Variability of yellow tulp (Moraea pallida Bak.) toxicity.

Yellow tulp (Moraea pallida Bak.), collected predominantly during the flowering stage from a number of sites in South Africa, showed large variation in digoxin equivalent values, indicating variability in yellow tulp toxicity. Very low values were recorded for tulp collected from certain sites in the Northern Cape.

Evaluation of activated charcoal as treatment for Yellow tulp (Moraea pallida) poisoning in cattle.

The efficacy of activated charcoal as a treatment for cattle (n = 57) poisoned by Yellow tulp (Moraea pallida) was investigated. Treatment with activated charcoal resulted in full recovery, irrespective of the degree of posterior paresis, provided that this clinical sign did not develop within the first 12 hours after initial exposure to Yellow tulp-infested grazing. For instance, despite treatment, 1 of 7 cattle succumbed after manifesting mild posterior paresis 6 to 8 h after initial exposure and 3 of 3 treated cattle died after developing severe posterior paresis within 6 to 12 h.

Changes in sheep oesophageal diameter and function during Geigeria ornativa (vermeerbos) poisoning and subsequent recovery.

Changes in the oesophageal diameter and function together with changes in body weight, feed intake and the cardiac pulmonary flow index were investigated during experimentally induced poisoning with Geigeria ornativa and subsequent recovery. This was performed under varying conditions for individual sheep. Results showed an increase in the oesophageal diameter index (ODI) during vermeersiekte, accompanied with a decrease in oesophageal function (OF). Cessation of G. ornativa intake resulted in a considerable although incomplete recovery of the ODI. Recovery of the OF for the different sheep, however, varied between 0 and 100%. Detrimental changes in the oesophageal diameter and function were also measured in sheep receiving only subclinical doses of G. ornativa. Decreases in body weight and feed intake commenced 1 to 3 weeks before the onset of vermeersiekte, while indications of a decline in these 2 parameters were also noticed with ingestion of subclinical amounts of G. ornativa. An increase in the cardiac pulmonary flow index (CPFI) to a value indicating the onset of heart failure was found in 1 of the sheep showing clinical signs of vermeersiekte. The CPFI returned to normal after termination of G. ornativa intake.

Continuous exposure to an aversive mixture as a means of maintaining aversion to vermeerbos (Geigeria ornativa O. Hoffm.) in the presence of non-averted sheep.

Continuous exposure to an aversive mixture was investigated as a means of maintaining aversion to vermeerbos in sheep subjected to the social influence of non-averted sheep. The use of an aversive mixture was based on a hypothesis that continuous exposure to an acceptable aversive mixture (containing both the aversive substance and the identification factors of vermeerbos mixed with maize meal) would tempt sheep to consume small quantities of the aversive mixture each day and that this would keep them averted to vermeerbos, despite the social influence of non-averted sheep. Persistent aversion to a vermeerbos-maize meal mixture (1:99 by mass) by sheep continuously exposed to such an aversive mixture, after an initial aversion conditioning with lithium chloride (LiCl, 160 mg/kg BM), was demonstrated. Aversion in adjacent controls not exposed to the aversive mixture only lasted for some time. A similar result was obtained when sheep were challenged for intake of a pure stand of established vermeerbos. Three sheep continuously exposed to an aversive mixture after an initial aversion conditioning totally refused grazing the vermeerbos during a 42-day trial, despite the social influence of three non-averted control sheep grazing vermeerbos on an adjacent site. These results were confirmed by a second replication the following year. Joint grazing for an hour a day by averted and non-averted sheep during the last seven days of this replication also resulted in total avoidance of vermeerbos by the averted animals, despite continued intake of vermeerbos by the control sheep

A study on the function of some subcellular systems of the sheep myocardium during gousiekte. I. The energy production system.

