Open Access

Influence of ruminal degradable intake protein restriction on characteristics of digestion and growth performance of feedlot cattle during the late finishing phase

  • Dixie May1,
  • Jose F Calderon1,
  • Victor M Gonzalez1,
  • Martin Montano1,
  • Alejandro Plascencia1,
  • Jaime Salinas-Chavira2,
  • Noemi Torrentera1 and
  • Richard A Zinn3Email author
Journal of Animal Science and Technology201456:14

https://doi.org/10.1186/2055-0391-56-14

Received: 29 April 2014

Accepted: 16 July 2014

Published: 13 August 2014

Abstract

Two trials were conducted to evaluate the influence of supplemental urea withdrawal on characteristics of digestion (Trial 1) and growth performance (Trial 2) of feedlot cattle during the last 40 days on feed. Treatments consisted of a steam-flaked corn-based finishing diet supplemented with urea to provide urea fermentation potential (UFP) of 0, 0.6, and 1.2%. In Trial 1, six Holstein steers (160 ± 10 kg) with cannulas in the rumen and proximal duodenum were used in a replicated 3 × 3 Latin square experiment. Decreasing supplemental urea decreased (linear effect, P ≤ 0.05) ruminal OM digestion. This effect was mediated by decreases (linear effect, P ≤ 0.05) in ruminal digestibility of NDF and N. Passage of non-ammonia and microbial N (MN) to the small intestine decreased (linear effect, P = 0.04) with decreasing dietary urea level. Total tract digestion of OM (linear effect, P = 0.06), NDF (linear effect, P = 0.07), N (linear effect, P = 0.04) and dietary DE (linear effect, P = 0.05) decreased with decreasing urea level. Treatment effects on total tract starch digestion, although numerically small, likewise tended (linear effect, P = 0.11) to decrease with decreasing urea level. Decreased fiber digestion accounted for 51% of the variation in OM digestion. Ruminal pH was not affected by treatments averaging 5.82. Decreasing urea level decreased (linear effect, P ≤ 0.05) ruminal N-NH and blood urea nitrogen. In Trial 2, 90 crossbred steers (468 kg ± 8), were used in a 40 d feeding trial (5 steers/pen, 6 pens/ treatment) to evaluate treatment effects on final-phase growth performance. Decreasing urea level did not affect DMI, but decreased (linear effect, P ≤ 0.03) ADG, gain efficiency, and dietary NE. It is concluded that in addition to effects on metabolizable amino acid flow to the small intestine, depriving cattle of otherwise ruminally degradable N (RDP) during the late finishing phase may negatively impact site and extent of digestion of OM, depressing ADG, gain efficiency, and dietary NE.

Keywords

Cattle Degradable protein Digestion Growth performance

Background

Because of its low cost per unit of N compared with most sources of natural protein, urea is a primary source of supplemental N in conventional steam-flaked corn-based finishing diets for feedlot cattle [1]. In a review of nutrition consultant recommendations across 11 states in the USA, Vasconcelos and Galyean [2] observed that on average, flaked corn-based finishing diets contained 13.5% CP with 1.2% of supplemental urea (approximately 64% DIP). Although dietary formulation in this manner is expected to meet urea fermentation potential (UFP) for optimal microbial growth, it may exceed protein requirements for cattle growth, particularly during the late finishing phase. Preston [3] proposed the feasibility of restricting protein supplementation during the late finishing phase as a means of minimizing N excess and associated environmental impact [1, 4] without detrimentally affecting cattle performance. However, the impact of this practice on digestive function and cattle growth-performance has received limited research attention. The aim of this study was to evaluate the influence of UFP for optimal microbial growth on characteristics of digestion and growth performance of feedlot cattle during the late finishing phase.

Methods

All procedures involving animal care and management were in accordance with and approved by the University of California, Davis, Animal Use and Care Committee.

