Video 12: Why we don’t recommend ASTs

The results of ASTs do not accurately reflect the expected performance of anticoccidials in the field for 2 primary reasons.

• Firstly, the coccidial challenge is a large dose of oocysts, often 100,000 or more oocysts, given as a bolus dose to each bird. Much unlike the challenge that broilers face in the field, ingesting smaller doses of oocysts often thought to be no more than 100 oocysts per day. Assuming that an effective anticoccidial is in the ration, this relatively small daily oocyst uptake will only result in subclinical coccidiosis, being the ideal condition for community development.
• Secondly, ASTs do not allow immunity development to affect the results because they are short 6-to-7-day tests. Birds used in these tests have neither innate immunity nor protective passive immunity passed. To replicate the field condition for immunity development, they would need to be administered small numbers of oocysts daily for many more than the 6 or 7 days used in the ASTs.

Videos 1 – 4 from the series:

Video 1: Quantifying the costs of coccidiosis

Video 2: Measuring the efficacy of an anticoccidial

Video 3: Evaluating chemicals for coccidiosis control and prevention

Video 4: Evaluating vaccines as a coccidiosis control option