Journal of Animal Science and Biotechnology

Table 6 Nitrogen output and partitioning in lactating cows selected for phenotypic divergence in residual feed intake (RFI)

From: Nitrogen partitioning and microbial protein synthesis in lactating dairy cows with different phenotypic residual feed intake

Items	Low RFI	High RFI	SEM	P value^a
Items	Low RFI	High RFI	SEM	RFI	Day	RFI × Day
N intake, g/d	590	644	18.6	0.06	0.01	0.92
N output, g/d
Feces	202	218	10.3	0.31	0.77	0.64
Urine	206	204	13.1	0.91	0.15	0.59
Milk	175	171	8.42	0.75	< 0.01	0.59
Retention^b	5.72	51.4	14.1	0.04	0.15	0.82
% of N intake
Feces	34.6	33.8	1.55	0.73	0.24	0.69
Urine	35.1	32.3	2.28	0.39	0.03	0.80
Milk	29.7	26.5	0.89	0.02	0.22	0.71
Retention	0.37	7.08	2.50	0.06	0.17	0.86

^aP value associated with RFI, time, and the interaction of RFI and time
^bNitrogen retention = ingested N − fecal N − urinary N − milk N

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ISSN: 2049-1891

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