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The Texas A&M University SystemThe Texas A&M University SystemAgricultural Research and Extension Center at AmarilloAgricultural Research and Extension Center at Amarillo

Manure Concentration of N:P, Animal Performance, and Blood Urea Nitrogen

Concentrations of Feedlot Steers Phase Fed Different Levels of Protein.

L.W. Greene1, 2 and J. T. Vasconcelos1,3

1Texas Agricultural Experiment Station - Amarillo2West Texas A&M University, Canyon3Texas A&M University


Introduction• Cattle are started on high concentrate finish diets at

approximately 750 lbs and fed to an average weight of 1250 lbs.

• Early in the feeding period, cattle have a greater deposition of lean tissue and less deposition of fat compared to later in the feeding period.

• As animals mature through the feeding period, the composition of gain changes -- protein gain decreases and fat gain increases in relative proportion.


Introduction

• The typical feedlot diet in the Southern Plains contains 13.0 to 13.5% Crude Protein (% N X 6.25)


Days on Feed-400

-300

-200

-100

0

100

200

300

14 42 70 99 127

Crude protein excess or deficiency (g/d) during feeding period given a

typical diet (adapted from Galyean)

Days on Feed

Average excess = 50 g/d


-10

0

10

20

30

40

1 2 3

14.5% CP13% CP

11.5% CP

Nitrogen retained, % of intake

Collection Period

%


• The typical feedlot diet in the Southern Plains contains approximately 0.33% P

• The typical feedlot steer requirement for P is likely < 0.18%.

Introduction


-4

-2

0

2

4

6

8

10

12

14

14 42 70 99 127

Phosphorus excess or deficiency (g/d) during feeding period given a typical

diet (adapted from Galyean)

Days on Feed

Average excess 6.7 g/d


0

10

20

30

40

50

60

1 2 3

14.5% CP13% CP11.5% CP

Phosphorus retained, % of intake

Collection Period

%


• The typical feedlot diet does not contain supplemented P.• The dietary P is supplied from the dietary ingredients.

Introduction

0.90+28.0Dried distillers grains

0.9346.0Cottonseed meal

0.3022.0Alfalfa hay

0.2511.0Sorghum silage

0.279.0Corn silage

0.319.8Corn grain

Phosphorus, %Crude Protein, %Source


Objective• Determine the effects of phase-

feeding of protein in finishing steers on– Steer performance– Blood urea nitrogen concentration– Manure N concentration– Manure P concentration– Carcass characteristics


Methods

One hundred eighty four steers

Randomized block design (blocked by weight into heavy medium and light and by start date)

54 steers started on June 6, 2003130 steers started on June 17, 2003

Steers were housed in 21 pens (7 pens/treatment)


Methods Three dietary treatments

1. Control diet – 13% Crude protein diet fed continually throughout the feeding period

2. 11.5% Crude protein – 13% Crude protein diet fed until cattle the average of the block reached 477 kg, then switched to an 11.5% crude protein diet

3. 10.0% Crude protein – 13% Crude protein diet fed until cattle the average of the block reached 477 kg, then switched to no supplemental crude protein diet


MethodsThe supplemental protein was supplied from equal amounts of nitrogen from urea and cottonseed meal


MethodsIngredient composition of finishing diets (DM basis)Item 13.0% CP 11.5% CP 10.0% CP

