Table 4.

Effects of rumen-protected L-Arg supplementation or injected L-Arg-HCl on ruminal fill, pH, ammonia, and volatile fatty acids in forage-fed steers

	Treatmentsa					P-values
Item	CON	Arg-INJ	Arg-RP180	Arg-RP360	SEMb	Treatment	Hour	Treatment × Hour
Total ruminal fill, kg	73.0	71.7	65.2	69.1	4.3	0.30	–	–
Ruminal DM fill, kg	9.83	8.71	8.55	9.94	0.73	0.40	–	–
Fluid dilution rate, %/h	7.99	6.15	4.87	7.98	1.44	0.13
Ruminal pH	6.98	6.94	7.05	6.98	0.07	0.19	0.39	0.60
NH3, mM	2.43b	2.73b	3.59b,c	4.52c	0.44	0.004	<0.001	0.20
Total VFA, mM	77.9	78.3	78.1	79.5	1.0	0.28	0.05	0.82
VFA concentration, mol/100 mol
Acetate	51.0	50.2	50.7	51.0	1.1	0.44	<0.001	0.44
Propionate	24.6	25.5	24.0	24.6	0.8	0.10	<0.001	0.96
Butyrate	18.0	18.1	18.4	18.7	0.6	0.43	0.005	0.38
Isobutyrate	1.92c,d	1.75b,c	1.97d	1.64b	0.10	0.01	0.16	0.58
Valerate	1.81	1.78	1.90	1.81	0.09	0.21	<0.001	0.79
Isovalerate	2.63b,c	2.47b	2.92c	2.26b	0.23	0.03	0.003	0.28
Acetate:Propionate	2.09c	1.96b	2.11c	2.08c	0.09	<0.001	<0.001	0.69

^aTreatments included: ad libitum grass hay (CON), CON hay with 27-mg L-Arg-HCl/kg BW injected twice daily (54 mg/kg BW daily; Arg-INJ), CON hay with 90-mg rumen-protected L-Arg/kg BW supplemented twice daily (180 mg/kg BW daily; Arg-RP180), and CON hay with 180-mg rumen-protected L-Arg/kg BW supplemented twice daily (360 mg/kg BW daily; Arg-RP360).

^b,cMeans within a row without a common letter superscript differ (P ≤ 0.05).