• TABLE OF CONTENTS
HIDE
 Title Page
 Table of Contents
 Acknowledgement
 Main














Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 689
Title: Roselawn St. Augustinegrass as a perennial pasture forage for organic soils of south Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027166/00001
 Material Information
Title: Roselawn St. Augustinegrass as a perennial pasture forage for organic soils of south Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 19 p. : ill. ; 23 cm.
Language: English
Creator: Haines, C. E
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1965
 Subjects
Subject: Cattle -- Feeding and feeds -- Florida   ( lcsh )
Grasses -- Florida   ( lcsh )
Forage plants -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 18-19.
Statement of Responsibility: C.E. Haines ... et al..
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station) ;
 Record Information
Bibliographic ID: UF00027166
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000929274
oclc - 18361270
notis - AEP0051

Table of Contents
    Title Page
        Page 1
    Table of Contents
        Page 2
    Acknowledgement
        Page 2
    Main
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
Full Text
BULLETIN 689
MARCH 1965

Roselawn St. Augustinegrass

As a Perennial Pasture Forage

For Organic Soils of

South Florida


RM' Undergrazed






""* Properly Grazed
S_ C. E. HAINES
H. L. CHAPMAN, JR.
R. J. ALLEN, JR.
) r------12 3- --^- -'---





r,'R. W. KIDDER



Overgrazed

12
6 -



G
---- --------------1~C .HIE








AGRICULTURAL EXPERIMENT STATIONS
UNIVERSITY OF FLORIDA, GAINESVILLE
J. R. BECKENBACH, DIRECTOR














TABLE OF CONTENTS


Page
3


Introduction
Experimental Procedure
Results
Estimated Yields
Discussion
Summary
Literature Cited


ACKNOWLEDGMENTS

Many persons were involved in the collections of portions of
the data presented in this report. A few that the authors wish
to acknowledge are D. W. Beardsley, A. E. Kretschmer, Jr.,
R. A. Bair, and R. H. Webster for their assistance. Apprecia-
tion is also extended to M. Koger for processing the data and
assistance with the statistical analysis.














TABLE OF CONTENTS


Page
3


Introduction
Experimental Procedure
Results
Estimated Yields
Discussion
Summary
Literature Cited


ACKNOWLEDGMENTS

Many persons were involved in the collections of portions of
the data presented in this report. A few that the authors wish
to acknowledge are D. W. Beardsley, A. E. Kretschmer, Jr.,
R. A. Bair, and R. H. Webster for their assistance. Apprecia-
tion is also extended to M. Koger for processing the data and
assistance with the statistical analysis.











Roselawn St. Augustinegrass as a Perennial
Pasture Forage for Organic Soils
of South Florida

C. E. Haines, H. L. Chapman, Jr., R. J. Allen, Jr.,
and R. W. Kidder1

INTRODUCTION
Beef cattle lead all classes of livestock in the consumption of
grass and forage crops. Lush (22) 2 estimates that beef cattle use
about one third of the permanent pastures and three fourths of
the range areas in the United States, and Morrison (25) con-
tends that forage crops make up about 82 percent of the feeds
consumed by beef cattle. It has also been predicted by Ahlgren
(1) that expanding the research in forages and the application
of the results could lead to a 475 percent increase in livestock
production in the southeastern part of the United States. Perma-
nent forages should become progressively more important to
cattlemen as the length of grazing season increases.
South Florida has a great potential for beef production be-
cause of a long grazing season and the high yields of forage
crops on the organic soils. Chapman et al. (6) have indicated
that the basic feed for most cattle operations in Florida should
be pasture forage, and Cunha (7) states that "The area sur-
rounding Lake Okeechobee is a very important one as far as
the beef cattle industry is concerned. In fact, the heaviest con-
centration of beef cattle is in this area of Florida."
According to Neller and Daane (26) the first pastures to be
successfully established at the Everglades Experiment Station
were in 1929, and they consisted of Dallas, carib, carpet, and
centipede grass. A few years before this, paragrass had been
established in pastures but plantings were killed out by the 1925
winter freeze and close grazing. It was not until the 1943 and
1944 season that the Roselawn strain of St. Augustinegrass
(Stenotaphrum secundatum (Walt.) Kuntze) was released for
use as a pasture forage, although St. Augustinegrass had been
1Assistant Animal Husbandman, Animal Nutritionist, Assistant Agrono-
mist, and Animal Husbandman, Everglades Experiment Station, Belle
Glade, Florida.
Numbers in parentheses refer to Literature Cited.







