Extending grazing season reduces costs

Ed Rayburn
Forage Agronomy Specialist
WVU Extension Service
8/00

Feed—especially winter feed—represents over half of the cost of producing livestock. The winter feed cost for a beef cow often ranges between $1 and $1.50 per head per day. Since pasture costs one-half to one-third as much to produce as harvested feeds, extending the grazing season is one of the most effective ways to reduce costs. One can minimize feed costs by striving to achieve as close to a 12-month grazing season as practical.

Managing a forage crop by accumulating forage produced during a period of active growth for grazing when forage growth has ended is called "stockpiling" or "deferred grazing." Deferred fall and winter grazing can reduce the need for hay feeding and the cost of maintaining cattle. The amount and quality of forage available for grazing in late fall and winter are determined by the starting date of accumulation, nitrogen fertilization rate, forage species present, and date of forage use.

Average snow-free wintering season

Experience has shown that most livestock accustomed to winter grazing will actively graze through new snow that is 8 inches deep. Cattle grazing is limited by compacted or crusted snow, but horses and sheep are adept at pawing through heavy snow or crust to reach the grass underneath. When you allow animals to graze in deep snow, it is important to keep an eye on body condition to ensure that they are obtaining enough feed. The length of the snow-free wintering season varies with elevation.

Forage species for deferred grazing

Forage species adapted to deferred grazing include perennials such as tall fescue, orchardgrass, and companion perennial legumes; winter annual grasses such as rye and wheat; and annual forbs such as the brassicas. Among the perennials, the legumes are the most damaged by hard frosts and need to be grazed before frost damage and weathering cause excessive dry matter and quality loss. If planning to graze alfalfa after frost, keep in mind that bloat is likely to be a problem on recently frosted alfalfa.

Perennial grasses differ in their tolerance to freezing and weather damage. Reed canarygrass and bromegrass are the most sensitive to frost damage; orchardgrass and Kentucky bluegrass are intermediate in sensitivity; and tall fescue is the most tolerant.

Tall fescue is the best grass species to use for late fall and winter grazing. In the late fall, stockpiled tall fescue can be leafy, palatable, and high in protein, sugars, and digestible energy. Livestock producers have mixed feelings about tall fescue due to poor animal performance on this forage during the summer. With the exception of lactating dairy animals and pregnant mares, there is seldom a problem when tall fescue is used as part of a system containing other forages.

Other perennial forage species have growth response and forage quality similar to tall fescue until they are killed by frost and undergo weather damage caused by rain and snow.

Table 1. Fall grazing gain of gestating beef cows on stockpiled tall fescue in Ohio at the Jackson Branch, OADC (adapted from Boyles et al. 1998).

Year

Days

No. cows

Daily gain

1996

78

123

1.65

1997

89

131

1.64

1998

92

121

1.71

1999

111

120

1.85

4-year avg.

93

124

1.71

Quality of deferred pasture

When pasture is managed for deferred grazing, a compromise has to be made between yield and quality. Management that provides the highest yield often produces lower quality forage. Forage quality and yield depend on date of deferral, soil fertility, legume content, rate and timing of nitrogen fertilizer, and weather conditions after growth ends.

The quality of stockpiled tall fescue is more than adequate for dry mature livestock that need only to maintain body weight. If fertilized with 50 pounds to 100 pounds nitrogen per acre in July or August, tall fescue harvested in December will yield 2,000 pounds to 4,000 pounds dry matter per acre, containing 8% to 16% crude protein and 60% to 65% digestible energy.

Crude protein content increases as nitrogen application date is delayed from June to September. It increases with nitrogen fertilization rate, but decreases as deferral date and environmental conditions improve growth potential. Digestibility and palatability of tall fescue increase in the fall as cool weather causes the nonstructural carbohydrates (sugars) to increase. Forage deferred from August and September with nitrogen fertilization will have the high digestibility and intake (61% TDN, 2.5% DMI) but intermediate to low yields.

After killing frosts, forage quality will decline as rain leaches nutrients from the forages. This results in a gradual loss of crude protein and digestibility as winter progresses. As new growth begins in the spring, quality will increase.

A study at the Jackson Branch of the Ohio Agricultural Research and Development Center evaluated the body weight and condition score gain by gestating beef cows grazing stockpiled tall fescue (Table 1). During the four-year study, body weight gains averaged 1.71 pounds per head per day, ranging from 1.64 pounds to 1.85 pounds. Increase in body condition score over the fall grazing season averaged 0.71 unit, with a significant reduction in the number of cows in body condition 4 or lower, which is considered critical for cow productivity and profitability (Table 2).

Table 2. Change in body condition score of gestating beef cows grazing stockpiled tall fescue in Ohio at the Jackson Branch, OADC (adapted from Boyles et al. 1998).

