Ash (%)

Calcium (%)

Phosphorus (%)

Magnesium (%)

Potassium (%)

Sodium (%)

Sulfur (%)

Copper (mg/kg)

Iodine (mg/kg)

Iron (mg/kg)

Manganese (mg/kg)

Selenium (mg/kg)

Zinc (mg/kg)

Cobalt (mg/kg)

Molybdenum (mg/kg)

5.2

0.43

0.20

0.09

1.99

0.07

0.14

29.0

140

93

54

8

3

4

3

4

3

3

2

2

2

1

0.813

0.09

0.01

0.04

0.51

0.09

0.01

33.9

24.9

16.9

11.2

1.74

0.26

0.40

3.26

0.11

0.25

12.8

176

83

31

0.49

7

8

8

6

8

6

1

5

5

5

5

6

3.25

0.40

0.05

0.12

1.66

0.05

3.4

125

13.6

7

0.21

7.4

1.70

0.23

0.51

1.92

0.07

0.25

9.26

227

29

77

0.11

5

3

3

3

4

1

1

1

3

1

1

1

0.79

0.09

0.01

0.20

0.25

149

6.6

0.14

1.27

0.63

1.37

0.06

0.24

14.2

163

134

0.57

110

108

37

30

29

17

17

13

8

8

10

8

5

6

3

0.60

0.03

0.21

0.07

0.10

0.02

0.02

1.8

56

14

0.25

36

0.03

5.0

0.17

1.01

0.40

1.81

0.02

0.19

12.6

170

124

102

2.1

30

69

70

55

56

44

18

50

51

49

45

39

0.99

0.15

0.13

0.09

0.14

0.06

0.04

3.13

118

23

35

37

13.3

0.42

0.40

0.21

3.50

0.18

0.22

100

1

1

1

1

1

2

2

1

0.14

0.03

2.01

0.05

0.44

0.13

0.40

0.01

0.14

6.48

45.1

36.6

0.05

38.1

0.12

25

90

91

16

16

2

15

16

16

16

1

15

1

0.26

0.03

0.14

0.01

0.02

0.01

0.01

1.3

5.6

2.4

2.8

7.9

0.15

0.20

0.12

0.99

0.21

0.22

200

4

8

8

1

5

2

2

1

2.05

0.02

0.08

0.44

0.1

0.03

7.5

0.44

0.29

0.17

2.24

0.04

0.21

9.0

386

79.5

28.0

1.61

1

177

177

169

169

168

36

159

169

169

169

169

0.32

0.09

0.15

0.73

0.10

0.06

6.0

322

47

11.0

1.06

7.7

0.17

0.05

0.12

1.40

0.14

0.19

3.6

157

41

6

0.05

46

51

48

37

39

5

5

34

35

34

30

2

2.61

0.07

0.02

0.02

0.70

0.01

0.01

1.2

39.5

13.7

0.77

0.01

or less. Pelleting is an improvement over grinding because it produces less dust. The average effect of pelleting and grinding was an 11 percent increase in intake for cattle, with a greater response from young compared to mature animals (Greenhalgh and Reid, 1973). In a summary of research with bulls, Sundstol (1991) reported that grinding by itself and grinding with pelleting enhanced intake of straw by 7 and 37 percent, respectively. The above summary applies mostly to hays and straws. Silages are rarely processed as finely as dry forages although the amount of chopping and particle size reduction that occurs during harvesting can vary significantly. From a summary of available literature on corn (Wilkinson, 1978) and grass silage (McDonald et al., 1991) and within the range of particle lengths commonly observed for silage (mean length, 5 to 15 mm), there is a negative relationship of length to intake; however, the intake decrease is generally less than 10 percent.

Digestibility of roughages is decreased by grinding, with or without pelleting, and the decrease is usually in proportion to the intake increase (Blaxter et al., 1956). For 21 studies, Minson (1963) found an average 3.3 percent decrease in dry matter digestibility. Thomson and Beever (1980) reported greater decreases for ground grasses (0 to 15 percent) than for ground legumes (3 to 6 percent). Digestibility decreases are usually attributed to a faster rate of passage of food, with more digestion occurring in the hindgut. In contrast, pelleting and grinding roughages results in lowering heat increment so that the net dietary energy from these roughages is often higher than for the parent product (Osbourne et al., 1976).

Chemical alkali is used to upgrade roughages; it hydro-



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