Florida Agricultural Experiment Stations


described in 1788. Today, it is considered the most dependable
pasture grass for the organic soils of south Florida. Morrison
(25) reports that it produces 690 to 780 pounds of gain per acre
annually on these soils. A report by Kidder and Allen (20) indi-
cated that St. Augustinegrass probably contained a greater
amount of total digestible nutrients than paragrass or carib-
grass due to its higher dry matter content.
Observations on grazing animals to determine the value of
pasture forages is an ancient procedure. More modern tech-
niques have been developed in recent years. Grazing animals
have been used because they reflect the true nutritive value of
the forage consumed. The production achieved by the animal is
a function of the rate of intake of the forage combined with its
nutritive content. However, results from short term grazing
trials are not as reliable as those from more extensive studies,
and Blaser et al. (3) found that grazing experiments should be
conducted for several years duration for reliable information.
In order to obtain a true estimate of forage yield it is also
necessary to maintain a correct balance between the forage yield
and the number of grazing animals used per unit of pasture
land. In other words, grazing management is a compromise
between plants and animals.
Jones et al. (16) reported beef yields of 165 and 195 pounds
per acre from cow herds grazing the year around on improved
pastures on mineral soils in central Florida. These same workers
secured a yield of 970 pounds of beef per acre with young stock
that grazed heavily fertilized pangolagrass just between spring
and the following fall (not year-around grazing).
During the past 35 years various pasture grasses have been
evaluated at the Everglades Experiment Station in grazing
studies. Many of the species studied have been eliminated after
a year or two of observations, but a few species have remained
under test for many years. The grass upon which the most
extensive data have been collected is the Roselawn strain of
St. Augustinegrass. Over a period of years it has been superior
to all other grasses tested as a forage for grazing cattle. An
early study by Kidder (18) indicated that it was possible to
produce 2,000 pounds of beef per acre from St. Augustinegrass
pastures on organic soil. The animals averaged 550 pounds and
were provided a pound of cottonseed meal or pellets per head
daily in addition to the forage. These gains have not been dupli-







Rosela u St. Augustinegrass


cated, and later observations indicated that these experimental
blocks were located in an area that possessed very favorable
moisture and temperature conditions. Average productivity of
Roselawn St. Augustingrass over a five-year period in a later
study reported by Kidder et al. (19) was 1004 pounds of weight
gains. The annual stocking rate was 2.76 yearlings per acre and
90 to 92 percent of the total gains came in the eight months
between March and October. More recent studies by Haines
et al. (9. 10, 12, and 13) comparing the annual productivity of
Roselawn St. Augustinegrass with pangolagrass, paragrass, and
Pensacola and Argentine bahiagrass, have indicated St. Augus-
tinegrass to be superior to the other grasses in terms of animal
gains.
This report is a summary of 10 years of data on the pro-
ductivity of Roselawn St. Augustinegrass as a pasture forage
for beef cattle yearlings. The productivity has been measured
by both weight gains and stocking rates employed.

EXPERIMENTAL PROCEDURE
Data reported herein were obtained from blocks of Roselawn
St. Augustinegrass that were grazed continuously for 10 differ-
ent years by groups of yearling cattle. The years were not con-
secutive, but the information was accumulated over 111/ years.
Each block was 2 acres in size, and there were two blocks within
each of the test years. The grass blocks were fertilized at rates
and with mixtures recommended from soil analysis determina-
tions. Annual applications ranged from 300 to 500 pounds per
acre of fertilizer of a 0-8-24, 0-10-20, or 0-12-16 mixture con-
taining 1 percent CuO. These fertilizers were applied once a
year, usually in the fall or winter season.
In some years the test animals were steers, while in other
years they were combinations of heifers and steers. The animals
consisted of various breeds in each year and were allotted by
breed, sex, and weight to the various test blocks. The yearlings
were placed in the pasture blocks between June and October of
each year and kept on the blocks for one year, after which an-
other group of yearlings was started on the cycle for the next
year of the study. The stocking rate and carrying capacity
varied from season to season within each year, since it was
dependent upon the quantity of forage available during the par-
ticular period. When forage was abundant, additional yearlings







Florida Agricultural Experiment Stations


were placed in the blocks, and as forage became scarce, the num-
ber of animals per block was reduced. This procedure is referred
to as the "put and take system" of grazing management often
used in this type of study. Usually, the changes in the number
of grazing animals occurred at biweekly intervals, but occasion-
ally changes took place at weekly intervals.
The yearlings were weighed when changes in stocking rates
occurred and at biweekly intervals throughout the year. The
animal weights were used to compute the total pounds of weight
gains or losses for the various periods throughout the test year.
The years were subdivided into 26 biweekly periods for deter-
mining the seasonal variations in forage productivity as mea-
sured by animal gains and carrying capacity. All data were
converted to an acre basis and are reported in this manner.
Proximate analyses of the grass in the test blocks were not
available for all the years and months involved, .but available
data were compiled. The AOAC method (24) was used for these
analyses.
Productivity data were tested for statistical significance by
methods described by Snedecor (27). The estimated yield of
forage and nutrients per acre was determined by systems de-
scribed by Harris (15), Maynard and Loosli (23), Knott et al.
(21), Swift (28), and Kidder (17).

