Search Results
You are looking at 1 - 2 of 2 items for
- Author or Editor: Michael F. Witt x
- Refine by Access: All Content x
Abstract
Objective—To determine whether, and at what time, penicillin enters milk at a concentration that is detectable following bulbar subconjunctival injection in lactating dairy cows.
Design—Randomized clinical trial.
Animals—66 Holstein cows that were at least 2 weeks past calving and had not been treated with antibiotics in the preceding 30 days.
Procedure—Cows were randomly assigned to receive a treatment of 1 ml (300,000 units) procaine penicillin G by bulbar subconjunctival injection or remain untreated. Composite milk samples were collected immediately before treatment and 4, 10, 16, 22, 28, and 40 hours after treatment. Milk samples were tested by use of a commercial test for β-lactam antibiotics.
Results—Among penicillin-treated cows, the first positive test results were observed 4 hours after treatment, and the last positive result was observed 22 hours after treatment. The percentages of positive test results before treatment and at 4, 10, 16, 22, 28, and 40 hours after treatment were 0, 9, 87, 42, 8, 0, and 0%, respectively. None of the untreated cows had positive test results for β-lactam antibiotics at any sampling time.
Conclusions and Clinical Relevance—Penicillin was detected in milk for up to 22 hours after a single subconjunctival injection of procaine penicillin G in cows. This result should be considered when recommending milk withholding periods following the administration of penicillin by this route in lactating dairy cows. (J Am Vet Med Assoc 2000;217:369–371)
Abstract
Objective—To evaluate the health and performance of young dairy calves vaccinated with a commercial Mannheimia haemolytica and Pasteurella multocida vaccine.
Design—Randomized clinical trial.
Animals—358 Holstein dairy calves between 14 and 20 days of age on 8 farms.
Procedure—Calves were randomly assigned to a control or vaccinated group. The vaccine used was a commercial modified-live M haemolytica and P multocida vaccine that was administered on days 0 and 14. Calf weight was measured on day 0 and monthly for 3 months. Farmers were asked to record any treatment given to the calves and the reason for treatment during the 4 months of the study. Blood was collected from all calves on days 0 and 28, and titers of antibodies to M haemolyticawere determined by means of direct bacterial agglutination.
Results—Mean daily gain was not significantly different between vaccinated and control calves. Vaccinated calves had a significantly greater increase in antibody titers (5.3-fold increase), compared with control calves (3.6-fold increase). There was no significant difference between vaccinated and control calves for any of the treatment outcomes (number and duration of treatments and age at first and last treatments).
Conclusions and Clinical Relevance—Results suggest that the M haemolytica and P multocidavaccine, given twice 2 weeks apart, was effective in increasing titers of antibodies against M haemolytica in young dairy calves but did not improve calf performance or health. (J Am Vet Med Assoc 2001;219:1739–1742)
