J. Anim Sci.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Ludden, P. A.
Right arrow Articles by Hess, B. W.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Ludden, P. A.
Right arrow Articles by Hess, B. W.
J. Anim. Sci. 2002. 80:3021-3026
© 2002 American Society of Animal Science

Effects of oscillating dietary protein on nutrient digestibility, nitrogen metabolism, and gastrointestinal organ mass in sheep1,2

P. A. Ludden3, T. L. Wechter and B. W. Hess

Department of Animal Sciences, University of Wyoming, Laramie 82071

3 Correspondence:
AS/MB Rm. 123B (phone: 307-766-4213; fax: 307-766-2355; E-mail:
ludden{at}uwyo.edu).


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 
Twenty-four wether lambs (BW = 37.5 ± 0.8 kg) were used in a 64-d randomized complete block design experiment to evaluate the effect of oscillating dietary CP with undegradable intake protein (UIP) on diet digestibility, N retention, and gastrointestinal (GI) organ mass. Four treatments consisted of a 13, 15, or 17% CP diet fed daily or a regimen in which dietary CP was oscillated between 13 and 17% on a 48-h basis (ACP). All diets consisted of 65% bromegrass hay (10.5% CP, 61.9% NDF, 37.2% ADF) and 35% corn-based supplement, and were formulated to contain the same amount of degradable intake protein (9.6% of dry matter), plus additional UIP (from SoyPLUS) to accomplish CP levels above 13%. Beginning on d 52, N balance collections were conducted for 8 d, after which lambs were killed on d 62 and 64 of the trial for measurement of GI organ mass. Because intake was restricted to 3.0% of initial body weight (dry matter basis), dry matter intake did not differ (P >= 0.67) and no treatment effects (P >= 0.36) on ADG, feed efficiency, or total tract DM digestibility were observed. Increasing dietary CP from 13 to 17% linearly increased (P = 0.0001) N digestibility, but lambs fed ACP had lower (P = 0.07) total tract N digestibility than those fed 15% CP daily. Although urinary N excretion increased linearly (P = 0.0001) with increasing CP, a linear increase (P = 0.07) was observed in N retention (g/d) with increasing dietary CP. Although the quantity of N retained by lambs fed ACP was not statistically different (g/d, P = 0.19; % of digested N, P = 0.23) from those fed 15% CP daily, N retention in lambs fed ACP was 42% lower than in those fed 15% CP daily (1.8 vs 3.1 g/d, respectively). Increasing CP linearly decreased (P <= 0.09) weights of the reticulorumen, abomasum, and small intestine, but did not affect (P >= 0.16) liver or omasum weights. Length of the small intestine was not affected (P >= 0.45) by treatment, but lambs fed ACP had greater (P = 0.03) small intestine weights than those fed 15% CP daily. Increasing dietary CP linearly decreased (P = 0.03) total GI organ mass, and lambs fed ACP had a greater (P = 0.03) total GI organ mass than those fed 15% CP daily. Oscillating dietary CP may increase the weights of the GI organs, which may subsequently have negative effects on N and energy metabolism in the animal. Likewise, the potential for decreased GI organ mass in response to increased supply of CP with UIP deserves further investigation.

Key Words: Nitrogen Retention • Oscillation • Protein • Sheep


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 
Decreasing the frequency of supplementation, in some cases up to weekly intervals, is one management practice that decreases labor and equipment costs while producing little detrimental effect on animal performance. Researchers (Collins and Pritchard, 1992; Cole, 1999) have noted improvements in N utilization with decreased frequency of protein supplementation. Cole (1999) found that oscillating the CP content of the diet at 48-h intervals resulted in improved N retention in lambs, which was further enhanced with provision of natural protein vs urea. Collins and Pritchard (1992) observed that alternate-day supplementation with undegradable intake protein (UIP; corn gluten meal) improved N retention of lambs compared to supplementation of degradable intake protein (DIP; soybean meal).

