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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Dairy Forage Research » Research » Publications at this Location » Publication #303006
Title: Relative excretion of nitrogen from alfalfa silage, corn silage, corn grain, and soybean meal in urine and feces by lactating dairy cows

Author
item Powell, Joseph
item BARROS, T - University Of Wisconsin
item DANES, M - University Of Wisconsin
item WATTIAUX, M - University Of Wisconsin

Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2014
Publication Date: 7/28/2014
Citation: Powell, J.M., Barros, T., Danes, M., Wattiaux, M.A. 2014. Relative excretion of nitrogen from alfalfa silage, corn silage, corn grain, and soybean meal in urine and feces by lactating dairy cows [abstract]. Joint Meeting of the ADSA, AMSA, ASAS and PSA. Paper No. 1592.

Interpretive Summary:

Technical Abstract: The main objective of this trial is to determine the partitioning of nitrogen (N) from different feed ingredients in milk, feces, and urine. This abstract focuses on relative excretion of N in feces and urine. Twelve multiparous late-lactation Holstein cows (means±SD; 264±18 days in milk) were fed a pretreatment total mixed ration (TMR) once a day for 11 days containing (dry matter basis) 35.5, 28.6, 20.3, 12.9 and 2.6% of corn silage (CS), alfalfa silage (AS), corn grain (CG), soybean meal (SBM), and a mineral and vitamin premix, respectively. On day 12, cows were grouped by milk yield and randomly assigned to 1 of 4 dietary treatments corresponding to each feed ingredient at natural abundance of 15N being replaced by its homologue ingredient enriched with 15N (except for CS treatment, for which only 75% of the unlabeled CS was replaced by 15N-enriched CS). After 4 days feeding the 15N-enriched TMR’s, cows were fed the pretreatment non-enriched TMR during days 16 to 19. Total fecal and urinary collection was conducted on each cow every 6 hours during days 12 to 19. Feed intake and lactation performance were also measured from days 12 to 19. Corn silage and CG had the highest 15N enrichment (atom % 15N of 1.857 and 2.040, respectively), whereas AS and SBM had the lowest (atom % 15N of 0.730 and 1.385, respectively) due to 15N dilution by the atmospherically-fixed N by these legumes. Feeding 15N-enriched ingredients had no effects on dry matter intake (23.2±2.4 kg/d), milk yield (26.1±5.2 kg/d), N intake (601±61 g/d), protein yield (0.89±18 kg/d) and N use efficiency (milk N/N intake; 0.23±0.05). Cumulative 15N recovery (% of total 15N fed) in feces from days 12 to 19 was similar between AS and CS treatments (29.8 vs. 28.2%), which were greater (P<0.05) than CG (21.5%) and SBM treatments (12.5%). Highest (P<0.05) cumulative 15N recovery (%) in urine was measured in AS (27%), intermediate in CS and CG (21.6 and 19.4%, respectively) treatments, and lowest in the SBM (17.0%) treatment. Results from this study suggest that AS and CS contributed most to fecal N excretion, and AS contributed most to urinary N excretion.