| Range Cattle REC, Research Report RC-1998-2 |
| Cattle and Forage Field Day |
| A Tribute to Mac Peacock |
|
October 8, 1998 Ona, Florida |
| Range Cattle REC, Research Report RC-1998-2 |
| Cattle and Forage Field Day |
| A Tribute to Mac Peacock |
|
October 8, 1998 Ona, Florida |
One of the purposes of crossbreeding is to utilize the phenomenon of heterosis, or hybrid
vigor. Heterosis is measured by the improvement that we get for many traits, particularly those
of greatest economic importance to the cattleman, when we cross various breeds. Heterosis
generally results in an improvement in cow fertility, calf newborn vigor and survival rate, milk
production and calf growth rate. Crossbreeding does not, however, generally have much of an
impact on carcass traits, like ribeye area, fat thickness, marbling, etc. The impact of heterosis
on the traits that it does increase, however, is so great that the use of purebreds as commercial
animals, even in other parts of the country, usually is not economically feasible.
Crossbreeding offers another advantage besides heterosis; producers can select breeds
whose superior traits will complement each other in a particular crossbreeding system, producing
crossbred animals with a more desirable combination of traits than can be found in existing breeds.
The effect of combining desirable traits from two or more different breeds to produce superior
crossbred animals is referred to as "complementarity."
Breed complementarity can be illustrated in terms of adaptation to the Florida climate.
Angus cattle are at a disadvantage in Florida during summer months due to their inability to
control body temperature during periods of heat stress. Brahman cattle, on the other hand, are
comfortable during the summer because they are well-adapted to high temperatures; but they often
suffer in the winter during wet, cold, and windy periods. The F1 animal that results from crossing
Angus and Brahman breeds is comfortable during both summer and winter months in Florida; its
level of adaptation to cold, and to heat, is intermediate to the corresponding levels of adaptation
exhibited by each parental breed. Through proper selection of breeds for use in a crossbreeding
system, cattle producers can "genetically engineer" the desired level of performance for traits in
the crossbred progeny.
One of the givens regarding crossbreeding programs in Florida has been the use of
Brahman crossbred cows as a part of the system. A particular advantage of the F1 Brahman
×Angus or Brahman ×Hereford crossbred cow (and other cows with Brahman breeding) is her
ability to restrict her calf's birth weight and thus be able to calve easily even when bred to bulls
of large breeds such as Simmental, Gelbvieh, or Charolais. The calves from this type of mating,
while relatively small at birth, have the genetic potential for very rapid growth due to the
combination of the effect of 50% of the genes being from the large sire breed and the positive
effects of both individual and maternal heterosis on growth. Individual heterosis is the
improvement due to the calf being crossbred and impacts calf vigor and growth while maternal
heterosis relates to the dam of the calf being crossbred and the increase in performance is due in
large part to the increased milk production of the calf's dam. This combination of the crossbred
calf's potential for growth, along with the high and sustained milk yield of the Brahman F1
crossbred cow, can result in exceptional calves at weaning. Unfortunately, however, such
explosive growth to weaning may be related to lowered growth postweaning. Also, the current
market demands regarding Brahman-influenced cattle may cause us to reconsider the crossbreeding
programs that are most appropriate.
When choosing breeds for a crossbreeding system, the environment--both nutritional and
climatic--must also be considered. For example, the growth potential of the Simmental breed
is much higher than that of the Angus and Hereford breeds, but cows sired by Simmental bulls
may not maintain sufficient body condition to rebreed while lactating unless the level of nutrition
provided is adequate to support their higher requirements. This problem is especially acute for
lactating first-calf heifers. So, under low-input production systems (native range, for example),
use of the larger, heavier-milking breeds--likely to produce cows weighing over 1100 lb--will not
be feasible. The higher nutritional requirements of the Simmental and other heavy-milking breeds
and their crosses must be considered in order to avoid lowered fertility. Traditional crosses
involving the Angus, Hereford, and Brahman breeds and(or) Brangus and Braford are likely to
be more profitable because they will be able to maintain higher reproductive rates under lower
pasture quality. Under improved, fertilized pastures and adequate supplementation during the
winter months, the use of larger, heavier-milking breeds can produce highly productive cows (as
long as excessively large-framed bulls that will produce extremely large daughters are not used).
Another factor that must be considered in breed selection is market demand. Breeds
selected must be utilized in a system that will produce calves that are in demand by stockers and
feeders. It is for this reason that the Brahman can no longer play as large a role in crossbreeding
programs as it has in the past; or, it must be utilized differently to avoid production of calves with
distinctive Brahman characteristics. Usually this will limit the level of Brahman in feeder calves
to less than 50% Brahman breeding. Feeder calves must also have moderate frame sizes, an
indicator of the weight of the carcass that they will produce, in the range from 5 to perhaps as
high as 7 and possess adequate muscling. Therefore, the breeds selected must also have bulls
available with appropriate frame scores and muscling to produce medium-framed, muscle score #1
feeder calves.
To produce a consistent set of calves year after year, it is essential that an appropriate
crossbreeding system with a particular set of breeds be established and continuously maintained.
Thus, availability of superior bulls for each breed included in the system is, necessarily, an
important criterion for breed selection. Availability of bulls of some breeds that may be useful
for crossbreeding programs in Florida is a major concern. While adequate numbers of Brahman
and Brahman-derivative breed bulls are produced here, only a relatively small number of bulls of
the Bos taurus breeds are produced in Florida. It is also important that the bulls that are
purchased be able to maintain their body condition and breed cows under your ranch's conditions,
and to continue to do so for at least four years. Generally, this requires that the bulls be born and
raised in the Southeast.