The most common theory for such an improvement in protein utilization efficiency is that alternate-day supplementation stimulates recycling of endogenous N into the rumen (Hunt et al., 1989). Alternatively, Swanson et al. (1999) suggested that the form of dietary protein (DIP vs UIP) could influence size and metabolism of splanchnic tissue, especially the liver. Burgwald-Balstad et al. (1999) reported a decrease in liver mass as a percent of empty BW in heifers consuming increasing amounts of UIP. Subsequently, it is our hypothesis that intermittent protein supplementation with UIP may enhance N utilization, either by providing the animal with a source of recyclable N (Ludden et al., 2002) and/or by reducing the metabolic activity of the gastrointestinal tract organs and their subsequent amino acid catabolism. Our goal was to examine the effects of oscillating dietary protein concentrations with a UIP source on total tract nutrient digestibility, N retention, and gastrointestinal tract (GIT) and liver organ mass in growing lambs.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results and Discussion
 Implications
 Literature Cited
 
Animals and Diets

Twenty-four Western White-Face wether lambs (average initial BW = 37.5 ± 0.8 kg) were used in a 64-d randomized complete block design experiment. All animal care followed procedures that were previously approved by the University of Wyoming Animal Care and Use Committee. Lambs were blocked by initial BW and randomly assigned within block to treatment. The wethers were maintained in individual metabolism crates (1.4 x 0.6 m) under continuous lighting and were allowed free access to water. The wethers were weighed at the beginning of the experiment and DMI was restricted to 3.0% of initial BW throughout the trial. The diets (Table 1Go) were fed once daily at 0700 and consisted of 65% chopped (2.54 cm) bromegrass hay (10.5% CP, 61.9% NDF, 37.2% ADF; DM basis) and 35% corn-based supplement. Four treatments consisted of a 13, 15, or 17% CP diet fed daily or a regimen in which dietary CP was oscillated between 13 and 17% on a 48-h basis (i.e., 13, 13, 17, 17, 13, 13, . . .; ACP). These CP levels were chosen to bracket the CP requirement for a 40-kg early-weaned lamb (14.5% of DM), as suggested by NRC (1985). The diets were formulated to contain the same amount of DIP (9.6% of DM) using a combination of soybean meal and urea. This level was chosen because other research has demonstrated that DIP at this level will support maximal forage digestion (Hollingsworth-Jenkins et al., 1996; Mathis et al., 2000). Treatment CP concentrations above 13% were accomplished with the addition of a UIP source (SoyPLUS, West Central Cooperative, Ralston, IA) to replace a portion of both the corn and soybean meal/urea. The resulting diets were approximately isoenergetic on a TDN basis (65.6 ± 0.3% TDN) based upon tabular values. Ammonium chloride was included in the supplement at 0.5% of the total diet DM to avoid problems associated with urinary calculi. The concentrate portion of the diet (35% of diet DM) was top-dressed at feeding.


View this table:
[in this window]
[in a new window]
  		Table 1. Composition of diets fed to lambs
 
Sample Collection and Analyses

Following feeding on d 52, lambs were fitted with canvas fecal bags and allowed 2 d for adjustment, after which, total feces and urine were collected for 8 d. Total daily urine output was collected into plastic collection vessels containing 100 mL of 6 N phosphoric acid. Total fecal and urinary output was collected and weighed daily. A 10% aliquot of the daily fecal output was composited within lamb, dried in a 55°C oven, and then ground (2 mm). Urine samples were composited by lamb, stored covered at room temperature (20°C), and subsampled at the end of the collection period. Feed samples were collected on d 1 to 8 of the collection period, oven-dried at 55°C for 48 h, and then ground (1 mm screen).

Feed and fecal samples were analyzed for DM and OM content (AOAC, 1990). Feed, feces, and urine were analyzed for Kjeldahl N (AOAC, 1990). Feed and feces were also analyzed for NDF and ADF content using an ANKOM 200 Fiber Analyzer (ANKOM Technology, Fairport, NY).