Trial 1

Six Holstein steers (160 ± 10 kg) with cannulas in the rumen and proximal duodenum [5] were used in 3 × 3 replicated Latin square experiment. Burroughs et al.[6] proposed that amount of degradable intake protein (DIP) necessary to optimize microbial growth was equivalent to the net microbial protein synthesis. Accordingly, the urea fermentation potential of the diet (percentage of additional urea that may be added to the diet in order to optimize microbial growth) would be equivalent to: (0.104TDN- DPI)/2.8, where TDN is expressed as a percentage, and DPI is expressed as the percentage of RDP in the basal diet before urea supplementation. Accordingly, treatments consisted of a steam flaked corn-based finishing diet adjusted for restriction of rumen DIP to provide urea fermentation potentials of 0 (UFP-0), 0.6 (UFP-0.6) and 1.2% (UFP-1.2). Composition of experimental diets is shown in Table 1. Chromic oxide (0.40%, DM basis) was included in diets as a digesta marker. Dry matter intake was restricted to 4.0 kg/d (2.2% of BW daily), and feed was offered in equal portions at 0800 and 2000 daily. The three experimental periods consisted of a 10-d diet adjustment period followed by a 4-d collection period. During the collection period duodenal and fecal samples were taken from all steers, twice daily as follows: d 1, 1050 and 1450; d 2, 0900 and 1500; d 3, 0730 and 1330, and d 4, 0600 and 1200. Individual samples consisted of approximately 750 mL of duodenal chyme and 200 g (wet basis) of fecal material. Samples from each steer and within each collection period were composited for analysis. During the final day of each collection period, 4 h after feeding, ruminal and blood samples were collected from each steer via ruminal cannula and caudal venous respectively. Ruminal fluid pH was determined by inserting a pH electrode into the freshly collected samples. The ruminal fluid sample was divided into two parts: 40 mL was measured into a plastic bag, placed in an ice bath, and carried to a laboratory for determination of N-NH in fresh ruminal fluid [7]. The remainder was strained through four layers of cheesecloth. Ten mL of freshly prepared 25% (wt/vol) metaphosphoric acid was added to 40 mL of strained ruminal fluid, 10 mL were then centrifuged (17,000 × g for 10 min), and supernatant fluid was stored at −20°C for VFA analysis. Upon completion of the trial, ruminal fluid was obtained via the ruminal cannula from all steers and composited for microbial isolation via differential centrifugation [8]. The microbial isolates were prepared for analysis by oven drying at 70°C and then grinding with mortar and pestle. Feed, duodenal, and fecal samples were prepared for analysis by oven drying at 70°C and then grinding in a laboratory mill. Samples were then oven dried at 105°C until no further weight loss occurred and stored in tightly sealed glass jars. Samples were subjected to all or part of the following analysis: DM (oven-drying at 105°C until no further weight loss), ash, N-NH, Kjeldahl N [9], NDF-adjusted for insoluble ash [10], purines [11], starch [12] and VFA concentrations of ruminal fluid (gas chromatography; [13]), GE (adiabatic bomb calorimetry), and chromic oxide [14]. Duodenal flow and fecal excretion of DM were calculated based on marker ratio, using chromic oxide. Microbial organic matter (MOM) and microbial N (MN) leaving the abomasum were calculated using purines as a microbial marker [11]. Organic matter fermented in the rumen was considered equal to OM intake minus the difference between the amount of total OM reaching the duodenum and MOM reaching the duodenum. Feed N escape to the small intestine was considered equal to total N leaving the abomasum minus N-NH, microbial, and endogenous N (0.195 g/kg W0.75; [15]). Methane production (mol/mol of glucose equivalent fermented) was estimated based on the theoretical fermentation balance for observed molar distribution of VFA [16]. Whole blood samples were centrifuged and the plasma frozen for BUN analysis. The blood samples collected were centrifuged and the plasma analyzed for Blood Urea Nitrogen (BUN) by slide method using Vitros Bun/Urea DT60 II (Ortho Clinical Diagnostics, Inc., Rochester, NY), and ruminal N-NH [7]. The effects of the urea level on characteristics of digestion in cattle were analyzed as a 3 × 3 replicated Latin square design using the MIXED procedure (SAS Inst. Inc., Cary, NC). The fixed effect consisted of treatment, and random effects consisted of steer and period. The statistical model for the trial was as follows:
Table 1

Diet composition of experiment 1 and 2 1

 

Urea fermentation potential

Item

0

0.6

1.2

Ingredient (g/kg of DM)

   

Steam flaked corn

797.5

803.0

809.0

Sudangrass hay

50.0

50.0

50.0

Alfalfa hay

50.0

50.0

50.0

Urea

12.5

7.0

1.0

Cane molasses

50.0

50.0

50.0

Yellow grease

20.0

20.0

20.0

Limestone

14.0

14.0

14.0

Trace mineral salt2

4.0

4.0

4.0

Magnesium oxide

2.0

2.0

2.0

Monensin3

0.022

0.022

0.022

Nutrient composition (DM basis)4

   