RESULTS
Average gains per yearling were calculated for each 14-day
period. The average daily gains were more than 1.4 pounds per
animal for seven of these 26 periods. These seven test periods
were consecutive and started on March 12 and ended June 17.
The highest average daily gains were 2.18 pounds, between
April 9 and April 22. The only period in which animals lost
weight was between December 3 and December 16. Losses in
weight averaged 0.19 pounds per animal daily during this period.
Average gains of less than 0.5 pounds per animal daily occurred
in the months of January, October, November, and December.
(See Table 1 and Figure 1.)
Average total gains per acre in a 14-day period ranged from
a total loss of 5.0 pounds to a total gain of 100.5 pounds. This
is a difference of 105.5 pounds between the maximum and mini-
mum producing periods or 7.5 pounds per day. This maximum
production occurred during the two weeks between June 4 and








Roselawn St. Augustinegrass


Table 1.-Average stocking rates and animal gains per
mental periods for the 10-year period.

Test Days Number of Total Weight
Period Included Animals Gain (Ibs.)

1 Jan. 1 Jan. 14 1.7 7.5
2 Jan. 15 Jan. 28 1.6 13.8
3 Jan. 29 Feb. 11 1.7 16.3
4 Feb. 12 Feb. 25 1.8 20.9
5 Feb. 26 Mar. 11 2.1 40.0
6 Mar. 12- Mar. 25 2.3 57.6
7 Mar. 26 Apr. 8 2.4 54.9
8 Apr. 9 Apr. 22 3.0 91.5
9 Apr. 23 May 6 3.2 67.9
10 May 7 May 20 3.3 67.1
11 May 21 June 3 3.4 70.0
12 June 4 June 17 4.1 100.5
13 June 18 July 1 4.3 61.6
14 July 2 July 15 4.4 63.9
15 July 16 July 29 4.3 57.6
16 July 30 Aug. 12 4.2 46.5
17 Aug. 13 Aug. 26 4.4 38.3
18 Aug. 27 Sept. 9 3.9 63.3
19 Sept. 10 Sept. 23 3.7 41.5
20 Sept. 24 Oct. 7 3.3 7.1
21 Oct. 8 Oct. 21 3.0 28.8
22 Oct. 22 Nov.4 2.6 13.9
23 Nov. 5 Nov. 18 2.5 13.5
24 Nov. 19 Dec. 2 2.2 13.6
25 Dec. 3 Dec. 16 1.9 -5.0
26 Dec. 17 Dec. 31 1.7 6.8


acre by experi-


Average Daily
Gain (lbs.)

0.32
0.62
0.69
0.83
1.36
1.79
1.63
2.18
1.52
1.45
1.47
1.75
1.02
1.04
0.96
0.79
0.62
1.16
0.80
0.15
0.69
0.38
0.39
0.44
-0.19
0.29


June 17, while the minimum yields occurred in the 14 days
between December 3 and 16. (See Table 1 and Figure 1.) Other
periods in single years sometimes showed negative productivity,
but the average of combined data from all years was positive
except for the December 3-16 period. The average productivity
per 14-day period in the 10 years was 40.7 pounds per acre.








Florida Agricultural Experiment Stations


5
UJ
Il

- ANIMALS /

U) 3
-J /



\POUNDS

a--.
0 0-


I 14 28 11 25 11 25 8 22 6 20 3 17 1 IS 29 12 26 9 23 7 21 4 18 2 16 31
J F M A M J J A S 0 N O
Figure 1.-Average daily gains and stocking rates per acre by
14-day intervals.

The total pounds of gain realized in each of the experimental
years are shown in Table 2. The experimental year with the
poorest record of total productivity was 1952-1953, while the
highest overall productivity occurred in the 1956-1957 year. The
average total pounds of gain realized in these two years per
acre of pasture were 795 pounds and 1369 pounds, respectively.
Since the overall annual average was 1059.4 pounds, it is safe
to expect at least 1000 pounds of beef per acre from yearlings
grazing well-managed Roselawn St. Augustinegrass during nor-
mal years provided that animal numbers can be adjusted to the
feed supply.
As would be expected, there was a tremendous variation in
the carrying capacity of the pastures from season to season or
between periods. The maximum daily range was from 1/2 to 51/2
yearlings per acre within any one year of the study. This range
was narrowed when data for the periods of all 10 years were
averaged. When this was done, the smallest number of animals
per acre at any one time was 1.6 and occurred during the last
two weeks of January. Daily stocking rates averaged less than
2.0 animals per acre in the months of December, January and
February. However, during the months of June, July, and
August an average of over 4.0 animals was maintained per acre.
The highest average daily carrying capacity was 4.4 animals







