Volume 13 Number 2 (March 1960)

American

Society of Range Management

The American Society of Range Management was created allied technologists, and to encourage professional improvement in 1947 to foster advancement in the science and art of grazing of its members.

land management, to promote progress in the conservation and Persons shall be eligible for membership who are interested greatest sustained use of forage and soil resources, to stimu- in or engaged in practicing range or pasture management or late discussion and understanding of scientific and practical animal husbandry ; administering grazing lands ; or teaching, range and pasture problems, to provide a medium for the or conducting research, or engaged in extension activities in exchange of ideas and facts among society members and with range or pasture management or related subjects.

T

AGEMENT , published bi-monthly, is the official organ of the American Society of Range Management. The Society, however, assumes no responsibility for the statements and opinions expressed by authors and contributors.

Off ice, Executive Secretary. Address all inquiries and correspondence including memberships, renewals, replacements of JOURNALS, etc., to Executive Secretary, American Society of Range Management, P.O. Box 5041, Portland 13, Oregon. Dues. Membership dues should be sent to the Executive Secretary. The dues are $8.00 per year including a subscrip- tion to the JOURNAL OF RANGE MAN- AGEMENT. Dues for student members are $4.00 per year, including the JOURNAL. All subscriptions mailed outside the North American continent and insular possessions of the U. S. are $8.50 per year. Subscrip- tions must be paid in advance. Remit by draft or check on U. S. banks in U. S. funds. Reprinting. The reprinting of articles or parts of articles published in the JOURNAL OF RANGE MANAGEMENT is author- ized on the express condition that full credit be given the JOURNAL and the author. The date of original publication must be shown with the credit line.

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Printers. The Nebraska Farmer Company, 1420 P Street, Lincoln, Nebraska.

Copyright 1960 by the American Society of Range Management.

JOURNAL OF RANGE MANAGEMENT

EDITOR E. J. WOOLFOLK

Pacific Southwest Forest 8; Range Exp. Sta. Berkeley 1, California

EDITORIAL BOARD

1958-60

ARNOLD HEERVVAGEN W. R. HANSON

Soil Conservation Service Eastern Rockies Forest 321 New Customs Building Conservation Board

Denver 2, Colorado Calgary, Alberta

1959-61

DONALD R. CORNELIUS JACK R. HARLAN

Agricultural Reskarch Service P. 0. Box 245

Oklahoma State University

Berkeley 1, California

Stillwater, Oklahoma

1960-62

L. T. BURCHAM LYNN RADER

California Division of Forestry University of California Sacramento, California Berkeley, California

OFFICERS OF THE SOCIETY President:

FRED H. KENNEDY U. S. Forest Service Albuquerque, N. Mex.

President Elect: Executive Secretary:

V. A. YOUNG JOHN G. CLOLJSTON

733 West 2nd St. P. 0. Box 5041 Mesa, Arizona Portland 13, Oregon

BOARD OF DIRECTORS

1958-60

JAMES L. FINLEY MELVIN S. MORRIS

P. 0. Box 136 University of Montana Gilbert, Arizona Missoula, Montana

1959-61

JOHN CHOHLIS C. H. MCKINNON

Western Livestock Journal LK Ranches, Ltd. Sacramento, California Calgary, Alberta

1960-62

KARL G. PARKER GERALD W. THOMAS

Montana State College Bozeman, Montana

Texas Technological College Lubbock, Texas

Past President: DONALD F. HERVEY Colorado State University

Fort Collins, Colorado

IN THIS

ISSUE

Cultural Methods and Their Relation fo Establishment of Native and Exotic Grasses in Range Seedings

Donald S. Douglas, A. L. Hafenrichter, and K. H. Klages

Forage Preference and Grazing Habits of Cattle at the Eastern

Colorado Range Sfafion... _____ ___ ____ _________________ _._. . . . ..Jack N. Reppert

Graduafes in How fo Interest High School Students and

Management as a Career... .__.

Range

. . . ..Robert S. Corless

Forage Production on Ozarks ____ ___ ____ _________.

Sprayed and Burned Areas in the Missouri

. . . ..John H. Ehrenreich and John S. Crosby

Effect of Fertilization and Date of Planting on Establishment of Perennial Summer Grasses in South Central Oklahoma

LyeZZ F. Thompson and C. C. SchaZZer

Herbage Production in Four Range Plant Communities in South Texas

Thadis W. Box

Moisture Relationships of Some Rangeland Soils of the Souihern

Greai P’lains..._.._~~._~.___.__.~.__.~_.~ _____ ____ ._____ . ..Howard M. Taylor

Soil Porosity and Bulk Density on Grazed and Protected Kentucky

Bluegrass Range in fhe Black Hills... ________ _____ ._._ ____ __.__ -Howard K. Orr

Breeding Superior Forage Plants for the Great Plains...J. R. Harlan

Lupine Polisoning as a Possible Factor in Congenital Deformities

in Cattle... _.__ _________________________________ _____ __ .____ ____ .___ ___ ____ _ ____ _ __.____ Kenneth A. Wagnon

A Comparison of Crested Wheafgrass and Native Grass Mixtures Seeded on Rangeland in Eastern Montana

Jesse L. McWiZZiams and Philip E. Van Cleave

Germination and Longevity of Velvet Mesquite Seed in Soil

Fred H. Tschirley and S. Clark Martin

Effects of Site and Season on Oxalafe Content of Halogefon

C. Wayne Cook and DiZZard H. Gates

Book Reviews: Wafer Facts for the Nation’s fuiure (Holscher);

Grazing Controls (Wright); Recreational Use of Wild Lands

(Wagar); Goat Husbandry (RagsdaZe)..._..._.__..._..__.~.~~._~~_~_~.~__

Current Liierafu~e...__._~...~...._ ... -Lee A. Sharp and E. W. Tisdale

Wiih the Secfions..._._~_~._.~.~_ ...

