Enzymatic activation of Clostridium perfringens epsilon prototoxin removed a small basic part of the molecule, causing a slight change in molecular weight (32,700 to 31,200) and a large change in isoelectric point (from pH 8.02 into fractions of 5.36 and 5.74).

The serological response to Brucella ovis and the shedding of the organism in semen was followed for a period of 13-14 months in 42 naturally infected rams. Most rams remained chronically infected and excreted the organism in their semen throughout the investigation. B. ovis was isolated from 87.9% of the semen samples from the infected rams. The most common sites from which B. ovis could be isolated at necropsy were the epididymides and accessory sexual glands. In one ram the organism was isolated from lung, spleen, kidney and iliac lymph nodes. Three rams ceased to shed B. ovis in their semen during the course of the investigation. Seventy-five (11%) of 686 sera from infected rams were negative in the complement fixation test (CFT) although 76% and 77% of CFT-negative sera were positive in the gel diffusion precipitin test (GDT) and enzyme labelled immunosorbent assay (ELISA) respectively. The high incidence of CFT-negative infected rams was due to the selection for the investigation of many rams with histories of negative or vacillating CFT titres. Sera from five rams which never shed B. ovis in their semen reacted erratically in the three serological tests. The five rams were from heavily infected flocks and were kept in contact with infected rams throughout the investigation.

Heat-stable enterotoxins (ST-124 and ST-1261) have been isolated from two different enterotoxigenic Escherichia coli of bovine (124) and porcine (1261) origin. The enterotoxin preparations were isolated by ultrafiltration and ionexchange chromatography and were both active in the suckling mouse test and pig ligated loop test in the nanogram range. The bovine (ST-124) enterotoxin was not stable to heating in its isolated form, and significant differences in amino acid composition were observed between the two enterotoxins. Although both toxins were active at similar levels in the suckling mouse and pig ligated loop tests, ST-124 lacked the ability to cause the profound secretary responses seen with ST-1261 in the weanling pig ligated loop.

Heat-stable enterotoxins from a bovine and porcine strain of Escherichia coli were isolated and showed significant differences in amino acid composition and heat stability.

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