Roselawn St. Augustinegrass


per acre, and this occurred in the first two weeks of July and
the last two weeks of August. (See Table 1 and Figure 1.) At
this time, the animals averaged approximately 640 pounds.
On a yearly basis, the most grazing days occurred in the
1951-1952 year. This was a total of 1260 days per acre. The
least productive year, in regard to animal grazing days, was
the 1954-1955 experimental year, which had a daily average
of 2.3 animals per acre or supplied 840 grazing days. The
average daily stocking rate for all years was 2.9 animals per
acre, which is a total of 1066 animal grazing days per year.
The variations in total grazing days are shown in Table 2.


Table 2.-A comparison of the total productivity between experimental
years.
Experimental Total per Acre
Year Animal days Pounds gain
1951-1952 1260 983.8
1952-1953 1089 795.0
1953-1954 1085 1122.5
1954-1955 840 870.0
1955-1956 1036 1233.8
1956-1957 1159 1368.8
1958-1959 1043 1005.0
1959-1960 1043 916.3
1960-1961 1001 1116.3
1961-1962 1106 1182.5
Average 1066 1059.4



An analysis of variance showed that differences in produc-
tivity between years, as measured by pounds of gain per acre,
were statistically significant (P<0.05). Differences between
periods or seasons of the year were highly significant (P<0.01),
as were differences between replications, or blocks, within years.
The first order interaction between years and periods was highly
significant (P<0.01). The summary of this analysis is shown
in Table 3.
The seasonal fluctuations in the total weight gains from the
grass blocks are illustrated in Figure 2. The enclosed columns
indicate the actual pounds of gain obtained, and the super-
imposed curve indicates the production obtained by averaging
the total weight gains in three consecutive weigh periods and








Florida Agricultural Experiment Stations


Table 3.-Variance analysis of animal gains.
Source df MS "F" Value
Total 511
Years 9 0.900 2.24*
Periods 25 6.134 15.26**
Blocks 1 3.385 8.42**
Years x Periods 225 1.451 3.61**
Years x Blocks 9 0.659 NS
Period x Blocks 25 0.338 NS
Years x Period x Blocks 217 0.402
* P <.05
** P <0.1


then using that average as the value for the middle period of
the three. This procedure tends to minimize extreme individual
period variations and at the same time produces a "smoother"
productivity curve. Although this procedure might introduce
more error than it removes, the adjusted productivity curve
also indicates that June has been the highest yielding month in
regard to the total pounds of beef produced per acre, while
December and January are the lowest months for this factor.
The two weeks period between June 4 and 17 accounted for
almost 9.5 percent of the total pounds of beef obtained in a year


I 14 28 II 25 II 22 6 20 3 17 15 29 12 26 9 23 7 21 4 18 2 16 31
J F M A M J J A S O N D
Figure 2.-Total pounds of beef produced per acre by 14-day intervals
and adjusted production.







Roselawn St. Augustinegrass


from an acre of forage. A total of 43.3 percent of the annual
gains was obtained in the three months of April, May, and June
(12-week period), and the nine months between February and
October (40-week period) were responsible for 94.8 percent of
the total annual gains. Therefore, the three months of Novem-
ber, December, and January (12-week period) accounted for
only 5.2 percent of the total annual gains.
The results of preliminary digestibility trials reported by
Chapman et al. (5) showed that there are seasonal differences
in the nutritive value of grasses in south Florida. Digestibility
coefficients for St. Augustinegrass in a test conducted in the
spring (May) were 71.2 percent for crude protein and 65.6
percent for the amount of total digestible nutrients (TDN) in
the dry matter. Coefficients for these same factors in the fall
season (September) were 51.6 percent and 56.6 percent, re-
spectively. Thus, the digestibility was slightly higher in the
spring season.
The results of several years of chemical analyses tend to
show that the crude protein content is slightly higher in the
grass during the months of March and April. On the other
hand, the crude fiber was slightly lower during these same
months. Crude protein was generally the lowest and fiber the
highest during the months of August, September, and October.
Seasonal differences in fat, ash, and nitrogen free extract were
not evident. The overall annual averages for crude protein,
fiber, fat, and ash on a dry weight basis were 15.3, 28.1, 3.1,
and 8.8 percent, respectively. The average monthly moisture
content ranged from 70.5 to 80.5 percent. A summary of the
chemical analysis of Roselawn St. Augustinegrass and the num-
ber of years involved is shown in Table 4, and the seasonal
fluctuations in chemical composition are illustrated in Figure 3.
The grass samples for these analyses were collected in the middle
of each month from the pasture blocks used in this grazing study.

