This research program included a series of experiments to investigate the effect of starter diet protein level on the performance of broilers vaccinated with CoccivacA,A(R)-B and subsequently challenged with a mixed species Eimeria challenge compared to nonvaccinated broilers. Pre-challenge performance data indicates that vaccination may decrease body weights and increase feed conversion ratio (FCR) with vaccination. The time period associated with the observed effects is between 13 to 17 d of age. This reduction in performance of vaccinated broilers versus non-vaccinated broilers was eliminated by the conclusion of the experiments (27 d) in the higher protein diets. Vaccination was effective at generating protective immunity against the Eimeria challenge evidenced by significantly increased body weight gains, improved feed conversions, reduced post-challenge mortality, and reduced lesion development in vaccinated broilers compared to non-vaccinated. The final experiment included the comparison of CoccivacA,A(R)-B to Bio-CoxA,A(R) (salinomycin) for controlling field strain Eimeria in broilers reared on two different dietary rations varying in protein concentration. Diet A had a lower protein concentration than Diet B. On day 14, Eimeria collected from commercial broiler farms in Texas were spray applied to the litter in all pens. Broilers reared on Diet B were heavier at Day 40 while body weights at day 50 were similar for all groups. Broilers fed Diet B had lower FCR during the starter and finisher diets. Broilers fed salinomycin had lower FCR for the starter and grower diets while vaccinated broilers had lower FCR during the withdrawal period. Cumulative FCR for the entire grow out period were similar for all groups. These data indicate that vaccination can be utilized as an anticoccidial preventive and are suggestive that reduced protein concentration of starter diets can lead to significant losses in broiler performance when utilizing a vaccination program to prevent coccidiosis. Feeding an appropriately formulated diet while vaccinating broilers with CoccivacA,A(R)-B as an alternative to the use of salinomycin yields at least equivalent if not elevated performance in the presence of field-strain Eimeria during grow-out with no effect on the cost of production.