Corn grain, Steam flaked, % 74.07 76.25 79.50

Sorghum-sudan silage, % 7.50 7.50 7.50

Molasses, cane, % 4.00 4.00 4.00

Fat, % 3.00 3.00 3.00

Limestone, % 1.00 1.00 1.00

Mineral and vitamin premix, % 5.00 5.00 5.00

Urea, % 0.75 0.46 -

Cottonseed meal, % 4.68 2.79 -


Analyzed chemical composition of finishing diets.Item 13.0% CP 11.5% CP 10.0% CP

Crude protein, % 12.07 10.57 8.30

NDF, % 13.70 15.47 13.47

NEl, (Mcal/lb) 0.83 0.82 0.87

NEm, (Mcal/lb) 0.87 0.86 0.91

NEg, (Mcal/lb) 0.58 0.57 0.61

Ca, % 0.94 1.03 0.82

P, % 0.31 0.31 0.27

Methods


2.0062.042 1.965

1

1.2

1.4

1.6

1.8

2

2.2

13.0%CP

11.5%CP

10.0%CP

kg/d

Average Daily GainBeginning until diet change

P-value =0.912


1.622

1.713

1.526

11.11.21.31.41.51.61.71.8

13.0%CP

11.5%CP

10.0%CP

kg/d

Average Daily GainDiet change until finish

P-value =0.213


1.743

1.8581.687

1

1.2

1.4

1.6

1.8

2

13.0%CP

11.5%CP

10.0%CP

kg/d

Average Daily GainBeginning until finish

P-value =0.094


10.229 10.17910.328

5

6

7

8

9

10

11

13.0%CP

11.5%CP

10.0%CP

kg/d

Dry matter intakeBeginning until diet change

P-value =0.619


11.077 10.777 10.079

56789

101112

13.0%CP

11.5%CP

10.0%CP

kg/d

Dry matter intakeDiet change until finish

P-value =0.008


10.751 10.61 10.151

5

6

7

8

9

10

11

13.0%CP

11.5%CP

10.0%CP

kg/d

Dry matter intakeBeginning until finish

P-value =0.056


0.19

0.201 0.196

0.1

0.12

0.14

0.16

0.18

0.2

13.0%CP

11.5%CP

10.0%CP

Kg gain/Kg intake

Gain efficiencyBeginning until diet change

P-value =0.832


0.151

0.159 0.146

0.1

0.12

0.14

0.16

0.18

0.2

13.0%CP

11.5%CP

10.0%CP

Gain efficiencyDiet change until finish

P-value =0.294

Kg gain/Kg intake


0.166

0.175 0.162

0.1

0.12

0.14

0.16

0.18

0.2

13.0%CP

11.5%CP

10.0%CP

Gain efficiencyBeginning until finish

P-value =0.094

Kg gain/Kg intake


Plasma Urea Nitrogen (mg/dL)

7.72 7.31 6.52

1

6

11

P-value =0.8280

Day 0

6.56 6.94 6.12

1

6

11

P-value =0.8100

Diet change

9.847.02 4.75

1

6

11

P-value =0.0001

Harvest


2.8

2.42

2.6

1

1.5

2

2.5

3

13.0%CP

11.5%CP

10.0%CP

Pen surface manure concentrationNitrogen P-value =0.600

%


0.10.11

0.12

00.020.040.060.08

0.10.120.14

13.0%CP

11.5%CP

10.0%CP

Pen surface manure concentrationAmmonia Nitrogen P-value =0.931

%


2.72

2.33

2.47

1

1.5

2

2.5

3

13.0%CP

11.5%CP

10.0%CP

Pen surface manure concentrationOrganic Nitrogen P-value =0.549

%


0.780.72 0.68

0.40.45

0.50.55

0.60.65

0.70.75

0.8

13.0%CP

11.5%CP

10.0%CP

Pen surface manure concentrationPhosphorus P-value =0.642

%


3.56 3.45

3.87

2

2.5

3

3.5

4

13.0%CP

11.5%CP

10.0%CP

Pen surface manure concentrationNitrogen:Phosphorus P-value =0.038


1.15

1.281.15

0.50.60.70.80.9

11.11.21.3

13.0%CP

11.5%CP

10.0%CP

Carcass CharacteristicsFat thickness, cm P-value =0.227


87.33 85.9487.33

505560657075808590

13.0%CP

11.5%CP

10.0%CP

Carcass CharacteristicsLongissimus area, cm2 P-value =0.192


1.891.92

1.97

1

1.2

1.4

1.6

1.8

2

13.0%CP

11.5%CP

10.0%CP

Carcass CharacteristicsKidney, Pelvic and Heart Fat, % P-value =0.459


360.1361.1

363.76

300310320330340350360370

13.0%CP

11.5%CP

10.0%CP

Carcass CharacteristicsHot carcass wt, kg P-value =0.663


577579

580

500

520

540

560

580

13.0%CP

11.5%CP

10.0%CP

Carcass CharacteristicsLive weight, kg P-value =0.763


62.8 62.7 62.28

58

59

60

61

62

63

64

13.0%CP

11.5%CP

10.0%CP

Carcass CharacteristicsDressing percentage, % P-value =0.874


430.43 409.44

438.1

200

250

300

350

400

13.0%CP

11.5%CP

10.0%CP

Carcass CharacteristicsMarbling score P-value =0.173


2.69

2.912.92

2

2.2

2.4

2.6

2.8

3

13.0%CP

11.5%CP

10.0%CP

Carcass CharacteristicsYield grade P-value =0.174


• Variation of crude protein in the experimental diet resulted in lower than expected crude protein intake.

• Reducing crude protein intake to 8.3% reduced feed intake and tended to reduce ADG when summarized across the entire feeding period.

• No differences were detected in manure nutrient concentrations but the N:P ratio was increased when the lower CP diet was fed.

• No differences were detected in USDA Carcass Characteristics.

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