Table 4.

Effect of essential oils on ileal bacterial populations of broilers on day 21

Item a	Total bacteria	Lactobacillus	Escherichia	C. perfringens
Treatment
Basal diet, unchallenged	9.00	7.89	8.00	2.27
60 mg/kg EO, unchallenged	9.28	7.98	7.60	2.35
120 mg/kg EO, unchallenged	9.35	8.30	7.55	2.34
240 mg/kg EO, unchallenged	9.22	8.14	7.15	2.34
Basal diet, challenged	9.41	8.11	8.72	2.50
60 mg/kg EO, challenged	9.48	8.38	8.99	2.39
120 mg/kg EO, challenged	9.44	8.39	8.26	2.43
240 mg/kg EO, challenged	9.29	8.27	8.03	2.57
SEM	0.068	0.073	0.137	0.033
P-value
Challenge	0.185	0.169	<0.001	0.030
EO	0.735	0.438	0.095	0.805
Challenge × EO	0.828	0.888	0.713	0.655
Linear b	0.945	0.366	0.027	0.553
Quadratic b	0.261	0.172	0.853	0.707

^a Values are means of eight replicates per treatment, and expressed as log₁₀ (copy/g digesta). EO, essential oils; unchallenged, birds without challenge of C. perfringens; challenged, birds challenged with C. perfringens from day 14 to 20; SEM, pooled standard error of the mean; Challenge × EO, interaction between C. perfringens challenge and EO supplementation

^b When interaction between C. perfringens challenge and EO supplementation was not significant, linear and quadratic polynomial contrasts were performed on the main-effect means to EO dosages