Table 9.

Nitrogen balance, urinary excretion of creatinine and purine derivatives (PD), and microbial N supply (LSM) of lactating cows fed diets containing (HBFG) or not (CG) hydroponic barley forage.

Item	Group		SEM	p
	CG	HBFG
N balance, g/d
N intake	574.82	603.31	8.81	0.04
Faecal N excretion	189.16	191.46	5.45	0.76
Urinary N excretion	182.63	194.27	8.17	0.33
N in milk	186.55	195.01	9.23	0.52
N retained	16.47	22.57	9.08	0.64
Productive Na	217.58	223.41	9.33	0.28
Total N excretionb	371.80	385.73	9.33	0.30
Urinary excretion
Urine volume, L/d	26.21	31.96	2.11	0.07
Creatinine, mmol/d	1188.83	1204.24	39.16	0.78
Allontoin, mmol/d	363.52	384.90	10.68	0.17
Uric Acid, mmol/d	63.15	71.79	5.37	0.27
Total PD, mmol/d	426.67	456.69	11.67	0.08
Microbial N supplyc, g/d	267.93	289.34	8.08	0.07

^aCalculated as sum of N in milk and N retained (57).

^bCalculated as sum of faecal N and N in urine (57).

^cCalculations based on equation from Chen and Gomes (56).