The three-breed terminal cross has certain very desirable attributes. Both individual and
maternal heterosis are fully utilized in the terminal cross progeny because the dams are F1 crosses
and the terminal sire breeds used do not have any breed composition in common with the F1 dams
(i.e. there is no Charolais in the ½ Brahman: ½ Angus dams). The terminal cross allows a
producer to design the optimal type of F1 cow which suits the ranch's environment, and the choice
of a terminal sire breed is made to complement the F1 dam to produce fast-growing calves that will
produce appropriately-sized carcasses with adequate muscling and meat quality. Perhaps the most
effective method of using this system in Florida would be to: (1) breed moderate-framed Brahman
bulls to small Angus cows to produce 1000 to 1100 lb Brahman × Angus F1 cows, and (2) breed
these F1 cows to Frame Score 6 or 7 bulls of a muscular sire breed with high growth potential
(Charolais, Limousin, Simmental, Belgian Blue etc.) to produce rapidly growing muscular
terminal cross calves which will have .4 in of fat before reaching 1300 lb.
As both the heifer and steer progeny of the three-breed terminal cross are slaughtered, the
major problem with the three-breed terminal cross is the lack of an efficient method to produce
replacement heifers. Unless the replacement heifers can be purchased (which is not generally
possible), about 50% of the cowherd must be straightbred Angus (in this example) to allow the
production of replacement heifers. About half of the purebred cows (25% of the total herd) must
be bred to Angus bulls to provide Angus replacement heifers for the system. The other half of
the Angus cows would be bred to Brahman bulls to produce the F1 cows. Since half the cows in
the system are purebreds, this half does not utilize any of the positive effects of maternal heterosis.
If sexed semen were to become available, the production of the F1 brood cows would be made
easier as only half as many Angus cows would be needed to produce the F1 replacement heifers
(since no bull calves would be produced). With the increased interest in F1 bulls for
crossbreeding, however, the sale of the Brahman × Angus F1 bulls that would be produced along
with the F1 cows could improve the profitability of the system.
It is possible for owners of small herds (< 50 cows) and a few larger producers to use this
system, or an approximation of it, by utilizing purchased crossbred heifers or young cows which
are then bred to terminal sires (Charolais, Simmental, Gelbvieh, etc). Quality F1 heifers or cows
are seldom available at commercial prices, and while crossbred heifers and young cows that have
a Brahman influence may be available through auction markets, the exact breed composition and,
therefore, expected heterosis, is not known. In any case, the likelihood of them being F1s is
remote. The purchase of auction market females as replacements also brings with it a considerable
risk of introduction of diseases. If quality crossbred heifers from well-managed rotational
crossbreeding programs can be obtained, then a terminal crossbreeding system may be a good
alternative to rotational systems for producers with smaller herds.
Rotational Crossbreeding Systems
Two-Breed and Three-Breed Rotational Crossbreeding
The traditional crossbreeding programs in Florida have been two- and three-breed
rotational crosses of the Brahman and Bos taurus breeds such as the Angus and Hereford. Such
crossbreeding systems have worked well and produced productive cows which were well adapted
to Florida. The nutrient requirements of cows produced by these systems are moderate and
generally not difficult to meet under typical Florida pasture and winter supplementation programs.
In a two-breed rotational crossbreeding system (diagramed in Figure 2), two breeds of bulls are
used. The daughters of Angus bulls are bred to Brahman bulls and the daughters of Brahman bulls
are bred to Angus bulls. Such a two-breed rotation involving the Brahman has fallen out of favor
in recent years as half the calves from such a cross would be about two-thirds Brahman (after the
proportions have stabilized after the system has been in place for several generations) and would
be subject to large price docks as feeder calves. Another problem with this system is that the
Angus-sired heifers will reach puberty much earlier than the Brahman-sired heifers. Angus and
Brahman-sired calves would also be very different in appearance and for this reason could not be
sold as a uniform group. This illustrates the need for the bulls of the breeds involved in two- as
well as three-breed rotations to be similar in frame size and level of milk production so that
replacement heifers and cows can be managed as groups, except during the breeding season, and
uniform sets of calves can be sold.
The three-breed rotation involving the Brahman and two Bos taurus breeds, such as the
Brahman × Hereford × Angus (Figure 3), however, continues to be used to some extent in
Florida. The calves sired by Brahman bulls (after the proportions have stabilized after the system
has been in place for several generations) are about 4/7ths Brahman, slightly over half, and might
be discriminated against by some feeder buyers. The Brahman-sired heifer calves, on the other
hand, should perform nearly as well as the highly productive F1 Brahman × Hereford or
Brahman × Angus cow. As with the two-breed rotation, however, the Brahman-sired females
will be distinctly different from the Angus and Hereford-sired females, in both appearance and
in expected age at puberty.
Rotational Crossbreeding Systems Using Brahman-Derivative Breed or Crossbred Bulls
A criticism of the two- and three-breed rotations that were just discussed is the variability
that can be produced in terms of degree of Brahman characteristics. It is possible to maintain a
constant level of Brahman influence, say three-eighths, in all calves produced through use of a
rotation of Brahman-derivative breeds (each with three-eighths Brahman), such as the rotation of
Brangus × Braford × Simbrah (Figure 4).