NEm (Mcal/kg)

2.23

2.24

2.25

NEg (Mcal/kg)

1.56

1.56

1.58

DE (Mcal/kg)

3.86

3.86

3.89

CP (g/kg)

130.0

115.0

99.1

RDP (g/kg of CP)

648

600

530

NDF (g/kg)

125.0

125.0

125.0

Calcium (g/kg)

6.6

6.6

6.6

Phosphorus (g/kg)

2.8

2.8

2.8

1Chromic oxide (0.40%) was added in substitution of corn grain as a digesta marker in Trial 1. RDIP, rumen degradable intake protein. UFP, estimated urea fermentation potential.

2Trace mineral salt contained: CoSO4, 0.068%; CuSO4, 1.04%; FeSO4, 3.57%; ZnO, 1.24%; MnSO4, 1.07%; KI, 0.052%; and NaCl, 92.96%.

3Rumensin80 (Elanco Animal Health, Greenfield, IN).

4Based on tabular values for individual feed ingredients (NRC, [17]).

Y ijk = µ + R l + S i l + P j l + T k + E ijk ,

where: Yijk is the response variable, μ is the common experimental effect, Rl is the replicated effect, Si is the steer effect within replicate, Pj is the period effect within replicate, Tk is the treatment effect and Eijk is the residual error. Treatment effects were tested using the following contrasts: 1) linear effect of the urea level, and 2) quadratic effect of the urea level, which were determined according to SAS (SAS Inst., Inc., Cary, NC; Version 9.1).

Trial 2

Ninety crossbred steers with an average initial weight of 468 ± 8 kg were used in a 40 d finishing trial to evaluate the treatment effects on growth performance. Steers had a purchase weight of 214 ± 14 kg and had been on feed 197 d before initiation of the study. Steers had been implanted with Synovex-S (Zoetis, Florham Park, NJ) upon arrival into the feedlot and with Revalor-S (Merck Animal Health, Summit, NJ) on d 98. Ten d prior to initiation of the study steers were weighed, reimplanted with Revalor-S, blocked by weight and randomly allotted within weight groupings to 18 pens (5 steers/pen). Pens were 43 m2, with 22 m2 of overhead shade, automatic waterers, and 2.4 m long fence-line feed bunks. Dietary treatments were the same as those used in Experiment 1. All steers received the UFP-0 diet for 10 d prior to initiation of the trial. Diets were prepared at weekly intervals and stored in plywood boxes located in front of each pen. Steers were allowed free access to dietary treatments. Fresh feed was provided twice daily. Individual steers were weighed upon initiation and completion of the trial. In the calculation of steer performance live weights were reduce 4% to adjust for digestive tract fill. Estimates of steer performance were based on pen means. Net energy values for each diet were calculated from estimates of energy gain (EG, Mcal/d) based on growth-performance; EG = 0.0557 BW0.75 (ADG1.097), where EG is the daily energy deposited (Mcal/d), BW is the mean shrunk body weight (full weight × 0.96) and maintenance energy expended (EM, Mcal/d); EM = 0.077 BW0.75[18]. Dietary NEg was derived from NEm by the equation: NEg = 0.877 NEm - 0.41 [19]. Dry matter intake is related to energy requirements and dietary NEm according to the equation: DMI = EG / NEg), and can be resolved for estimation of dietary NE by means of the quadratic formula: x = b ± b 2 4 ac 2 a , where x = NEm, a = -0.877 DMI, b = 0.877 EM + 0.41 DMI + EG, and c = -0.41 EM [19].

All steers were harvested on the same day. Each carcass was weighed at time of slaughter to determine dressing percentage [20]. Performance (gain, gain efficiency, and dietary energetics) and carcass data were analyzed as a randomized complete block design; the experimental unit was the pen. The MIXED procedure of SAS [21] was used to analyze the variables. The fixed effect consisted of treatment, and pen was the random component. Treatments effects were tested using the following contrasts: 1) linear effect of the urea level, and 2) quadratic effect of the urea level, which were determined according to SAS [21].