Society Business... ___.________. _____ _______ ____ .___ _ ____ _ ____ ____ ._____ _____________________

News and Nofes..._... ______ ____________________..._.~._ _.__ _________________________________ 53

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Journal of

RANGE MANAGEMENT

~~

Cultural Methods and Their Relation to

Establishment of Native and Exotic

Grasses in Range Seedings’

DONALD S. DOUGLAS, A. L. HAFENRICHTER, AND K. H. KLAGES

Plant Materials Technicians, Soil Conservation Service, Aberdeen, Idaho and Portland, Oregon; and Head, De- partment of Agronomy, University of Idaho, Moscow, Idaho

Others have developed criteria for determining the need and the suitability for reseeding range lands based upon range condi- tion, land capability factors, and economics. This paper treats with methods for re-establish- ment of range forage species by seeding. It has particular appli- cation to the lands of the Snake River plains, specifically on Si- erozem soils. The work was done at Aberdeen, Idaho where aver- age rainfall is 8.8 inches but varies widely among years as shown in Table 1. A gradual de- cline in annual precipitation was encountered during the time that

Table 1. September-August precipi- tation, Aberdeen, Idaho

Year Inches

1947-48 9.24 .

1948-49 8.69

1949-50 7.69

1950-51 7.25

1951-52 6.50

1952-53 5.90

1953-54 6.54

1954-55 6.19

1913-1950 average 8.79

Based on a presentation at the an- nual meeting of the American So- ciety of Range Management in Phoenix, Arizona, January 1958.

most of the data discussed in this paper were taken. Elevation is approximately 4,500 feet.

The soil was mapped as Port- neuf fine sandy loam. It was farmed during World War I, abandoned shortly thereafter, and then grazed as spring-fall sheep range. The land had been severely eroded by wind and water during the period of culti- vation. It is typical of large areas in the Snake River plains.

The principal vegetation at the beginning of the se trials was cheatgrass ( B r o mu s tectorum), with invasions of big sage brush

(Artemisia tridentata), squirrel- tail (Sitanion hystrix), and rab- bitbrush (Chrysothamnus nause- osus) from the unplowed road- sides. Some residual patches of streambank wheatgrass (Agro- pyron riparium) survived the pe- riod of cultivation.

Procedures

Based upon results and expe- riences gained in earlier work re- ported by Stark, et aL2 these

trials were designed with the following objectives: (1) to de- termine the effect of five land preparation methods, (2) to com- pare methods of planting, (3) to compare times of seeding, and

53

(4) to determine the effect of the age of the stand on yield. These factors affect establishment, de- velopment, and production of grass stands. Plantings were made in each of five successive years to sample the effect of cli- mate, one of the principal limit- ing factors. Comparisons were made among several species and varieties of grass with standard cultural methods.

Two basic mixtures were used in all trials except in those com- paring species and varieties. One, which will be referred to as the “crested mixture,” contained standard crested wheatgrass

(Agropyron desertorum), streambank wheatgrass (A. rip- arium), and Sandberg bluegrass

(Poa secunda). The other, re- ferred to as the “Whitmar mix- ture,” contained Whitmar wheat- grass (A. inerme), streambank wheatgrass, and Sandberg blue- grass. Standard field equipment was used in all cases. All plots were one-seventh acre in size.

Plantings were made in the fall and the following spring of each year. Harvests were made annually beginning with the third season following planting. Basal density data by species were recorded from ten quad- rats within each plot. Each quad- rat was marked and later har- vested by hand and the vegeta- tion was separated into compo- nent parts.

Land Preparafion Methods

The principal purposes of land preparation for making seedings

DOUGLAS, HAFENRICHTER, AND KLAGES

were to remove the weedy

grasses and brush, create a fa- vorable medium for the estab- lishment of plants, and facilitate the use of seeding equipment. Methods of land preparation varied from simple to intensive. The more intensive land prepa- ration methods gave several ad- vantages: (1) greater reduction of competing weedy plants and the quicker establishment of planted grasses, (2) lengthening of the safe seeding season, (3) reducing the time required by the planted for

age

Several methods, “summer f al- low,” (( early burn, ” “late burn,” “cultivated,” and “no treatment” were used for preparing the land. The principal objective of the “summer fallow” operation was to eliniinate competing plants. The tillage operations, whether with plow, sweeps, or oneway, were timed to kill the cheatgrass at late-boot or early heading stage, about the third week in May. This was early enough to prevent seed formation by the cheatgrass but late enough that most of the soil moisture had been removed to prevent the growth of summer weeds. No further weed killing operations were necessary in this winter- wet and summer-dry climate.

For the “early burn” treatment cheatgrass was permitted to come to the “red” stage and tlien burned, usually about mid-June. Some regrowth occurred on rab- bitbrush and perennial grasses following the burn. In some in- stances the fire was not hot enough to kill the green and growing big sagebrush. The “late burn” was made in September

after cheatgrass seed had

dropped.

The “cultivated” 1 an d treat- ment was once-over with a tan- dem disk. The “no treatment” land was seeded directly without

any tillage or burning. A deep- The intensity of land prepara- furrow press drill was used to tion influenced the date the make all seedings where land stand reached sufficient produc- preparation methods were com-

pared. tion to permit grazing. Table 3 illustrates this rate of develop-

Table 2. The effect of method of land preparation on the basal density

of squirrelfal (Sitankn hystri~) and of planted perennial grasses.

Method of land preparation None Early burn Late burn Disked Fallow

Basal Density in Percent

Crested Mixture Whitmar Mixture

Planted Squirrel- Planted Squirrel-

grass tail grass tail

.85 1.63 .36 2.13

1.35 1.50 .31 1.51

2.16 1.24 .62 1.44

3.07 .18 1.65 .86

3.58 .44 1.99 .76

The data given in Table 2 are ment for the “crested mixture” typical of the results obtained when fall planted with the deep- with land preparation methods furrow press drill.

in this study. They show how the

basal densities of planted grasses These assumptions were made: and of common competitive (1) a seeding is ready for grazing weedy grasses were influenced use during the growing season by land preparation. The dom- when production of the planted inant planted grasses were perennials exceeds 300 pounds crested wheatgrass and Whitmar per acre, and (2) under grazing wheatgrass. The stands had use, at least 300 pounds of stub- reached full production at the ble per acre are required for ero- _{sion control and to maintain} time of basal density readings.

The more intensive land prepa- plant vigor. Using these criteria, ration methods, plowing and fal- the plantings made on fallow lowing or disking in the fall, re- were ready for light use by the duced the competing squirreltail end of the second growing sea- and allowed full development of son. Those planted with no land the planted grass. Burning re- preparation were not ready for duced the squirreltail slightly. use until the fifth growing sea- son. Basal density of the squirrel- _{Several factors must be taken} tail as influenced by method of

land preparation was also nega- into account when choosing a tively correlated with the yield method for preparing an area for of planted grass. The value for seeding. The more common ones _{are those inherent with the land} “r” was -.648 (n = 8) . The basal

density of all annual weeds and the soil, such as susceptibil- taken together was not corre- ity to erosion by water or wind, lated with either the density or slope, salinity, stoniness, texture, the yield of planted grass. _vegetation depth, and profile. The kinds of _{that predominate on}

Table 3. Herbage production of fhe “crested mixture” by method of land

preparation and age of stand.

