The Nutritional Value of Rotationally Grazed Pasture
in Jefferson County

Craig W. Yohn
WVU Extension Agent
Jefferson County
Ed Rayburn
Extension Forage Agronomist
WVU Extension Service
7/00

This fact sheet describes the results of a study funded by a grant awarded to William W. Grantham, T. Neill Banks, Michael Boyd and Dr. O. C. Stine from SARE - Northeast Region. This Grant was submitted to SARE in the Northeast Region for funding by William (Bill) W. Grantham. Without his leadership and financial commitment, this study would not have been completed. Thanks also go out to Dr. O. C. Stine, T. Neill Banks and Michael Boyd who participated in this study with Bill to provide diversity in the types, locations and utilization of pastures in Jefferson County.

This fact sheet is based on three years of work by four livestock producers in Jefferson County West Virginia. The county, which lies in the northern end of the Shenandoah Valley, is in the rain shadows from the Appalachian and the Blueridge mountain ranges. In the past, this has led to a reliance on row crop production and continuous grazing for feed rather than the use of rotational grazing. These long time traditions have discounted the use of pasture as a source of high quality forage. This fact sheet will discuss the potential nutritional value of three types of pasture/meadow grown in this area of West Virginia.

Pasture Quality

A total of 64 samples were submitted to Dairy One Forage Lab for analysis. The samples were divided into three classes of pasture: Tall Grass-Alfalfa, Tall Grass-Clover and Bluegrass-Clover. Table 1 provides an overview of the quality of the three different forage categories.

Table 1: Analysis Results

Forage # of Samples Days Between Grazing Plate Height When Grazed % Crude Protein % TDN NEL NEG ADF NDF % Ca % P Relative Feed Value
Tall Grass-

Alfalfa

9 24 6.2 28 65 .68 .41 24 37.6 1.10 .43 179
Tall Grass- Clover 32 27 7.3 22 64 .66 .39 27 45.8 .79 .31 141
Bluegrass- Clover 23 36 4.3 20 64 .66 .39 29 49.8 .75 .30 126
Total

\ Average

64 30 6.1 22 64 .66 .39 27 46.1 .83 .33 141
Quality Standard       Prime       Prime #1     #1
Standard Deviation   13.5 3.5 5.0 2.8 .04 .04 4.2 7.1 .28 .07 31.6

Dairy Cattle Performance

Using the average crude protein, energy, and fiber of all samples and values representing 33 percent above and below the average, provided the opportunity to relate management of forage quality to animal production. Three different rations were formulated based on the average forage value and 33 percent above and below average. The Cornell Dairy Pasture Ration Balancer (1991), was used to formulate rations that would support a three year old, 1300 pound Holstein cow that is 120 days in milk, producing 3.5% fat. The assumption was made that the cow will lose no more than one Body Condition Score during a 305-day lactation. The theoretical cow had a body condition score of 2.5 using the descriptions developed at Michigan State University. The pasture is assumed to be unlimited and supplemented with orchardgrass hay and rolled shelled corn.

Table 2: Average Forage Analysis (Half of the samples are better and half the samples are poorer)

Level of Milk Production

Pounds of Pasture (DM)

Pounds of Orchardgrass Hay

Rolled Shelled Corn (as fed)

40

25

7.5

4.0

50

25

10

4.0

60

25

11.5

5.5

70

25

13.5

6.0

80

24

11.5

13.0

90

24

13

14.0

100

24

14

16.0

 

Table 3: Forage Analysis 33 percent above average (only 17% of the samples are bettter)

Level of Milk Production

Pounds of Pasture (DM)

Pounds of Orchardgrass Hay

Rolled Shelled Corn (as fed)

40

30

5.5

3.0

50

29

8.0

4.0

60

29

9.0

5.5

70

29

10.0

7.5

80

28

10.0

11.5

90

27

12.0

13.0

100

27

13.0

15.0

Table 4: Forage Analysis 33 percent below average (83% of samples better)

Level of Milk Production

Pounds of Pasture(DM)

Pounds of Orchardgrass Hay

Rolled Shelled Corn ( as fed)

40

22

4.0

11.5

50

22

4.5

14.0

60

22

5.0

16.5

70

20

6.5

20.0

80

20

7.0

22.0

90

20

8.0

24.0

100

19

8.0

27.5

One of the concerns of dairymen is the loss of butterfat by cows on pasture. A key component contibuting to this loss is the Acid Detergent Fiber (ADF) level in the ration. According to the Nutrient Requirements of Dairy Cattle, a level above 21% is desirable, but a level as low as 19% could be tolerated. The rations above were kept between these levels, with levels dropping as the production requirements went up.

Using the values of $5 per ton for pasture, $75 per ton for orchardgrass hay and $140 per ton for rolled corn, the following observations were made.

The average cost of the rations was:

Poor Quality: $2.09 per cow per day
Average Quality: $1.55 per cow per day
Excellent Quality: $1.48 per cow per day

The greatest economic incentive is to improve from the below-average pasture to the average pasture. An average cost difference of $.54 per day or $164.70 per cow per 305 -day lactation.

Improving the pasture to the above average quality forage from the average reduces the cost per cow per day by only an additional $.07 or $21.35 per 305-day lactation.

Beef Calf Performance

Rations were formulated using the Cornell Cattle System II Feedlot Edition (1989), to evaluate the rate of gain of a 550-pound steer with a supplement of shelled corn:

Table 5: Steer Rate of Gain

Ration (%)

Rate of Gain (Cost per Pound of Gain)

Pasture

Shelled Corn

Poor Quality
Forage

Average Quality Forage

Excellent Quality
Forage

100

0

1.37(.14)

1.68(.11)

1.97(.10)

90

10

1.68(.32)

1.93(.28)

2.2(.25)

80

20

1.95(.43)

2.19(.39)

2.42(.35)

70

30

2.25(.48)

2.44(.45)

2.62(.42)

60

40

2.51(.50)

2.67(.48)

2.81(.45)

50

50

2.76(.50)

2.87(.48)

2.99(.46)

Average

****

2.09(.40)

2.30(.37)

2.50(.34)

Table 5 demonstrates the improvement in the rate of gain when forages are of higher quality. The cost per pound of gain also decreased. Weather can affect these projections. Table 5 can be used to evaluate the use of improved pasture to wean calves and show how improved pastures can affect stocker cattle profitability.

Summary

This three-year study demonstrated that the quality of rotationally grazed pastures found in the Northern Shenandoah Valley can support a high level of production with the addition of energy and fiber to balance the ration. The biggest challenge is to utilize the high level of protein found in these forages to its greatest advantage.

Reference:

Rayburn, E.B. and D.G. Fox. 1991. Cornell dairy pasture ration balancer - user's guide. Cornell Coop. Ext., Cornell Univ. Ithaca NY. Anim. Sci. Mimeo Series.

Rayburn, E.B. and D.G. Fox. 1990. Predicting growth performance of Holstein steers. J. Anim. Sci. 68:788-798.

Rayburn, E.B., and D.G. Fox. 1989. Cornell cattle system II user manual. p.17-34. IN D.G. Fox, E.B. Rayburn, and C.N. Rasmussen. Beef growing and finishing spreadsheets for Lotus 1-2-3, a user's guide. Cornell Coop. Ext., Cornell Univ., Ithaca NY. Anim. Sci. Mimeo Ser. No. 115. 54p.