Over an Easter weekend on duty three recumbent ewes in late pregnancy were presented which had been misdiagnosed by farmers as listeriosis, pregnancy toxaemia and acute respiratory disease, respectively. All three ewes responded within five minutes to veterinary treatment of 40 mL of 40% of calcium borogluconate administered intravenously; relapse did not occur despite the lack of subcutaneous depot calcium injection. It is often assumed that hypocalcaemia should be readily recognised by shepherds but a UK survey revealed that 61.4 per cent of suspected hypocalcaemic ewes treated by farmers died, which raises serious doubts concerning diagnosis and/or treatment. An internet search also revealed some surprisingly confusing articles (Nosdol & Waage, 1981; Bickhardt et al., 1998) regarding the diagnosis and treatment of ovine hypocalcaemia. These data, and the increasing trend to sourcing information and advice via the internet, highlights the importance of veterinary practitioner diagnosis, treatment and advice for hypocalcaemia in sheep.
In the UK, hypocalcaemia is not uncommon in 3-crop or older ewes during late gestation, but can also occur sporadically during early lactation. Hypocalcaemia is often observed when ewes are brought down off hill grazing onto improved pastures prior to lambing. ‘Outbreaks’ of hypocalcaemia can result from errors in formulating home-mix rations, incorrect mineral supplementation, stress related events such as dog-worrying, movement on to good pastures prior to lambing, or following housing. A UK survey reported 0.4% prevalence of hypocalcaemia in pregnant ewes but only 3% of farmers sought veterinary attention.
[ Recumbent ewe diagnosed as respiratory disease by the farmer due to dullness and an increased respiratory rate. ]
[ The greyface ewe featured in Fig. 1 five minutes after intravenous calcium injection. ]
[ Recumbent ewe diagnosed as ovine pregnancy toxaemia by the farmer due to dullness and inappetence. ]
[ The greyface ewe featured in Fig. 3 five minutes after intravenous calcium injection. ]
The highest demand for calcium in sheep occurs 3–4 weeks prior to parturition due to calcification of fetal bones. Mobilisation of calcium from bone stores takes more than 24 hours; therefore periods of transient hypocalcaemia may result. During the early stages affected ewes become isolated from the flock and, although able to extend the pelvic limbs, are unable to raise themselves from their knees and assume sternal recumbency again within 10 to 30 seconds. Some sheep appear disoriented and hyperaesthetic, and pant. Over two to six hours the ewe becomes dull, weak, and unable to stand even when supported. There is rumen stasis with the development of bloat. The rectum is flaccid and may contain pellets of dried faeces which are not voided. Passive reflux of rumen contents may occur with green fluid present at the external nares and around the lower jaw. These findings, plus the presence of stridor, often result in treatment of the ewe for respiratory disease by the shepherd with a consequent delay in the request for veterinary assistance. There may be partial prolapse of the rectum/vagina. Unlike cattle, sheep do not assume lateral recumbency in the advanced stages of hypocalcaemia. Without appropriate therapy, the condition develops to coma, and death follows 24 to 48 hours after onset of recumbency.
[ Hypocalcaemia following movement of group onto lush pasture ahead of lambing. ]
[ The greyface ewe featured in Fig. 5 five minutes after intravenous calcium injection. ]
- • Ovine pregnancy toxaemia
- • Listeriosis
- • Acidosis resulting from carbohydrate overfeed
- • Respiratory disease
- • Copper poisoning
- • Rhododendron poisoning
- • Polioencephalomalacia
- • Sarcocystosis.
In sheep recumbent due to hypocalcaemia, serum calcium concentrations are below 1.0 mmol/L; serum 3-OH butyrate concentrations can be elevated, especially if the ewe has been inappetant for more than 24 hours. The rapid response of hypocalcaemic ewes to intravenous calcium infusion differentiates this condition from ovine pregnancy toxaemia and the other differential diagnoses listed above.
There is a rapid response to slow intravenous administration of 25–40 mL of a 40% calcium borogluconate solution given over 30 to 60 seconds (45–80 kg ewes). Eructation is observed 1–2 minutes after intravenous calcium administration. Characteristically, ewes will stand within five minutes of intravenous injection, urinate, defaecate, and wander off to rejoin the rest of the flock.
