TABLE 1.

Abundance of total bacteria and abundance and activity of methanogenic archaea in the rumen of nonlactating cows fed methane-reducing additives

Parameter	Abundance and activity
	Study 1a					Effect			Study 2b					Effect
	CTL	LIN	NIT	LIN+NIT	SEM	Linseed	Nitrate	lin×nit	CTL	TEA	NIT	TEA+NIT	SEM	Saponin	Nitrate	sap×nit
Total bacterial concn (log10 rrs copies/ng DNA)	5.09	4.94	4.95	4.98	0.051	0.50	0.54	0.33	5.04	4.96	5.02	5.15	0.057	0.64	0.12	0.05
Methanogen concn (log10 mcrA copies/ng DNA)	2.95	2.68	2.72	2.76	0.051	0.36	0.15	<0.1	2.97	2.84	2.97	3.07	0.081	0.84	0.25	0.24
Methanogen activityc (2−ΔCT × 106)	23.91	21.54	10.49	8.19	3.384	0.51	<0.01	0.99	18.67	16.08	7.40	8.28	4.463	0.76	<0.01	0.53

^aIn study 1, cows were fed a control (CTL) diet and CTL diet supplemented with linseed (LIN), nitrate (NIT), and linseed plus nitrate (LIN+NIT). Tested effects were linseed (CTL and NIT versus LIN and LIN+NIT) and nitrate (CTL and LIN versus NIT and LIN+NIT) and their interaction, lin×nit.

^bIn study 2, cows were fed a control (CTL) diet and control diet supplemented with tea saponin (TEA), nitrate (NIT), and tea saponin plus nitrate (TEA+NIT). Tested effects were saponin (CTL and NIT versus TEA and TEA+NIT) and nitrate (CTL and TEA versus NIT and TEA+NIT) and their interaction, sap×nit.

^cMethanogen activity is measured as mcrA expression levels.