Method of - Age of stand-years from planting

land preparation 3 4 5 6 7

Fallow 572

Disked 224

Burned 194

No cultivation 81

(Pounds per acre)

891 938 873 788

418 580 658 1190

328 465 682 913

NATIVE AND EXOTIC GRASSES 55

the areas to be seeded are as im- portant as the land factors. The presence of perennial fire-toler- ant vegetation requires the more intensive types of land prepara- tion. The plants in this group that have given the greatest com- petition to seeded grass are rab- bitbrush, squirreltail, stream- bank wheatgrass, and Sandberg bluegrass. Wherever these plants occurred, singly or in combina- tion, seedings were successful only to the degree that they were eliminated by land preparation. Rabbitbrush was not a serious problem in this study.

Methods of Planting

The effects of five methods of

planting on production are

shown in Table 4. All plantings were made in the fall on land that was prepared by the fallow method. Fall plantings were made as soon after September 15 as soil. moisture conditions justi- fied.’ In three of five years, plantings were made in early Oc- tober. In two years, plantings were delayed until late October and finally made in dry soil. The first three methods of planting used were: broadcasting, double- disk drilling, and deep-furrow press drilling. Broadcasting was done with a hand-operated broadcast seeder followed by harrowing with a spike-tooth harrow. The double-disk drill was a standard grain drill with 6-inch spacing. The deep-furrow press drill was a single-disk type with 14-inch spacing and stand- ard press wheels.

Two additional methods of planting were used which are

Table 5. Average yield of two mixtures planfed fall and spring with a deep-furrow press drill by methods of land preparafion.

Land Preparation

Time of Non-

planting Early Late Culti- culti-

Fallow burn burn vated vated

(Pounds per acre)

Fall planted 543 446 424 552 320

Spring planted 432 200 193 406 138

adaptable to arable land. These were (1) drilling the grass in alternate rows with wheat, and (2) planting the grass into wheat stubble without 1 and prepara- tion. For planting in alternate rows, a fallow such as would be suitable for the production of winter wheat was prepared. A standard 6-inch double-disk drill was used with a divider in the drill box so that wheat and grass were planted through alternate feeds. Spring pressure was re- leased from the openers planting grass and the grain was seeded at one-half the normal rate.

The data in Table 4 show that drilling was superior to broad- casting, both in the rate of devel- opment of stands and in total annual production. Deep-furrow drilling was slightly superior to seeding with a double-disk drill. Drilling produced more uniform stands each year and better stands among years than did broadcasting. Planting grass in alternate rows with winter wheat gave yields slightly, but not significantly, superior to the best method of drilling without a companion crop. The wheat ap- parently provided less competi- tion to the grass during the es- tablishment year than did volun- teer annual grasses where no

Table 4. Herbage production of ihe “crested mixture” by planting method. fall planted o’n fallow.

- -m

Age of stand-years from planting

Method of Planting -

3 4 5 6 7

(Pounds per acre)

Broadcast 284 564 745 767 758

Double-disk 524 730 818 835 765

Deep-furrow 572 891 938 873 788

Alt. row with grain 581 810 836 1081 849

Seeded in stubble 168 299 464 647 576

companion crop was used. Vol- unteer grasses and weeds were never prominent in the alter- nate-row seedings. When rye was used for making alternate- row seedings, poor results were obtained. Drilling into wheat stubble gave good stands, but the rate of development of the plants was greatly retarded. Both seed- ing in alternate rows with wheat and into stubble provided protec- tion against wind erosion.

Time of Seeding

Fall planting was more de- pendable for establishing stands than spring planting. The de- tailed data showed no complete failures with the “crested mix- ture,” but one year the “Whitmar

mixture” failed to establish from fall seeding. Spring plantings have been erratic, ranging from high density, vigor, and pro- duction to a relatively high pro- portion of failures. Planting on fallow reduced the incidence of failure from spring planting, while failures were frequent with other methods of land prep- aration. Table 5 summarizes the comparative production from fall and spring plantings.

Species Comparisons

56 DOUGLAS, HAFENRICHTER, AND KLAGES

crested wheatgrass in pro du c- tion. In this table the older stands were on an adjacent and similar piece of land and were maintained from plantings begun in 1939. They were used for com- parison with the detailed data reported from the present study that was begun in 1947.

Whitmar and bluebunch

wheatgrasses were similar, par- ticularly in rate of establishment and production potential on this site. Differences in the table be- tween these two grasses were in age, not species.

More important than yield are the differences in use and management of the two grasses. Crested is adapted to early spring and late fall grazing.

Whitmar and bluebunch are

adapted to late spring, summer, fall, and winter use and stay green about 2 weeks longer into the summer than does crested wheatgrass. On the individual ranch, forage needs by season will influence the choice of grass for reseeding, as well as will soil and climatic factors.

Another interesting compari- son, although not in such detail, can be made between the plant- ings for which the data are shown in Table 7. These were planted in each of five successive years. Siberian wheatgrass (Ag- ropyron sibiricum) was similar to standard crested wheatgrass in adaptation and season of use but differed in several important respects. It was more drought resistant, had better seedling vigor, and was more productive

Table 7. Herbage production of three wheatgrasses and an alfalfa-grass mixture, fall planted on fallow with double-disk drill, 1947-1951.

Age of stand-years from planting

Species 3 4 5 6 7 Average

Fairway crested 656 671

Standard crested 443 779

Siberian wheatgrass 808 1012 Standard crested

8~ alfalfa 531

_____- 947

than crested on the lighter soils and on the lower rainfall sites. Siberian showed superior forage characteristics: awnless heads, finer stems, more leaves, and it stayed green 10 to 14 days longer into the season than crested wheatgrass, Siberian wheatgrass has maintained this production advantage over crested wheat- grass in a l&year-old stand. Fair- way crested wheatgrass (A. cris- tatum) consistently produced less forage than the other two but made a more uniform ground cover and reseeded more readily. Ladak alfalfa was satisfactorily established in three of the five years from fall planting. Grass- hoppers and rodents grazed it closely in the early years. The data suggest that alfalfa in a range seeding may have stimu- lated the vigor and production of the grass.