In order to determine the status of the energy production system of the heart during cardiac failure of sheep with gousiekte, observations were made of the heart tissue levels of adenosine triphosphate (ATP), creatine phosphate (CrP), inorganic phosphate, reduced nicotine adenine dinucleotide (NADH) and lactate. Some measurements on oxidative phosphorylation were also made. A significant decrease in ATP and CrP levels coincided with a simultaneous rise in the ATP:CrP ratio and lactate levels in gousiekte hearts. No significant deviations in inorganic phosphate and NADH levels could be demonstrated. These abnormalities were accompanied by a decreased uptake of oxygen by isolated mitochondria of gousiekte hearts. There was a marked increase in the anaerobic state of the hearts of dying gousiekte sheep, while the values of NADH and the ATP:CrP ratio at a presymptomatic stage indicated a possible early derangement in the energy metabolism of sheep fed the toxic material. No hypertrophy could be detected for the failing ventricles of gousiekte sheep after being corrected for a significant amount of oedema found in the heart tissue of these animals. It was concluded that the depressed ATP and CrP levels in the heart tissue of gousiekte sheep during cardiac failure could at least in part, be attributed to a depressed aerobic energy production. It is not possible, however, to state whether this is a primary or a secondary response due to intoxication and also whether it could be seen as a cause or effect of cardiac failure.

A study on the function of some subcellular systems of the sheep myocardium during gousiekte. II. The contractile protein system.

Two groups of Merino sheep were intoxicated separately and at different times with "gousiektebossie" (Pachystigma pygmaeum) until definite symptoms of heart failure were auscultated. Cardiectomy was carried out and some ventricular muscle from 1 group was stored in 50% glycerol at -20 degrees C for about 4 months. Natural actomyosin (n-actomyosin) was subsequently extracted and tested for magnesium, calcium and adenosine triphosphate (ATP)-dependent adenosine triphosphatase (ATP-ase) activity as well as for superprecipitation characteristics. Muscle strips were taken from the other group and stored for 2 weeks in 50% glycerol at -20 degrees C, whereafter it was analysed for an isometric tension-calcium response. The data showed no difference between gousiekte and control sheep in the sensitivity of the contractile system to the activating effect of calcium ions with respect to isometric tension development. A significant reduction of the magnesium dependent ATP-ase was found for gousiekte n-actomyosin in either the presence or absence of calcium ions. A depressed sensitivity for this enzyme to increasing concentrations of ATP in comparison to controls was also found ([ATP] less than 1 mM, [MgCl2] = 1 mM). No significant difference could be detected in the sensitivity of the n-actomyosin:ATP-ase system to magnesium. n-Actomyosin:ATP-ase of gousiekte hearts revealed a depressed sensitivity to calcium ions. Gousiekte n-actomyosin also showed a significant depression in the rate of superprecipitation with a concomitant increase in the duration of the clearing phase. We conclude from these observations that a definite biochemical lesion is induced in the contractile proteins of heart muscle obtained from sheep intoxicated with "gousiektebossie" at the stage of cardiac failure. This condition is characterized by abnormal superprecipitation characteristics and a depressed n-actomyosin:ATP-ase activity, showing a reduced sensitivity to the activating effect of calcium ions.

Conditioned feed aversion as a means to prevent tulp (Homeria pallida) poisoning in cattle.

Conditioned feed aversion was investigated as a means to prevent tulp (Homeria pallida) poisoning in cattle on tulp-infested grazing. Aversion treatment with a combination of epoxyscillirosidin and lithium chloride together with a tulp-hexane extract, which served as identification factor for tulp, resulted in a significantly lower (P < 0.001) proportion of severe tulp poisoning. In a first trial where 21 averted and 21 non-averted control cattle were exposed to a tulp-infested grass pasture, only two of the averted cattle were severely poisoned compared to 13 of the non-averted control cattle. In a second trial, with cattle being exposed to a pure stand of tulp supplemented with maize residues, only two of 21 averted cattle were severely poisoned compared to 14 of 21 non-averted control cattle. Occurrence of mild tulp poisoning, however, did not differ much between averted and non-averted control cattle. The results show that conditioned feed aversion effectively restricted severe poisoning in cattle on tulp-infested grazing.