This is the system that has been used at the Deseret
Ranch for nearly 15 years. A simplification of the system would be to use just two Brahman-derivative breeds
in the system, Beefmaster × Brangus, for example. One advantage of this type
of rotation is that the appearance of most of the calves from each of the sire breeds is similar in
terms of Brahman characteristics and other traits. This is especially true when bulls of each sire
breed are approximately the same frame size. While some variation in the amount of ear and skin
occurs in the calves from this type of crossbreeding program, the majority of the calves should
appear to have roughly the same degree of Brahman influence as the parental 3/8 Brahman breeds.
One of the disadvantages of this system is that the growth and reproductive rates of the calves
produced are likely to be somewhat less than that from the three-breed rotation involving the
"purebred" sire breeds (Brahman, Angus, Hereford) due to a lower level of heterosis maintained
using this system. The weaning weights of the calves from such a system may not be much less
than that of the traditional three-breed rotation of Angus, Hereford and Brahman, however, if a
larger breed such as the Simbrah is included in the rotation. Because of the general availability
of bulls of these breeds and the fact that this type of crossbreeding system produces both
replacement heifers that will work in Florida and feeder calves that are acceptable to the western
stockering and finishing programs makes it one of the most practical for use in Florida today.
I would like to end this by reiterating my comments regarding Mac Peacock and his career here at Ona. His Master's Thesis which was entitled "Factors Affecting the Weaning Weight of Range Calves" and was dated January, 1953 used data collected on calf weaning weights from 1945 to 1951 at this Range Cattle Station. Mac worked here in crossbreeding research for nearly 35 years. Mac was responsible for two major, long-term crossbreeding studies. The first involved crosses of the Brahman and Shorthorn breeds maintained under different pasture conditions. A major result of this study was one of the first documentations of genotype by environmental interactions as the crossbred cows had a greater response to the improved pastures. The second major crossbreeding study utilized the Angus, Charolais and Brahman breeds and this study was planned and conducted by Mac along with Dr. Koger from start to finish. The Charolais, Angus, Brahman study continued for many years and multiple generations and yielded much useful information regarding the levels of heterosis to be expected from terminal-cross and rotational crossbreeding systems as well as the use of both purebred and crossbred sires.
Biosolids can also be applied to agricultural land to improve physical properties (e.g., water
retention, infiltration, aggregate stability) and chemical characteristics of soils. In the past there had
been concern over heavy metal contamination from sludges and biosolids. Over the past 30 years
biosolids and sludges have become substantially cleaner and thus heavy metal contamination of the
environment from sludge application is of little concern. The concentrations of nutrients and heavy
metals in sludge should be provided by the suppliers.
Using biosolids as an organic slow release fertilizer for crops and grasses grown in Florida
would be a beneficial source of nutrients compared to inorganic fertilizers which can leach more
readily than slow release fertilizers in sandy soils. Before biosolids can be used by growers in Florida
there is a need to demonstrate that it is a safe and viable source of nutrients for crops in Florida.
There is also a need to determine how fast nitrogen is made available to the grass.
The objectives of this study were to evaluate granular biosolids as a potential source of
nutrients for bahiagrass as well as to determine the rate of nitrogen availability.
Table 1 shows the chemical analyses of the granular biosolids used for the study. The
biosolids were surface applied in April the first year and March the second year of the study. There
were also an additional 5 treatments which only received biosolids the first year in order to evaluate
how long biosolids would last. Treatments were applied to 10 X 20 ft plots and randomized in a
complete block design with 4 replications.
Soil samples were collected periodically at 6 inch increments to a depth of 3 feet, during the
growing season and analyzed for pH, macro- and micronutrients and selected heavy metals (Pb, Cd,
and Ni). Bahiagrass was harvested every 35 days for yield and tissue analyses of various nutrients
as well as protein, digestibility and heavy metals.
In both 1994 (Figure 1) and 1995 (Figure 2) total bahiagrass yields increased with increasing
rates of biosolid application. Yields in 1994 ranged from 4.5 to 10 tons/acre for the 0 and 8 ton
biosolid/acre treatments, respectively. In 1995 similar yield increases were observed. Yield increases
from biosolid application were observed in all harvests.
Residual treatments which only received biosolids in the first year of the study still showed
yield responses in the second and third year (Figure 2). This indicates that biosolids are a slow release
source of nutrients providing nutrients for up to 2 years after application. Thus when considering the
economics of biosolid application one needs to consider the long term benefits as well as the
immediate ones.
Tissue Composition
Crude Protein
Crude protein content of bahiagrass was increased with increasing rates of biosolids in both
1994 (Figure 3) and 1995. This is a result of biosolids providing needed nitrogen for protein
production of the grass. The residual treatments in 1995 which again had only received biosolids at
the beginning of the study also showed increases in crude protein content 1 year after application.
This again indicates the long term benefits from biosolid application.
In Vitro Digestibility
In the first year an increase for in vitro dry matter digestibility was observed in the first harvest
with increasing rates of biosolids (Figure 4). However, over time these increases were reduced with
no effect in the second year of the study.
Rate of Nitrogen Availability
Availability of nitrogen from biosolids increased as rate of biosolids decreased.
Approximately 75% of the nitrogen in the biosolids was available to bahiagrass the first year at the
low rate of biosolid application rate (0.25 tons/acre) (Figure 5). At the highest rate of biosolid
application (8 tons/acre), nitrogen availability the first year was reduced to 30%. This is probably a
result of bahiagrass nitrogen uptake being maximized.
Laboratory studies were also conducted to evaluate the rate of nitrogen release as affected
by the size of the pellets. The study showed that smaller granulation of the biosolids (ground vs
pellets) contributed to a faster release of nitrogen (Figure 6).
