Sheep at the best of times don't give a lot away when being assessed by a clinician. This can be a daunting trait when the examining clinician does not have the benefit of experience.
This article is not aimed at offering any ground breaking new concepts, but merely presenting observations that may help in the differentiation of observed cases.
The metabolic conditions that are seen in the Central West are pregnancy toxaemia, hypocalcaemia or a combination of both. I have not seen evidence of hypomagnesaemia, but accept that it may be involved in some of the cases we see, however, correction of low magnesium levels has not been undertaken as a primary treatment option.
The vast majority of metabolic cases are primary pregnancy toxaemia.
A mob of 800 mixed age ewes, with a majority being full mouth, in the Nyngan area, starting to lamb in August 2010, with about 5 months wool.
The history was that there was no supplementary feed provided. The producer had been noticing that a ewe was found down every couple of days. These downer ewes had been brought back to the yards, fed oats, and watered, but none of the six or so ewes had recovered and eventually died after 2-3 days. The LHPA was contacted when there were two recumbent ewes noted on one day. Both ewes were still alive on arrival, but were depressed with no inclination to rise when approached. BCS was determined to be about two for both of them. The pasture was inspected and found to be tall dried off natural grasses with a small amount of green butt growth. Post mortem examination on both ewes revealed a similar picture of twin foetuses, near full term, and a bronze coloured, slightly swollen liver.
A diagnosis of pregnancy toxaemia was made on the presenting signs, with the salient points that ticked the boxes for me of: Low, but constant losses occurring in older ewes that were being fed a poor quality feed in the last month of pregnancy, carrying twin lambs. For those younger clinicians that gain comfort from ancillary testing, I would have expected urinalysis to have revealed a ketonuria, but one was not performed here.
The advice was to move the ewes onto a lucerne paddock that was being saved to wean the lambs onto and trickle feed out oats with an Eskalin® additive.
Follow up with the producer 1 month later, reported a couple more losses in the ensuing week, then losses ceased.
I would classify this as a classic presentation. The producer may also have reported that, other than the recumbent ewes, other ewes were noted as standing with their chin elevated, or 'stargazing', and did not move when approached by dogs or humans while being aware of their presence - but he didn't.
The remaining metabolic cases diagnosed in the Central West are cases of hypocalcaemia.
A mob of 320 First cross ewes that had lambed in August-September 2010 in the Trangie area were yarded in October to treat with Clik® as a few had been noted as struck. The sheep were yarded on Monday, but the applicator gun was noted as non-functional when commissioned on Tuesday mid- morning. By the time a replacement gun was obtained from one of the neighbours late on Tuesday, a decision to start on Wednesday was made by the management. The sheep were left yarded. Management comprised of two brothers, 19 and 20 who had commitments to footy training on Tuesday night.
Wednesday morning revealed about 15 ewes down, mostly in sternal recumbency with their legs stretched out behind them. Those in this position showed depression and had an excess of clear mucous exudate around the nostrils. Others were still alert and making unsuccessful efforts to rise. Two were dead.
Upon arrival, armed with a box of Hypovec®, a presumptive diagnosis of hypocalcaemia was made based on the history, and management was supplied with a bag of Hypovec® , a 50ml syringe and an 18 gauge needle and instructed to dose every affected sheep subcutaneously in front of the shoulder, starting with the worst affected ewes. Management was instructed not to treat the two dead ewes.
The response was dramatic, with some of the severely depressed ewes first treated gaining their feet and wandering off just as the last couple of sheep were being treated. Most of the ewes recovered uneventfully, but two further ewes were euthanased after failing to recover within 48 hours.
This type of response is proof that the age of miracles has not completely left the veterinary profession.
The diagnostic indicators for me in this case were: Affected animals were mostly ewes with young lambs at foot, a large number were affected at once with a history of prolonged food withdrawal, the classic sternal recumbency with legs stretched out behind, the clear nasal exudates, but mainly the response to therapy. No ancillary tests were conducted in this case.
A mob of 250 four tooth Dohne cross ewes in the Coonamble district were yarded for crutching in October 2011. The ewes had lambs weaned off them about 1 month previously. They had not been joined. The shearers had failed to arrive on Wednesday morning to start crutching. The ewes had been yarded on Tuesday afternoon. No replacement shearers could be sourced, so the ewes were let out of the yards into a small holding paddock adjacent to the yards, some 36 hours after being initially yarded. Four ewes went down into sternal recumbency, with another one showing a staggering gait. Two of the original four died overnight, and a visit from the LHPA was sought by the breeder.
Clinical examination of two of the recumbent ewes revealed sternal recumbency with legs stretched out behind and an excessive clear mucous nasal discharge. Both ewes were assessed as having a BCS of four. Both ewes were moderately depressed. The third ewe was still attempting to get up, but, while being very alert, could do no more than drag herself along on her knees.
Based on history and presenting signs, an initial diagnosis of hypocalcaemia was made, and intravenous Hypovec® was administered with difficulty due to venous collapse. All three affected ewes were treated and a rapid response was expected. It did not eventuate. The first ewe died within 10 minutes of treatment and a post mortem revealed twin full term foetuses. The second ewe was showing a nil response to calcium therapy and the decision was made to euthanase. A post mortem inspection also revealed this ewe to be carrying twin full term foetuses.
A revised diagnosis of hypocalcaemia associated with pregnancy toxaemia was made.
Ancillary tests would have been useful in this case to help clarify the diagnosis, but Friday is not a good day to get samples sent from Coonamble.
The producer was embarrassed that his management was not as he had thought and the clinician was embarrassed because his initial treatment had not resulted in the recovery he had smugly predicted.
This case highlighted a number of important points: the history is not always accurate, both hypocalcaemia and pregnancy toxaemia can occur together - particularly in high BCS ewes, response to therapy is a very useful diagnostic tool, and it pays not to bet money on therapeutic outcomes.