Use of a direct-fed microbial product as a supplement during the transition period in dairy cattle.

Two studies were conducted. The objective of the first study was to assess the effects of a direct-fed microbial (DFM) product on dry matter intake, milk yield, milk components, disease incidence, and blood metabolites in dairy cattle. The objective of the second study was to assess the effects of DFM on apparent total-tract nutrient digestibility (ATTD). One hundred twenty primiparous and multiparous Holstein cows housed in a tiestall facility at the University of Guelph were used in study 1, and a subset (21) of the same cows participated in study 2. Cows were blocked by anticipated calving date (6 blocks) and then randomly assigned within parity to receive either a DFM supplement (Chr. Hansen Ltd., Milwaukee, WI) or placebo (control). The DFM supplement provided cows with 5.0 × 10(9) cfu/d of 3 strains of Enterococcus faecium and 2.0 × 10(9) cfu/d of Saccharomyces cerevisiae. The DFM supplement was mixed with 0.5 kg of ground dry corn and top-dressed during the morning feeding. The placebo supplement contained the corn only. Individual feed intakes and milk yields were recorded daily. The experiment commenced 3 wk before calving and ended 10 wk postcalving. Milk samples for component analysis were collected on 3 d per week and pooled by week. Body weights and body condition scores were assessed 1 d before enrollment in the study (wk -3), postcalving (wk 1), and at the end of wk 3, 6, and 9. Blood samples were collected before calving (wk -3) and the end of wk 1 and 3. Study 1 showed that treatment had no effect on average dry matter intake or milk yield (kg/d) over the duration of the experiment. The changes in body weights and body condition scores and net energy balance over the duration of the experiment did not differ due to treatment. Treatment had no effect on plasma concentrations of ß-hydroxybutyrate, nonesterified fatty acids, glucose, or haptoglobin. Study 2 investigated the effects of DFM on ATTD of starch and neutral detergent fiber (NDF) using insoluble NDF and lignin as internal markers. Study 2 used 21 cows (block 6) from the cows that participated in study 1 while the cows were between 60 and 70 d in milk. Cows receiving DFM had lower fecal starch content (0.88 ± 0.10 vs. 1.39 ± 0.25) and greater ATTD for starch (98.76% ± 0.28 vs. 97.87% ± 0.24) compared with those receiving placebo, and the AATD of NDF did not differ. Additionally, we detected no difference between internal markers for the measurement of ATTD. In conclusion, we were unable to detect a change in overall dry matter intake, milk yield, or milk and blood parameters with DFM supplementation. However, our results demonstrated that DFM can have a positive effect on total-tract starch digestibility. More studies are needed to investigate the effects of DFM and their modes of action under multiple management conditions.

Immunoassays of field isolates of Mycobacterium bovis and other mycobacteria by use of monoclonal antibodies.

Antigen extracts obtained by sonication of 22 strains of Mycobacterium bovis from cattle and badgers together with extracts of strains of M. tuberculosis, M. paratuberculosis, M. avium, M. africanum, M. kansasi, M. leprae and BCG were examined with a panel of 10 monoclonal antibodies to M. tuberculosis or M. leprae. Antigen extracts were coated in aqueous solution (wet coating) and the extracts were also dried on to the polyvinyl plates (dry coating). When dry coating was compared to wet coating, there was a major increase in the binding of monoclonal antibody ML03 to M. avium and M. paratuberculosis, monoclonal antibody ML02 to M. paratuberculosis, and monoclonal antibodies TB71 and TB72 to the majority of M. bovis isolates. The study confirmed that on wet-coated plates, monoclonal antibodies TB71 and TB72 bind poorly or not at all to M. bovis and that monoclonal antibodies TB68, TB78, TB77 and TB23 each bind to field strains of M. bovis while TB23 binds poorly to BCG in wet-coating conditions. Antibodies TB72 and TB71, originally thought to be specific for M. tuberculosis, each reacted with M. africanum. Antibody TB78 bound to M. paratuberculosis but did not react with M. avium, and M. avium and M. paratuberculosis were distinguished from M. bovis and M. tuberculosis by the binding of antibody ML03 to dry-coated plates. When wet-coated plates were used, ML03 bound strongly only to M. leprae. The panel of monoclonal antibodies did not demonstrate distinct serotype differences between the field isolates of M. bovis.