Search Results
You are looking at 1 - 3 of 3 items for
- Author or Editor: Alan B. Richards x
- Refine by Access: All Content x
SUMMARY
Classical hemolytic complement (C) of calves was analyzed during a protocol designed to imitate the usual market handling of feeder calves from the southeastern United States. Serum C concentrations of the calves (n = 100 × 4 years) were evaluated on their farm of origin, on arrival at an auction market, on arrival at a feedyard, and during their first 4 weeks in the feedyard. Complement concentrations (measured in ch 50 units) were typically lowest at the farm of origin and highest when the calves entered the auction market 28 to 133 days later. Serum C concentrations decreased after the calves encountered the severe stresses of being in the auction market for 7 days, 24-hour truck transport (1,932 km) to the feedyard, and the first 7 days in the feedyard. The C concentrations recovered after 21 to 28 days in the feedyard. Steers had significantly (P ≤ 0.05) lower C concentrations than did heifers in 3 of 4 years at the farm of origin, and in 2 of 4 years at the auction market. Morbid calves had significantly (P ≤ 0.05) lower C values than did healthy calves on day 7 in the feedyard in 3 of 4 years. There were significant differences in C concentrations of calves from different farms of origin in each of the 4 years. There was no significant difference in C concentrations of calves that were vaccinated vs those not vaccinated with Pasteurella haemolytica.
SUMMARY
A commercially available microbiological identification system and dna:dna hybridization were used to determine relationships between and within serovars 1-13 of Pasteurella haemolytica, and between P haemolytica and P multocida and 4 species of Actinobacillus. All serovars of P haemolytica that belonged to biovar A were related with mean dna homology of 78%, whereas all serovars of P haemolytica that belonged to biovar T were related to each other with mean dna homology of 90%. The dna:dna hybridization between strains of biovars A and T ranged from 3 to 13%, indicating little or no genetic relationship between the 2 biovars of P haemolytica. The dna homology between all serovars of P haemolytica and other species of non-P haemolytica bacteria tested (P multocida and actinobacilli) was < 14%, suggestive of essentially no genetic relationship of P haemolytica with the atcc reference strains of the genus Pasteurella or the genus Actinobacillus.
Enzymatic differences were observed between P haemolytica and the other non-P haemolytica bacteria tested; however, the microbiological identification system that uses enzymatic reactions could not distinguish among biovars of P haemolytica. Results of this research support other data that suggest that biovars A and T of P haemolytica should be classified as separate species, but do not support the inclusion of either biovar A or T within the genus Actinobacillus.
