Table 5.

Effect of SC supplementation on rumen microbial populations and percentage of target species relative to total bacteria of steers fed diets with different concentrate-to-forage ratios

Item	CTFR				SEM	SC		SEM	P-value			Probability3
	30:70	50:50	70:30	90:10		N1	Y2		CTFR	SC	CTFR × SC	Linear	Quadratic	Cubic
Total bacteria,	6.95	9.62	13.08	6.21	1.09	7.86	10.07	0.77	<0.01	0.05	0.61	0.82	<0.01	0.04
×1010 copies/mL
Rumen fungi,	6.57	5.10	11.80	3.57	0.91	5.99	7.51	0.64	<0.01	0.10	0.22	0.63	<0.01	<0.01
×105 copies/mL
Protozoa,	4.03	3.64	17.44	7.44	1.47	6.74	9.54	1.04	<0.01	0.06	0.30	<0.01	<0.01	<0.01
×105 copies/mL
Percentage relative to total bacteria
R. flavefaciens	0.45	0.20	0.28	0.16	0.03	0.25	0.29	0.02	<0.01	0.25	0.87	<0.01	0.07	<0.01
R. ablus	0.02	0.01	0.01	0.00	0.00	0.01	0.01	0.00	<0.01	0.63	0.08	<0.01	0.40	0.02
FibSuc4	1.03	0.39	0.23	0.11	0.09	0.46	0.43	0.06	<0.01	0.72	0.85	<0.01	0.03	0.41
ButFib5	0.01	0.01	0.00	0.00	0.00	0.01	0.01	0.00	<0.01	0.37	0.61	<0.01	0.68	0.75
StrBov6	0.03	0.05	0.01	0.01	0.00	0.03	0.02	0.00	<0.01	0.64	0.83	<0.01	<0.01	<0.01
RumAmy7	0.13	0.14	0.10	0.07	0.01	0.12	0.10	0.01	<0.01	0.01	0.53	<0.01	0.03	0.19
SelRum8	3.10	3.24	1.80	1.07	0.21	2.04	2.55	0.15	<0.01	0.02	0.46	<0.01	0.09	0.05
Lactobacillus9	0.02	0.02	0.04	0.05	0.01	0.04	0.03	0.01	<0.01	0.16	0.73	<0.01	0.51	0.14

¹N: without yeast supplementation;

²Y: with yeast supplementation;

³Linear indicates linear effect of dietary CTFR; quadratic indicates a quadratic effect of dietary CTFR; cubic indicates a cubic effect of dietary CTFR;

⁴FibSuc: Fibrobacter succinogenes;

⁵ButFib: Butyrivibrio fibrisolvens;

⁶StrBov: Streptococcus bovis;

⁷RumAmy: Ruminobacter amylophilus;

⁸SelRum: Selnomonas ruminantium;

⁹Lactobacillus: Lactobacillus species.