Serum changes following the feeding of ragwort (Senecio jacobea) to calves

Experimental production of hypocalcemia by EDTA infusion in calves: a critical appraisal assessed from the profile of blood chemicals and enzymes

Physiological studies of the effects of Ca2+ withdrawal using Na2EDTA have been conducted with the prior basic assumption that Na2EDTA-specific direct or indirect effects on the functions under study were negligible. The present study aimed at providing unequivocal confirmation of such assumption by establishing the pattern of response of blood constituents to intravenous infusions of Na2EDTA in calves. Na2EDTA infusion in calves allowed effective chelation of blood Ca2+, leading to a progressive hypocalcemia. Magnesium levels remained constant and concentrations of other ions (Na+, K+, Pi, H+, HCO3-), although significantly altered (P < or = 0.0001), remained within the normal range. Comparison of enzymes, urea, and creatinine changes precluded renal, hepatic, or muscular parenchymatous damages as being the cause of dysfunctions in the context of Na2EDTA-induced hypocalcemia. It was not possible, however, to standardize the Na2EDTA infusion characteristics (flow, volume) to obtain previsible Ca2+ decay in different animals. Conversely, monitoring of systemic arterial pressure (SAP) offered a precious tool to estimate the degree of hypocalcemia reached. Infusion rate must, therefore, be manipulated using careful on-line monitoring of SAP to obtain an experimental range of Ca2+ as large as possible. It was concluded that physiological data collected during Na2EDTA perfusions can be reliably discussed in terms of Ca2+ dependence rather than in terms of either Na2EDTA toxicity, electrolytes maladjustment, acid-base imbalance, impaired blood oxygenation, or hepatic, renal, myocardic, or skeletal muscle damages.

Experimental copper and heliotrope intoxication in sheep: morphological changes

Young Merino wethers were used to determine the effects of copper and heliotrope, fed together or separately, on the development of toxicity and the concentration of trace elements in the liver and kidney. In one experiment copper and heliotrope were given concurrently, in a second experiment heliotrope was fed for 12 weeks and copper administration commenced 8 weeks later. The 10 sheep fed heliotrope alone did not show signs of clinical illness but one died and was found to have severe liver damage. Eleven sheep were given copper alone and three developed the clinical signs and lesions of haemolysis. Fourteen sheep were given copper and heliotrope and 13 became ill. Of these, three developed haemolysis, eight became jaundiced and two became weak without developing jaundice. The concentrations of copper in the livers of control and heliotrope-treated sheep, were comparable. In the animals given copper alone, the concentration of copper in the liver was twice as high as that in controls and in those given heliotrope and copper, it was three times as high as in the liver of control sheep. Feeding heliotrope alone induced the histological changes of pyrrolizidine alkaloid toxicity in the liver, but this was not associated with an excessive accumulation of copper or the development of clinical illness. However, it did predispose the animals to the effects of a second toxin since giving heliotrope and copper concurrently, or giving copper subsequent to feeding heliotrope, markedly enhanced the toxicity of the two substances and caused an excessive accumulation of copper in the liver.

Outbreak of ragwort (Senecio jacobea) poisoning in horses

Five out of 20 horses (25 per cent) on one farm died from an acute hepatic encephalopathy typical of ragwort toxicosis. Circumstantial evidence implicated pasture rather than hay as the principal source of the toxic alkaloids. Plasma levels of gamma glutamyl transferase (GGT) were determined on three occasions in all surviving ragwort-exposed horses. Elevated GGT levels were a useful early indicator of hepatic damage although not all horses with this biochemical sign developed clinical disease.

The mechanisms relating to increases in plasma enzymes and isoenzymes in diseases of animals

Changes in plasma or serum enzymes and isoenzymes are useful indicators of tissue damage in many diseases. Enzyme increases are usually related to leakage of enzymes from damaged cells. The amount of increase depends on factors such as the concentration of enzyme in the cells, the rate of leakage of enzyme from cells and the rate of clearance of enzyme from plasma. There are important species variations in the tissue concentrations and plasma clearance rates of enzymes and isoenzymes.