ESTIMATED YIELDS
Although the nutritive value of a forage expresses itself
in the gains and carrying capacity realized from a unit of
pasture, there are several factors involved in the production of
these end results. The nutrients produced must provide for both
the maintenance and growth of the test animals, and there are
several methods for measuring these requirements.









Florida Agricultural Experiment Stations


Table 4.-Average chemical analyses of Roselawn St. Augustinegrass
samples secured from two test blocks within each year.


Month

Total
Samples
Jan.
Feb.
Mar.
Apr.

May
June

July
Aug.
Sept.
Oct.
Nov.

Dec.

Average


Ether
Moisture Protein* Fiber* Extract*


138
72.8(7)**
72.7(7)
74.0(7)
76.5(7)
79.2(6)
77.5(4)
80.5(6)
80.4(4)
77.6(5)
74.1(4)
74.4(6)
70.5(6)
75.6


139
15.9(7)
15.8(7)
16.6(7)
16.7(7)
16.2(5)t

16.2(4)
14.9(6)

13.7(4)
12.8(5)
14.0(5)
14.9(6)
14.7(6)
15.3


103
29.2(5)

27.7(5)
26.3(5)
25.0(5)
28.2(4)t
29.1(4)

28.1(5)

30.7(3)
29.8(4)
31.4(3)

27.7(4)
26.9(4)
28.1


103
2.6(5)
3.3(5)
3.4(5)
3.6(5)
2.9(4)"
3.9(4)

2.9(5)

3.6(3)
2.1(4)
3.0(3)
3.2(4)
2.3(4)
3.1


Ash'

103
8.6(5)

8.1(5)
9.0(5)
8.6(5)
9.6(4)t

9.5(4)
9.8(5)

9.5(3)
8.1(4)

7.3(3)
8.7(4)
8.7(4)
8.8


* Expressed as the percentage of the dry matter.
** Number of years furnishing data in parenthesis; two blocks
t Plus one sample instead of two from an additional year.


.5o
*


sampled each year.


CRUDE FIBER
.-- \


. . .........
DRY MATTER



*. ..........
'' o
Oo oo


CRUDE PROTEIN

15



10-


J F M A M J J A S 0 N D
Figure 3.-Monthly trends in the percentage of dry matter, crude protein,
and crude fiber in Roselawn St. Augustinegrass.







Rosclaiti St. Augn.sti ne...rass


The nutritive value of a pasture may be expressed as ap-
parent digestible energy (ADE). The ADE factor is the amount
of energy, expressed in units of heat, that has been digested and
taken into the body, and Harris (15) proposed equations for
determining this by the responses of grazing cattle. Using an
average weight of 592 pounds for yearlings in this study, we
found that 9.19 megcals per day were necessary for maintenance
purposes by each yearling. Since there were 1066 grazing days
per year, the total annual yield of ADE for maintenance per
acre was 9797 megcals. Next, the ADE for weight gains was
calculated by multiplying the ADE required for a pound of gain
(4.16 megcals) by the total pounds of gain secured per acre
(1059 pounds) ; this was 4405 megcals. The sum of the ADE
consumed for both maintenance and gain gives a total yield of
14,202 megcals per acre of grass in a year.
Another way to estimate the annual production of forage is
to determine the total digestible nutrients (TDN) produced by
an acre of pasture from the performance of grazing animals.
In an early report by Kidder (17) the TDN requirement of
cattle for maintenance was based on the theory that an allow-
ance of 7.93 pounds of TDN was needed for daily maintenance
by a 1000 pound cow and was expressed as a function of the
live weight raised to the 0.73O power. A more recent study by
Kidder and Allen (20) used the 0.7 power of the live weight for
determining the TDN maintenance requirements and a value of
3.53 pounds of TDN needed for each pound of gain. (Many
years ago, Knott et al. (21) proposed the value of 3.53 pounds
of TDN needed for each pound of animal gain, and this recom-
mendation is still used even though its shortcomings have been
pointed out by Maynard and Loosli (23).) Using the methods
of Kidder and Allen (20), we estimated that yearlings in this
study weighing an average of 592 pounds needed 5.47 pounds
of TDN per day for maintenance purposes. Since an acre of
pasture provided an average of 1066 annual grazing days per
year, 5831 pounds of TDN per year was consumed for mainten-
ance only. The next step involved the determination of the
amount of TDN used for growth or body-weight gains and
showed that a total of 3738 pounds of TDN was used for gains
by the yearlings. The sum of the TDN consumed for mainten-
ance and growth indicated that an acre of Roselawn St. Augus-
tinegrass yielded an average of 9569 pounds of TDN per year
in this study. Swift (28) showed that TDN could be converted







