The present study was conducted with the objectives to: (a) determine the cyanogenic potential of various livestock fodder and grasses, (b) determine CN? content in blood of ruminants feeding cyanogenic plants, (c) develop a simple, reliable and inexpensive assay for the determination of CN? in blood, (d) evaluate the efficacy of various antidotes against CN? toxicity in a rabbit model, (e) find out the effect of CN? on hematological and biochemical profile, (f) study the postmortem and histopathological changes associated with CN? toxicity in various organs and (g) study alterations in tissue oxygenation and metabolic variables during acute CN? toxicity in pigs. For this purpose a total of 500 samples of various plants being used as fodder to livestock were collected from the field and analyzed for CN? content spectrophotometerically. To develop a simple picrate method for CN? estimation in blood, two goats were infused with KCN at 0.6mg/kg for 1 hours. Blood samples were collected at intervals and were subjected to the general method. Standard curve was developed using standard solutions of various concentrations of CN?. Additionally 6 rabbits were also given CN? orally for 40 days and blood samples were collected for CN? estimation. Later on, this method was successfully used to determine CN? levels from 500 blood samples of cattle, buffaloes, sheep and goats (n=125 each) feeding cyanogenic plants which were collected from the field. For antidotal studies forty two rabbits were randomly divided into seven groups viz. A, B, C, D, E, F and G each comprising of six animals. Rabbits in group A were given feed only and served as negative control, while the rabbits in group B received feed plus oral solution of potassium cyanide (KCN) and were positive control. Animals in group C were given feed, KCN and intraperitoneal (IP) injection of garlic extract. Rabbits in group D were treated with feed, KCN and IP injection of sodium thiosulfate (STS). Members in group E received feed, KCN and IP injection of both garlic extract and sodium nitrite (SNT). Animals in group F were treated with feed, KCN and IP injection of both STS and SNT whereas the rabbits in group G were given feed, KCN and hydroxocobalamin IP. The treatments were given to respective groups for a period of 40 days. At the end of 40 days, serum and fresh urine samples were drawn from each rabbit to study biochemical panel. Subsequently the rabbits were euthanized for postmortem and histopathological changes in various organs. For hematological and growth rate studies 12 rabbits were divided into two groups of six viz. A and B. Rabbits in group A were given feed only while members in group B were treated with feed and oral KCN at 3mg/kg for 40 days. The animals were weighed after every 10 days. Feed consumption rate, feed efficiency and weight gain for the members of each group were recorded. Blood samples were also collected for hematological studies at 0, 10, 20, 30 and 40 days. To study tissue oxygen and metabolic variables during acute CN? toxicity, 26 piglets were anesthetized. The non-invasive monitors were used to measured oxygen saturation, heart rate and rhythm and cerebral response to sedation. The invasive monitors were placed to measured beat to beat variability of the arterial blood pressure, pulmonary artery pressures. Mixed venous oxygen saturation (SvO2) and cardiac output were continuously monitored. Regional brain O2 (cerebral cortex) and skeletal muscle O2 saturation (rSO2) were also measured via sensors. After getting baseline metabolic and hemodynamic measurements that included arterial and venous blood gas analysis, lactates and cyanide levels, all pigs were started on an infusion of NaCN (0.55 mg/kg/hr). The infusion continued until the occurrence of sustained apnea (?3 minutes). A non-significant difference was found in the CN? content of Sorghum bicolor and S. sudanese, while a significant difference was observed between the CN? content of Jumbo grass (S. bicolor x S. Sudanese hybrid) and S. halepense. Jumbo grass and S. halepense were found to have significantly higher CN? concentrations than S. bicolor or S. Sudanese. Maize has significantly lower CN? content compared to S. bicolor, S. sudanese, Jumbo grass, or S. halepense. A gradual increase in CN? content with increasing height of plants was also observed. Highest CN? levels were observed at heights of 91-100 cm in sorghum varieties. At greater heights, a gradual decrease in CN? content was seen in all plant species, with the lowest levels at heights of 200 cm or above. No CN? was detected in maize at heights over 131 cm. In picrate method, the calibration curve was linear (R2=0.99) in the range of 0.3-120 mg CN?