Results and discussion

The influence of dietary treatments on ruminal and total tract digestion is shown in Table 2. Decreasing supplemental urea decreased (linear effect, P ≤ 0.05) ruminal OM digestion. This effect was mediated by decreases in ruminal digestibility of NDF (linear effect, P = 0.05), starch (linear effect, P = 0.09) and N (linear effect, P = 0.04). Likewise, Zinn et al.[22] observed decreased ruminal digestion of OM, NDF and starch in response to decreasing urea supplementation of a steam-flaked corn-based finishing diet fed to feedlot steers [22].
Table 2

Influence of dietary treatments on characteristics of digestion

 

Urea fermentation potential

P - value

 

Item

0

0.6

1.2

Linear

Quadratic

SEM

Steer replications

6

6

6

   

Intake (g/d)

 

DM

3556

3553

3551

   

OM

3343

3359

3378

   

NDF

453

455

457

   

N

66.2

57.6

48.2

   

Starch

1907

1919

1932

   

GE (Mcal/d)

15.2

15.2

15.3

   

Flow to the duodenum (g/d)

 

OM

1655

1749

1894

0.05

0.76

83.0

NDF

338

370

456

0.05

0.55

42.0

Starch

385

441

533

0.08

0.77

61.0

Total N

76.4

68.8

64.4

0.04

0.70

4.0

Microbial N

40.6

34.7

31.4

0.04

0.69

3.0

NH-N

2.30

2.04

1.58

0.06

0.72

0.3

Non-ammonia N

74.1

66.7

62.9

0.04

0.66

3.8

Feed N

24.7

23.2

22.7

0.20

0.71

0.9

Ruminal digestibility, %

 

OM

62.6

58.3

53.23

0.04

0.91

0.3

NDF

25.3

18.6

0.30

0.05

0.54

0.9

Starch

79.8

77.0

72.4

0.09

0.78

0.3

Feed N

62.6

59.7

52.9

0.04

0.64

0.5

Microbial efficiency1

19.4

17.8

17.5

0.06

0.40

0.7

N efficiency2

1.12

1.16

1.30

0.05

0.44

0.07

Fecal excretion (g/d)

 

OM

624

705

756

0.06

0.77

48.0

NDF

282

319

348

0.06

0.87

25.0

Starch

35.9

49.0

56.6

0.10

0.78

9.4

Total N

20.9

22.2

21.8

0.48

0.44

1.0

GE (Mcal/d)

3.28

3.66

3.90

0.05

0.75

0.84

Postruminal digestibility (% of flow to duodenum)

 

OM

62.2

59.7

60.0

0.37

0.49

1.9

NDF

15.3

11.2

22.8

0.41

0.33

7.3

Starch

90.5

89.1

89.3

0.60

0.69

1.9

Total N

72.6

67.6

66.2

0.08

0.53

2.7

Total tract digestibility (% of intake)

    

OM

81.3

79.0

77.6

0.06

0.75

1.4

NDF

37.8

29.8

23.9

0.07

0.85

5.3

Starch

98.1

97.4

97.1

0.11

0.77

0.5

Total N

68.5

61.5

54.9

0.04

0.97

4.5

DE, %

78.5

76.0

74.5

0.05

0.74

1.4

DE, Mcal/kg

3.36

3.26

3.20

0.05

0.73

0.06

1Microbial N, g/kg OM fermented.

2Nonammonia N flow to the small intestine as a fraction of N intake.

Passage of non-ammonia N to the small intestine decreased (linear effect, P = 0.04) with decreasing dietary urea level. This effect was due to decreased (linear effect, P = 0.04) MN synthesis. Taking into consideration energy intake alone, predicted flow of MN to the small intestine was 48g/d ([17], Level 1). Accordingly, with decreasing urea level, the observed flow of MN to the small intestine was 85, 73, and 65% of predicted flow for UFP-0, UFP-0.6, and UFP-1.2, respectively. This decline in net synthesis is consistent with [19] who observed that MN flow to the small intestine declines with decreasing DIP below 100 g/kg of total tract digestible OM. For the present study, DIP averaged 95, 81, and 61g/kg total tract digestible OM for UFP-0, UFP-0.6, and UFP-1.2, respectively. Thus, it is apparent that as DIP intake drops below 95 g/kg digestible OM there is not sufficient compensation in ruminal N recycling to maintain microbial growth, and as microbial growth declines, likewise, ruminal OM digestion declines.

