Background This study was conducted to explore new approaches of animal biocontrol via biological control feed. Method White rats were subjected to 140 highly lytic designed phages specific against E. coli. Phages were fed via drinking water, oral injection, and vegetable capsules. Phage feeding was applied by 24 h feeding with 11d monitoring and 20d phage feeding and monitoring. Group of rats received external pathogenic E. coli and another group did not, namely groups A and B. Results Phage feeding for 20d via vegetable capsules yielded the highest reduction of fecal E. coli, 3.02 and 4.62 log, in rats group A and B respectively. Second best, feeding for 20d via drinking water with alkali yielded 2.78 and 4.08 log in rats groups A and B respectively. The peak reduction in E. coli output was 5–10 d after phage feeding. Phage control declined after 10th day of feeding. Conclusions The use of cocktail of designed phages succeeded in suppressing flora or external E. coli. The phage feed biocontrol is efficient in controlling E. coli at the pre-harvest period, precisely at the 6th-8th day of phage feeding when the lowest E. coli output found.