Other Species Comparisons A number of other species were tested, but none is as well adapted to the conditions of this trial as those already discussed. Sherman big bluegrass (Poa ampla) was earlier in season of use than crested, Siberian, or

Table 6. Herbage production by two mixtures, crested wheatgrass, and bluebunch wheaigrass fall planted on fallow with a deep-furrow

press drill as influenced by age of stand.

Age of stand-years from planting

Species 3 4 5 6 7 10 11 12 13

(Pounds per acre)

Crested mix 572 891 938 873 788

Whitmar mix 76 176 339 466 631

Crested wheatgrass 400 626 891 923

Bluebunch

wheatgrass 479 814 1009 1277

(Pounds per acre)

730 994 756 761

859 1142 969 838

902 909 1114 949

1030 1333 1266 1021

Whitmar wheatgrass and just as productive, but in these trials it was more difficult to establish. Livestock men have shown a def- inite interest in this member of the vernal dominant grass group, and under less rigorous climatic conditions Sherman makes a val- uable contribution as very early feed. Russian wildrye (E Zymus junceus) established as readily as crested wheatgrass, but under this low rainfall production per acre was low. This grass is rec- ognized for its high quality feed at any season of the year; and this factor must be considered

when making comparisons.

Other field plantings have indi- cated that at higher elevations with summer rainfall, Russian wildrye is a definite adjunct to planned summer-long grazing. It is singular among the grasses west of the Continental Divide in this respect.

Considering the late-maturing grasses, tall wheatgrass (Agro- p y ro n elongatum) established satisfactorily but developed more slowly than crested. It was es- pecially valuable in the sequence of species, producing green and usable forage in midsummer. However, under the conditions of soil and climate in this trial, tall wheatgrass was short-lived. In the older plantings, estab- lished stands died from the cen- ter of the crown and disappeared in 10 to 15 years.

NATIVE AND EXOTIC GRASSES 57

trials were conducted were too stringent for these species.

Mixtures

The use of two mixtures in the cultural phases of these trials was an attempt to reconstitute the grass phase of the prairie as- sociation. Each mixture con- tained a dominant bunch wheat- grass, sod-forming streambank wheatgrass, and vernal dominant Sandberg bluegrass. In these trials excellent ground cover and species balance was maintained in the absence of grazing. How- ever, observations made on field plantings u n d e r grazing indi- cated t h at exceptionally go o d management would be needed to maintain a balance, otherwise streambank wheatgrass would tend to become dominant. The bunchgrass-vernal dominant as- sociation maintains ground cover and balance under good grazing

management. Other grasses

tested for understory use were not suitable for one reason or another.

Summary

In summary, the choice of land preparation methods for reseed- ing range lands depended, to a considerable degree, up on the kind and amount of vegetation on the land. Summer fallow was the best method, especially if weedy, fire-tolerant perennials were abundant. Burning was ef- fective if big sagebrush and

cheatgrass were the only plants present, but disking just before planting was more effective than burning. Planting directly into unprepared land gave the poor- est stands and slowest develop- ment.

Five methods of planting were compared on summer fallow. The deep-furrow drill gave best results, broadcasting was poor- est, and seeding with a double- disk drill gave intermediate re- sults. Planting the grass in alter- nate rows with winter wheat re- sulted in good establishment. When this method was used ero- sion and weeds were never seri- ous. Seedings made in grain stubble with a deep-furrow drill consistently made good stands, but they developed slowly.

Fall plantings produced better stands and higher yields than spring plantings. Spring plant- ings were variable but presented possibilities on higher capability land and with the more intensive land preparation methods.

Crested wheatgrass estab- lished easier and faster than Whitmar wheatgrass or blue- bunch wheatgrass and reached grazing readiness one or two years earlier. As the stands reached maturity, Whitmar and

bluebunch wheatgrass first

equalled, then exceeded produc- tion of crested. Crested provided spring-fall use and Whitmar and bluebunch late-spring, summer, fall, or winter grazing. Thus they

supplement each other.

Siberian wheatgrass estab- lished more rapidly and outpro- duced standard and Fairway crested wheatgrasses. Siberian had more desirable forage char- acteristics and stayed green about 10 days later into the sea- son. Ladak alfalfa planted with grass was established in good years and had recognized value in the mixture.

Sherman big bluegrass was even earlier than crested for sea- sonal grazing readiness but more difficult to establish. Russian wildrye was established easily and contributed to lengthening the grazing season with high quality feed, but the production of dry matter was low. Tall wheatgrass established well but was short-lived under the low rainfall conditions of these studies. Pubescent and inter- mediate wheatgrasses were er- ratic in establishment and pro- duction. They were below their range oi adaptation.

Mixtures containing un de r - story grasses have recognized ad- vantage for soil and water con- servation on range lands, but ex- ceptional management is needed to maintain the balance of spe- cies.

The choice of a species depends upon the seasonal feed require- ments of the ranch operation, the soil and climatic resources, and the grazing management plan for the ranch.

Summer Meeting In South Dakota

Forage Preference and Grazing Habits of Cattle

at the Eastern Colorado Range Station1

JACK N. REPPERT

Range Conservationist, Pacific Southwest Forest and Range Experiment Station, Forest Service, U. S. De- partment of Agriculture, Berkeley, California

The purpose of this study was to determine what native forage species and parts of these species were selected and consumed by cattle grazing upon sandhill ranges. In addition, grazing hab- its of the animals were studied.

It is an established fact that the chemical composition of range forage undergoes seasonal changes which may affect the nutrition of grazing animals

(Hart, 1932; Stanley, 1938a and 1938b). Cook and Harris (1950) pointed out that preference for certain forage species was an important factor affecting the nutritive value of ingested for- age. The need has been stressed for determination of botanical and nutritive composition of a grazing animal’s diet so that grazing and range supplementa- tion plans can be made (Cook and Harris, 1950; Harris et al., 1952).

The many studies initiated by researchers to determine the bo- tanical and nutritive content of the diet of grazing animals fol- low three general lines of meth- odology similar to those recog- nized by Lucas (1950) : (1) nu-

tritional methods, (2) observa- tional methods, and (3) sampling before and after grazing. The work reported herein was ac-

Wolorado Agricultural Experiment Station Scientific Journal Article No. 603. Excerpt from a thesis pre- sented to the Department of Range Management, Colorado State Uni- versity, Fort Collins, Colorado, in partial fulfillment of the require- ments for the Degree of Master of Science, 1957.

complished by observational methods.