Other Nutrients and Metals
Iron uptake in bahiagrass increased at increasing rates of biosolid application (Figure 7). This
shows that biosolids are a source of iron for grasses. A typical sign of iron deficiency in bahiagrass
is yellow chlorotic patches which normally appear early in the growing season soon after nitrogen
application. Zinc, Cu, and Mn levels were also increased in the bahiagrass as a result of biosolid
application. Thus, biosolids appear to be a good source of micronutrients. There were also trends
showing P levels in tissue to increase with application of biosolids. Levels of heavy metals (Cd, Pb,
Ni, and Ba) were low in all the bahiagrass harvests at any of the biosolid rates.
Soil Analysis
Soil samples taken below the 6 inch depth indicated low levels of all nutrients including P and
N. Heavy metals (Pb, Cd, Ni) levels were very low in all soil samples. This indicates biosolid
application to soils at agronomic rate to pose no environmental problems.
| Table 1. Composition of the Municipal Biosolids (Dry Weight Basis) for the First Year (1994) and Second Year (1995) of Application (Average Values from 3 Analyses Performed). | ||
| Element | ||
| Year 1 | Year 2 | |
| N (TKN) (%) |
4.14 |
4.91 |
| NH4-N (%) | 0.35 | 0.41 |
| NO3-N (%) | <0.01 | <0.01 |
| P (%) | 4.14 | 2.05 |
| K (%) | 0.11 | 0.10 |
| S (%) | 3.43 | 3.27 |
| Ca (%) | 2.0 | 1.9 |
| Mg (%) | 0.60 | 0.58 |
| Na (%) | 0.15 | 0.20 |
| Fe (ppm) | 19,400 | 19,500 |
| Mo (ppm) | 4.75 | 6.8 |
| Mn (ppm) | 430 | 418 |
| Cu (ppm) | 777 | 821 |
| Zn (ppm) | 1,105 | 923 |
| Cd (ppm) | 7.47 | 6.61 |
| Ni (ppm) | 45.9 | 48.0 |
| Pb (ppm) | 262 | 208 |
| pH | 7.02 | 7.29 |
There may be two situations when livestock respond positively to legumes growing in
bahiagrass. First, when bahiagrass is deficient in protein and can not meet needs of the cattle. Here,
there must be a sufficient amount of leafy legume to provide the protein. A second situation is when
a very nutritious legume is present in large amounts and is a major part of the diet. Here, protein and
TDN from the legume can increase animal performance over bahiagrass even though bahiagrass alone
is a good pasture. We are going to look for these situations in two studies.
The first study involved Aeschynomene evenia (evenia) and bahiagrass continuously grazed
(no pasture rotation) by 1.5-yr old steers (530 lb shrunk) in 1996 and 2-yr old heifers (709 lb shrunk)
in 1997. Cattle were stocked at 1.2 head/A (3 head on 2.5 acre pastures). Evenia+bahiagrass was
compared to unfertilized bahiagrass in both years (two replicates of each treatment in each year).
Evenia was sown in February 1996 after burning bahiagrass, and in 1997 it came back from live-over
plants and from seed. These were fair to good stands of evenia with average plant densities of 2.5
and 1.3 plants / ft2 in 1996 and 1997, respectively.
In August 1996, steers grazing evenia+bahiagrass had greater ADG than steers grazing
bahiagrass alone (Table 1), otherwise there were no differences in ADG between treatments. I do
not attribute this lack of response to evenia being an unpalatable legume compared with American
jointvetch (A. americana), with which you are more familiar. When grazing began, evenia was about
12" tall and was readily eaten.
| Table 1.Average daily gain and live weight gain (LWG) of yearling steers grazing bahiagrass + evenia or bahiagrass alone over 112 d in 1996. | |||||
| July | Aug | Sept | Oct | LWG | |
| ------------------------ lb/head/day ------------------------ | - lb/A - | ||||
| bahiagrass + evenia | 1.1 | 2.1 | 1.2 | 1.1 | 187 |
| bahiagrass alone | 1.1 | 1.1 | 1.2 | 1.3 | 158 |
| Table 2. Available forage (dry matter), crude protein and total digestible nutrients (TDN) in bahiagrass + evenia or bahiagrass alone in 1996. | ||||
| July | Aug | Sept | Oct | |
| ------------------------ yield, lb/A ------------------------ | ||||
| bahiagrass + | 2710 | 2720 | 2020 | 2030 |
| evenia (whole plant) | 440 | 1310 | 1480 | 2510 |
| Total | 3150 | 4030 | 3500 | 4540 |
| bahiagrass alone | 2540 | 2380 | 2260 | 1880 |
| ------------------------ Crude protein, % ------------------------ | ||||
| evenia (leaves) | 23.3 | 21.2 | 24.7 | 18.4 |
| evenia (whole plant) | 11.7 | 11.9 | 11.6 | 7.8 |
| bahiagrass alonet | 8.0 | 7.6 | 8.7 | 8.5 |
| ------------------------ TDN, % ------------------------ | ||||
| evenia (leaves) | 72.1 | 67.9 | 68.4 | 63.3 |
| evenia (whole plant) | 44.0 | 43.7 | 35.7 | 31.3 |
| bahiagrass alonet | 54.8 | 53.7 | 51.7 | 52.7 |
| tHand plucked leaves. | ||||
In the second study, June-weaned (9-month old) steers (525 and 561 lb shrunk in 1996 and
1997, respectively) continuously grazed leucaena (1 acre) + bahiagrass (1 acre) vs. bahiagrass alone
(2 acres). Steers were stocked at 1.5 head/A (3 head on 2 acres), and there was no supplement fed.
