and glucose.

Vaginal prolapses were treated initially by the stud manager with gentle washing with lukewarm water, copious veterinary lubricant, and gentle reduction of the eversion with gloved hands. Once replaced, a prolapse harness was attached to support the tissue in position. If ewes continued to strain, went down or dystocia was detected, private veterinary intervention was sought.

Image of ewe wearing prolapse harness
Image 1. Southdown ewe with Rurtec Limited ADLAM™ Versatile Lambing Harness as management for vaginal prolapse. Image thanks to Jennie Curtis.

Four of the affected ewes required intervention from a private veterinarian for dystocia, and three of them died of complications. There were six neonatal mortalities across these three, with only one lamb surviving. Two had started labour prematurely, and their lambs were aborted/stillborn or non-viable.

There were also two lambs found dead presumed either stillborn or non-viable to an affected ewe. The eight lamb mortalities accounted for 28% of the lambs bred.

The private veterinarians remarked that the clinical picture included failure of cervical dilation, poor contraction strength, and in one case blood calcium was low even after successful treatment with the '4-in-1' metabolic mineral injection.

The stud manager also noted that in recent months some sheep would suddenly stumble for no obvious reason while walking. At the peak of the problem, the flock lacked appetite and was not eating the supplementary pellets.

Aside from treatment with a '4-in-1' mineral injection, the manager reported that the greatest improvement seemed to be the result of providing ad lib high quality lucerne hay.

Background

The frequency of vaginal prolapse is reportedly higher in sheep than in any other of the domestic mammals. Its incidence is usually less than 1% but can reach 15% in certain conditions in certain flocks. The condition can have a significant economic impact associated with treatment costs, dystocia and subsequent complications, perinatal mortalities and culling.

The aetiology of the disease is not fully understood with vaginal prolapse considered to be a multifactorial disease. A combination of relaxed reproductive structures and increasing abdominal pressure at the end of pregnancy, combined with predisposing or other factors, causes eversion of the vaginal mucosa. Severity can vary, from mild eversion only when the ewe is recumbent, to large chronic prolapses to the level of the cervix and involving the bladder.

Based on a dozen references, there is a good evidence base for some of the reported risk factors, while others appeared more anecdotal. Reported risk factors are listed as subheadings with case findings described below each subheading:

Vitamin D, calcium, or phosphate status

Uncertain. There were indications of a potential association with a ewe having low blood calcium at time of treatment, and the syndrome including poor muscle contractility and several ewes showing a rapid response to supplementation with a combination of calcium, magnesium, phosphorus and glucose. This factor was also of interest because there had been a period of unusually low sun exposure due to unusually high rainfall and overcast days, including during the preceding summer when most of the cholecalciferol (vitamin D3) would normally be produced in the skin in response to direct overhead sun. During the event, the diet was primarily grains-based, which contain little Vitamin D. Additionally, Abbot (2018) reports that a tendency to stumble and a slight stiffness of movement may be early signs of osteomalacia. The provision of well sun-cured lucerne hay, typically a good source of vitamin D, appeared to improve the situation.

Pregnancy, particularly just prior to lambing

Yes.

Breed or type/hereditary

Yes. British breeds seem to be more susceptible. There was an annual low incidence in the source stud.

High plane of nutrition in early pregnancy

Yes.

Overfeeding or being in high body condition

Uncertain. The stud manager prioritised obesity prevention and had attempted to reduce weight in mid-pregnancy. Rations were calculated using Department of Primary Industries Drought and Supplementary Feed Calculator App.

Multiple foetuses

Uncertain. Foetal numbers ranged from one (n=1) to three (n=3).

Multiparity

Uncertain. Parity ranged from one (n=1) to five (n=1), with four of the affected ewes having a parity of four.

Short tail docking

Uncertain. All affected ewes had very short tails and short tail length is frequently anecdotally linked to vaginal prolapse. However, peer-reviewed evidence is hard to come by. Fisher et al. (2004) wrote that while certainly associated with the incidence of rectal prolapse, the incidence of vaginal prolapse does not appear to be affected by tail length.

Fat mobilisation

Uncertain. The report of inappetence and restricted feed are suggestive, however histopathology of the liver of one deceased ewe showed no significant abnormalities.

Lying down/recumbency

Uncertain. Some ewes did go down, but there wasn't a clear temporal link with eversion of vaginal tissue.

Non-flat / sloping country

No. The property has a minor slope of 4%.

Bulk, weight, or 'fill' of feed in gut/high fibre diet

No. There was low fibre in the diet.

Previous vaginal prolapse

No. None of these individuals had prolapsed previously.

The role of Vitamin D in vaginal prolapse

Vitamin D is vital in calcium homeostasis and musculoskeletal function. It is known that deficiency leads to rickets and osteomalacia, but more recently it has been suggested that insufficiency (a milder form of deficiency) may have clinical significance in a range of different conditions and organ systems, and a role in the pathophysiology of some cancers, cardiovascular disease, diabetes and skeletal and smooth muscle function. Studies in humans have suggested an association between Vitamin D status and muscle function of the pelvic floor. Allot et al. (2020) found that when a 1ml dose of a Vitamin A, D and E parenteral injection was given to pregnant sheep, the odds of suffering vaginal prolapse were reduced compared to controls.

Diagnostic Tests

Pursuing the curiosity regarding Vitamin D status, all 11 surviving ewes (including the four that had prolapsed and recovered) were tested one week after the end of lambing. Blood samples were collected in serum tube, immediately wrapped in aluminium foil to prevent sun exposure, kept chilled, and serum separated within two hours of collection by centrifuge. Phosphate, Albumin, β-hydroxybutyrate (BHB) and Calcium were tested at Benalla Regional Laboratory, and 25-hydroxyvitamin D3 at PathWest.