There were no treatment effects (P = 0.20) on passage of feed N to the small intestine. Notwithstanding decreased non-ammonia N flow to the small intestine with decreasing urea level, ruminal N efficiency (non-ammonia N flow to the small intestine as a fraction of N intake) increased (linear P < 0.05), reflecting increased contribution of recycled N into microbial protein synthesis, consistent with the observation that ruminal N flux increases inversely with dietary N concentration [23]. Observed DIP (Table 2) averaged 103% of expected based on tabular values ([17]; Table 1) for the three dietary treatments.

Total tract digestion of OM (linear effect, P = 0.06), NDF (linear effect, P = 0.07), N (linear effect, P = 0.04) and dietary DE (linear effect, P = 0.05) decreased with decreasing urea level. Treatment effects on total tract starch digestion, although numerically small, likewise tended (linear effect, P = 0.11) to decrease with decreasing urea level. Decreased fiber digestion accounted for 51% of the variation in OM digestion. In a previous study involving steam-flaked corn-based finishing diets in which urea was the sole source of supplemental N [22], increasing urea level from 1.0 to 1.6% of the steam-flaked corn in the diet (an upper level similar to that of the present study; Table 1) likewise enhanced total tract OM and fiber digestion. In contrast Zinn and Shen [19] observed removal of urea from a steam-flaked corn-based growing-finishing diet markedly depressed ruminal OM digestion and flow of MN to the small intestine but did not affect total tract OM digestion. Treatment effects on apparent N digestion were largely a function of the N content of the diet brought about by changes in dietary urea level [24].

Treatment effects on ruminal pH, VFA molar proportions, and BUN are showen in Table 3. Ruminal pH (measured 4-h postprandium) was not affected (P = 0.51) by treatments, averaging 5.82. Upon hydrolysis, dietary urea can have an appreciable alkalizing effect on ruminal pH during the first hour post-feeding [25]. However by 4 h postprandium, the effect of urea supplementation of corn-based diets on ruminal pH has been negligible [22, 26, 27].
Table 3

Treatment effects on ruminal pH, VFA molar proportions and BUN

 

Urea fermentation potential

P – value

 

Item

0

0.6

1.2

Linear

Quadratic

SEM

Ruminal pH

5.75

5.86

5.84

0.51

0.59

0.10

Ruminal N-NH (mg/dL)

5.37

4.69

3.89

0.05

0.91

0.56

Total VFA (mM)

95.9

105

94.2

0.83

0.21

5.4

Ruminal VFA (mol/100 mol)

      

Acetate

46.8

49.2

57.5

0.08

0.54

4.6

Propionate

36.1

30.1

20.3

0.04

0.74

5.7

Isobutyrate

1.19

1.17

0.89

0.30

0.60

0.23

Butyrate

12.0

15.1

17.7

0.17

0.93

3.1

Isovalerate

1.53

1.77

0.83

0.19

0.20

0.41

Valerate

2.36

2.63

2.83

0.42

0.95

0.48

Acetate:propionate

1.34

1.85

2.94

0.05

0.63

0.59

Methane1

0.35

0.44

0.60

0.04

0.70

0.09

BUN (mg/dL)

4.43

2.80

1.45

<0.01

0.53

0.25

1Methane production (mol/mol of glucose equivalent fermented) was estimated based on the theoretical fermentation balance for observed molar distribution of VFA [16].

Decreasing urea level decreased (linear effect, P < 0.01) ruminal N-NH. The N-NH concentration has been reported to increase immediately after feeding for 2 to 3 h [28, 29]. Satter and Roffler [30] observed a close relationship (R2 = 0.92) between the level of dietary CP and ruminal N-NH concentration at given dietary TDN. Likewise, in the present study dietary CP explained 88% of the variation ruminal N-NH concentration. Blood urea nitrogen (BUN) concentration 4 h postprandium also decreased (linear effect, P < 0.01) with decreasing urea supplementation. Blood urea nitrogen is also closely associated dietary CP and ruminal N-NH concentrations [31, 32]. Consistent with Zinn et al.[22], decreasing urea level increased ruminal acetate:propionate molar ratio (linear effect, P = 0.05), and estimated methane production (mol/mol glucose equivalent fermented; linear effect, P = 0.04).