There were three replicates of each treatment in each year. Bahiagrass was fertilized with 50 lb N/A
in March and was grazed periodically before steers were placed on bahiagrass in June. All steers
grazed 9 acres of bahiagrass and had access to a small leucaena area not used for the study so they
could become accustomed to the legume. At the first of July, steers were assigned to their respective
pastures.
Average daily gain at every 28-day weigh date was greater for steers grazing leucaena and
bahiagrass compared to ADG of steers grazing bahiagrass alone (Table 3). It is estimated that
leucaena leaves made up at least 40% of the diet dry matter from July to mid-September. By mid-October,
leucaena leaves made up <5% of the diet.
| Table 3. Average daily gain and liveweight gain (LWG) of June-weaned steers grazing leucaena + bahiagrass and bahiagrass alone over 112 d. Average 1996 and 1997. | |||||
| July | Aug | Sept | Oct | LWGt | |
| ------------------------ lb/head/day ------------------------ | - lb/A - | ||||
| leucanena + bahiagrass | 1.4 | 1.5 | 0.5 | 0.8 | 116 |
| bahiagrass alone | 0.9 | 0.3 | -0.6 | 0.0 | 19 |
| Table 4. Available forage (dry matter), crude protein and total digestible nutrients (TDN) on 2 acre units grazed by June-weaned steers. Treatments were 1 acre bahiagrass + 1 acre leucaena vs 2 acres bahiagrass alone. Average 1996 and 1997. | ||||
| July | Aug | Sept | Oct | |
| ------------------------ yield, lb/A ------------------------ | ||||
| bahiagrass (1 acre) | 2580 | 2010 | 2470 | 2060 |
| leucaena leaf (1 acre) | 1970 | 1880 | 850 | 210 |
| Total (2 acre) | 4550 | 3890 | 3320 | 2270 |
| bahiagrass alone (2 acre) | 6050 | 4740 | 6020 | 4820 |
| ------------------------ Crude protein, % ------------------------ | ||||
| leucaena leaf | 28.0 | 25.7 | 27.8 | 34.1 |
| bahiagrass alonet | 10.1 | 9.1 | 8.9 | 8.9 |
| ------------------------ TDN, % ------------------------ | ||||
| leucaena leaf | 61.8 | 57.9 | 59.0 | 68.1 |
| bahiagrass alonet | 53.1 | 48.2 | 46.9 | 43.8 |
| tHand plucked leaves. | ||||
A factor contributing to the large increase in acreage of limpograss in Florida is its ability to
produce during the cool season. It has been determined that 30 to 40% of the total annual production
from limpograss occurs during the cool season. Limpograss tends to be greater in energy but lower
in crude protein (CP) than most other tropical grasses. It holds its energy value with advancing
maturity, and this along with its ability to grow during the cool season has contributed to ranchers
stockpiling this grass during the late summer and fall for use during the winter and dry early spring.
Limpograss is better adapted to wetter, higher organic matter soils, and some producers suggest that
this is the only type soil that limpograss should be planted on. However there is large acreage of
limpograss on typical flatwoods soil. It has been suggested that limpograss has a lower N
requirement than some other stem-type tropical grasses. Generally limpograss is not affected by
armyworms or loopers.
In terms of the challenges facing the use of limpograss, it is affected by spittle bug. The way
we graze limpograss at the Range Cattle REC by allowing it to stockpile during the early summer
probably contributes to the spittle bug problem. However we have never lost a stand due to spittle
bug. I believe this is because our grazing management does not impose a great deal of stress on the
stand which allows it to recover from various stressors. Yellowing of limpograss pasture particularly
after heavy grazing or fertilization is an issue that has increased over the past 3 to 4 years. Although
yellowing of limpograss forage is related to an iron deficiency, in my opinion management of the grass
relative to the stress that is placed on the stand is also a major contributing factor.
We have not seen a problem with mole crickets in limpograss pastures at the Range Cattle
REC, although there may have been some reports among producers during 1997. These reports may
have been related to marginally inappropriate soils that the limpograss was established on. Although
Floralta is more persistent than other hemarthrias, in my opinion it potentially has a persistence
problem relative to some of the stars and bermudas. This makes management of this grass very
important.
We have grazed limpograss under both continuous and rotational systems, and as a general
statement concerning stem-type tropical grasses, and especially limpograss, in my opinion they
should be rotationally grazed. The ranchers that I think are doing the best job with limpograss are
using a rotational system. Rotational grazing means different things to different people in terms of
grazing duration and rest period, but no one I know is grazing limpograss continuously during an
entire growing season.
Grazing evaluation comparing limpograss to bahiagrass conducted by Lynn Sollenberger
(Agronomy Journal, 1989, 81:760) showed similar daily gain between the two grasses, but due to
greater forage production, gain per acre was greater for limpograss. Crude protein was greater for
bahiagrass forage while IVOMD was greater for limpograss forage. Due to greater IVOMD, it was
thought that cattle grazing limpograss would have a greater daily gain, however it was noted that low
CP of the limpograss forage may have limited animal performance.
