TABLE 2.

Differences in concentrations and molar proportions of SCFA in ileal and cecal digesta of low- and high-RFI broiler chickens fed either ad libitum or restrictively^a

Parameter	Valueb				SEM	P value
	Ad libitum feeding		Restrictive feeding
	Low RFI	High RFI	Low RFI	High RFI		FL	RFI	FL × RFI
Ileum
Concn (µmol/g)
Total SCFA	61.8	57.3	48.1	49.2	3.99	0.009	0.672	0.483
Acetate	56.1	52.2	43.5	44.0	3.61	0.006	0.628	0.549
Propionate	0.7	0.6	0.5	0.7	0.07	0.462	0.223	0.064
Butyrate	0.5	0.3	0.2	0.4	0.16	0.707	0.861	0.240
Isobutyrate	4.5	4.2	3.8	3.8	0.42	0.224	0.731	0.702
Valerate	0.05b	0.05b	0.01b	0.12a	0.02	0.405	0.024	0.033
Isovalerate	0.02b	0.02b	0b	0.07a	0.01	0.390	0.017	0.026
Caproate	0.09b	0.07b	0.05b	0.17a	0.03	0.202	0.062	0.008
Molar proportions (%)
Acetate	90.8	91.1	90.7	89.3	0.45	0.034	0.191	0.055
Propionate	1.1	1.1	1.0	1.4	0.11	0.269	0.060	0.079
Butyrate	0.63	0.39	0.48	0.73	0.21	0.647	0.992	0.245
Isobutyrate	7.2	7.2	7.6	7.9	0.51	0.281	0.846	0.767
Valerate	0.06b	0.08b	0.04b	0.23a	0.04	0.154	0.014	0.040
Isovalerate	0.03b	0.04b	0b	0.12a	0.02	0.184	0.003	0.014
Caproate	0.15b	0.12b	0.12b	0.35a	0.05	0.048	0.063	0.012
Ceca
Concn (µmol/g)
Total SCFA	160.4	154.6	140.6	118.5	13.29	0.046	0.304	0.544
Acetate	131.9	127.4	109.9	93.4	11.30	0.020	0.362	0.600
Propionate	8.4	6.4	6.7	7.2	1.06	0.682	0.457	0.247
Butyrate	15.6b	16.3b	19.7a	11.8b	1.76	0.898	0.050	0.020
Isobutyrate	1.0b	1.3b	1.0b	2.2a	0.18	0.023	<0.001	0.025
Valerate	1.6	1.3	1.9	1.6	0.20	0.128	0.220	0.878
Isovalerate	1.1	1.3	1.0	1.7	0.21	0.436	0.031	0.183
Caproate	0.8	0.6	0.5	0.6	0.16	0.224	0.914	0.413
Molar proportions (%)
Acetate	82.2	82.5	77.6	79.4	1.21	0.003	0.413	0.546
Propionate	5.3a	4.0b	4.7ab	5.8a	0.50	0.255	0.769	0.020
Butyrate	9.7b	10.6b	14.5a	9.4b	1.04	0.090	0.054	0.006
Isobutyrate	0.7b	0.9b	0.8b	2.1a	0.19	0.003	<0.001	0.009
Valerate	1.0	0.8	1.4	1.4	0.11	<0.001	0.539	0.554
Isovalerate	0.7b	0.9b	0.7b	1.6a	0.15	0.024	0.003	0.046
Caproate	0.5	0.4	0.3	0.50	0.09	0.930	0.676	0.110

^aData are presented as least-squares means and pooled SEM. n = 7 per FL group, residual-feed-intake (RFI) rank, and sex except for n = 8 high-RFI ad libitum females. RFI was calculated for the experimental period from 9 to 30 days posthatch. FL, feed intake level; SCFA, short-chain fatty acids.

^bDifferent letters within a row indicate significant differences (P ≤ 0.05).