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By using the limulus-amebocyte-lysate- assay a test procedure was developed that could be used to quantify the endotoxin- neutralizing capacity of bovine blood. 11 was shown that the endotoxin neutralization by bovine blood is dose as well as time dependent. That was proved for different types of endotoxins (Escherichia coli 0111:134 and Salmonella minnesota endotoxin).In further investigations the endotoxin- neutralizing capacity and the total protein content of blood samples from 158 calves of 3 different farms were tested. The following findings were made:1. The age of the animals had a definite influence on the neutralization capacity. It was shown that calves with an age of two weeks had significantly higher neutralization capacity as with an age of six weeks.2. The content of minerals in food could have a indirect influence on the neutralization capacity. Three groups of calves were compared. In addition to cows milk each group was fed hay ad libitum (group A), hay ad libitum and calf mix food with,,normal" mineral content (group B) hay ad libitum, and calf mix food with double the normal content of copper and zinc (group C).While group A and B showed no difference in the neutralization capacity, group C had a significantly lower neutralization capacity.3. The clinical symptom of diarrhoea was shown to have an definite association with neutralization capacity in blood. Neutralization capacity was significant lower in calves with diarrhoea compared to clinical healthy animals. Particularly lower readings were found in two calves presenting with pyrexia, collapse and signs of dehydration.4. Respiratory tract diseases had no influence on the neutralization capacity in blood. No difference was demonstrated between the neutralization capacity in the group of calves with pyrexia and respiratory symptoms compared to clinical healthy calves.5. Calves of the breed "German black and white" and "Bavarian Fleckvieh" were tested. The neutralization capacity of blood was demonstrated to be independent on the breed.6. No correlation was found etween blood total protein content and neutralization capacity.7. The total colony number of aerobe gram-negative bacteria in faces was determined for the calves of the feeding groups and the calves with diarrhoea. This number did not correlate with the neutralization capacity of blood. Furthermore, there was no difference between the total colony numbers of aerobe gram-negatives in the faces among the three feeding groups.