Table 2.

Protein balance¹ of diets during period 1 (days 0 to 87) and period 2 (days 88 to 170)

	Treatment2
	CON	ARG	LYS	LYS + ARG
Crude protein, %	12.4	12.5	12.5	12.6
RDP3, % of crude protein	47.4	47.0	47.0	46.6
RUP4, % of crude protein	52.6	53.0	53.0	53.4
Metabolizable protein and amino acid balance
Period 1 (Day 0 to 87)
Metabolizable protein supply, g	873.9	907.3	890.6	877.9
Metabolizable protein balance, g	60.6	71.7	69.8	72.0
Arginine supply, g	36.6	47.6	36.8	45.9
Arginine balance, g	9.7	20.0	9.7	19.3
Lysine supply, g	41.8	42.7	52.2	51.0
Lysine balance, g	−10.3	−10.8	−0.3	−0.5
Supplied Lysine:Methionine	2.6	2.5	3.2	3.2
Period 2 (Day 88 to 170)
Metabolizable protein supply, g	1012.4	990.4	964.5	970.2
Metabolizable protein balance, g	265.8	257.0	244.4	250.1
Arginine supply, g	42.3	51.0	39.9	49.7
Arginine balance, g	17.7	26.8	16.1	25.9
Lysine supply, g	48.2	46.6	55.7	55.3
Lysine balance, g	0.5	−0.3	9.6	9.2
Supplied Lysine:Methionine	2.5	2.5	3.2	3.1

¹Calculated using the Beef Cattle Nutrient Requirements Model (BCNRM) of NASEM (2016) using period 1 and 2 initial and final body weights as well as average period dry matter intake from the study.

²Treatments were 1) a diet with no arginine or lysine supplementation (CON), 2) rumen-protected arginine (16% metabolizable arginine, Ajinomoto Heartland, Chicago, IL) top-dressed at 63 g/steer daily (ARG), 3) rumen-protected lysine (25% metabolizable lysine, AjiPro-L, Ajinomoto Heartland) top-dressed at 40 g/steer daily (LYS), and 4) a diet with both arginine and lysine top-dressed at 63 and 40 g/steer daily, respectively (ARG + LYS).

³Rumen degradable protein.

⁴Rumen undegradable protein.