Production Animal Clinical Toxicology

Plants | Epidemiology | Pathogenesis | Clinical Signs | Clinical Pathology | Necropsy | Diagnosis | Treatment | Control

Return to Production Animal Clinical Toxicology Index

Click on the images for more information

Plants

Oxaps pes-caprae - soursob

Rumex spp. - dock, sorrel

Acetosella vulgaris sheep sorrel

Portulaca oleracea - pigweed

Salsola kap - soft roly poly

Threlkeldia proceriflora - soda bush

Emex austraps - spiny emex

Setaria anceps

kikuyu, panic, buffel, elephant grasses

Epidemiology

animal factors

• hungry animals placed onto restricted pasture dominated by oxalate containing plants
• animals unaccustomed to oxalates in diet
• pregnant/lactating animals may be more susceptible

plant/environmental factors

• oxalates highest at the leafy stage of growth especially during autumn flush after dry summer

Pathogenesis

• normally rumen microflora break down oxalate to formate
• Ca precipitates oxalate which is excreted as it is insoluble
• both processes contribute to oxalate neutralisation and prevent systemic uptake
• toxicity if
• (i) excess in diet
• (ii) reduction of ruminal microbe activity due to fasting, and/or
• (iii) low dietary Ca
• (iv) animals unaccustomed and have few oxalate degrading bacteria
• result is one or combination of 3 syndromes
• (i) hypocalcaemia
• (ii) nephrosis from precipitation of Ca oxalate in renal tubular lumens
• (iii) vascular injury especially of the gastrointestinal tract and lungs - shock
• in addition horses may develop osteodystrophia fibrosa

Clinical Signs

• hypocalcaemia
• paresis
• muscle tremor, staggering
• frothy nasal discharge, frequent attempts to urinate
• collapse on brisket, coma, death
• chronic renal damage
• poor appetite
• failure to thrive
• anaemia

Clinical Pathology

• decreased serum Ca
• increased serum oxalate
• increased BUN
• proteinuria

Necropsy

• pulmonary oedema, froth in airways
• hyperaemia, inflammation and necrosis of forestomachs
• renal oxalate crystals - grey line at the cortico-medullary junction
• chronic - shrunken fibrotic kidneys
• urinary calculi

Diagnosis

• history
• clinical pathology
• necropsy

Treatment

• only partial or nonresponse to Ca borogluconate

Control

• pasture and animal management