On d 62 and 64 of the trial, lambs were killed randomly by block using 10 mL of Beuthanasia-D (Schering-Plough Animal Health Corp., Union, NJ), after which lambs were weighed to determine ending BW. An incision was made into the jugular vein prior to evisceration to allow blood to drain from the body. A lateral incision was made from the base of the neck to the anus, at which time the esophagus was externalized and tied-off. All visceral organs were immediately removed and eviscerated BW (EBW; BW after removal of all visceral organs) recorded. Gastrointestinal tract organs (reticulorumen, omasum, abomasum, small intestine, and cecum and colon) and liver were individually stripped of contents, cleaned of all extraneous tissues, rinsed with cold water, blotted dry, and weighed. Length of the small intestine from the pylorus to the ileocecal junction was also determined.

Statistical Analyses

Lambs were killed and weighed off the trial on different days; therefore, average daily gain calculations were based on the number of days that each lamb was on their respective treatment. All data were analyzed using the GLM procedures of SAS (SAS Inst., Inc., Cary, NC) for a randomized complete block design. Single degree of freedom orthogonal contrasts were used to determine linear and quadratic effects of protein concentration in the diet and to compare the 15% CP diet fed daily vs ACP.


   Results and Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
Implications
 Literature Cited
 
Average daily gain, DMI, and feed efficiency did not differ (P >= 0.36) across treatments and averaged 0.12 kg/d, 1.14 kg/d, and 10.2 (kg of gain per 100 kg of feed), respectively (Table 2Go). Similarly, no treatment effects (P >= 0.34) on total tract DM digestibility (DMD) were observed. Our results agree with Cole (1999), who reported that DMD was not affected by oscillating dietary protein concentrations between 10 and 15% at 48-h intervals, and with Collins and Pritchard (1992), who observed that feeding protein supplements to wethers at 24- or 48-h intervals did not affect DMD. Similarly, Brown et al. (1995) demonstrated that supplementation in lambs at intervals of 24, 48, and 72 h did not affect apparent DMD of low-quality forage. However, Cole (1999) did observe a tendency for DMD to decrease when dietary protein increased from 10 to 15% in lambs fed a high concentrate diet. In contrast to Cole (1999) and our study, Beaty et al. (1994) reported that DMD of low-quality forage increased (P <= 0.01) with increasing CP concentration and in steers supplemented three times per week but also observed corresponding changes in DMI, which were prevented from occurring in our study.


View this table:
[in this window]
[in a new window]
  		Table 2. Performance and DM digestion in lambs fed increasing CP or oscillating CP concentrations
 
Intakes of NDF and ADF did not differ (P >= 0.22) across treatments and averaged 531 and 301 g/d, respectively (Table 3Go). Total tract NDF and ADF digestibilities were not different (P >= 0.38) in lambs fed ACP compared to those fed 15% CP daily. Similarly, Brown et al. (1995) reported that NDF and ADF digestibility were not affected by supplementation frequency in lambs fed a straw-based diet. Coleman and Wyatt (1982) also observed that feeding intervals up to 96 h with cottonseed meal did not influence digestion of fiber components in steers consuming forage. However, total tract NDF and ADF digestibility linearly increased (P = 0.02) with increasing dietary protein concentrations in our experiment. In contrast, Swanson et al. (2000) reported that increasing levels of supplemental UIP in mature ewes did not affect NDF and ADF digestibility. The increase in fiber digestibility with increasing UIP in the present study may be a result of greater N availability for fiber fermentation, either from greater ruminal degradation of protein or from enhanced endogenous N recycling, particularly at times removed from feeding. When cannulated lambs were fed the same diets as in the present study (Ludden et al., 2002), DIP values were calculated as 8.7, 10.7, 10.2, and 10.5% of DM for the 13, 15, 17% CP daily and ACP treatments, respectively, suggesting a greater than anticipated ruminal degradation of our UIP source had occurred. However, a portion of the increasing UIP was being catabolized after absorption as indicated by the increase (P <= 0.0001) observed in urinary N excretion (Table 4Go), which suggests an increase in the supply of blood urea. This increase in blood urea may have enhanced N recycling at times further removed from feeding, thereby sustaining a more constant ruminal N supply and thus may have supported the overall increase in fiber digestion observed in the current experiment. Likewise, because a portion of the DIP in the 13% CP diet was from urea, the pattern of ruminal N release associated with that treatment may have depressed fiber digestion at times further removed from feeding, resulting in the lower fiber digestion associated with that treatment.