Body Condition score

Beginning (9-08-99)

Ending (12-30-99)

Thin

No. cows

3

3

0

4

31

3

5

54

37

6

28

55

7

4

19

8

0

6

Fat

When to start stockpiling

Highest yields of stockpiled tall fescue are obtained by early deferral. Due to low light intensity and cool temperatures, little forage growth occurs after early to mid-November. For high yield and quality, stockpiling of tall fescue should start between mid-July and mid-August. The earlier stockpiling starts, the greater the late fall yield will be. If fescue is stockpiled before July, quality will be lower, but yield will be about the same.

Response to nitrogen fertilization

Adequate nitrogen will increase yield and quality of stockpiled fall pasture. Nitrogen can be provided by growing clovers or by applying nitrogen from commercial fertilizer, manure, or chicken litter. Grasses need adequate nitrogen to grow actively, produce proteins, and accumulate sugars during the cool fall weather. The accumulation of proteins and sugars makes fescue more tolerant to freezing and provides a greener, higher quality forage for grazing.

The response to nitrogen is reduced when legumes make up a large part of the stand, when there is a high residual soil nitrogen from previous applications of manure, or if other factors such as drought limit plant growth.

Typical fall yield response per unit of nitrogen applied averages about 20 pounds dry matter per pound of nitrogen (DM/lb. N) applied. This occurs when nitrogen is applied at rates under 100 pounds per acre (lb./a). On the other hand, when there is a high legume content in the stand or when other minerals or drought limit growth, only 5 to 10 pounds DM/lb. N may be achieved.

The cost of additional forage produced with nitrogen fertilization can be estimated using the forage yield response per pound of nitrogen and the price of nitrogen. If a yield response of 20 pounds of forage DM/lb. N can be expected and nitrogen costs $0.36 per pound, then each additional pound of forage grown costs:

$0.36 / 20 pounds of forage = $0.018/lb or $36/ton DM

For a 1,200-pound cow eating 2% of her body weight (24 lb. DM), this would cost:

$0.018 x 24 = $0.432 / cow/ day

When using nitrogen, apply it at 50 to 100 pounds per acre, depending on the amount of forage desired. Fertilizer nitrogen should be applied soon after stockpiling starts. If using urea, apply it just before a rain to reduce the loss of nitrogen by volatilization. Ammonia formulations of nitrogen do not run the same risk of loss as urea.

Table 3. The average yield above a 2-inch stubble of stockpiled tall fescue in Virginia in mid-November based on date of deferral and rate of nitrogen fertilizer (11 site years reported by Green, Rayburn, and White).

Initiation of deferral

Sept. 15

Aug. 15

July 15

Days of growth

60

90

120

Nitrogen fertilization rate

Average yield Nov. 15

0

884

1327

1769

50

1239

1858

2477

75

1416

2124

2832

100

1593

2390

3186

125

1770

2655

3540

Productivity, grazing management, and acreage requirement

Stockpiled tall fescue yield is determined by the number of days the stand is deferred and the rate of nitrogen fertilizer applied. The dry matter yield will vary due to differences in fall weather, soil conditions, and management before stockpiling and at harvest. Table 3 shows the average dry matter yield obtained in Virginia based on days regrowth before November 15 and nitrogen rate. The average yield over seven years in Ohio was 3,576 lb./a, with 74 lb. N /a in August. Depending on frost and weathering damage, losses from November into December will range from 0-1,000 pounds with an additional 600-1,200 pounds DM/a from December to February.

If animals are allowed free access to stockpiled forage, they will eat only a part of the forage and walk much of it into the ground. By providing only what the herd will consume in one to seven days, more forage will be eaten and less wasted.

The highest utilization will be achieved by using daily strip grazing. One acre of a dense 8- to 10-inch high tall fescue pasture will feed 50 1,000-pound dry cows for two to three days. In cold weather, forage intake may be higher. In rainy weather, treading damage may decrease utilization. Grazing to a 2-inch stubble increases forage use, decreases the competitive nature of endophyte-infected tall fescue, and helps maintain more legumes in the stand. When grazing endophyte-free tall fescue, leave a 2- to 4-inch stubble at the end of grazing. This encourages a vigorous spring growth that will improve long-term stand persistence. When grazing tall fescue during cold weather, livestock do not refuse the forage near manure piles as they do during summer grazing.

When legumes are used to provide nitrogen, the fall growth should be lightly grazed to use the legume before it is lost to freezing weather. Weaned calves can make good use of this high-quality legume forage. The grass can be saved for later use by dry cows. If the legume forage is not used before or shortly after frost, the usable forage yields from legume-tall fescue stands will be reduced.

Tall fescue stands containing clover or lespedeza should be grazed close during the winter or spring to encourage the establishment of legume seedlings. Dragging the pasture in early spring will spread the manure and seeds, ensuring a better distribution of seedlings and plant nutrients. By grazing the area after dragging, the cattle will walk the seed into the soil surface, improving seedling establishment.