Florida Agricultural Experiment Stations


to digestible energy (DE) values by considering a pound of
TDN to be equal to 2000 kcals. Therefore, the 9569 pounds of
TDN obtained by the above method is equal to 19,138,000 kcals
or 19,138 megcals. The energy determined by these two methods
do not agree, as there is a difference of almost 5000 megcals in
yield. It is suspected that a large share of this discrepancy may
be caused by a difference in the maintenance estimates by the
two methods.
A third method, proposed by Garrett et al. (8), was used for
estimating the amount of DE needed for cattle. This method
includes both the maintenance and gain factors in individual
and combined formulas. Calculations for the maintenance of a
592 pound yearling indicated that 9.12 megcals were required
per day. This is slightly below the 9.19 megcal value determined
by the method of Harris (15). A value of 0.99 pounds was used
as the average daily gain figure for inserting in the formula to
determine the total needs of DE for both maintenance and gains.
The calculations by this method showed that each acre of pasture
yielded a total of 15,304 megcals of digestible energy, which is
rather close to that determined by the method of Harris (15).
The energy requirements by this method, however, are higher
than those proposed by Brody (4).
The report by Garrett et al. (8) also contained a formula
for TDN determinations for both maintenance and gains. Cal-
culations by this formula show that only 4.32 pounds of TDN
were needed daily for maintenance purposes by a 592 pound
yearling, while the combined TDN required daily for both main-
tenance and gain was 6.76 pounds per animal. When this was
multiplied by the total number of animal-days, 7,206 pounds of
TDN was yielded per acre of grass. This is lower than the
value determined by the methods described by Kidder, but in
closer agreement to those found by the other methods.
By applying the data collected in this study to these several
methods for estimating the yields of TDN and DE, we found
that an acre of Roselawn St. Augustinegrass produced approxi-
mately 15,000 megcals of DE or 7,500 pounds of TDN. It should
be emphasized, however, that more refinements are desired in
the equations used for obtaining these estimates that will con-
sider the variations in classes of cattle, the type of forage, and
environmental conditions.
An estimate of the total amount of fresh grass consumed per
acre in a year was computed by an indirect method. The yield







Roselc win St. Augustinegrass


of TDN, as previously estimated, was converted into the pounds
of grass required to provide those nutrients. Computations are
based on the estimate of 7,500 pounds of TDN per acre and
the fact that the average dry matter content of the grass was
24.4 percent which contained 61.0 percent TDN (average of
two coefficients reported on page 11. The calculations in-
dicated that approximately 50,400 pounds or 25.2 tons of green
grass were consumed per acre in a year.


DISCUSSION
Daily gains of the grazing animals as well as the stocking
rate varied a great deal throughout the year. These variations,
of course, are dependent upon both the quality and quantity
of forage during the different seasons. Either temperature or
rainfall or both of these factors affect the growth of pasture
forage and cause variations in its productivity.
An analysis of grazing trial data by Randolph in 19583
gave several indications of influences on animal gains, not ac-
counted for by stocking rates or measurable pasture growth.
He developed graphic multiple correlations which showed that
lighter weight animals failed to gain as well as those of heavier
weights. Other correlations showed a possible relationship be-
tween animal gains and rainfall. When heavy rainfall occurred,
the first effect was a decided increase in gains. As the rainfall
continued, there was a severe loss in weight, and the gains re-
turned to normal as the rainfall diminished. Less than 0.5
inches of rain per week produced the highest gains, with a ten-
dency for an upsurge following 2 inches of rain, but losses
occurred whenever the rainfall exceeded 3 inches. Other graphic
multiple correlations also showed that animals lost weight when
the average maximum temperatures were above 90F or below
70F. Highest gains were evident when the average maximum
temperatures were between 75 and 84F.
As illustrated in Figure 1, the periods of highest individual
daily gains do not exactly coincide with the peak periods for
stocking rates. Individual gains were the highest in March,
April, May, and June, while stocking rates were the highest in
June, July, August, and September. Thus, the nutritive value
of the forage may be highest in the early spring, and yet maxi-
: Unpublished data compiled by John Randolph of the Everglades Experi-
ment Station on paragrass, 1958.