View this table:
[in this window]
[in a new window]
  		Table 3. Fiber digestibility in lambs fed increasing CP or oscillating CP concentrations
 

View this table:
[in this window]
[in a new window]
  		Table 4. Nitrogen balance in lambs fed increasing CP or oscillating CP concentrations
 
As intended, N intake linearly increased (P <= 0.0001) with increasing dietary CP, while no difference (P = 0.22) was observed between ACP-fed lambs and those fed 15% CP daily (Table 4Go). Increasing dietary CP from 13 to 17% linearly increased (P = 0.0001) N digestibility, which would indicate that our source of additional CP (SoyPLUS) was readily digested by the animal. However, lambs fed ACP had lower (P = 0.07) total tract N digestibility than those fed 15% CP daily. Because ACP-fed sheep received the 13 and 17% CP diets alternated every 48 h, the expected value of N digestibility should have been comparable to that in lambs consuming 15% CP daily.

Although urinary N excretion increased linearly (P <= 0.0001), N retention (g/d) increased linearly (P = 0.07) with increasing dietary CP. Cole (1999) also demonstrated that urinary N excretion and N retention increased as dietary protein increased from 10 to 15% in lambs supplemented with cottonseed meal, while Swanson et al. (2000) demonstrated that increasing levels of UIP supplementation also increased N retention. Although not statistically significant (P >= 0.23), N retention (as a percentage of N intake or digested N) was 42% lower for lambs fed ACP than for lambs fed 15% CP daily. In contrast, Cole (1999) observed that oscillating the protein content of high-concentrate diets between 10 and 15% CP with cottonseed meal at 48-h intervals increased N retention in lambs by 38% compared with animals fed 12.5% CP daily. Collins and Pritchard (1992) also observed an increase in N retention in lambs fed corn stalk-based diets and supplemented with protein every 48 h compared to daily supplementation.

In spite of receiving the same quantity of protein over the course of the trial, ACP-fed lambs had increased (P = 0.05) small intestine weights and higher (P = 0.03) total GIT and liver weights when compared to lambs fed 15% CP daily (Table 5Go). Likewise, ACP-fed lambs tended (P = 0.10) to have heavier large intestine and cecum weights than lambs consuming 15% CP daily. Krehbiel et al. (1998) demonstrated that infrequent protein supplementation increased urea N removal by the portal-drained viscera on days between supplementation in ewes consuming forage. However, these researchers also suggested that the increase in urea N output may represent an energetic cost to the animal due to an increased liver energy expenditure incurred during hepatic ureagenesis. Hepatic ureagenesis is energetically expensive, costing 1 to 4 moles of ATP per mole of urea synthesized (Huntington, 1999), and was estimated to account for 9.4, 17.8, and 11.3% of liver oxygen consumption on d 1, 2, and 3 in ewes supplemented with soybean meal every 72 h (Krehbiel et al., 1998). Additionally, a great deal of the metabolic activity associated with splanchnic tissues (GIT, pancreas, spleen, liver, and associated adipose and connective tissue) is due to a high rate of protein synthesis or protein turnover. Huntington and Reynolds (1987) noted that although the gut and liver tissues account for only 10 and 3% of total body tissue by weight, respectively, each account for about one-fourth of whole body energy expenditures, and normally account for over 40% of all oxygen consumption in ruminants (Lindsay, 1993; Huntington, 1999). As a consequence, an increase in visceral organ mass could have potential negative effects on energy utilization by the animal via increased maintenance energy expenditure associated with those organs.


