Chapter 22 Lactation tetany/transport tetany/idiopathic hypocalcaemia Synchronous diaphragmatic flutter Blister beetle (cantharidin) toxicosis 22.17 Free fatty acid metabolism Plants containing pyrrolizidine alkaloids Castor bean (Ricinus communis) Plants producing CNS dysfunction Plants containing cyanogenic glycosides Plants containing cardiac glycosides Wild jasmine (Cestrum diurnum) 22.26 Feed-associated poisonings • Ionized calcium is the biologically active form. • This represents 40–60% of the total calcium stores. • Alkalosis increases protein-binding of calcium, thereby reducing the concentration of ionized calcium. • Acidosis decreases protein-binding thereby increasing the concentration of ionized calcium. Serum calcium is more than 3.5 mmol/L in hypercalcaemia. • Both acute and chronic renal failure may cause hypercalcaemia, but hypercalcaemia is present in less than 50% of renal disease cases. • Possibly due to a decrease in renal excretion of calcium due to a decrease in glomerular filtration rate, renal epithelial death, and decreased gastrointestinal absorption due to decreased 1,25-dihydroxycholecalciferol. 1. Wild jasmine, day-blooming jasmine (Cestrum diurnum): • Found in tropical and sub-tropical America and the Caribbean islands. • Toxic all year round – all parts of the plant are toxic. • Clinical signs of toxicity are weight loss, stiffness, progressive lameness and eventually recumbency. • Dystrophic calcinosis of the elastic tissues of the heart, arteries, tendons and ligaments. • Contains a steroidal glycoside that is hydrolysed in the digestive tract to vitamin D3. • Causes an increase in intestinal absorption of calcium beyond that which can be physiologically accommodated. 2. Other plants that cause similar syndromes:
Metabolic diseases and toxicology
22.1 Calcium metabolism
Ionized calcium
22.3 Hypercalcaemia
Renal failure
Plant toxicity
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