Abstract
The objective of this study was to evaluate effects of 2 different sources
of rumen available nitrogen on cattle performance, rumen nitrogen
dynamics, and rumen microbial metabolism in lactating dairy cattle.
Eight ruminally cannulated multiparous Holstein cows averaging 60 ±
10 DIM and 637 ± 38 kg of BW were assigned to one of 2 treatment
sequences in a switchback design. Diets contained (DM basis) 44% corn
silage, 13% alfalfa haylage, 12% ground corn, and 31% protein premix
containing either a control mix of urea and wheat middlings (CON) or
Fermenten at 3% diet inclusion rate (EXP). Both diets provided similar
level (DM basis) of aNDFom (31%), CP (16.5%), RDP (8.2%) and metabolizable energy (64 Mcal ME/d). Diets were formulated to provide
approximately 115% of rumen NH3-N requirement as predicted by the
CNCPS. The trial consisted of 3 28 d experimental periods, where each
period consisted of 21 d of diet adaptation and 7 d of data and sample
collection. Digestion markers were infused continuously during the
sampling period and composited omasal samples were used to calculate
nutrient flows. All data were analyzed using the Proc Mixed procedure
in SAS. Dry matter intake was 25.5 and 25.2 kg/d for CON and EXP,
respectively (P = 0.73). Energy corrected milk yield was 42.2 and 43.2
kg/d for CON and EXP, respectively (P = 0.43), with no treatment differences
(P > 0.05) in milk fat and protein yield or content. Compared
with CON, EXP increased milk urea nitrogen (10.7 vs. 13.5 mg/dL; P =
0.01) and rumen NH3-N (4.4 vs. 5.3 mg/dL; P = 0.03). Rumen bacteria
and omasal protozoa N content tended to increase with EXP inclusion (P
< 0.1), while rumen protozoa and omasal bacteria N content increased
(P < 0.05) with EXP inclusion. Effects of Fermenten inclusion on rumen
microbial metabolism, especially microbial N content, were consistent
with previous observations of increased microbial growth and turnover
associated with supplementation of rumen available non-NH3-N in N
efficient diets.
Original language | English |
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Publication status | Published - 2014 |
Event | ADSA - ASAS Joint Annual Meeting - Orlando, Florida, United States of America Duration: 12 Jul 2015 → 16 Jul 2015 http://www.jtmtg.org/JAM/2015/ |
Conference
Conference | ADSA - ASAS Joint Annual Meeting |
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Country/Territory | United States of America |
City | Orlando, Florida |
Period | 12 Jul 2015 → 16 Jul 2015 |
Internet address |
Keywords
- microbial protein
- omasum
- Fermenten