Because CP of limpograss is relatively low and IVOMD is relatively high, it was thought that
improved cattle performance could be obtained by providing a protein supplement to cattle grazing
limpograss. Lynn Sollenberger's research group (Table 1) utilized a grazing only control, and fed a
corn-urea supplement to provide two levels of supplemental protein from urea to cattle rotationally
grazing limpograss.
| Table 1. Protein supplementation of steers grazing limpograss pasture. | ||
| Daily gain, lbs | BUN | |
| Control - grazing only | 0.6 | 6.0 |
| Low protein | 1.2 | 8.2 |
| High protein | 1.3 | 11.4 |
| Forage availability data from pasture, lbs DM/acre | ||
| Start of a rotational cycle 6280 | ||
| End of a rotational cycle 3410 | ||
| Crude protein of pasture | 6.9 | |
| IVOMD of pasture | 59.0 | |
| TDN/CP | 8.6 | |
| BUN = blood urea nitrogen, mg/dL, DM = dry matter, | ||
| IVOMD = in vitro organic matter digestion, TDN = total digestible nutrients. | ||
| Holderbaum (1991; Journal of Production Agriculture, 4:437) | ||
Studies at the Range Cattle REC evaluated protein supplementation of steers grazing
limpograss pastures from May through December. Steers were fed 5 lbs per head daily of a molasses
based supplement containing a control (no additional protein), urea which is a ruminally degraded
protein, feathermeal which is a high ruminal escape protein or a combination of urea and feathermeal.
No response to protein supplementation was found over 3 years of the study. Near the start of the
study, there was over 10,000 lbs forage DM per acre and near the end there was over 7500 lbs.
Why the response to protein supplement in studies at Gainesville and not at the Range Cattle
REC? Pitman et al. (1994; Crop Science, 34:210) conducted CP and IVOMD analyses on separated
leaf and stem fractions of limpograss pasture (Table 2). They found that IVOMD and CP of
limpograss leaf were relatively high and fairly well balanced, while for the stem, IVOMD was high,
but CP was very low, and the TDN to CP ratio was highly out of balance.
| Table 2. Crude protein and in vitro organic matter digestion of leaf and stem fractions of limpograss pasture. | |||||||
| Leaf | Stem | ||||||
| Forage lbs DM/a | IVOMD | CP | TDN/CP | IVOMD | CP | TDN/CP | |
| Summer | 14,500 | 52 | 7 | 7.4 | 50 | 2 | 25.0 |
| Fall | 10,800 | 56 | 9 | 5.6 | 54 | 4 | 15.4 |
| DM = dry matter, IVOMD = in vitro organic matter digestion, %;CP = crude protein, % TDN = total digestible nutrients, %. | |||||||
These studies led us to initiate a heifer development program utilizing limpograss. We are
using a 5 pasture rotation with 1 week of grazing and 4 weeks of rest. Heifers are weaned in
September and bred in March and April. Pastures are fertilized with 300 lbs per acre of a 20-5-10
in the spring and 200 lbs per acre of ammonium nitrate in the fall.
A major objective of our study is for limpograss to be the sole source of forage such that no
hay is fed during the winter and early spring. To do this we have to stock the pastures to get through
the time of year where forage availability is at its lowest, which for us is the early spring. Under these
conditions at our location this stocking rate is 1 heifer per acre.
During the first two years of the study we compared two treatments from weaning (early
October) until the end of the breeding season (April 30): 6 lbs per head daily of a molasses (93%)-urea (7%)
or a molasses (83%)-urea (2%)-feathermeal (15%) supplement. During this time we were
evaluating the response to natural protein.
| Table 3.Performance of weaned heifers grazing limpograss and fed molasses based supplements containing urea or urea and feathermeal. | ||||||
| Initial weight, lbs | Weight at bulls in | % that met target weight | Weight at bulls out | % pregnant | ||
| Year 1 | Urea | 528 | 668 | 65 | 711 | 65 |
| Urea-FM | 528 | 675 | 75 | 750 | 65 | |
| Year 2 | Urea | 557 | 640 | 80 | 737 | 57 |
| Urea-FM | 557 | 654 | 86 | 770 | 79 | |
| Initial weight taken in early October; Bulls in is the start of the breeding season (March 1); % that met target weight at the start of the breeding season (650 lbs in year 1 and 600 lbs in year 2); Bulls out is the end of the breeding season (April 30). | ||||||
The response to protein supplementation was related to occurrence of first frost, and number
of cycles through the rotational grazing system. From the start of the trial until first frost, heifers
gained slightly more than 1.0 lbs daily, there was no difference between treatments. This also totaled
approximately three grazing cycles, and condition of the upper layers of the sward was deteriorating
with regard to leaf percentage and forage quality. From first frost until end of the breeding season,
heifers fed the supplement containing urea-feathermeal had a greater daily gain.
During the first two years of the study, there were approximately 200 days of supplementation
from weaning until the end of breeding. Early in the trial, there was no response to protein
supplementation, and based upon the fall data after breeding we questioned whether any
supplementation was needed in the fall prior to frost. Therefore, in the third year we are evaluating
two treatments from weaning until first frost : no supplement - grazing only, and 6 lbs daily of the
molasses - urea - feathermeal supplement. After frost, all heifers are fed the supplement until the end
of breeding. Beginning October and using an average frost date of mid-January, this potentially could
save about 100 days of supplementation.
| Table 4. Effect of timing of supplementation on the performance of weaned heifers grazing limpograss. | |||||
| Initial weight, lbs | Weight at suppl. | Weight at bulls in | % that met target weight | Weight at bulls out | |
| Control | 523 | 612 | 632 | 56 | 770 |
| Supplement | 520 | 611 | 667 | 69 | 814 |
| Initial weight taken in early October; Wt at suppl. = weight when supplement was started for control cattle, also time of first frost (1-14-98); Bulls in is the start of the breeding season (March 1); % that met target weight at the start of the breeding season (650 lbs); Bulls out is the end of the breeding season (April 30). | |||||
After the breeding season, heifers were rerandomized and placed on either a control - no
supplement, grazing only, or 2 lbs daily of a 32% CP molasses-urea supplement for the spring -
summer - fall season. For three years, we have not seen a response to supplementation with 2 lbs of
a 32% CP molasses - urea supplement from the end of the breeding season (April 30) until the heifers
begin to calve in early December. Heifers are gaining from 1.0 to 1.4 lbs daily during this period.
