Table 2.

Number of ESBL/ AmpC Escherichia coli (EEC) challenge organisms (mean log₁₀ cfu/g of 4 birds) in caecal contents of broiler chickens pre-treated with a competitive exclusion (CE) culture on day 1 of life or untreated controls exposed to seeder birds infected with EEC 1478 N (SHV-12) or EEC 1479 N (CMY-2) at 2 days of life (5 contact birds/ 1 seeder bird) (experiment 2)

Day of life	Group 1	Group 2	Group 3	Group 4
1	20 contact birds pre-treated with a CE culture	20 contact birds untreated	20 contact birds pre-treated with a CE culture	20 contact birds untreated
2	Addition of 4 seeder birds infected with EEC 1478 N (105 cfu/ bird)	Addition of 4 seeder birds infected with EEC 1478 N (105 cfu/ bird)	Addition of 4 seeder birds infected with EEC 1479 N (105 cfu/ bird)	Addition of 4 seeder birds infected with EEC 1479 N (105 cfu/ bird)
	Caecal contents	Caecal contents	Caecal contents	Caecal contents
9	2.3a	6.6	3.2b	6.1
16	4.4a	6.3	4.9b	6.5
23	3.5a	6.5	3.0b	6.6
30	2.8a	5.5	2.8b	6.4
37	2.4a	5.9	3.3b	5.9

^asignificantly lower than group 2; ^bsignificantly lower than group 4

Standard error: 0.487