The biochemistry results were largely unremarkable, with a mild hypophosphataemia in three individuals. Ten of the 11 ewes had Vitamin D3 levels below 50 nmol/L.

Date 28/09/2021
Sample Vitamin D3 25 OH mmol/L (LCMS)
0001 43
0002 35
0003 71
0004 26
0005 23
0006 30
0007 41
0008 45
0009 34
0010 49
0011 47

There is no established reference range for Vitamin D3 25 OH in sheep. Hurst et al. reviewed the profile of Vitamin D across species in 2020. Based on that review, it seemed reasonable to use the human reference range (0-25 nmol/l severe deficiency, 25-50 nmol/l insufficiency, and > 50 nmol/l sufficient) as a guide to interpreting these results.

Chart of vitamin D profiles in sheep blood
Image 2. Vitamin D metabolite concentrations across species measured by LC-MS/MS (Hurst et al. 2020)

The results were suggestive of Vitamin D insufficency. Given that there had been a month of normal spring sunshine preceding the test, it was hypothesised that Vitamin D levels may have risen since the outbreak. The normal nadir of Vitamin D levels in sheep is in late winter-spring.

Vitamin D3 25 OH was then repeated 10 months later, in the following late winter, prior to the high risk period for prepartum vaginal prolapse. Nine ewes from the initial group were still available for testing, and samples were taken five weeks before they were due to lamb. Sun exposure had again been below average during the preceding summer (2021/2022). On this occasion there was clearly a deficiency.

Date 25/07/2022
Sample Vitamin D3 25 OH mmol/L (LCMS)
0001 15
0002 <10
0003 14
0004 <10
0005 18
0006 22
0007 11
0008 <10
0009 <10

Management changes and follow up

In response to the diagnosed Vitamin D deficiency, all pregnant ewes were given 1ml of a Vitamin ADE parenteral injection, four weeks before they were due to lamb.

The stud manager made numerous other changes in 2022 to avoid a repeat of the syndrome. Weight gain was restricted in early pregnancy, supplementary feeding of pellets pre-lambing was kept to a minimum, and high quality lucerne hay was provided. Voluntary recumbency was limited, and exercise increased, by manipulation of feed on offer and its location: these changes meant sheep were grazing most of the day and had to take exercise to receive 'treats'. They were also provided with more palatable mineral lick blocks. Waterlogging of the pasture also did not occur over the winter to the same extent.

The 2022 lambing was very successful, and the outbreak of vaginal prolapse that occurred in 2021 was not repeated. Of 20 ewes bred in 2022, there were no significant prolapses. Two of four that prolapsed previously had a harness attached pre-emptively as they were displaying a minor eversion of vaginal mucosa when lying down. No veterinary intervention was required, and only two ewes required minor lambing intervention from the stud manager. There was only one neonatal lamb mortality (3%) and nil ewe mortalities.

Conclusion

As to what part Vitamin D played in this case is hard to say, because many management factors changed between 2021 and 2022 and the response to Vitamin D supplementation cannot be assessed in isolation. However, it is possible that Vitamin D insufficiency was a contributing factor, and the recording of this small case report may contribute to the body of knowledge if the role of Vitamin D in vaginal prolapse continues to be investigated by others.

References

  1. Abbot K (2018) Disorders of ewes in late pregnancy in The Practice of Sheep Veterinary Medicine pp184-198 University of Adelaide Press
  2. Allot BS, Dittmer KE, Kenyon AD and Elder PA (2020) Preliminary investigation of the effect of treating sheep during pregnancy with a vitamin A, D, E formulation on the incidence of vaginal prolapse New Zealand Veterinary Journal 68(3):193-197
  3. Dittmer KE and Thompson KG (2011) Metabolism and Rickets in Domestic Animals: A Review Veterinary Pathology 48(2):389-407
  4. Edgar D (1952) Vaginal eversion in the pregnant ewe Veterinary Record 64(1):852-858
  5. Ennen A, Kloss S and Wehrend A (2010) Prolaps vaginae ante partum beim Schaf. Tierärztliche Praxis Ausgabe G: Großtiere/Nutztiere 38(2):120-126
  6. Fisher M, Gregory N, Kent J, Scobie D, Mellor D and Pollard J (2004) Justifying the appropriate length for docking lambs' tails - a review of the literature Proceedings of the New Zealand Society of Animal Production 64:293-296
  7. Hurst EA, Homer NZ and Mellanby RJ (2020) Vitamin D Metabolism and Profiling in Veterinary Species Metabolites 10(9):371
  8. Low JC and Sutherland HK (1987) A census of the prevalence of vaginal prolapse in sheep flocks in the Borders region of Scotland The Veterinary Record 120(24):571-575
  9. McLean JW (1956) Vaginal prolapse in sheep New Zealand Veterinary Journal 4(2):38-55
  10. McLean JW (1957) Vaginal prolapse in ewes—Part III: The effect of topography on incidence New Zealand Veterinary Journal 5(3):93-97
  11. Noakes DE (2001) Chapter 5 - Prolapse of the vagina and cervix in Noakes DE et al. (Ed.) Arthur's Veterinary Reproduction and Obstetrics (Eighth Ed.) pp145-153 W.B. Saunders
  12. Parker-Autry CY, Burgio KL and Richter HE (2012) Vitamin D status: a review with implications for the pelvic floor International Urogynecology Journal 23(11):1517-1526

 


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