Effects of a wide range of dietary forage-to-concentrate ratios on nutrient utilization and hepatic transcriptional profiles in limit-fed Holstein heifers

Table 1 Effects of dietary forage levels on ruminal fermentation in Holstein heifers

Items	Forage levels (% of diet DM)				SEM^f	P-value
Items	20	40	60	80	SEM^f	Treatment	Linear	Quadratic	Cubic
NH₃-N, mg/dL	8.27^a	3.93^b	2.22^b	2.40^b	0.583	<0.01	<0.01	<0.01	0.78
TVFAs^e, mM	94.64	92.49	89.53	86.10	1.806	0.43	0.11	0.87	0.98
VFAs, molar % of TVFAs
Acetate	53.85^c	58.04^bc	62.48^ab	65.97^a	1.135	<0.01	<0.01	0.81	0.85
Propionate	25.44^a	23.31^ab	22.10^ab	20.99^b	0.624	0.04	0.01	0.63	0.86
Butyrate	16.91^a	12.42^b	11.05^b	9.69^b	0.688	<0.01	<0.01	0.09	0.43
Valerate	0.56	1.08	0.58	0.52	0.100	0.11	0.42	0.11	0.08
Isobutyrate	0.93	2.16	2.29	1.24	0.226	0.10	0.59	0.02	0.97
Isovalerate	2.27	2.99	1.49	1.59	0.223	0.05	0.06	0.43	0.04
A:P^g	2.16^b	2.53^ab	2.89^ab	3.18^a	0.115	<0.01	<0.01	0.81	0.96

(n = 6)
^a–cMeans within a row with different superscripts differ significantly (P < 0.05)
^eTVFAs total volatile fatty acids
^fSEM standard error of the mean
^gA:P acetate:propionate

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