Observational methods, which involve following the animal as it freely grazes, have been em- ployed by several workers. Many researchers in game management have used a method similar to that used by Dixon (1934) in California who followed deer and recorded the time they spent grazing each plant species. Stod- dart (1952) however, noted that the time spent may not have any relationship to the amount of forage consumed.

Culley (1937) in Arizona found by observation that cattle gen- erally showed indiscriminate use of most grasses, weeds, and shrubs. However, definite pre- ference was shown for some spe- cies at certain times of the year. Preference was primarily influ- enced by summer temperature and stage of growth of plants.

Doran (1943) observed sheep in Colorado with the aid of field glasses. It was found that the time spent grazing grasses and forbs was closely correlated with their relative abundance. In a grazing habit study conducted in Kansas with range cattle, it was observed that preference chang- ed through the seasons. The stage of growth of the plant and temperature influenced prefer- ence. It was noted that pastures must not be heavily grazed in order to obtain an expression of preference by the cattle (Moore- field and Hopkins, 1951).

The method of following graz- ing cattle and making an ocular estimate of the forage species consumed was utilized by Hub-

58

bard (1952) in Alberta, Canada. It was reported that availability and not palatability was a pri- mary factor governing species intake.

Halls (1954) conducted a study in Georgia in which an approxi- mation of cattle diet was made by observing tame cattle and recording the forage species and portion as it was eaten. The rela- tive amount that each species contributed to the total intake was estimated. Forage samples were collected and chemically analyzed. Evidence was found of preference for certain species and certain parts of those spe- cies. However, the estimate of a species ratio was found to vary considerably without an appreci- able change in the chemical composition. It was further con- cluded that the actual plant part being selected was of more im- portance than the species being consumed.

Grazing habit studies have been conducted for many classes of livestock in many areas of the United States. Several of these habits are of interest as they may influence or have direct bearing upon preference. They are also of interest in learning of the methods of observation used.

The activities observed have been many and include time spent traveling, feeding, licking salt, drinking water, resting while lying down, standing, ru- minating while standing and ly- ing, idling while standing, graz- ing, browsing, miscellaneous f ceding, and supplemental feed- ing (Cory, 1927; Grelen and Thomas, 1957).

The time spent for observation of cattle varied from one 24-hour period a month (Cory, 1927) and four hours, two consecutive days a month (Halls, 1954) to 12 hours once a week (Moorefield and Hopkins, 1951).

FORAGE PREFERENCE AND GRAZING HABITS OF CATTLE

59

(1954) found that with tame

cattle it was best to observe the

animals on foot. Peterson and

Woolfolk (1955) utilized both a

horse and a truck from which

they observed cows and calves;

a pickup truck was recommended

by Grelen and Thomas (1957).

Both Cory (1927) and Moore-

field and Hopkins (1951) found

it advisable to use field glasses.

The results of grazing habit

studies are varied. Definite pat-

terns of early morning and late

afternoon grazing were reported

by several workers (Culley, 1937;

Moorefield and Hopkins, 1951;

Grelen and Thomas, 1957).

Time spent grazing each day

varied from 5 hours 36 minutes

(Atkeson, et al., 1942) to over

11 hours (Peterson and Wool-

folk, 1955) and often depended

upon the abundance of forage.

Some researchers, such as Moore-

field and Hopkins (1951)) found

grazing to occur primarily dur-

ing daylight hours, while others,

such as Peterson and Woolfolk

(1955)) reported some night graz-

ing.

The Study Area

The Eastern Colorado Range

Station, which is located about

midway between Akron

and

Sterling, is typical of a consider-

able area of sandhills in north-

eastern Colorado. The predomi-

nant relief is that of dune type

topography made up of many

small depressions with no ap-

parent drainage pattern. Such

areas predominate

and are

termed “sandhill” range sites.

Where the topography tends to

be more nearly level, the range

site designation is “sandy plains.”

The vegetation on the study

area is made up primarily of a

tallgrass, sandreed (CaZamoviZfa

Zongifoliu) and a shortgrass, blue

grama (Boutelouu

These two warm season grasses

W+ntific names follow nomencla- ture of Harrington, H. D. 1954. Manual of the plants of Colorado. Sage Books, Denver. 666 pp.

grow

a close mixture in cer-

tain areas and in separate

patches in other areas.

An important bunch grass

which commonly occurs on the

better condition ranges is needle-

and-thread

This

mid-grass is a cool season plant

which contributes greatly to the

quality of forage early and late

in the growing season, provided

there is adequate moisture.

Sand bluestem

western

wheatgrass

and sand

dropseed (Sprobolus

are occasionally abundant.

Little bluestem

sideoats

grama

and

switchgrass

are desirable grasses which oc-

cur only sparsely on the study

area. Sun sedge (Curex

is the most abundant

grasslike plant.

Three undesirable

grasses

commonly found are sandhill

muhly

six-weeks fescue

and red threeawn

The sandhill site usually has

some sand sagebrush

which is considered

desirable in small amounts.

Yucca (Yucca gluucu) occurs to

a lesser extent than sand sage-

brush.

The following forbs are some

of the many which occur widely

over the range; cudweed! sage

bush

morning-glory

puccoon

sand lilly

and rush pea

Under

certain conditions the following

forbs are common in localized

areas: western ragweed

Russian

thistle (SuZsoZu kuZi), common

sunflower

scarlet globemallow

ironplant golden-

weed

pepperweed

florum),

and chimaya (Cymop-

sp.). Many other species of

forbs occur, but they usually do

not make up much of the total

composition.

The estimated species compo-

sition as determined by ocular

reconnaissance for all pastures

in the study averaged approxi-

mately 40 percent sandreed, 40

percent blue grama, 4 percent

needle-and-thread,

2 percent

sand bluestem, 4 percent other

grasses, 4 percent forbs, and 6

percent shrubs.

The climate of the study area

is semi-arid with much of the

precipitation falling as rain dur-

ing the summer growing season.

The 1956 growing season was 177

days from May 1 to October 14.

The average growing season is

probably nearly 146 days based

on records from Akron. The

average annual precipitation for

the Station was 13.8 inches for a

three-year period

from 1955

through 1957.

Procedure

This s t u d y was conducted

from February, 1956, to January,

1957, to determine preference for

native forage by yearling heifers.

