Effects of the dietary nonfiber carbohydrate content on lactation performance, rumen fermentation, and nitrogen utilization in mid-lactation dairy cows receiving corn stover

Table 4 Urinary nitrogen, purine derivatives (PD), and estimated microbial protein (MCP) supply to the dairy cows fed 3 experimental diets

Items^d	Treatment^c			SEM	P-value
Items^d	AH	L-NFC	H-NFC	SEM	P-value
Urine volume, L/d	34.3^a	32.7^a	28.6^b	1.52	0.02
Urinary PD, mmol/d
Allantoin	358	377	325	22.0	0.26
Uric acid	60.8	59.2	52.7	4.97	0.22
Endogenous PD	52.6	52.7	52.5	1.28	0.68
MCP, g/d	1690	1766	1516	117	0.31
Urea nitrogen, mg/dL	670	730	664	30.1	0.09

^a-b Least squares means within a row with different superscripts differ significantly (P < 0.05)
^cAH = Total mixed rations containing alfalfa hay; L-NFC = Total mixed rations containing corn stover with a low content of non-fiber carbohydrates; H-NFC = Total mixed rations containing corn stover formulated to have similar non-fiber carbohydrate concentrations as the AH diet
^dUrine volume (L/d) = BW (kg) × 29 (mg/d)/creatinine (mg/L) [18]; Microbial protein (MCP) was indirectly estimated by the following eq. [15]: MCP = (allantoin + uric acid − endogenous PD) × 70 × 6.25/(0.116 × 0.83 × 1000)

ISSN: 2049-1891