TY - JOUR
T1 - Effects of slow-release urea on ruminal digesta characteristics and growth performance in beef steers
AU - Taylor-Edwards, C. C.
AU - Hibbard, G.
AU - Kitts, S. E.
AU - McLeod, K. R.
AU - Axe, D. E.
AU - Vanzant, E. S.
AU - Kristensen, N. B.
AU - Harmon, D. L.
PY - 2009/1
Y1 - 2009/1
N2 - Two experiments were conducted to evaluate the effects of slow-release urea (SRU) versus feed-grade urea on ruminai metabolite characteristics in steers and DMI, gain, and G:F in growing beef steers. Experiment 1 used 12 ruminally cannulated steers (529 ± 16 kg of BW) to monitor the behavior of SRU in the ruminai environment. Compared with feed-grade urea, SRU decreased ruminal ammonia concentration (P = 0.02) and tended to increase ruminal urease activity (P = 0.06) without affecting ruminai VFA molar proportions or total concentrations (P > 0.20). After 35 d of feeding, the in situ degradation rate of SRU was not different between animals fed urea or SRU (P = 0.48). Experiment 2 used 180 Angus-cross steers (330 ± 2.3 kg) fed corn silage-based diets supplemented with urea or SRU for 56 d to evaluate the effects on feed intake, gain, and G:F. The design was a randomized complete block with a 2 × 4 + 1 factorial arrangement of treatments. Treatments included no supplemental urea (control) or urea or SRU at 0.4, 0.8, 1.2, or 1.6% of diet DM. Over the entire 56 d experiment, there were interactions of urea source x concentration for gain (P = 0.04) and G:F (P = 0.01) because SRU reduced ADG and G:F at the 0.4 and 1.6% supplementation concentrations but was equivalent to urea at the 0.8 and 1.2% supplementation concentrations; these effects were due to urea source x concentration interactions for gain (P = 0.06) and G:F (P = 0.05) during d 29 to 56 of the experiment. The SRU reduced DMI during d 29 to 56 (P -0.01) but not during d 0 to 28, so that over the entire experiment there was no difference in DMI for urea source (P = 0.19). These collective results demonstrate that SRU releases N slowly in the rumen with no apparent adaptation within 35 d. Supplementation of SRU may limit N availability at low (0.4%) concentrations but is equivalent to urea at 0.8 and 1.2% concentrations.
AB - Two experiments were conducted to evaluate the effects of slow-release urea (SRU) versus feed-grade urea on ruminai metabolite characteristics in steers and DMI, gain, and G:F in growing beef steers. Experiment 1 used 12 ruminally cannulated steers (529 ± 16 kg of BW) to monitor the behavior of SRU in the ruminai environment. Compared with feed-grade urea, SRU decreased ruminal ammonia concentration (P = 0.02) and tended to increase ruminal urease activity (P = 0.06) without affecting ruminai VFA molar proportions or total concentrations (P > 0.20). After 35 d of feeding, the in situ degradation rate of SRU was not different between animals fed urea or SRU (P = 0.48). Experiment 2 used 180 Angus-cross steers (330 ± 2.3 kg) fed corn silage-based diets supplemented with urea or SRU for 56 d to evaluate the effects on feed intake, gain, and G:F. The design was a randomized complete block with a 2 × 4 + 1 factorial arrangement of treatments. Treatments included no supplemental urea (control) or urea or SRU at 0.4, 0.8, 1.2, or 1.6% of diet DM. Over the entire 56 d experiment, there were interactions of urea source x concentration for gain (P = 0.04) and G:F (P = 0.01) because SRU reduced ADG and G:F at the 0.4 and 1.6% supplementation concentrations but was equivalent to urea at the 0.8 and 1.2% supplementation concentrations; these effects were due to urea source x concentration interactions for gain (P = 0.06) and G:F (P = 0.05) during d 29 to 56 of the experiment. The SRU reduced DMI during d 29 to 56 (P -0.01) but not during d 0 to 28, so that over the entire experiment there was no difference in DMI for urea source (P = 0.19). These collective results demonstrate that SRU releases N slowly in the rumen with no apparent adaptation within 35 d. Supplementation of SRU may limit N availability at low (0.4%) concentrations but is equivalent to urea at 0.8 and 1.2% concentrations.
KW - Metabolism
KW - Nitrogen
KW - Nonprotein nitrogen
KW - Ruminant
KW - Steer
KW - Urea
UR - http://www.scopus.com/inward/record.url?scp=60549114228&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=60549114228&partnerID=8YFLogxK
U2 - 10.2527/jas.2008-0912
DO - 10.2527/jas.2008-0912
M3 - Article
C2 - 18820164
AN - SCOPUS:60549114228
SN - 0021-8812
VL - 87
SP - 200
EP - 208
JO - Journal of Animal Science
JF - Journal of Animal Science
IS - 1
ER -