A pasture observation method

was used monthly for a 48-hour

period and consisted of follow-

ing 20 heifers as they freely

grazed in loo-to 400-acre p a s -

tures. Observations were limited

to daylight hours. A pickup

truck was found to be least dis-

turbing to the heifers, and when

supplemented by sixpower field

glasses, a very good view of for-

age being selected could be

maintained. Valid observations

were made from as close as 6

feet to as much as 20 and 30 feet

60

A unit was devised upon

which an estimate could be based. This unit was called the mouthful. It was recognized that as the heifers grazed they gath- ered quantities of forage that ranged from nearly nothing to relatively large amounts. The mouthful unit allowed this dif- ference in relative size of forage quantity consumed to be taken into account by recording in a relative manner l/4, l/2, 3/4, or 1 mouthful. A portion of a mouth- ful unit was considered to com- mence when the animal, having taken a stance over some for- age, lowered her head and began to graze. The same unit was con- sidered to end when the animal either stopped grazing to walk forward or simply took a step forward. In this manner the mouthful unit consisted of one to several actual bites of forage.

It was estimated what species and in what relative size each unit of observation consisted. A record was also made of the parts of plants being grazed and whether or not these parts con- sisted of green or old forage. The parts were considered to be stems and leaves, leaves, stems and heads, or all parts. Old for- age included a previous season’s herbage and most of the herb- age after the first heavy frost.

The grazing habits of the herd of 20 heifers were also noted and

REPPERT

recorded. The observed habits consisted of the time spent graz- ing, lying, traveling, i d 1 i n g

(standing at rest) , watering,

salting, and supplemental feed- ing. Also of importance were observations of the phenology of important forage species. Forage

samples were collected by

species for chemical analyses, but this study does not deal with these analyses.

The yearling heifers were fed daily 4 pounds of alfalfa hay at feedbunks during the period of early November to early May each year.

Results

The yearling heifers observed at monthly intervals for one year exhibited a preference for cer- tain species and plant parts. Preference was a phenomenon which changed to favor certain species at various seasons. This is indicated by the following presentation of observational data.

February lo-12 and March 9- 11, 1956: Sandr eed was the largest single component of the diet ranging from 41.1 to 45.9 percent (Table 1). Considerable use was made of blue grama, needle-and-thread, s a n d blue- stem, and western wheatgrass. Forbs were rarely grazed. Shrubs comprised 14.6 percent of the diet d u r in g the February

period and only 3.4 percent in March.

The diet was made up predom- inantly of old forage, although some green forage was obtained fro% yucca and very few green leaves of sun sedge and needle- and-thread. Leaves, or a mix- ture of stems and leaves, were the most abundantly selected plant parts making up from 78 percent (February) to 84 per- cent (March) of the total diet. Light snowfall during both per- iods resulted in tall stubble heights for most species.

April 5-7 and April 26-28,1956: The new growth of needle-and- thread attracted the cattle to this species, which made up from 55.2 percent to 56.8 percent of the total diet (Table 1). Sand- reed and blue grama made up important amounts of the diet. Sun sedge and western wheat- grass furnished some early green forage in important amounts. Forbs were grazed very little and sand sagebrush was less im- portant than earlier.

In early April, 54 percent of the diet was estimated to be green forage, while in late April green forage was estimated to be 67 percent of the diet. Plant parts preferred were leaves, which made up over 80 percent of the diet during both periods. June l-3,1956: Green sandreed was very important during this

Table 1. Percent composition by species of fofal forage consumed by yearling heifers af fhe Eastern Colorado

Range Station, Februaky 10, 1956-January 20, 1957.

Starting Dates of Observation Periods

Feb Mar Apr Apr Jun Jun Jul Aug Sep Ott Nov Dee Jan

Species 10 9 5 26 1 27 24 21 15 18 16 17 18

Percent

Sandreed 41.1 45.9 19.9 27.2 53.9 62.1 55.1 25.9 46.6 1.8 1.4 7.8 2.5

Blue Grama 10.7 17.5 6.9 7.5 9.0 23.3 29.9 62.8 43.2 85.0 56.8 20.2 84.8

Needle-and-Thread 13.5 14.1 56.8 55.2 31.4 5.1 4.0 2.5 2.3 10.1 32.8 63.4 9.6

Sand Bluestem 12.4 13.9 4.5 * 2.0 3.1 3.3 1.5 .7 .5 .8 .O *

Sand Dropseed 6.3 .7 .O * .O 1.8 3.0 2.5 .l 2.3 2.8 2.2 2.4

Western Wheatgrass 1.0 3.0 4.6 3.5 .2 .4 .3 .o .o .3 * .3 *

Sun Sedge .O .7 5.6 6.6 * .o .2 .o .o * .3 * .O

Forbs .5 .8 * * .4 3.5 4.2 4.8 6.8 * .o .o .o

Sand Sagebrush 6.2 1.7 1.7 * 3.1 .O .O .O .O .O 5.1 6.1 .7

Yucca 8.4 1.7 .O .O * .7 .o .o .3 .o .o .o .o

FORAGE PREFERENCE AND GRAZING HABITS OF CATTLE

period making up 53.9 percent of the diet while needle-and-thread still was important at 31.4 per- cent (Table 1). Blue grama, sand bluestem, and western wheat- grass were also selected in small amounts. Slight use was made of forbs. Possibly due to the ex- tremely dry conditions for this time of year, new green sand sagebrush leaves and twigs made up 3.1 percent of the diet. Ninety-five percent of the for- age selected was green. In addi- tion, 99 percent of the plant parts taken was equally divided be- tween a mixture of stems and leaves and leaves alone.

June 27-28 and July 24-25, 1956: During these periods sand- reed made up from 55.1 to 62.1 percent of the total diet (Table 1). Blue grama responded to summer rains and gradually be- came more important in the diet, making up 23.3 to 29.9 percent of the forage selected. Needle-and- thread was preferred much less as it matured. Several other grasses were taken in small amounts. Selection of forbs be- came more common, although they were only 4.2 percent of the diet in July. Grazing of shrubs was uncommon.

Sandreed w a s observed to reach bloom stage by the July date while blue grama was in the dough stage by July. Needle- and-thread had matured by the July period. Over 98 percent of the forage grazed was green. The plant parts selected became more stemy with a combination of stems and leaves making up over 50 percent of the diet. Leaves alone still made up from 36 to 41 percent of the diet.