/L. In standard CN? solutions a color change in picrate paper from yellow to brown was observed at a concentration of 3 mg CN?/L and above. This method was sufficiently sensitive to quantify the low concentrations (0.3mg CN?/L) of CN? found in ruminant blood. In goats infused with KCN, the CN? concentration in blood was time-dependent and continued rising during infusion, gradually declining after infusion ceased after 1 h. Blood CN? levels showed a time-dependent increase in all experimental rabbits with the maximum concentration (1.34 mg/L) at day 40. The highest blood CN? concentrations were found in cattle, followed by goats and buffalo, with the lowest in sheep. When blood CN? levels of these species were compared statistically, a non-significant difference was observed. A non-significant difference was found between males and females. No relationship was observed between blood CN? levels and age of the animal for any species. Buffalo, cattle, sheep, and goats allowed to graze showed significantly higher blood CN? levels than animals kept in a stall feeding system. Animals grazing on jumbo grass were found to have significantly higher blood CN? levels than those fed S. bicolor or S. sudanese with a non-significant difference found between animals fed S. bicolor or S. sudanese. No CN? was detected in blood samples of animals fed maize. Hydroxocobalamine was found to be a significantly more effective CN? antidote than garlic, STS, SNT plus garlic extract, or SNT and STS, either alone or in combination. A combination of SNT and garlic extract was the second most effective CN? antidote. The efficacy of garlic alone was significantly higher than STS or SNT in combination with STS. The efficacy of combined SNT and STS was superior to STS alone in treating rabbits with CN? toxicity. No rabbits in any group demonstrated gross deviation from the normal organ structure. The activities of serum ALT, AST, ALP, and LDH enzymes, as well as serum bilirubin, were significantly increased in CN? treated rabbits compared to controls. Severe hepatocyte vacuolation and degeneration were present in liver of rabbits in the CN? treated group. Liver of rabbits in the control group showed normal morphological patterns. The concentrations of serum urea, uric acid and creatinine were significantly higher in CN? treated rabbits than in control group. Urinary thiocyanate levels were also significantly higher in the CN? group than in controls. Kidneys of rabbits in the CN? group demonstrated severe glomerular and tubular necrosis and congestion. Pyknotic nuclei were present in tubular epithelial cells, whereas a normal histological pattern was observed in kidneys of rabbits in control group. Serum T3 and T4 levels were significantly lower in the CN? group compared to controls. A non-significant difference in blood glucose levels was recorded between rabbits in control and CN? treated groups, and histological examination of pancreas revealed no microscopic lesions. No significant differences were observed in serum cholesterol levels of CN? and control group rabbits. The serum albumin and total protein concentration in CN? treated rabbits were significantly lower than in the control group. Heart of rabbits in both CN? and control group did not show histopathological changes under microscopic examination. The erythrocyte count, the hemoglobin concentration, packed cell volume and mean corpuscular hemoglobin were all found to be significantly lower in blood of CN? treated rabbits than control group. The mean corpuscular hemoglobin concentration was significantly higher in the CN? group rabbits than control group animals. On the other hand, the difference in leukocyte count, differential leukocyte count and platelets were non-significant. The difference in total and daily feed consumption between CN? and control group rabbits was non-significant, whereas the feed efficiency of rabbits in the control group was significantly higher than for rabbits in CN? fed group. The net weight gain of rabbits in the control group was significantly higher than in the CN? fed group. Cyanide infusion to pigs resulted in toxic levels of blood CN? accompanied by lactic acidosis. In addition, there was a progressive increase in cardiac output, Venous oxygen saturation, heart rate, elevation of central venous pressure and pulmonary artery blood pressure. Skeletal muscle rSO2 progressively and significantly decreased with increasing lactate and CN? levels. However, there was no significant change in brain rSO2.