Table 5.

Effects of steam conditioning time on the production of VFAs from in vitro cultures of mixed ruminal microorganisms fed steam-flaked grains as substrate

	Conditioning time, min				P-value
VFA, mmoles/g substrate DM1	15	30	45	SEM	Linear	Quadratic
Acetate	1.56	1.67	1.51	0.063	0.13	<0.01
Propionate	1.75	1.99	1.73	0.063	0.56	<0.01
Acetate:propionate	0.89	0.85	0.88	0.048	<0.01	<0.01
Butyrate	0.50	0.58	0.48	0.067	0.16	<0.01
Isobutyrate	0.002	0.004	0.001	0.0021	0.11	0.03
Valerate	0.058	0.073	0.058	0.0117	0.95	<0.01
Isovalerate	0.007	0.005	0.005	0.0026	0.02	0.22
Total VFA	3.88	4.32	3.78	0.082	0.25	<0.01

¹VFAs were measured by gas chromatography following 24-h incubation of cultures containing 3 g (DM) flaked corn as substrate, 10 mL ruminal fluid inoculum, and 140 mL McDougall’s Buffer at 39 °C. Initial incubation was repeated with two replicates per sample (90 samples, 180 observations, 60 per treatment).