View this table:
[in this window]
[in a new window]
  		Table 5. Empty body weight (EBW) and gastrointestinal organ (GIT) and liver mass in lambs fed increasing CP or oscillating CP concentrations
 
As noted for ADG and feed efficiency, EBW were unaffected (P = 0.19) by increasing dietary UIP. Liver, omasum, cecum and colon weights, and small intestine length were not affected (P >= 0.16) by CP concentration in the diet. As a percentage of EBW, weights of the reticulorumen, abomasum, and small intestine linearly decreased (P <= 0.09) with increasing CP in the diet, resulting in a linear decrease (P <= 0.09) in total weights of the gastrointestinal organs. Decreased total gastrointestinal organ mass that occurred with increasing dietary protein was unexpected. Increasing dietary protein increases liver weights in nonruminants (Pond et al., 1990), which has been attributed to the greater physiological demand placed on the liver. However, Burgwald-Balstad et al. (1999) found that UIP supplementation to growing heifers consuming forage decreased hepatic tissue mass. Swanson et al. (1999) observed a decrease in RNA concentration in jejunal and ileal tissue in ewes fed increasing levels of UIP, which suggests that these tissues may be less metabolically active in spite of lack of change in organ mass. Further, Swanson et al. (1999) also reported increased RNA concentrations in jejunal and ileal tissue from ewes fed DIP with lower levels of UIP, suggesting a more metabolically active tissue. Because UIP was increased at the expense of DIP, this suggests that energy use by intestinal tissues may be greater in DIP supplemented lambs. Thus, form of protein supplied to the ruminant animal could influence size and metabolic activity of the gut and liver tissues, suggesting that higher levels of DIP, rather than UIP, may have a greater influence on increasing gut and liver growth. This could especially occur under conditions of oversupply of DIP, in which the process of detoxifying excessive ruminal ammonia via hepatic ureagenesis might stimulate liver growth and subsequent energy consumption. Consequently, the increase observed in urinary N excretion with increasing UIP in the current study suggests that excess protein was catabolized and converted to urea N, which might have resulted in increased liver weights. We suggest that if maintaining lower circulating ammonia levels and subsequently circulating urea levels via supplementation of UIP vs DIP, the stimulus for growth of the hepatic tissues as observed in nonruminant animals may be diminished. Jiang et al. (2000) speculated that the reduction in intestinal mass in pigs fed animal plasma protein is linked to the reduction in circulating urea concentrations, which further supports our contention. Therefore, the apparent effects of UIP supplementation on gastrointestinal organ mass and associated protein and energy metabolism in the ruminant warrants further investigation.


   Implications
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
 Implications
Literature Cited
 
Although decreasing the frequency of protein supplementation generally has no detrimental effect on body weight gain, oscillating dietary protein concentrations may increase gastrointestinal organ mass, which may contribute to this response. Such increases in gastrointestinal organ mass may ultimately influence efficiency of protein and energy use by ruminant livestock. Conversely, the potential alterations in protein and energy efficiency related to decreased visceral organ mass when undegradable intake protein is supplemented warrants further investigation.


   Footnotes
 
1 We gratefully acknowledge the assistance of E. Scholljegerdes and J. Heeg for their assistance with sample collection associated with this project. Appreciation is also extended to D. Rule for his assistance with manuscript preparation. We also thank West Central Cooperative, Ralston, IA, for donation of the SoyPLUS used in this project. Back

2 This research was supported in part by the University of Wyoming Faculty Grant-In-Aid Program. Back

Received for publication February 28, 2002. Accepted for publication July 11, 2002.


   Literature Cited
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 


AOAC, 1990. Official Methods of Analysis. 15th ed. Assoc. Offic. Anal. Chem., Arlington, VA.

Beaty, J. L., R. C. Cochran, B. A. Lintzenich, E. S. Vanzant, J. L. Morrill, R. T. Brandt Jr., and D. E. Johnson. 1994. Effect of frequency of supplementation and protein concentration in supplements on performance and digestion characteristics of beef cattle consuming low-quality forages. J. Anim. Sci. 72:2475–2486.[Abstract]

Brown, D. R., F. C. Hinds, and R. M. Collins. 1995. Effect of supplementation frequency on diet digestion and nitrogen metabolism of growing lambs fed low-quality forage. Prof. Anim. Sci. 12:24–27.