Treatment effects on growth performance of feedlot steers are shown in Table 4. Decreasing urea level did not affect DMI (P = 0.32), but decreased ADG (linear effect, P < 0.01), gain efficiency (linear effect, P < 0.01), and dietary NE (linear effect, P = 0.03). Few research has evaluated the influence of marked RDP restriction on growth-performance and dietary NE in feedlot cattle fed steam-flaked corn-based finishing diets. As with the present study, Zinn et al.[22] observed a linear increase in urea resulted in a linear increase in ADG, gain efficiency and dietary NE linearly increased. The UFP of the basal unsupplemented diet in that trial was 1.36%, indicating that cattle performance may be enhanced when level of urea supplementation exceeded that necessary for maximal ruminal microbial protein synthesis. As with steam-flaked corn, urea supplementation of dry rolled corn-based finishing diets to meet the UFP also enhanced ADG and gain efficiency [26, 33].
Table 4

Treatment effects on growth performance and carcass weight of feedlot steers

 

Urea fermentation potential

P- value

 

Item

0

0.6

1.2

Linear

Quadratic

SEM

Days on test

40

40

40

   

Pen replicates

5

5

5

   

Live weight (kg)1

      

Initial

469

465

470

0.83

0.28

3.22

Final

510

502

501

0.17

0.54

4.40

DMI (kg/d)

7.32

6.99

6.94

0.32

0.67

0.26

ADG (kg/d)

1.04

0.93

0.78

<0.01

0.71

0.06

G:F

0.142

0.134

0.112

<0.01

0.32

0.005

Diet NE (Mcal/kg)

      

Maintenance

2.37

2.33

2.18

0.03

0.37

0.21

Gain

1.67

1.64

1.50

0.03

0.37

0.21

Observed/expected NE

      

Maintenance

1.07

1.05

0.98

0.03

0.37

0.02

Gain

1.09

1.07

0.98

0.03

0.37

0.03

HCW (kg)

336

331

330

0.16

0.67

3.02

Dressing (%)

65.9

66.0

65.8

0.80

0.67

0.23

1Initial and final weights were reduced 4% to adjust for digestive tract fill.

The decrease in dietary NE due to restriction of rumen degradable intake protein observed in the growth performance trial (Table 4) is consistent with the decrease in dietary DE observed in the metabolism trial (Table 2). However, why cattle didn’t simply compensate for this difference in NE by increasing energy intake to maintain their growth potential is puzzling. A comparison of requirements and estimated supply of metabolizable protein and the amino acids methionine and lysine for the various dietary treatments is given in Table 5. As per NRC [17], metabolizable protein supply was estimated as 80% of undegraded intake crude protein plus microbial crude protein entering small intestine in Trial 1 (Table 2), adjusted for level of intake of steers in Trial 2 (Table 4). Metabolizable amino acid supply was based on diet composition (Table 1) and corresponding tabular amino acid composition of RUP for individual feed ingredients and average amino acid composition of ruminal bacteria [17]. Metabolizable protein and amino acid requirements were based on average body weight and daily weight gain (Trial 2; NRC, [17], Level 1). As expected, estimated metabolizable protein and amino acid supply decreased with increasing UFP. Across treatments, estimated metabolizable protein supply exceeded requirements by an average of 11%. Nevertheless, metabolizable protein supply for UFP-0.6 and UFP-1.2 were less (2 and 8%, respectively) than the estimated requirement to achieve daily weight gain observed with UFP-0 treatment. Particularly notable is the very close association between metabolizable methionine and lysine and requirements versus supply, indicative that daily weight gain may have been closely mediated by supply of these two amino acids. As corn (the major contributor of protein to the basal diet) is a particularly poor source of lysine, and methionine, the diminution of microbial protein synthesis brought about by restriction in RDP, was sufficient to restrict growth.
Table 5

Treatment effects on metabolizable protein and amino acid supply 1 versus requirements 2

 

Urea fermentation potential

Item

0

0.6

1.2

Metabolizable protein, g/d

   

Supply

688

600

565

Requirement

613

574

493

Metabolizable methionine, g/d

   

Supply

12.4

10.6

9.9

Requirement

12.3

11.5

9.9

Metabolizable lysine, g/d

   

Supply

39.2

32.9

30.1

Requirement

39.3

36.7

31.5

1Metabolizable protein supply estimated as 80% undegraded intake crude protein and microbial crude protein entering small intestine (Trial 1), adjusted for level of intake. Metabolizable amino acid supply based on diet composition and corresponding tabular amino acid composition of undegradable intake protein for individual feed ingredients and average amino acid composition of ruminal bacteria (NRC, [17]).

