Table 2 Animal characteristics, nitrogen intake and excretion of dairy cows with high (HMU) and low milk urea concentration (LMU) fed a normal (NP) and a low dietary crude protein level (LP) under conditions of interval feeding (97% of ad libitum intake).

From: Hepatic urea, creatinine and uric acid metabolism in dairy cows with divergent milk urea concentrations

Parameter	NP				LP				P value¹
Parameter	HMU	LMU	SE	P value²	HMU	LMU	SE	P value²	Diet	Group	Diet × group
DIM	347	313	28	0.399	328	330	27	0.958	0.977	0.562	0.515
Parity	2.5	3	0.28	0.209	3	2.6	0.26	0.236	0.918	0.918	0.088
BW, kg	653	693	25	0.137	702	716	23	0.892	0.588	0.425	0.555
BCS	3.5	3.8	0.2	0.376	3.6	3.5	0.2	0.791	0.813	0.642	0.409
Backfat, mm	14	17	2	0.340	16	13	2	0.311	0.683	0.999	0.168
DMI, kg/d	16.4	15.8	0.7	0.545	17.0	17.1	0.7	0.924	0.189	0.707	0.613
MEI, MJ/d	167	161	9	0.623	172	174	9	0.904	0.304	0.783	0.660
Water intake, L/d	62	60	4	0.724	58	64	4	0.260	0.958	0.601	0.303
Milk yield, L/d	22.2	20.8	1.7	0.564	22.8	23.4	1.6	0.773	0.329	0.824	0.537
ECM, kg/d	26.4	22.4	1.8	0.130	25.3	25.3	1.7	0.993	0.621	0.268	0.263
Milk fat, %	5.0^a	4.2^b	0.2	0.016	4.6^ab	4.3^ab	0.2	0.390	0.440	0.020	0.214
Milk protein, %	4.0	3.7	0.1	0.196	3.6	3.7	0.1	0.932	0.201	0.374	0.316
Milk lactose, %	4.7	4.6	0.1	0.485	4.7	4.8	0.1	0.657	0.237	0.838	0.418
FPR	1.3	1.1	0.1	0.144	1.3	1.2	0.1	0.284	0.746	0.076	0.735
Total N measures
N-water intake, mg/d	35.9	34.7	2.5	0.724	33.5	37.4	2.4	0.260	0.958	0.601	0.303
N-feed and water intake, g/d	486	467	23	0.555	437	440	21	0.933	0.094	0.709	0.626
N-milk, g/d	142	123	10	0.191	142	143	9	0.916	0.288	0.374	0.304
N-feces, g/d	159	150	10	0.512	151	150	9	0.954	0.698	0.605	0.661
N-urine, g/d	146^ac	148^ab	9	0.861	115^bd	120^cd	8	0.712	0.002	0.704	0.900
N-balance, g/d	39.9	45.9	20	0.831	29.1	26.6	19	0.926	0.440	0.927	0.826
Milk N metabolites
Urea, g/d	8.44	6.37	0.79	0.076	6.41	5.81	0.75	0.577	0.105	0.095	0.350
Urea, g/L	0.37^a	0.31^ab	0.03	0.074	0.28^b	0.25^ab	0.02	0.291	0.004	0.046	0.547
Urine N metabolites
Urea, g/d	244^ac	247^ab	18	0.903	182^bd	176^cd	17	0.791	< 0.001	0.926	0.787
Hippuric acid, g/d	113	93.2	12	0.245	109	119	11	0.544	0.351	0.647	0.207
Creatinine, g/d	13.2	13.5	0.8	0.771	12.7	13.0	0.8	0.807	0.565	0.705	0.965
Creatine, g/d	9.9	10.7	1	0.582	9.8	11.6	1	0.192	0.724	0.197	0.614
Uric acid, g/d	5.2	6.3	0.8	0.323	6.4	7.1	0.7	0.477	0.227	0.230	0.815

Data are given as least square means and standard error (SE).
^a-dDifferent superscript letters within one row indicate P < 0.05 (Tukey-test).
DIM: days in milk; DMI: dry matter intake; MEI: metabolizable energy intake; ECM: energy corrected milk; FPR: milk fat% -to-milk protein%-ratio.
¹P value from ANOVA analysis.
²P value from Tukey slice test.

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Table 2 Animal characteristics, nitrogen intake and excretion of dairy cows with high (HMU) and low milk urea concentration (LMU) fed a normal (NP) and a low dietary crude protein level (LP) under conditions of interval feeding (97% of ad libitum intake).

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