Again forage availability has been very ample during this time.
Mole cricket damage to bahiagrass pastures in south-central Florida was severe during 1996-97 but negligible during 1997-98.
The average annual cost of mole crickets to Florida pasture and
turf in terms of pasture damage, replanting and chemical control is estimated at $50 million. In order
to understand the year-to-year variation in mole cricket outbreak on pasture and develop timely
control measures, studies were initiated by the South Florida Beef and Forage Extension group in
1997 with the following goals in mind:
1) Monitoring of Mole cricket Populations in Relation to Environmental Factors:
"Pit fall" traps were installed directly on three ranches in Polk county; one ranch each in
DeSoto, Pasco, Highlands and Manatee counties and two at the Range Cattle Research and
Education Center (RCREC) in Hardee county. With the exception of the RCREC, Ona sites, all the
remaining sites contained at least 20 acres of bahiagrass pasture. Three traps were installed on each
10-acre block of pasture. Mole crickets trapped were removed and counted every week beginning
from July 1997 through August 1998. The weekly average mole crickets counted in a trap for the
various sites and corresponding weekly rainfall are shown in Figure 1.
In DeSoto county, the pasture that was used suffered minor damage during the 1996-97 mole
cricket outbreak. The weekly average number of trapped mole crickets in July 1997 was 10 nymphs
per trap. The catch declined to 2 adults per trap by October 1997, and dropped to zero between
December 1997 and mid May 1998. In late May 1998, a sharp increase occurred in young nymphs
trapped at the DeSoto site which now stands at a count of 5 per trap per week.
In Hardee county, a damaged and renovated bahiagrsss pasture showed a July 1997 weekly
average count of 2 nymphs per trap. This increased to 10 juveniles per trap between August and
September 1997. From October 1997 to March 1998, hardly any mole crickets were observed at this
renovated site in Hardee county. Since late May 1998 we have noticed a few nymphs here (1-2 per
trap weekly).
In the Pasco county ranch, pasture damage in 1996-97 season was moderate. Between July
and August 1997, weekly trapped numbers ranged from 5-10 nymphs per trap. The weekly count
declined to 2 adults per trap between November 1997 and April 1998. A resurgence in young
nymphs (12 per trap weekly) has been noticed since late May 1998.
For Polk county, two badly damaged pastures were monitored in the Green Swamp (GS)
area and one slightly damaged pasture on a deep Sandy Ridge (SR). At the Green Swamp locations,
nymph counts during July-August 1997 were 20-80 per trap. Following one heavy rainfall, 350
nymphs were recorded in one single trap. Weekly trapped cricket numbers declined to 5 adults by
November 1007 and to zero by March 1998. Since April 1998, weekly cricket counts have ranged
between 10 and 95 nymphs per trap in the Green Swamp. Weekly juvenile mole crickets trapped on
the Sandy Ridge remained low between 3 and 9 per trap from July to October 1997. Then it suddenly
increased to 43-75 winged adults per trap after one major rainfall in November 1997. Since then, the
weekly trapped counts of mole crickets on the ridge have stayed high (22 per trap) through June
1998 with an increasing proportion of young nymphs.
In Manatee county, weekly trapped nymphs in a pasture heavily destroyed were as high as
84 per trap in July and August 1997. We counted nearly 500 nymphs in one trap in July 1997 after
a 3-inch rainfall. The weekly counts declined sharply to 0-4 per trap between September 1997 and
March 1998. From April to July 1998 we have observed about 10 mole crickets per trap weekly, half
of which are newly hatched nymphs.
Mole crickets have a life span of one year so we deal with a new generation each year. The
transition from old to new normally occurs between May and July. Soil moisture seems to control
the movement and activity of mole crickets on bahiagrass pasture. The longer the juvenile and young
adult mole crickets remain undisturbed in the soil during fall and winter the greater the damage to
pasture is going to be. The record 1997-98 fall and winter rainfall and associated flooding flushed
out a large number of juvenile-adult mole crickets from low-lying pastures, resulting in the decline
of numbers trapped in all counties. This probably accounts for the negligible damage to pasture
during 1997-98 period. Migration of crickets from flooded pasture to sandy ridges as was observed
in Polk county indicates that mole crickets are fighters in inclement weather. Golf courses and home-owner
lawns, which are normally well drained could provide additional shelter in wet weather. We
are already experiencing a resurgence of nymphs on most south-central bahiagrass pastures since the
rains subsided.
2) Testing Effectiveness of Commercially Available Pesticides for mole cricket Control
Mole crickets can be controlled biologically. Specific nematodes, red-eyed Brazilian fly and Larra wasp have been used to reduce mole cricket infestation. An advantage of biological control is that the agents continue to attack mole crickets throughout the year. Secondly, biological control does not usually have a negative environmental impact. Unfortunately, production of UF-IFAS's patented nematode (Steinernema scapterisci) for mole cricket control, which is marketed as "Proactant" has been on hold for nearly a year. A spring application of Proactant biopesticide will kill 50-80% of adult twany mole crickets before they lay their eggs. Fall applications have proven effective when performed as part of a two-pronged approach (10 Proactant for adult mole crickets and (2) a chemical insecticide for nymphs and juvenile crickets.