2Metabolizable protein and amino acid requirements based on average body weight and daily weight gain (Trial 2; NRC, [17], Level 1).

Conclusion

It is concluded that in addition to effects on net protein flow to the small intestine, depriving cattle of otherwise RDP during the late finishing phase may negatively impact site and extent of OM digestion, depressing ADG, gain efficiency, and dietary NE.

Declarations

Authors’ Affiliations

(1)
Instituto de Investigaciones en Ciencias Veterinarias, UABC
(2)
Facultad de Medicina Veterinaria y Zootecnia, UAT, Cd.
(3)
Department of Animal Science, University of California, Davis E. Holton Rd

References

  1. Vasconcelos JT, Cole NA, McBride KW, Gueye A, Galyean ML, Richardson CR, Greene LW: Effects of dietary crude protein and supplemental urea levels on nitrogen and phosphorus utilization by feedlot cattle. J Anim Sci. 2009, 87: 1174-1183.View ArticlePubMedGoogle Scholar
  2. Vasconcelos JT, Galyean ML: Nutritional recommendations of feedlot consulting nutritionists: The 2007 Texas Tech University survey. J Anim Sci. 2007, 85: 2772-2781. 10.2527/jas.2007-0261View ArticlePubMedGoogle Scholar
  3. Preston RL: Empirical value of the crude protein systems for feedlot cattle. Protein Requirements for Cattle: Symposium. Edited by: Owens FN. 1982, 201-217. Stillwater, OK: Oklahoma Experimental Station MP-109, Oklahoma State University,Google Scholar
  4. Hristov AN, Hanigan M, Cole A, Todd R, McAllister TA, Ndegwaand PM, Rotz A: Review: Ammonia emissions from dairy farms and beef feedlots. Can J Anim Sci. 2011, 91: 1-35. 10.4141/CJAS10034.View ArticleGoogle Scholar
  5. Zinn RA, Plascencia A: Interaction of whole cottonseed and supplemental fat on digestive function in cattle. J Anim Sci. 1993, 71: 11-17.PubMedGoogle Scholar
  6. Burroughs W, Nelson DK, Mertens DR: Protein physiology and its application in the lactating cow: The metabolizable protein feeding standard. J Anim Sci. 1975, 41: 933-944.PubMedGoogle Scholar
  7. Fawcett JK, Scott JE: A rapid and precise method for the determination of urea. J Clin Pathol. 1960, 13: 156-159. 10.1136/jcp.13.2.156View ArticlePubMedPubMed CentralGoogle Scholar
  8. Bergen WG, Purser DB, Cline JH: Effect of ration on the nutritive quality of rumen microbial protein. J Anim Sci. 1968, 27: 1497-1501.Google Scholar
  9. , : Official methods of analysis. 2000, Gaithersburg, MD: Association Official Analytical Chemists, 17,Google Scholar
  10. Van Soest PJ, Robertson JB, Lewis BA: Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. J Dairy Sci. 1991, 74: 3583-3597. 10.3168/jds.S0022-0302(91)78551-2View ArticlePubMedGoogle Scholar
  11. Zinn RA, Owens FN: A rapid procedure for purine measurement and its use for estimating net ruminal protein synthesis. Can J Anim Sci. 1986, 66: 157-166. 10.4141/cjas86-017.View ArticleGoogle Scholar
  12. Zinn RA: Influence of steaming time on site digestion of flaked corn in steers. J Anim Sci. 1990, 68: 776-781.PubMedGoogle Scholar
  13. Zinn RA: Comparative feeding value of supplemental fat in finishing diets for feedlot steers supplemented with and without monensin. J Anim Sci. 1988, 66: 213-227.PubMedGoogle Scholar
  14. Hill FN, Anderson DL: Comparison of metabolizable energy and productive determinations with growing chicks. J Nutr. 1958, 64: 587-603.PubMedGoogle Scholar
  15. Ørskov ER, MacLeod NA, Kyle DJ: Flow of nitrogen from the rumen and abomasum in cattle and sheep given protein-free nutrients by intragrastric infusion. Br J Nutr. 1986, 56: 241-248. 10.1079/BJN19860103View ArticlePubMedGoogle Scholar
  16. Wolin MJ: A theorical rumen fermentation balance. J Dairy Sci. 1960, 43: 1452-1459. 10.3168/jds.S0022-0302(60)90348-9.View ArticleGoogle Scholar