August 21-23 and September 15-17,1956: Blue grama was very important during these periods. It made up 62.8 percent of the diet in August and 43.2 percent in September (Table 1). Sand- reed was taken in large quanti- ties accounting for 25.9 and 46.6 percent of the diet in August and September respectively. Some

use was made of needle-and- thread, sand bluestem, and sand dropseed. Forbs made up from 4.8 to 6.8 percent of the total diet. Shrubs were only slightly used. The grasses were in various stages of seed production in Au- gust, while many had shattered seed by September. In Septem- ber needle-and-thread exhibited some basal leafage regrowth. The amount of green forage selected was in excess of 97 per- cent for both months although the quality of greenness was con- siderably less than found early in the summer. The forage was more stemy than in early sum- mer. About 55 percent of the diet was made up of all parts (stems, leaves, and seed heads) while over 30 percent was classified as stems and leaves.

October 18-20 and November 26-l 7, 1956: Blue grama con- tinued to be a very important forage plant during these months m akin g up from 56.8 to 85.0 percent of the total diet (Table 1). Sandreed was avoided by the heifers and in its place some of the cool season grasses exhibit- ing significant amounts of re- growth mixed with old forage were selected. Needle-and- thread was notable in this re-

spect, accounting for 10.1 and 32.8 percent of forage selected. Other grasses accounted for smaller amounts. Dried f orbs were only slightly used. Sand sagebrush comprised 5.1 percent of the forage consumption in November.

The growing season ended October 14 and much .of the past season’s green forage was in an “old forage” classif ication. In October green forage was esti- mated to account for 21 percent of the diet, while in November it was only 3 percent as a result of colder temperatures. In Octo- ber the plant parts grazed were 63 percent all parts, while in No- vember the parts were 56 per- cent leaves and only 42 percent all parts.

December 17-18, 1956: The preference for needle-and-thread during this period was the great- est of any period during the study. It was estimated that the diet of the heifers consisted of 63.4 percent needle-and-thread, 20.2 percent blue grama, 7.8 pre- cent sandreed, and 6.1 precent sand sagebrush (Table 1). A snow blanket, 2 to 3 inches deep, covered most of the range ex- cept where it had melted around sand sagebrush clumps. This

62 REPPERT

FIGURE 2. Heifers grazing abundant sandreed and blue grama at the maximum observa- tion distance, July 19, 1956.

fact, associated with the fact that needle-and-thread often grows in close association with sand sagebrush, made these two spec- ies most available for grazing heifers (Figure 1).

the forage selected was cured. Over 50 percent of the diet was made up of all parts (stems, leaves, and seed heads) and 40 percent leaves.

Needle-and-thread a n d sun sedge, both cool season plants, were able to withstand the cold night temperatures and utilize the moisture from the melting snow to maintain regrowth. All other species were dormant and dry. Only 6 percent of the for- age consumed was green. Leaves made-up 61 percent of the total diet.

Species Preference

Sandreed comprised most of the diet for six of the thirteen periods of observation (Figure 3). It was used primarily in the late winter periods and the sum-

90

1 SANDREgl -

January 18-20, 1957: This period was characterized by very little snow cover and a change in the preference for forage by the grazing heifers. Blue grama made up 84.8 percent of the diet and needle-and-thread composed 9.6 percent (Table 1). Little use was made of sandreed and other grasses. Forbs were not selected. Sand sagebrush was grazed very slightly.

10

The only green forage during this period was a very few green leaves remaining in protected clumps of needle-and-thread. It was estimated that 99 uercent of

Fob Mar Jun JUl Jul

10 9 Apt; Apr Aw SOP

Oot NOV Deo Jan

26 1 29 24 21 15 18 16 17 18

FIGURE 3. Seasonal consumption of three grasses at the Eastern Colorado Range Sta- _ L- _ _ _ _ __ tion, February, 1956--January, 1957.

mer periods, namely, February 10, March 9, June 1, June 27, July 24, and September 15. It was the second largest species component of the diet April 5, April 26, and August 21. During the December 17 and January 18 observations, sandreed was the third ranked component of the diet. It was less during the Octo- ber 18 period when it was fourth ranked behind sand dropseed and the November 16 period when it was fifth behind sand sagebrush and sand dropseed.

Blue grama was the largest species component of the diet of heifers for 3 of the 13 observa- tion periods (Figure 3). This preference was primarily ex- pressed in late summer, fall, and early winter months. The Au- gust 21, October 18, November 16, and January 18 periods were dominated by preference for blue grama while during the September period blue grama composed nearly as much of the diet as sandreed. Blue grama made up over 80 percent of the diet during the October 18 and January 18 observation periods. Blue grama ranked second for the five periods of March 9, June 27, July 24, September 15, and

FORAGE PREFERENCE AND GRAZING HABITS OF CATTLE 63

December 1’7. This species rank- ed third during the three periods of April 5, April 26, and June 1. Blue grama was fourth behind sand bluestem during the Feb- ruary 10 period.

Needle-and-thread was the

most preferred grass for 3 of the 13 observation periods (Figure 3). Two of these periods oc- curred in the spring and one in the late fall. They were April 5, April 26, and December 17. This species ranked second dur- ing the five periods of February 10, June 1, October 18, Novem- ber 16, and January 18. During the periods of March 9, June 27, and July 24 it was third. The August 21 period results showed needle-and-thread fourth-rank- ed, with sand dropseed behind summer-cypress, while during the September 15 period of ob- servation it was fourth-ranked behind ragweed.

The pattern of grazing use formed by sand sagebrush is of special interest, although it never comprised over 7 percent of the diet of the heifers. Use was made of this species during the spring, late fall, and winter months. During the June 1 pe- riod, use was made of green, leafy sand sagebrush and it made up 3.1 percent of the diet. In November it ranked third, making up 5.1 percent of the

diet. In December, in making up 6.1 percent of the diet it ranked fourth. Grazing use made of yucca, the other shrub, formed a pattern similar to that of sand sagebrush. During the period of February 10 it made up a sig- nificant 8.4 percent of the diet (Table 1). G razing use was made primarily of green yucca leaves and secondarily of old leaves with no observed use of flower stalks or roots.

Forbs were used for the most part during the summer when in a green condition. As a group they were the third ranked com- ponent of forage consumed dur- ing the periods of July 24, Au- gust 21, and September 15. In August summer-cypress made up 3.7 percent for third ranking, and in September ragweed made up 3.1 percent of the diet for third ranking.