[ Recumbency (weakness) caused by hypocalcaemia. ]
[ The ewe featured in Fig. 7 two minutes after intravenous calcium injection. ]
[ Urination five minutes after intravenous calcium injection. ]
[ The ewe featured in Figs. 7–9 five minutes after intravenous calcium injection. ]
[ Recumbent ewe misdiagnosed by farmer as listeriosis (depression and left-sided ear drop). ]
[ Urination five minutes after intravenous calcium injection. ]
The response to subcutaneous administration of 60–80 mls of 40% calcium borogluconate solution injected over the thoracic wall behind the shoulder may take up to four hours, especially if the solution had not been warmed to body temperature and injected at one site. There is a marked localised reaction to subcutaneous calcium injection.
Addition of appropriate minerals to the ration during pregnancy and thorough mixing are essential. Outbreaks of hypocalcaemia occurring over two to three days may still result after stressful events such as movement or housing but these sheep respond promptly to appropriate therapy. At present, sheep rations are not formulated on the basis of cation-anion balance because hypocalcaemia has a sporadic occurrence with an excellent treatment response providing the sheep are correctly treated.
Three groups of sheep were defined by Berkhardt et al. (1998) based upon plasma concentrations of 3-hydroxybutyrate (3-OHB) and calcium; 214 ewes suffered from ketosis (pregnancy toxaemia, 3-OHB > 1.6 mmol/L), 195 ewes and 5 rams suffered from hypocalcaemia (Ca < 2.0 mmol/L), and 40 ewes were sick with both diseases simultaneously. They concluded that a diagnosis was not possible on the basis of clinical findings. Diagnosis based upon incorrect biochemical normal ranges leads to erroneous diagnoses and treatments e.g. 3-OHB > 1.6 mmol/L is consistent with severe energy deficiency only, whilst concentrations above 3 mmol/L are suggestive of pregnancy toxaemia but can occur associated with inappetance of more than 24 hours. There is little logic to their recommended treatment strategy for all three groups which included daily oral application of Na-propionate, Ca-lactate and K-chloride, and additional subcutaneous injection of Ca-borogluconate, vitamin D3, alpha-tocopherol and selenium. In sheep practice, a thorough clinical examination and response to intravenous calcium borogluconate injection within five minutes will confirm the diagnosis of hypocalcaemia without recourse to often confusing serum biochemical analyses. Farmers must be encouraged to present recumbent sheep for veterinary examination.
[ Lack of menace response in a ewe with pregnancy toxaemia; the ewe is standing but wanders aimlessly. ]
[ Ewe with listeriosis. The ewe is ambulatory with left-sided trigeminal and facial nerve paralysis. Stupor is caused by involvement of the ascending reticular activating system. ]
[ Ewe with listeriosis. Walk forward (propulsive) tendency shown by sheep with listeriosis is often confused with ‘head pressing’ behaviour. Careful examination will reveal further evidence of brainstem dysfunction in listeriosis cases (see Fig. 16). ]
[ Ewe with listeriosis (see Fig 15). There is right-sided trigeminal and facial nerve paralysis. ]
[ Ewe with listeriosis; there is depression (ARAS involvement), and left-sided trigeminal and facial nerve paralysis. ]
[ Dull anorexic ewe with secondary bacterial infection of ovine pulmonary adenocarcinoma. Rumen contents at the nostrils of ewes with advanced hypocalcaemia may be confused with primary respiratory disease. ]
[ Polioencephalomalacia is much more common in growing lambs than adult ewes. ]
[ Sarcocystosis is poorly described in adult sheep – unresponsive pregnancy toxaemia cases could be further investigated by cerebrospinal fluid analysis. ]
[ Seizure activity in pregnant ewe with peracute sarcocystosis. ]
CONTINUING PROFESSIONAL DEVELOPMENT
In order to test your understanding of this article, answer these multiple choice questions, or if you are a subscriber, go online at http://www.ukvet.co.uk, and find many more multiple choice questions to test your understanding.
- 1What was the report success rate when farmers treated ewes they diagnosed as hypocalcaemia?a. about 40 per centb. about 60 per centc. about 80 per centd. about 100 per cent
- 2The annual incidence of hypocalcaemia in UK flocks is reported to bea. about 0.1 per centb. about 0.5 per centc. about 1 per centd. about 2 per cent
- 3hypocalacaemia is most commonly seen affectinga. 2-crop or younger ewes during late gestationb. 3-crop or older ewes during late gestationc. 2-crop or younger ewes during early lactationd. 3-crop or older ewes during early lactation
Answers to the above questions appear on page 43 of the print version, and as supporting information in the online version of this article at: http://www.wileyonlinelibrary.com/journal/coan
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S1: Continuing Professional Development – Answers