  17. , : Nutrient Requirements of Beef Cattle. 1996, Washington, DC: National Academy of Press, 7Google Scholar
  18. , : Nutrient Requirements of Beef Cattle. 1984, Washington, DC: National Academy Press, 6Google Scholar
  19. Zinn RA, Shen Y: An evaluation of ruminally degradable intake protein and metabolizable amino acid requirements of feedlot calves. J Anim Sci. 1998, 76: 1280-1289.PubMedGoogle Scholar
  20. , : United States Standards for Grading of Carcass Beef. 1997, Washington, DC: Agricultural Marketing Service, United States Department of AgricultureGoogle Scholar
  21. , : SAS/STAT User’s Guide: Version 9.1. 2004, Cary, North Caroline: SAS Institute Inc,Google Scholar
  22. Zinn RA, Borquez JL, Plascencia A: Influence of levels of supplemental urea on characteristics of digestion and growth performance of feedlot steers fed a fat-supplemented high-energy diets. Prof Anim Sci. 1994, 10: 5-10.Google Scholar
  23. Muscher AS, Schroder B, Breves G, Huber K: Dietary nitrogen reduction enhances urea transport across goat rumen epithelium. J Anim Sci. 2010, 88: 3390-3398. 10.2527/jas.2010-2949View ArticlePubMedGoogle Scholar
  24. Holter JA, Reid JT: Relationship between the concentrations of crude protein and apparently digestible protein in forages. J Anim Sci. 1959, 18: 1339-1349.Google Scholar
  25. Zinn RA, Barrajas R, Montaño M, Ware RA: Influence of dietary urea level on digestive function and growth performance of cattle fed steam-flaked barley- based finishing diets. J Anim Sci. 2003, 81: 2383-2389.PubMedGoogle Scholar
  26. Milton CT, Brandt RT, Titgemeyer EC: Urea in dry rolled corn diets: Finishing steers performance, nutrient digestion and microbial protein production. J Anim Sci. 1997, 75: 1415-1424.PubMedGoogle Scholar
  27. Brake DW, Titgemeyer EC, Jones ML, Anderson DE: Effect of nitrogen supplementation on urea kinetics and microbial use of recycled urea in steers consuming corn-based diets. J Anim Sci. 2010, 88: 2729-2740. 10.2527/jas.2009-2641View ArticlePubMedGoogle Scholar
  28. Chumpawadee S, Sommart K, Vongpralub T, Pattarajinda V: Effects of synchronizing the rate of dietary energy and nitrogen release on ruminal fermentation, microbial protein synthesis, blood urea nitrogen and nutrient digestibility in beef cattle. Asian-Australasian J Anim Sci. 2006, 19: 181-188.View ArticleGoogle Scholar
  29. Seo JK, Yang JY, Kim HJ, Upadhaya SD, Cho WM, Ha JK: Effects of synchronization of carbohydrate and protein supply on ruminal fermentation, nitrogen metabolism and microbial protein synthesis in Holstein steers. Asian-Aust J Anim Sci. 2010, 23: 1455-1461. 10.5713/ajas.2010.10247.View ArticleGoogle Scholar
  30. Satter LD, Roffler RE: Nitrogen requirements and utilization in dairy cattle. J Dairy Sci. 1975, 58: 1219-1237. 10.3168/jds.S0022-0302(75)84698-4View ArticlePubMedGoogle Scholar
  31. Hammond AC: Effect of dietary protein level, ruminal protein solubility and time after feeding on plasma urea nitrogen and the relationship of plasma urea nitrogen to other ruminal and plasma parameters. J Anim Sci. 1983, 57 (1): 435Google Scholar
  32. Hennessy DW, Nolan JV: Nitrogen kinetics in cattle fed a mature subtropical grass hay with and without protein meal supplementation. Aust J Agric Res. 1988, 39: 1135-1150. 10.1071/AR9881135.View ArticleGoogle Scholar
  33. Tedeschi LO, Baker MJ, Ketchen DJ, Fox DG: Performance of growing and finishing cattle supplemented with a slow-release urea product and urea. Can J Anim Sci. 2002, 82: 567-573. 10.4141/A02-018.View ArticleGoogle Scholar

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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