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United States Department of Agriculture

Agricultural Research Service

 Range Cow Grazed Diet Nutrient Content

In the fall of 2011, at weaning, and through the winter of 2011 and 2012, in response to the record rainfall of May 2011 and tremendous summer forage growth, ranchers asked if we knew the nutrient quality of range cows diets. We did using diet sampling ruminally cannulated cows. We have posted these analysis and will continue to do so into the future. Grazing is conducted on the native rangeland pastures at the USDA-ARS Fort Keogh Livestock and Range Research Laboratory, Miles City, Montana (LARRL). Cows that sample the forage previously graze those pastures. LARRL, is located approximately 1.6 km west of Miles City, MT (46°22´N 105°5´W), at an average elevation of 2400 ft. Native vegetation on the 55,500-ac research laboratory are primarily cool-season grasses consisting of needlegrass-wheatgrass (Stipa-Agropyron) mix. The long-term average precipitation is 13.5 inches with about 60-70% occurring during the mid-April through mid-June growing season. The average annual forage standing crop at the Fort is 1200 ± 300 lb/ac. Each month diet collections will be made and data added here. See table below. Here are some pasture picture comparisons to go along with the data - click here.
 

Two to four range cows are used in each pasture to sample forage representative of grazing cattle diets. The 4 animals usually graze continuously on each sampled pasture during the grazing season. Two sample collections from each cow are taken on each pasture during consecutive days in two month intervals . Usually the sampling scheme will involve taking one early morning grazing bout sample. Procedures for morning collections involved penning animals in late afternoon and initiation of collection the following morning at 0730 hours. Penned animals were provided with water. The collection procedure involves evacuating the rumens and then slowly moving the diet sampling cows through a pasture until they started to graze and then allowing them to graze freely for 45 minutes. A total of 2 samples will be collected from each cow on each pasture in each sampling month. Diet samples after collection are, later freeze dried for 7 days and then ground through a 1-mm screen. Crude protein was determined by AOAC (1975) methods. Acid and neutral detergent fiber were determined by the techniques of Van Soest and Wine (1968). In vitro digestibility was determined by the technique of Tilley and Terry (1963). All diet quality data are presented in the table below.

Sample Description

 

Nutrient Analysis

Date

Pasture

Lat & Long

Section range township

 

Dry Matter

Organic Matter

Crude Protein

Neutral Det. Fiber

Acid Det. Fiber

isndfdom

12/6/2011

Lone Pine trap

46.339817 -105.853744

section 21 7N 47 E

 

93.45

75.26

9.09

66.16

39.4

58.79

2/6/2012

Lone Pine trap

46.339817 -105.853745

section 21 7N 47 E

 

93.6

86.29

7.99

67.03

43

59.94

5/4/2012

Fish Hatchery

46o22'30"-105o51'15"

section 8 8N 47E

 

93.26

89.29

 

71.16

 

46.69

6/25/2012

W4

46o22'12"-105o53'29"

section 7 8N47E

 

87.74

87.68

 

46.65

 

56.96

8/29/2012

Moon creek

46o16'40"-105o59'57"

section 16 6N 46E 

 

91.88

85.99

 

61.56

 

58.81

11/6/2013

hogback a

46.326561 -105.812618

section 26   7N 47E

 

93.20

89.54

6.00

71.15

45.42

11/6/2013

hogback b

46.327379 -105.811821

section 26   7N 47E

 

92.95

88.31

5.81

69.29

49.57

11/6/2013

hogback c

46.327281 -105.810179

section 26   7N 47E

 

93.34

91.24

7.53

72.72

53.29

11/6/2013

hogback d

46.326339 -105.809442

section 26   7N 47E

 

93.41

90.12

5.56

71.98

54.56

11/6/2013

hogback e

46.325384 -105.810098

section 35   7N 47E

 

92.66

91.14

8.22

69.43

49.54

11/6/2013

hogback f

46.325026 -105.811928

section 35   7N 47E

 

92.85

88.78

4.97

70.3

57.86

1/23/2013

hogback a

46.326561 -105.812618

section 26   7N 47E

 

92.98

88.91

5.72

73.09

38.88

1/23/2013

hogback b

46.327379 -105.811821

section 26   7N 47E

 

0.93

89.36

8.16

74.81

35.17

1/23/2013

hogback c

46.327281 -105.810179

section 26   7N 47E

 

93.30

90.23

5.28

75.48

40.43

1/23/2013

hogback d

46.326339 -105.809442

section 26   7N 47E

 

92.50

90.66

5.5

76.38

46.76

1/23/2013

hogback e

46.325384 -105.810098

section 35   7N 47E

 

93.22

89.84

9.41

74.28

32.10

1/23/2013

hogback f

46.325026 -105.811928

section 35   7N 47E

 

92.88

86.73

6.44

70.64

54.23

6/18/2013

custer jk

46o17'58"-105o58'36.70"

section  5 6N 46E

 

91.28

90.87

11.56

69.83

58.68

2/19/2013

windmill

46o21'48.39"-105o54'9.07"

section 23 7N 46E

 

89.49

87.02

75.37

49.41

3/21/2013

windmill

46o21'48.39"-105o54'9.07"

section 23 7N 46E

 

89.10

89.54

76.34

36.84

3/28/2013

field 3

46o21'48.39"-105o54'9.07"

section 23 7N 46E

 

88.54

89.03

83.45

43.08

5/13/2013

field 3

46o21'48.39"-105o54'9.07"

section 23 7N 46E

 

88.40

87.33

66.71

74.10

7/18/2013

custer jk

46o17'58"-105o58'36.70"

section  5 6N 46E

 

90.19

92.53

6.94

74.77

61.37

8/30/2013

n

section  9 6N 46E

 

92.31

85.58

66.35

54.47

 

Definitions:
  Acid detergent fibre (ADF) - a chemical analysis that determines the amount of residue (primarily cellulose, lignin and variable amounts of silica) remaining after boiling a feed sample in an acid detergent solution. The ADF value is used to predict the energy content (TDN, NE) of forages.
  Crude protein - an estimate of the total protein content of a feed determined by analyzing the nitrogen content of the feed and multiplying the result by 6.25. Crude protein includes true protein and other nitrogen-containing substances such as ammonia, amino acids, nitrates.
  Dry matter - feed residue left after all moisture has been removed by drying (e.g., 100% dry matter).
  Neutral detergent fibre (NDF) - the insoluble fraction containing all plant cell wall components left after boiling a feed sample in a neutral detergent solution. NDF is of low digestibility but can be broken down somewhat by the digestive tract microorganisms. NDF value is used to predict ruminant feed intake Organic matter - total weight of the feed minus the mineral content.
  Organic matter - feed residue left after all the ash (minerals) and moisture has been removed by drying (e.g., 100% organic matter).
  Rumen nylon bag fiber digestibility (rnbndfdOM)– range forage selected by the cows used in the chemical analysis is returned to their rumens in a small nylon bag.   The pores from the weave in the nylon fabric are small enough that the diet sample cannot migrate out but large enough that rumen fluid and microbes can flow in.  The microbes attach and break down the diet sample in the bag like they digest vegetation after consumption.  The amount of feed in the bag is weighed and the amount coming out after 48hr, in the rumen, is weighed and the difference represents ruminal digestibility.  The NDF content is determined in the remaining feed to calculate the digestibility of the dietary fiber.  This is a highly regarded value since it uses the diet a cow actually ate herself and digested by the cow that ate it.

 


Last Modified: 1/24/2014
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