Data is limited evaluating infrequent supplementation of urea or biuret to
ruminants consuming low-quality forage (<6% crude protein). Therefore, a series
of experiments were designed to compare the effects of daily (D) and alternate day
(2D) supplementation of two non-protein nitrogen (NPN) sources (urea or biuret) to
ruminants consuming low-quality forage. Experiment 1 was a N balance study
using five wethers in an incomplete 5 x 4 Latin square design (five treatments; four
24-d periods) with a 2 x 2 factorial arrangement of treatments (two sources of NPN
and two supplementation frequencies) and an unsupplemented control.
Supplements, consisting of urea or biuret mixed with ground soy hulls and dried
molasses, were isonitrogenous (approximately 26% crude protein; dry matter basis)
and offered D or 2D. The 2D supplemented lambs received double the quantity of
supplemental N on their supplementation day compared with D lambs; therefore,
all D and 2D treatments received the same amount of supplemental N over a 2-d
period. Experiment 2 was a 70-d cow performance study using 80 spring-calving
cows during the last third of gestation. Cows were stratified by age, body condition
score, and expected calving date, and assigned randomly within stratification to one
of the five treatments described in Experiment 1 above. They were then sorted by
treatment and randomly assigned to 1 of 20 pens (4 cows/pen, 4 pens/treatment).
Experiment 3 was a site of digestion study using five ruminally and duodenally
fistulated steers to compare D and 2D supplementation of urea or biuret on forage
intake, ruminal fermentation, site and extent of nutrient digestion, and rumen
microbial efficiency. Five ruminally and duodenally fistulated steers were used in
an incomplete 5 x 4 Latin square design with the same treatments described in
Experiment 1. The results for Experiment 1 reported that DM, OM, and N intake,
DM, OM, and N digestibility, N balance, and digested N retained were greater (P<0.03) for supplemented wethers compared with CON with no difference (P>0.05)
because of NPN source or SF. Supplemented lambs had increased plasma urea N
(PUN) compared with CON (P<0.01) and urea treatments had greater PUN
compared with biuret (P<0.01). Also, PUN was increased (P=0.02) for D
compared with 2D treatments. In addition, data suggest that PUN exhibited less
fluctuation on the day of a supplementation event for biuret compared with urea.
Experiment 2 demonstrated that pre- and post- calving (within 14 d and 24 h of
calving, respectively) cow weight and body condition score changes were more
positive (P<0.05) for supplemented groups compared with the CON. In
Experiment 3, forage OM intake and OM digestibility were not affected (P>0.05)
by NPN supplementation, NPN source, or SF. However, total OM and N intake were increased (P<0.01) with supplementation. Duodenal flow of OM tended (P=0.08) to increase with NPN supplementation while N flow was greater (P=0.04) with NPN supplementation compared with the control. In addition, duodenal
bacterial N flow was increased with NPN supplementation (P=0.04) and for biuret
compared with urea (P<0.01). Bacterial efficiency (g bacterial N/kg OM truly
digested in the rumen) was greater for the control compared with NPN treatments
(P<0.01) while biuret had greater true N disappearance compared with urea (P=0.01). Intestinal disappearance (% of duodenal flow) of OM and N was not affected by NPN supplementation, NPN source, or SF. However, apparent total tract N digestibility was increased with NPN supplementation (P<0.01) and not
affected by NPN source or SF. In addition, ruminal NH���-N increased (P<0.04) on
the day all supplements were provided and the day only daily supplement were
provided with supplemental NPN. However, an NPN source x SF interaction (P=0.03) on the day all supplements were provided indicated NH���-N increased at a greater rate for urea as SF decreased compared with biuret. Ruminal NH���-N on the day only daily supplements were provided was greater for D compared with 2D (P=0.02). This data suggests that ruminal degradation of biuret to NH���-N was more
moderate and prolonged compared with urea, possibly improving use by ruminal
microflora. On the day all supplements were provided, D treatments had increased
(P=0.05) ruminal indigestible acid detergent fiber passage rate and ruminal liquid
volume compared with 2D treatments. Overall, NPN supplementation when
feeding low-quality forage (<6% CP) was more beneficial than compared to a
negative control, for increasing efficiency of forage digestion, N use, and animal
performance. While at the same time indicating that the infrequent
supplementation of urea or biuret was not detrimental to forage nutrient utilization,
N efficiency or cow performance. This research will provide researchers and
ruminant livestock producers with original information that can be used in
designing winter supplementation strategies that decrease supplementation costs.
Keywords: Urea, Biuret, Forage, Non-Protein Nitrogen, Supplementation, Frequency / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/31585 |
| Date | 22 July 2002 |
| Creators | Currier, Thomas A. |
| Contributors | Bohnert, David W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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