Daily Grazing Habits

The 13 observation periods al- lowed good opportunity to col- lect information about the habits of grazing heifers. These results are presented in Table 2. The active day was primarily a func- tion of day length and varied from 9 hours, 30 minutes, on De- cember 17, 1956, to 16 hours, 45 minutes, on both June 27 and July 24, 1956.

The time spent grazing is not

so closely correlated with day length as is the active day. Usual- ly grazing started in the early morning before dawn and con- tinued for 30 minutes to over an hour. Grazing occurred for periods during the mid-day, and in mid or late afternoon grazing intensified for a 3- to 5-hour pe- riod that often continued until after sundown. Little grazing was done in complete darkness, although a full moon at dusk seemed to prolong the evening grazing period significantly. Dur- ing the summer months grazing frequently occurred in the mid or late morning hours, while in the winter this time was spent at supplemental feeding. During the growing season on June 2, 1956, 12 hours, 11 minutes were spent grazing. During supple- mental feeding periods such as February, 1956, the grazing time was much less (Table 2).

Idling and lying were two ac- tivities indulged in nearly every day. When considered together they showed a tendency to in- crease in time with the increase was spent, varying from 35 min- utes to one hour, consuming sup- in the active day (Table 2). Time plemental feed for six of the 13 observation periods (Table 2). This practice greatly controlled the patterns of travel in the pas- ture. The heifers were usually

Table 2. Time spent by yearling heifers af various activities during observation periods at the Eastern Colorado

Range Station, February 11, 1956-January 19, 1957.

Active . Supplemental

Observation Date

Day Hours

Grazing

Hours

Idling

Hours

Lying

Hours

Feeding

Hours

Salting Drinking Traveling

Min. Min. Min.

Feb. 11, 1956 11.4 5.6 2.3 1.7 1.0 1 6

Mar. 10, 1956 13.2 6.1 1.6 4.3 1.0 5 5

Apr. 6, 1956 13.2 6.9 3.0 2.0 0.8 0 12

Apr. 27, 1956 15.0 9.8 2.7 2.1 0.0 8 11

June 2, 1956 15.9 12.2 2.5 1.0 0.0 3 6

June 27, 1956 16.7 8.1 5.7 2.4 0.0 0 13

July 24, 1956 16.7 8.4 3.6 4.5 0.0 0 12

Aug. 22, 1956 14.6 8.4 3.3 2.4 0.0 5 19

Sep. 17, 1956 13.8 9.9 2.5 1.0 0.0 5 10

Oct. 19, 1956 13.7 8.5 2.4 2.5 0.0 0 10

Nov. 16, 1956 11.6 7.6 1.7 1.2 0.6 0 6

Dec. 17, 1956 9.5 6.0 1.8 ’ 0.0 0.9 3 20

Jan. 19, 1957 12.0 7.7 1.3 1.6 0.9 1 10

43

64 REPPERT

at or near the feed areas as much as an hour before arrival of the feed. In addition, a rather direct course was often taken from the feeding area to water.

Water consumption occurred three times during the active day April 27, June 27, July 24, and August 22. On April 6, June 2, September 17, October 19, and December 17, the heifers were observed to drink twice; for the remaining four observation pe- riods the heifers journeyed to the windmill only once for water. There appeared to be little relationship between the taking of salt and the drinking of water. The December period was the only one in which the heifers drank immediately after taking salt. The salt was more than %-mile from the water tank. Frequently they drank water before salting, but there was considerable time lapse be- fore the salt was eaten. In No- vember it was observed that after drinking all heifers chang- ed their preference from grasses to sand sagebrush. In November the heifers were observed lick- ing snow into their mouths. Very little travel was noticed unless it was for the purpose of obtain- ing water, moving to the supple- mental feed area, or obtaining salt.

Discussion and Conclusions

Based on the analysis of the data collected at 13 times during the year, it can be stated that preference for certain species was very definite and varied considerably at different times of the year.

Sandreed, blue grama, and needle-and-thread as a group made up from 65.3 percent to 96.9 percent of all the forage consumed. The species which contributed the most to the diet was always found to be one of these three species. Both blue grama and sandreed were pres- ent in the vegetation complex to such an extent that they were

readily available to grazing heif- ers. This fact indicates that rela- tive availability of the species is one important factor influencing preference.

The cool season grass, needle- and-thread, consisted of green parts during the spring and fall, which caused this species to be much preferred at these times. Needle-and-thread was the most important source of forage dur- ing these periods. This occurred even though available needle- and-thread was estimated to be less than 5 percent of the species composition. At times when this species was preferred it had more green growth than sand- reed or blue grama. This indi- cates that the stage of develop- ment of the plant is a primary factor determining the prefer- ence exhibited by grazing ani- mals. The stage of development of a plant species may be impor- tant in the way it affects rela- tive palatability of the species and, in some cases, the manner in which it affects the availabil- ity.

Many climatic conditions were observed to have little effect upon the preferential selection of native forage. One exception to this trend was the effect of snowfall. This caused grazing heifers to seek forage that was not covered by snow, which led to increased use of taller grasses and shrubs. The onset of cold winter temperatures, and the consequent ending of the grow- ing season, resulted in a prefer- ence for the only “green” forage available, sand sagebrush and yucca.

The data indicate that certain parts of plant species are pre- ferred to other parts at different times of the year. A tendency was noted for the grazing heifers to select green forage in prefer- ence to old. In addition, a prefer- ence was exhibited for leaves rather than stems and coarser forage. This should have re- sulted in a more nutritious diet

for the animals, considering the higher nutritive value of green leafy forage compared to old or

stemy forage (Maynard and

Loosli, 1956).

It was observed that from mid-summer to the end of the growing season the parts of for- age consumed became increas- ingly more stemy. This occurred even though the forage was in what was considered a “green” stage. The quality of greenness was less than the bright green color of early summer. These facts were considered to indicate that the nutritive value of the forage grazed was lessening con- siderably with the passage of the growing season,

The 13 observations from Feb- ruary, 1956, to January, 1957, in- dicated that certain daily graz- ing habits were related to prefer- ence of native forage. The time spent grazing varied according to the presence of supplemental feeding and conditions of the na- tive forage. The longer periods of grazing, April 27 and June 2, may be associated with perfer- ence for needle-and-thread at this time. This period was lack- ing in precipitation, and green forage was at a premium. The difficulty in finding and select- ing green forage from the vege- tation complex may have re- sulted in increased time spent grazing.