Burgwald-Balstad, L. A., C. R. Krehbiel, G. D. Pulsipher, M. K. Peterson, K. K. Kane, D. E. Hawkins, B. M. Capitan, S. A. Soto-Navarro, J. E. Sawyer, and R. C. Waterman. 1999. Effect of increasing undegradable intake protein on visceral organ mass, digesta pH, and enzyme activity in heifers fed sudan grass hay. Proc. West. Sec. Am. Soc. Anim. Sci. 50:250–253

Cole, N. A. 1999. Nitrogen retention by lambs fed oscillating dietary protein concentrations. J. Anim. Sci. 77:215–222.[Abstract/Free Full Text]

Coleman, S. W., and R. D. Wyatt. 1982. Cottonseed meal or small grain forages as protein supplements fed at different intervals. J. Anim. Sci. 55:11–17.[Abstract/Free Full Text]

Collins, R. M., and R. H. Pritchard. 1992. Alternate day supplementation of corn stalk diets with soybean meal or corn gluten meal fed to ruminants. J. Anim. Sci. 70:3899–3908.[Abstract]

Hollingsworth-Jenkins, K. J., T. J. Klopfenstein, D. C. Adams, and J. B. Lamb. 1996. Ruminally degradable protein requirement of gestating beef cows grazing native winter sandhills range. J. Anim. Sci. 74:1343–1348.[Abstract]

Hunt, C. W., J. F. Parkinson, R. A. Roeder, and D. G. Falk. 1989. The delivery of cottonseed meal at three different time intervals to steers fed low-quality grass hay: Effects on digestion and performance. J. Anim. Sci. 67:1360–1366.[Abstract/Free Full Text]

Huntington, G. B. 1999. Nutrient Metabolism by Gastrointestinal Tissues of Herbivores. Pages 312–336 in Nutritional Ecology of Herbivores. H. J. G. Jung and G. C. Fahey Jr., Am. Soc. Anim. Sci., Savoy, IL.

Huntington, G. B., and C. K. Reynolds. 1987. Oxygen consumption and metabolite flux of bovine portal-drained viscera and liver. J. Nutr. 118:1082–1090.

Jiang, R., X. Chang, B. Stoll, M. Z. Fan, J. Arthington, E. Weaver, J. Campbell, and D. G. Burrin. 2000. Dietary protein plasma reduces small intestinal growth and lamina propia cell density in early weaned pigs. J. Nutr. 130:21–26.[Abstract/Free Full Text]

Krehbiel, C. R., C. L. Ferrell, and H. C. Freetly. 1998. Effects of frequency of supplementation on dry matter intake and net portal and hepatic flux of nutrients in mature ewes that consume low-quality forage. J. Anim. Sci. 76:2464–2473.[Abstract/Free Full Text]

Lindsay, D. B. 1993. Metabolism of the portal-drained viscera. Pages 267–289 in Quantitative Aspects of Ruminant Digestion and Metabolism. J. M. Forbes and J. France (ed.) CAB International, Wallingford, UK.

Ludden, P. A., T. L. Wechter, and B. W. Hess. 2002. Effects of oscillating dietary protein on ruminal fermentation and site and extent of nutrient digestion in sheep. J. Anim. Sci. (In Press).

Mathis, C. P., R. C. Cochran, J. S. Heldt, B. C. Woods, I. E. O. Abdelgadir, K. C. Olson, E. C. Titgemeyer, and E. S. Vanzant. 2000. Effects of supplemental degradable intake protein on utilization of medium- to low-quality forages. J. Anim. Sci. 78:224–232.[Abstract/Free Full Text]

NRC. 1985. Page 68 in Nutrient Requirements of Sheep. 6th Rev. ed. Natl. Acad. Press, Washington, D.C.

