Lameness in feedlot cattle.

This article examines the various causes of lameness in feedlot cattle, with an emphasis on clinical signs, treatment, and prevention. Specific conditions are discussed, including interdigital necrobacillosis, laminitis, feedlot injuries, and feedlot lameness associated with Mycoplasma bovis. Immune management of the foot is also reviewed.

Persistent bovine viral diarrhoea virus infection in US beef herds.

In the summer of 1996, we screened 18,931 calves in 128 beef herds located in five US states for persistent bovine viral diarrhea virus (BVDV) infection. Of these, 76 herds were randomly selected from the client database of collaborating veterinary practices, and 52 herds were suspected by the collaborating veterinarians to have BVDV infection based on history or clinical signs. Serum was obtained from each calf in the cooperating herds prior to 4 months of age and tested for the presence of BVDV by microtiter virus isolation. Information about each of the herds (including management practices, vaccination history, and breeding- and calving-season production measures) were collected by the collaborating veterinarians using standardized questionnaires. A total of 56 BVDV-positive calves in 13 herds were identified on initial screening. Ten (19%) of the BVDV-suspect herds and three (4%) of the randomly selected herds had > or = 1 BVDV-positive calf at initial screening. Multiple BVDV-positive calves were identified in 10 of those 13 herds. Follow-up information was obtained for 54 of the 56 positive calves. Ten out of 54 (18%) died prior to weaning, and 1 (2%) was sold because of unusually poor growth. Thirty-three out of 54 (61%) of the initially positive calves remained BVDV positive at 6 months of age - confirming persistent-infection (PI) status. Dams of 45 of the 56 positive calves were tested, with 3 (7%) identified as positive - indicating most PI calves were products of acute dam infection during gestation. The proportion of cows that were pregnant at the fall 1995 pregnancy examination was 5% lower in herds with PI calves born during the 1996 calving season than in randomly selected herds without PI calves. Most of the calves we identified with persistent BVDV infections survived to weaning, and could provide a constant source of virus to the herd throughout the breeding season and early gestation.

Serological and genotypic characterization of group A rotavirus reassortants from diarrheic calves born to dams vaccinated against rotavirus.

Two strains of bovine rotavirus (BRV), designated strain Nebraska Scottsbluff-1 (NS-1) and NS-2, were isolated from 2 neighboring cow-calf beef cattle ranches where dams had been vaccinated with a commercial vaccine containing group A BRV strain Neonatal Calf Diarrhea Virus (NCDV)-Lincoln (P1:G6). Northern blot hybridizations using whole genomic RNA probes indicated that strains NS-1 and NS-2 had identical group A RNA electrophoretic patterns and were homologous at all gene segments. Strain NS-1 was compared with reference group A BRV strains using serological and genotypic methods. In vitro virus neutralization assays indicated that strain NS-1 was neutralized by a G6-specific neutralizing monoclonal antibody (mAb) and guinea pig hyperimmune serum (GPHS) raised against BRV strain B641 (P5:G6), but not by G10-specific neutralizing mAb or GPHS raised against BRV strain B223 (P11:G10). Nucleic acid hybridization experiments using whole-genomic RNA probes revealed that gene segment 4 of strain NS-1 differed from BRV strains NCDV-Lincoln and B223, but hybridized with strain B641. Conversely, gene segment 5 of strain NS-1 hybridized with BRV strain B223, but not with BRV strains NCDV-Lincoln and B641. A G-specific cDNA probe produced by reverse transcription polymerase chain reaction (RT-PCR) amplification of strain NS-1 hybridized specifically only with G6 strains NCDV-Lincoln and B641, but not with G10 strain B223. Co-electrophoresis experiments using strains NS-1, B641, and B223 further confirmed these results, suggesting that strain NS-1 was a naturally-occurring reassortant BRV between strains B641 and B223. Taken together these results indicated that a naturally-occurring group A BRV reassortant with a P gene different from the vaccine virus was responsible for the diarrheal syndrome observed on both ranches. Results from this study also indicate the existence of at least 2 different gene segments 5 among group A BRV infecting cattle.

Vesicular adenitis syndrome in beef bulls.

Vesicular adenitis syndrome was diagnosed in 69.3% (52/75) of a group of yearling bulls on breeding soundness examination. Association of Haemophilus somnus infection with vesicular adenitis syndrome was confirmed in these bulls by microbial culture of vesicular gland fluid or semen samples and serologic testing.

Bovine trichomoniasis: Results of a slaughter survey in Colorado and Nebraska.

A total of 2,909 bulls was cultured for the presence of Trichomonas fetus at slaughter at 4 abattoirs in Colorado and Nebraska. Samples were collected using the dry pipette preputial scraping technique and were transported to diagnostic laboratories within 24 h. Of the bulls cultured, 5 were positive. The state of the last origin for each animal was Kansas, 1 bull, Montana, 1 bull, Nebraska, 1 bull, and Utah, 2 bulls. These results indicate and incidence of less than 1% (0.172%) of trichomoniasis in the populations tested, even in the states of Colorado and Nebraska where the larger numbers of bulls were cultured.