Florida Agricultural Experiment Stations


mum growth occurs later in the spring; or the peak periods for
quality and quantity do not occur at exactly the same time of
the year. It is also possible that some of this variance was due
to the judgment of the experimenter as to the proper time for
altering animal numbers. In this type of management, the rates
of stocking depend on the experimenter's assessment of the
correct carrying capacity of the unit of pasture from time to
time. Errors in this procedure may bias the data on output per
animal and output per acre, as highest production is obtained
by the proper balance between stocking rate and forage growth.
The seasonal fluctuations in pasture productivity suggest
that grazing cattle should be supplemented during the "lean
season" of the year. Several methods have been studied for ac-
complishing this task. Haines and leGrand (14) supplemented
yearlings on Roselawn St. Augustinegrass during three conse-
cutive winter periods with chopped sugarcane. The greatest
response to the supplemental sugarcane was in the coldest winter
when forage was the most scarce. Grass silage has been tried
as a winter supplement to pasture grazing by Allen (2), and
other types of supplements have been reviewed by Chapman
et al. (6). The stocking rate and the severity of the winter
determine the importance of pasture supplementation.
Although variable numbers of yearlings were used in this
study to secure data on the productivity of Roselawn St. Augus-
tinegrass, it is not practical to alter the number of animals on
pasture under normal farm grazing practices. Varying the num-
ber of animals is really equivalent to varying the number of
acres used for grazing purposes. Thus, the number of acres
grazed can be manipulated to fit the forage production. One
way of doing this in south Florida would be to make silage from
the extra forage produced during the peak growth periods of
the grass. Haines and Allen (11) suggested that it would be
possible to maintain three yearlings per acre all year long on
Roselawn St. Augustinegrass, by using excess forage for silage.
They estimated that the pastures would be undergrazed for 127
days or approximately four months, properly stocked for 57 days
or two months, and overgrazed for 181 days or six months in
each year.
Pastures may be grazed under three different systems: con-
tinuous grazing, rotational grazing, and strip grazing. Morrison
(25) contends that in most trials rotational grazing of perma-
nent pastures has not increased the yield of forage enough to







Roselaicw St. Augustinegrass


warrant the additional expense, and in some trials there has
been no difference in yields between rotational and continuous
grazing. Allen (2) reported similar results with Roselawn St.
Augustinegrass in south Florida. Strip grazing has not been
attempted in the Everglades area due to difficulties in the man-
agement of the grazing cattle and the rapid growth of pasture
plants in certain seasons of the year.
On the basis of several methods of determination, approxi-
mately 7500 pounds of TDN were consumed per acre of grass.
An estimation that 50,400 pounds of fresh grass were consumed
per acre yearly is considerably below the 94,000 pounds esti-
mated by Kidder (18). Since both estimates are on the basis
of actual animal performance as measured by calculated nutri-
ent requirements, the difference must be attributed to variations
in animal performance between the two studies. The earlier
study had an average total gain of 1801 pounds per acre com-
pared to only 1059 pounds recorded during this 10-year study.
The larger gains would require a greater yield of pasture forage
to furnish the nutrient requirements. Several years of data on
the total amount of forage material obtainable from an acre of
Roselawn St. Augustinegrass have been compiled by Allen4
using mechanical procedures. He found that approximately
35 tons (70,000 lbs.) of green grass were harvested from an
acre. This yield is just slightly higher than the value obtained
by converting data from animal performance and nutritive re-
quirements. However, this should be expected, since cattle do
not utilize all forage that is harvested by mechanical means.

SUMMARY
The productivity of Roselawn St. Augustinegrass pasture on
the organic soil of south Florida was determined by grazing
yearling cattle. Data were obtained by continuously grazing
pairs of 2-acre test blocks for yearly periods, and information
was collected over a total of 10 years. The number of yearlings
per acre was altered at frequent intervals to compensate for
seasonal variations in forage production. The productivity has
been determined by both the number of grazing days and the
total pounds of weight gained per acre in a years' period.
The average number of grazing days per acre was 1066 in
a year, which corresponds to an average daily stocking rate of
Unpublished data on clipping trials conducted by R. J. Allen, Jr., 1963.








Florida Agricultural Experiment Stations


2.9 yearlings per acre. The daily stocking rate ranged from a
high of 4.4 animals per acre in July and August to a low of 1.6
yearlings per acre in January. An average of 1059 pounds of
animal gain was produced per year from an acre of grass, and
only 5 percent of this production occurred during the three-
month period of November, December, and January. Differences
in productivity between years, seasons, and replicates were all
statistically significant.
The actual amount of nutrients and fresh forage produced
per acre was estimated by various methods in an attempt to
correlate data obtained in the field (gains) with that produced
by laboratory analysis, digestibility trials, and green grass
yields by clipping techniques. Computations showed that an
average of 50,400 pounds of green forage was consumed from
an acre is a years' time. An acre produced approximately 7500
pounds of total digestible nutrients or 15,000 megcals of ap-
parent digestible energy. Average chemical analyses values
were 24.4 percent dry matter, of which 15.3 percent was crude
protein, 28.1 percent crude fiber, 3.1 percent ether extract, and
8.8 percent ash.