Pond, W. G., J. S. Dickson, V. H. Varel, F. O. I. Anugwa, and G. S. Ross. 1990. Organ hypertrophy and responses of colon microbial populations of growing swine to high dietary protein. J. Nutr. 120:1248–1255.[Abstract/Free Full Text]

Swanson, K. C., J. S. Caton, D. A. Redmer, V .I. Burke, and L. P. Reynolds. 2000. Influence of undegraded intake protein on intake, digestion, serum hormones and metabolites, and nitrogen balance in sheep. Small Ruminant Res. 35:225–233.

Swanson, K. C., D. A. Redmer, L. P. Reynolds, and J. S. Caton. 1999. Ruminally undegraded intake protein in sheep fed low-quality forage: Effect on weight, growth, cell proliferation, and morphology of visceral organs. J. Anim. Sci. 77:198–205.[Abstract/Free Full Text]


This article has been cited by other articles:


Home page
 J ANIM SCIHome page
J. T. Vasconcelos, N. A. Cole, K. W. McBride, A. Gueye, M. L. Galyean, C. R. Richardson, and L. W. Greene
Effects of dietary crude protein and supplemental urea levels on nitrogen and phosphorus utilization by feedlot cattle
J Anim Sci, March 1, 2009; 87(3): 1174 - 1183.
[Abstract] [Full Text] [PDF]

Home page
 J ANIM SCIHome page
C. K. Reynolds and N. B. Kristensen
Nitrogen recycling through the gut and the nitrogen economy of ruminants: An asynchronous symbiosis
J Anim Sci, April 1, 2008; 86(14_suppl): E293 - E305.
[Abstract] [Full Text] [PDF]

Home page
 J ANIM SCIHome page
N. A. Cole and R. W. Todd
Opportunities to enhance performance and efficiency through nutrient synchrony in concentrate-fed ruminants
J Anim Sci, April 1, 2008; 86(14_suppl): E318 - E333.
[Abstract] [Full Text] [PDF]

Home page
 J ANIM SCIHome page
S. L. Archibeque, H. C. Freetly, N. A. Cole, and C. L. Ferrell
The influence of oscillating dietary protein concentrations on finishing cattle. II. Nutrient retention and ammonia emissions
J Anim Sci, June 1, 2007; 85(6): 1496 - 1503.
[Abstract] [Full Text] [PDF]

Home page
 J ANIM SCIHome page
S. L. Archibeque, D. N. Miller, H. C. Freetly, E. D. Berry, and C. L. Ferrell
The influence of oscillating dietary protein concentrations on finishing cattle. I. Feedlot performance and odorous compound production
J Anim Sci, June 1, 2007; 85(6): 1487 - 1495.
[Abstract] [Full Text] [PDF]

Home page
 J ANIM SCIHome page
S. L. Archibeque, H. C. Freetly, and C. L. Ferrell
Net portal and hepatic flux of nutrients in growing wethers fed high-concentrate diets with oscillating protein concentrations
J Anim Sci, April 1, 2007; 85(4): 997 - 1005.
[Abstract] [Full Text] [PDF]

Home page
 J ANIM SCIHome page
D. Valkeners, A. Thewis, S. Amant, and Y. Beckers
Effect of various levels of imbalance between energy and nitrogen release in the rumen on microbial protein synthesis and nitrogen metabolism in growing double-muscled Belgian Blue bulls fed a corn silage-based diet
J Anim Sci, April 1, 2006; 84(4): 877 - 885.
[Abstract] [Full Text] [PDF]

Home page
 J ANIM SCIHome page
N. A. Cole, L. W. Greene, F. T. McCollum, T. Montgomery, and K. McBride
Influence of oscillating dietary crude protein concentration on performance, acid-base balance, and nitrogen excretion of steers
J Anim Sci, November 1, 2003; 81(11): 2660 - 2668.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Ludden, P. A.
Right arrow Articles by Hess, B. W.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Ludden, P. A.
Right arrow Articles by Hess, B. W.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS