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Of 392 heifers vaccinated between 4 and 9.5 months of age and tested at 22 months or older, 3 (0.77%) had titres in the complement fixation test of between 30 and 98 international units per millilitre. The results confirm that persistent serological reactions can be a problem even in brucellosis-free herds. To reduce the incidence of these problem reactors, it is suggested that: in clean herds the age of inoculation be reduced to 3 months of age; the age at first testing be delayed as long as possible, but be done before the heifers are 4 months pregnant, c) consideration be given to reducing the vaccine dose for all heifers from the present 4 to 12 x 10(10) to between 3 x 10(8) and 3 x 10(9) and syringes used for strain 19 vaccination be exclusively reserved for this purpose to prevent the possibility of antigenic residues acting as a booster when used for other vaccinations.

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A survey of erythrocyte glutathione peroxidase (GPx) activity was undertaken in a herd of crossbred cattle after 3 cases of white muscle disease had been diagnosed. All animals examined, appeared to be deficient in selenium, relative to control animals sampled. Oral administration of sodium selenite or sodium biselenite was followed within 30 d by an increase in erythrocyte GPx activity. Despite an apparent improvement in the selenium status of cows after supplementation with selenium, no difference was seen in the conception rate after artificial insemination.

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This trial was designed to examine the integration of the transfer of frozen embryos and artificial insemination (A.I.) in a commercial herd of beef cows. Embryos were collected nonsurgically from 15 superovulated cows and all embryos judged viable (n = 69) were frozen in 0.25 ml plastic A.I. straws. Glycerol was used as a cryoprotectant and the embryos were frozen with omission of the traditional "seeding" step. On three consecutive days immediately preceding the onset of a 60-day breeding season, 54 embryos were transferred to multiparous cows with calves at foot. The remaining 82 cows in the same herd were used as controls. Cows receiving embryos were maintained under observation, but not inseminated for 21 days, after which cows exhibiting signs of estrus were inseminated up to Day 60. Cows in the control group were inseminated at observed estrus throughout the 60-day period. The overall pregnancy rate for the experimental and control groups did not differ (77.8 % and 73.2 % respectively). Of the experimental cows, 24.1 % conceived to the embryo transfer, and 53.7 % to A.I. The mean calving to conception interval for the experimental cows was 96.3 days (median 101 days) and for the control cows it was 92.3 days (median 88 days). The calving pattern in the experimental cows was biphasic, calvings resulting from embryo transfer of A.I. accounting for the two peaks. Reconception rates in the following breeding season were not different between the embryo transfer or A.I. groups or between experimental and control herds. Weaning masses of calves born of embryo transfer were significantly higher than the other groups, but calves resulting from A.I. in the experimental herd were not different from calves in the control herd. It was concluded that the transfer of frozen embryos could be successfully integrated into an A.I. program with a limited breeding season without detrimentally affecting the overall reproductive performance of the recipient herd.

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In two consecutive years a total of 3810 calves were inoculated with the Onderstepoort redwater live-blood vaccine, containing attenuated strains of Babesia bigemina and Babesia bovis. Twenty calves died 8-13 days later due to B. bigemina-infection. Necropsies were performed on 19 of these animals. In 11 calves the spleen was distinctly smaller than normal and its morphology was distorted, and showed changes of chronic splenitis. Histological lesions in the spleens of 6 of the 11 calves are described. The potentiating effect of the splenic lesions to reduce the ability to contain the vaccine reaction, is discussed.

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In the 427 heifers vaccinated at 12 to 14 months of age with the reduced dose (3 X 10(8) to 1 X 10(9) viable organisms per dose) 3 had antibody titres in the complement fixation test of 196, 688 and 748 IU ml-1, respectively, at 5 months post-inoculation. At 23 to 25 months of age 8/128 (6.3%) of these heifers had rose bengal test (RBT) reactions, at least 6/128 (4.7%) a serum agglutination test (SAT) antibody titre in excess of 30 IU ml-1 and 1/128 had a suspicious reaction in the complement fixation test (CFT) of 30 to 49 IU ml-1. In the 116 heifers inoculated with the standard dose (4 to 12 X 10(10) viable organisms) at 5 to 7 months of age and tested at 22 to 24 months of age, a reactor rate of 37/116 (31.9%) in the RBT was seen. At least 34/116 (29.3%) had antibody titres in excess of 30 IU ml-1 in the SAT. Only 1 animal had a suspicious reaction in the CFT of 18 to 24 IU ml-1. No abortions could be attributed to the vaccine strain and no other isolates of the vaccine strain were made. The possible role of vaccine residues in syringes as a cause of persistent reactions is discussed. The use of disposable syringes is recommended. On serological grounds there appears to be little advantage in using the reduced dose vaccine in yearling heifers as opposed to the standard dose vaccination of 5 to 7 month old heifers.

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The effects of locality on the copper, iron, manganese, zinc and magnesium levels in 407 bovine caudate lobe liver samples preserved in formalin for differing storage periods were examined. The mineral determinations, expressed on the wet basis (WB), were made by atomic absorption spectrophotometry after wet ashing of the liver. Two hundred and ten of the liver samples were from cattle from one farm (Farm 1) the remaining 197 cattle being from another farm (Farm 2). The copper, iron and magnesium levels were taken as indicative of the hepatic concentrations at slaughter. Locality had a significant effect (P less than 0,05) on the copper, iron and magnesium levels. All copper levels on Farm 1 fell well below the accepted minimum (33,0 mg/kg). The deficiency appeared to be secondary with the possible implication of sewage effluent. In terms of biological variation the different iron levels appeared of minor importance and no inverse relationship was found between iron and copper. The manganese and zinc levels were interpreted with caution due to the significant differences reported in their hepatic concentrations after six months of storage in formalin. Extremely high zinc levels in individual animals could have been associated with sewage effluent.

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Chlamydial infection in a large beef herd is illustrated and discussed. The pre-natal and post-natal losses that occurred during 1972 are highlighted. Total pre-natal losses for the nine calving herds comprising 2,915 animals varied between 3,7% and 12,4%. Between 1,2% and 11,4% of the calves born alive in the nine herds died before weaning with 70% of the losses occurring within the first three weeks of life. Chlamydial organisms were demonstrated in pre-natal and post-natal losses from all nine herds. Clinical manifestations and lesions involving the intestinal, respiratory, nervous, skeletal, reticulo-endothelial and urinary systems were observed in chlamydia-infected calves. Invariably at autopsy in chlamydia positive cases there was some degree of a fibrinous inflammatory process present. Serological evidence showed that chlamydial organisms had been present on both farms prior to the 1972 investigations.

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