TABLE 9–8 Diet Evaluation for Beef Cows

Mature Weight

533 kg

Milk Fat

4.0 %

 

Calf Birth Weight

40 kg

Milk Protein

3.4 %

Age @ Calving

60 months

Calving Interval

12 months

Age @ Weaning

30 weeks

Time Peak

8.5 weeks

Peak Milk

8 kg

Milk SNF

8.3 %

Breed Code

1 Angus

 

Ration

TDN % DM

ME Mcal/kg

NEm Mcal/kg

CP % DM

DIP % CP

DMI Factor

 

A

50

1.84

1.00

7.9

82.5

100%

B

60

2.21

1.35

7.8

100.0

100%

C

70

2.58

1.67

9.1

100.0

100%

Months since Calving

 

1

2

3

4

5

6

7

8

9

10

11

12

 

NEm Req. Factor

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

 

Milk kg/d

6.7

8.0

7.2

5.8

4.3

3.1

0.0

0.0

0.0

0.0

0.0

0.0

A

DM, kg

11.14

11.40

12.12

11.83

11.54

11.30

10.68

10.68

10.68

10.68

10.68

10.68

 

Energy Balance, Mcal/d

-3.90

-4.59

-3.31

-2.58

-1.88

-1.34

1.81

1.50

0.95

0.06

-1.30

-3.24

DIP Balance, g/d

7

7

7

7

7

7

6

6

6

6

6

6

UIP Balance, g/d

-201

-270

-169

-96

-24

34

175

170

142

93

14

-110

MP Balance, g/d

-161

-216

-136

-77

-19

27

149

136

113

75

11

-88

Ca % DM

0.65%

0.70%

0.62%

0.57%

0.52%

0.47%

0.34%

0.34%

0.34%

0.59%

0.59%

0.59%

P % DM

0.20%

0.21%

0.19%

0.18%

0.16%

0.15%

0.12%

0.12%

0.12%

0.17%

0.17%

0.17%

Reserves Flux/mo, Mcal

-148

-174

-126

-98

-71

-51

55

46

29

2

-50

-123

B

DM, kg

11.96

12.23

12.72

12.43

12.14

11.90

11.28

11.28

11.28

11.28

11.28

11.28

 

Energy Balance, Mcal

1.07

0.47

1.69

2.32

2.92

3.38

6.32

6.00

5.46

4.56

3.20

1.27

DIP Balance, g/d

5

5

5

5

5

5

5

5

5

5

5

5

UIP Balance, g/d

18

-47

44

114

182

233

221

221

221

221

209

85

MP Balance, g/d

14

-38

35

91

146

189

304

291

269

230

167

68

Ca % DM

0.27%

0.30%

0.27%

0.25%

0.22%

0.20%

0.15%

0.15%

0.15%

0.25%

0.25%

0.25%

P % DM

0.19%

0.20%

0.18%

0.17%

0.16%

0.14%

0.11%

0.11%

0.11%

0.16%

0.16%

0.16%

Reserves Flux/mo, Mcal

32

14

51

71

89

103

192

183

166

139

97

39

C

DM, kg

13.16

13.42

13.79

13.50

13.21

12.97

12.35

12.35

12.35

12.35

12.35

12.35

 

Energy Balance, Mcal/d

6.99

6.48

7.65

8.18

8.69

9.07

11.80

11.49

10.95

10.05

8.69

6.76

DIP Balance, g/d

3

3

3

3

3

3

2

2

2

2

2

2

UIP Balance, g/d

295

233

314

308

301

296

282

282

282

282

282

282

MP Balance, g/d

236

187

256

308

360

401

509

496

473

435

371

272

Ca % DM

0.25%

0.27%

0.25%

0.23%

0.20%

0.19%

0.13%

0.13%

0.13%

0.23%

0.23%

0.23%

P % DM

0.17%

0.18%

0.17%

0.15%

0.14%

0.13%

0.10%

0.10%

0.10%

0.14%

0.14%

0.14%

Reserves Flux/mo, Mcal

212

197

233

249

264

276

359

349

333

306

264

205

intake multiplier was set at 100 percent. All DIP values were then set at 80 percent, and diet CP was adjusted until DIP requirements were close to being balanced. Predicted DMI varies with daily milk production and forage quality. The CP required to meet diet DIP required for microbial growth is constant for a given diet but increased as diet TDN increased because microbial growth is a constant proportion of TDN. However, the UIP balance changes with milk and pregnancy requirements.

Diet A (50 percent TDN) met energy and UIP requirements in months 7 to 10 (cows just dry), became deficient in energy in month 11, and deficient in both energy and UIP in month 12. Diet B (60 percent TDN) is adequate in energy in all months and UIP in all but month 2 of lactation. Diet C (70 percent TDN) exceeded energy and UIP requirements in all months.

The energy reserves flux (Mcal/mo) is given for each month of the reproductive cycle for each diet evaluated. Appendix Table 13 can be used to estimate days for a CS change by dividing the Appendix Table 13 value by the predicted daily energy balance. To reduce a negative energy balance, 1 Mcal diet NEm will substitute for 1 Mcal negative energy balance. To utilize energy reserves, 1 Mcal diet NEm can be replaced by 0.8 Mcal tissue energy.

TABLE OF ENERGY RESERVES FOR BEEF COWS

Appendix Table 13 gives Mcal mobilized in moving to the next lower CS, or required to move from the next lower CS to the one being considered, for cows with different mature weights. For example, a 500-kg cow at CS 5 will mobilize 207 Mcal in declining to a CS 4. If NEm intake is deficient 3 Mcal/day, this cow will lose 1 CS in (207 * 0.8)/3=55 days. If consuming 3 Mcal NEm above



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