LITERATURE CITED

1. Ahlgren, Henry L. Still an infant, forage research pays dividends.
Livestock Breeder Journal 5(2): 96. 1962.
2. Allen, R. J., Jr. Summarization of grazing trial experiments. Ever-
glades Station Mimeo 57-11. 1957.
3. Blaser, R. E., J. R. Harlan, and R. M. Love. Grazing management.
Pasture and Range Research Techniques. Comstock Publishing As-
sociates, Ithaca, New York. 1962.
4. Brody, S. Bioenergetics and Growth. Reinhold Publishing Co. New
York, N. Y. 1945.
5. Chapman, H. L., Jr., R. W. Kidder, C. E. Haines, R. J. Allen, Jr.,
V. E. Green, Jr., and W. T. Forsee, Jr. Beef cattle production on
organic soils of south Florida. Fla. Agr. Exp. Sta. Bul. 662. 1963.
6. Chapman, H. L., Jr., F. M. Peacock, W. G. Kirk, R. L. Shirley, and
T. J. Cunha. Supplemental feeding of beef cattle on pasture in south
Florida. Fla. Agr. Exp. Sta. Bul. 665. 1964.
7. Cunha, T. J. Present status of cattle industry in south Florida. A
mimeo report presented to the Beef Cattle Field Day at Belle Glade.
Nov. 1963.
8. Garrett, W. N., J. H. Meyer, and G. P. Lofgreen. The comparative
energy requirements of sheep and cattle for maintenance and gain.
Jour. Animal Sci. 18: 528-547. 1959.








Roselawn St. Augustinegrass 19

D. Haines, C. E., and H. L. Chapman, Jr. Results of grazing experiments
with yearling calves on four major pasture grasses of the Everglades
for one year. Everglades Station Mimeo 60-16. 1960.
10. Haines, C. E., and R. J. Allen, Jr. Grazing trial results for one year
(1959-1960). Everglades Station Mimeo 61-11. 1961.
11. .. .. Making your grazing pay off. Florida Cattle-
man 25:48. 1961.
12. .-- Grazing trial results for one year (1960-1961).
Everglades Station Mimeo 62-26. 1962.
13. .- Grazing trial results for one year (1961-1962).
Everglades Station Mimeo 64-7. 1963.
14. Haines, C. E., and F. leGrand. Supplementing winter grazing with
sugarcane. Sugar Jour. 26:7. 1963.
15. Harris, L. E. Measure of the energy value of pasture and range forage.
Pasture and Range Research Techniques. Comstock Publishing As-
sociates, Ithaca, New York. 1962.
16. Jones, D. W., E. M. Hodges, and W. G. Kirk. Year-round grazing on
a combination of native and improved pastures. Fla. Agr. Exp. Sta.
Bul. 554A. 1960.
17. Kidder, R. W. A proposed method of measuring pasture yields with
grazing cattle. Jour. Animal. Sci. 5:187-193. 1946.
18. .. Ton of beef per acre of grass in 12 months.
Breeders Gazette. 117(11):8. 1952.
19. Kidder, R. W., R. J. Allen, Jr., H. L. Chapman, Jr., and D. W.
Beardsley. Yield of Everglades pasture as measured by growth of
yearling cattle. Jour. Animal Sci. 16:1058. 1957.
20. Kidder, R. W., and R. J. Allen, Jr. A method of estimating forage
consumption by grazing cattle. Everglades Station Mimeo 58-8. 1957.
21. Knott, J. C., R. E. Hodgson, and E. V. Ellington. Methods of measuring
pasture yields with dairy cattle. Wash. Agr. Exp. Sta. Bul. 295. 1934.
22. Lush, R. H. Pastures for beef cattle. Pasture Production and Man-
agement. The Blakiston Company Inc., Garden City, New York. 1952.
23. Maynard, L. A., and J. K. Loosli. Animal Nutrition, 5th Edition.
McGraw-Hill Book Company, Inc., New York, New York. 1962.
24. Methods of Analyses of A.O.A.C. Washington 4, D. C., 9th Edition.
1960.
25. Morrison, F. B. Feeds and Feeding, 22nd Edition. The Morrison
Publishing Company, Ithaca, New York. 1956.
26. Neller, J. R. and A. Daane. Yield and composition of Everglades
grass crops in relation to fertilizer treatment. Fla. Agr. Exp. Sta.
Bul. 338. 1939.
27. Snedecor, G. W. Statistical Methods, 5th Edition. The Iowa State
College, Press, Ames, Iowa. 1956.
28. Swift, R. W'. The caloric value of TDN. Jour. Animal Sci. 16: 753.
1957.




University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs