CASE NOTES


NSW STATE REPORT WINTER 2013

Many district veterinarians from across the state reported pregnancy toxaemia. Amy Shergold (based at Wagga) reported hypocalcaemia and pregnancy toxaemia in around 20 of 800 Merino lambing ewes, mostly with twins and triples. The ewes collapsed as they began lambing. They were running on a poor lucerne paddock but were fed hay and had ad lib access to corn in self-feeders and to a loose lick containing calcium. D-lactate levels were normal ruling out grain poisoning but BHB levels were elevated.

Belinda Edmonstone (from Forbes) has seen more cases of pregnancy toxaemia and/or weak ewes collapsing than usual. Belinda considered that the ewes ‘lost too much condition over autumn and the colder weather has been enough to push them over the edge.’ Further down the Lachlan, Kasia Hunter (based at Condobolin) reported pregnancy toxaemia in a mixed age group of first cross ewes that were yarded for assessment by a livestock agent during the last month of their pregnancy. Unfortunately, the farmer was unaware they were so close to lambing. Fifteen of 200 died. Attempts at treatment were unrewarding.

Dan Salmon commented that it was ‘close to the worst year for pregnancy toxaemia in the Riverina that I can recall.’ ‘A blip in nutrition in an otherwise unimpressive 2012 meant that there was a fairly good conception.’ ‘The return to poor seasonal conditions meant that the ewes were trying to maintain a lot of pregnancies on poor dry feed or whatever fell off the back of a truck.’

Dan remarked that ‘some ewes went down after crutching two months before lambing and the problem kept on going.’

‘Compounding this, on the pastoral country between the Billabong Creek and the Murrumbidgee River was an apparent preference for the dry residue of the summer-active perennial grasses that grew in the summer of 2011-12. These were almost worthless as anything but bedding or kindling (3MJ/kg) but some sheep preferred it to maize.’ Dan added that in his district, lamb-marking percentages ‘fluctuated wildly from quite good to relatively abysmal, mostly depending on the amount of supplementary feed.’

Alan Taylor (based at Molong) investigated a case of arthritis in six of 1,000 lambs at marking. The problem appeared in the late lambs at the end of an unusually wet period. Alan submitted an entire joint from a three-week-old lamb with a markedly swollen carpus from which Histophilus somni was isolated.

Jill Formosa saw a case of Mannheimia haemolytica mastitis in young Poll Dorset ewes near Merriwa. Jill speculated that a large number of multiple lambs contributed to spreading Mannheimia due to multiple suckling.

Kasia Hunter reported a case of urea poisoning with 17 of 700 ewes dying after consuming urea that had fallen from a truck. All three samples had elevated ammonia levels in the aqueous humour. On the subject of intoxication, Jillian Kelly investigated a case of marshmallow poisoning. The mob of ewes with 6-8 week old lambs at foot grazed a fresh lucerne paddock, with marshmallow the only alternate feed. Only the lambs were affected, developing muscle tremours, which seemed to start in the forelimbs and progress to the hind limbs. The lambs eventually could not stand making them candidates for predation unless euthanased. Jillian noted that the two lambs she necropsied both had full rumens with no milk in the abomasum. She speculated that these lambs might have lost their mothers and so grazed with more than otherwise and with less selectivity. ‘On post mortem the large muscle bellies of the forelimbs (and to lesser degree hind limbs) were pale yellow/orange.’

Jillian also saw a case of severe balanoposthitis in maiden border Leicester rams post joining associated with a 35% scanning percentage near Warren and a case of Mycoplasma ovis infection in merino weaners near Coonamble. The weaners suffered weight loss, some weakness on mustering and occasional deaths after shearing.

Tony Morton (based at Wagga) considered that both aflatoxins from silage and internal parasites contributed to a series of deaths and wasting in crossbred. Multiple necropsies revealed a range of findings including liver pathology and laboratory testing of the silage pointed to aflatoxicosis.

Tony saw two other interesting cases. About 30 of 900 wether weaners died from oxalate poisoning. He thought that despite supplementary feeding, shearing and cold stress may have contributed to the excess consumption of a relatively light infestation of pigweed. Of interest, their sisters were crutched, not shorn and experienced no losses. In the second case, twelve four week old lambs died from bacterial encephalitis. The aetiological agent was not cultured but Histophilus somni and Histophilus ovis were considered possibilities. Three lambs recovered after treatment with antibiotics.

In late May, Kasia Hunter was called to a case of blue-green algae toxicity in weaned Merino lambs in which 40/3000 died and another 120 suffered photosensitization. Fortunately, these recovered when removed from the water source. Kasia commented; ‘the algae bloomed in a dam, the only water source in the paddock, following 15-20 mm of rain.’ She suggested that sheep manure from a nearby sheep camp plus faeces from a large wild duck population washed into the dam contributing to the bloom. ‘The algae were clearly visible as a bright green scum on the water surface and covered approximately one third the dam.’ The laboratory confirmed Microcystis species in the water sample and blood and tissue samples from affected sheep confirmed a toxic hepatopathy.

 


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