AbstractA random sample of herds and cows within herds was used to determine the prevalence of Mycobacterium avium ssp. paratuberculosis (MAP) infection in Puerto Rico.The sample included only adult lactating or non-lactating animals on the sampling date.The number of samples per herd varied from 25 to 150, according to herd size (25 in herds with fewer than 150 cows or 25% of the larger herds) for a total of 2,053 cows in 28 herds. All adult animals (241) of the two herds of the University of Puerto Rico were sampled in order to compare the prevalence of MAP in these herds relative to the prevalence in the herds where only a sample of the animals was evaluated. The diagnosis of MAP was based on the ELISA seologic test of blood samples, according to the manufacturer's instructions, and the results were categorized as positive or negative. On the basis of the serologic test, the prevalence of MAP in herds and cows was 96.00 and 5.77%, respectively. No difference in the latter criterion was detected between the herds in which all the adult animals were tested and those where only 25% of the animals were tested (5.39 vs. 5.87%, respectively). The cows with positive ELISA test for MAP had numerically lower daily milk yield (17.64 kg) and yield adjusted to 305 days (5,489 kg), and significantly higher somatic cell counts (1,262,000 cells per milliliter) than those negative to the test (with respective values of 18.33 and 5,894 kg and 288,000 cells per milliliter).
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