The rapid identification of Escherichia coli using Bactident E. coli

165 (93.7%) of 175 E. coli strains isolated from various materials of different animal species were correctly identified as E. coli with help of commercially available Bactident E. coli (E. Merck, D-6100 Darmstadt). Further 52 strains of the family of Enterobacteriaceae (2x Providencia sp., 2x Salmonella sp., 7 Citrobacter sp., 9 Proteus sp., 15 Klebsiella sp., 17 Enterobacter sp.) were correctly not identified as E. coli by this test. Bactident E. coli is a suitable test for rapid identification of E. coli in veterinary bacteriology.     

Comparison of sire evaluation methods for carcass gain using field data

Four methods of predicting breeding values for carcass gain are compared: “regressed” least squares (RLSQ), mixed model (MM), mixed model with relationships among sires considered (MMR) and contemporary-comparison (CC). Very small changes in the ranking of the sires were observed from one method to another (rank correlations > 0.96). Consideration of the relationships among the sires or deleting the breed-group factor from the model did not lead to substantially different breeding values. The good correspondence of the predictors is mainly due to the well balanced distribution of the progeny over herds.     

In vitro viral expression as a criterion for development of control procedures for enzootic bovine leukosis

In a university beef herd of 304 cattle in which six died of lymphosarcoma between 1980 and 1984, 77% of the Angus and 26% of the Charolais cattle were determined to be infected with bovine leukemia virus (BLV). Changes in iatrogenic procedures were initiated as early control measures. In vitro viral expression (VE) was used as a criterion to identify cattle for subsequent segregation or culling. This involved determinations of percentages of BLV-associated lymphocyte profiles among thin-sectioned Ficoll-Paque-isolated blood lymphocytes that were processed into plastic after culture for 48 h. Cattle retained until completion of nutritional studies or as breeding stock were separated into two groups. The BLV-seronegative cattle, BLV-seropositive cattle with 0% VE, and BLV-seropositive cattle with 1% to 4% VE were placed in group 1. Seropositive cattle with greater than or equal to 5% VE were placed in group 2. In 1985, evaluation of in vitro VE in 108 mature BLV-seropositive cattle retained for breeding revealed 36 (33%) had no observable VE. In 1986, 58 of 108 cattle were available to be reexamined, and 21 (36%) had 0% VE in both years. The VE expression values for individual cattle were generally comparable over the 2-year period. Of 48 initial seronegative breeding stock housed in group 1 with BLV-seropositive cattle with low or no VE, 21 (44%) seroconverted during 1985 to 1986. A positive correlation of 0.585 was found between VE and age-related absolute lymphocyte number.