Innate and acquired immunity vs. anticoccidial medication in managing coccidiosis in turkeys.

Turkeys 2, 6, or 10 weeks old that had been reared free of coccidial infection were susceptibe to infection with Eimeria meleagrimitis, E. adenoeides, and E. gallopavonis. The 6- or 10-week-old birds were more resistant to infection than the 2-week-old birds (no deaths from coccidiosis vs. 100% mortality). Lesion scores were lower in 10-week-old birds than in 6-week-old birds, but significantly greater weight losses occurred in the older birds. Turkeys reared in floor pens contaminated experimentally with coccidia were immune to homologous challenge at 10 weeks old, with only slight (numerical) reduction of weight gains following challenge with 50,000 oocysts/bird of each species. These results demonstrated some degree of innate resistance associated with age, although not enough to protect against heavy challenge. The resistance of birds reared in floor pens was due largely to acquired immunity resulting from infection with coccidia. Amprolium (125 ppm), monensin (100 ppm), or Polystat (250 ppm) protected the turkeys against experimental infections in floor pens, as measured by weight gains, feed efficiency, death due to coccidiosis, and lesion scores.