Senecio lautus toxicity in cattle

Mortalities and a poor growth syndrome in cattle in the Hunter River valley of New South Wales were associated with pyrrolizidine alkaloid toxicity caused by Senecio lautus (common fireweed). A clinical problem of poor growth rate on a large property, where S. lautus was very common, was associated with consistent evidence of some degree of hepatic pyrrolizidine alkaloid lesions in young growing cattle and cows. S lautus subsp maritimus from this property caused the death of 2 experimentally fed calves within 77 days and depressed growth rate in a third calf. Pyrrolizidine alkaloidosis was evident histopathologically in the liver, biliary tree and gall bladder and other organs, especially kidney, of these calves. Histopathology of liver biopsy samples was the most sensitive monitoring technique of those used to indicate exposure to pyrrolizidine alkaloids in this investigation.

Effects of Jatropha curcas on calves

Jatropha curcas seed was fed to six calves at doses of 2.5, 1 and 0.25 g/kg once and to two other calves at 0.025 g/kg up to 14 days. The onset of toxic manifestations in the six calves was rapid and death occurred within 19 hours of administration. The two calves that received daily the lowest dose of J. curcas showed signs of poisoning and died within 10 to 14 days. The clinical signs of diarrhoea, dyspnoea, dehydration and loss of condition were well correlated with the pathological findings. There was an increase in aspartate aminotransferase, ammonia and potassium and a decrease in total protein and calcium in the serum of jatropha-poisoned calves.

Bromosulphophthalein clearance rates in sheep with pyrrolizidine liver damage

Sheep fed a ration containing 50% of dried Heliotropium europaeum showed a marked decline in bromosulphophthalein (BSP) fractional clearance rate during the first 3 months feeding. Thereafter, the response of individual animals varied widely on a time basis, although 3 groups could be identified. In the terminal stages, mean clearance rates were below 20% of initial values, with some sheep showing a decline in excess of 90%. Loss of liver functional capacity was generally much greater than indicated by the degree of damage revealed by histopathology. Thus, a suitably modified test could have considerable prognostic value in the field. In this investigation, all sheep with clearance rates below 0.15 died when exposed to a further period of H. europaeum feeding.

Toxicity of Jatropha cucurcas for goats

Eleven Nubian goats were fed with Jatropha curcas seeds at doses ranging from 0.25 g to 10g/kg/day. All dose levels were found to be toxic with fatal conswquences within 2 to 21 days. Liver biopsy samples taken 2 days after the start of feeding and subsequent biopsies showed congestion, varying degrees of fatty change, considerable reduction in glycogen content and necrosis of the hepatocytes. Lack of appetite, reduced water consumption, diarrhoea, dehydration, sunken eyes and a steadily deteriorating condition were important clinical signs of Jatropha intoxication goats. In all animals there was a decrease in the level of glucose and a marked rise in the concentration of arginase and glutamate oxaloacetate transminase (GOT) in the serum. Post-mortem examination revealed haemorrhage in the rumen, reticulum, kidney, spleen and heart, catarrhal or haemorrhagic abomasitis and enteritis, congestion and oedema of the lung and excessive fluid in serous cavities.

Location of liver injury and extent of bilirubinaemia in experimental liver lesions

Reports on experimental hepatotoxicities in domestic animals were reviewed in order to investigate the relationship between the location of liver lesions and hyperbilirubinaemia. A purely centrilobular lesion tends to produce little effect on bilirubin concentration in the circulation. A mild to moderate hyperbilirubinaemia is predictable if a centrilobular lesion is extensive enough to include cells of the outer zones, however, even an apparently mild periportal liver lesion, but one that affects the integrity of cell membranes, results in a marked rise in bilirubin concentration in the circulation.