Chemical methods of control have been ben difficult for two reasons. Since mole crickets live
mostly underground, it is difficult to spray with a contact insecticide. Additionally, mole crickets
sample their food before ingesting it. Feed that is not attractive enough is rejected. 'Prozap
Agriband' (10% Sevin bait granules) was developed using liquid molasses as an attractant blended
with carbaryl. Due to the lack of nematode biopesticide on the market, the efficacy of Prozap bait
for mole cricket control was tested alone in three separate trials in Polk county. Each of the three
sites used to monitor mole cricket populations in Polk county was subdivided into two 10-acre fields
and installed with three standard pitfall traps. Population histories of fields were developed from July
to September 1997. Bait was applied at 10 lb/A to a 10-acre field at each site on 4 September and
the other field used as a non-treated control. Due to unsatisfactory control, bait application was
repeated on 3 October 1997.
On site 1, on a Sandy Ridge, average weekly mole cricket counts remained about 6 during
both bait applications until the influx of adult crickets from low-lying pastures in November 1997
(Figure 2). Overall, there was no difference between treated and non-treated fields in weekly counts
of mole crickets.
On site 2, in the Green Swamp area, weekly mole cricket counts per trap
before Prozap bait
application ranged from 24 to 149 on field targeted for treatment and 0-20 for the non-treated field
(as shown in Figure 3). These crickets were mostly nymphs and juveniles. On 4 September when
bait was first applied, weekly mole cricket counts were 20 and 8 for the treated and non-treated fields,
respectively. There was a temporary 65% decrease in mole cricket counts on treated field 2 weeks
after bait application, but this increased back to 20 the following week, prompting us to administer
a second bait application on 3 October 1997. We observed that mole crickets (mostly adults) were
attracted to the treated site immediately after the second bait application. From then on, weekly
trappings declined sharply on both fields for the rest of the year because of heavy rains and flooded
soil conditions.
On site 3, also in the Green Swamp, weekly mole cricket counts declined 60% 2 weeks after
the 4 September bait application (Figure 4). However, a large number of mole crickets were attracted
to the treated field after the 3 October bait application. Flooded soil conditions prevented long term
evaluation of bait effectiveness at this site as well.
Our preliminary conclusions on Prozap bait were (1) the bait has a capacity to attract mole cricket immediately after application and is lethal when consumed (2) At 10 lb/A, a blanket application of Prozap will cost around $18/A. It will rather be cost effective if it is applied to known "hot spots" (areas with heavy concentrations of mole crickets) and (3) long term effectiveness could not be determined due to confounding heavy rainfall. We plan to test it again in fall of 1998.
3) Selection of tolerant Grasses under Various Fertilizer Regime
Strips (50 x 200 ft) of Pensacola bahiagrass, Floralta limpograss and Florona stargrass were
established alongside one another in Hardee, Pasco, DeSoto and Manatee counties in July 1997.
There are three replications at each location. Established grass strips were cut back in March 1998
and four fertilizer treatments (60 lb N/A, 60-25-60 lb/A of N-P2O5-K2O,
N-P2O5-K2O plus micro-nutrients, and a control)
were applied to 50 x 50 ft sections of each grass. Besides the fertilizer
treatments, bahiagrass also received lime vs. no-lime treatments. Metal exclosure cages are installed
on each plot to allow for cattle grazing and grass yield determination at each location. Grass is
harvested at 35 d intervals for yield and quality. Additionally, pitfall traps are installed on the 60 lb
N/A fertilizer treatment for each grass to monitor relative mole cricket infestation.
Preliminary cricket information in 1998 (Table 1) indicates a greater number of mole crickets
trapped on limpograss in Pasco and Manatee counties and least number trapped on stargrass.
However, these new stands of grass do not appear to be damaged by mole crickets enough to
influence forage yields.
| Table 1. Weekly trapped mole cricket counts in grass cultivars grown in several south central counties during 1998. | ||
| County | Grass | Mole cricket infestation - Weekly count per trap - |
| DeSoto | Pensacola bahiagrass
Floralta limpograss |
1.6a 1.3a |
| Hardee | Pensacola bahiagrass
Floralta limpograss Florona stargrass |
0.6a 0.6a 0.1a |
| Pasco | Pensacola bahiagrass
Floralta limpograss Florona stargrass |
5.8b 27.2a 1.0c |
| Manatee | Pensacola bahiagrass
Floralta limpograss Florona stargrass |
19.4b 39.4a 17.2b |
Smutgrass is a serious weed problem in many Florida pastures. The two main species of
smutgrass found in Florida are 1) Sporobolus indicus (small smutgrass type) and 2) Sporobolus
jacquemontii (large smutgrass type). Both smutgrass species are perennial bunch-type plants.
Sporobolus indicus is often affected with a black fungus which is found on the seed heads giving them
a spike like appearance. Sporobolus jacquemontii generally has an open type seed head with no
fungus and broad leaf blades at the base of the plant. The reddish smutgrass seeds which may remain
attached to the seed head for sometime after maturing, are spread mainly by adhering to livestock,
by water, or wind and may remain viable for two or more years.
Smutgrass produces in excess of 45,000 seeds per plant with over 1400 seeds per head
(Currey et al., 1973). Seed production takes place continuously throughout the growing season with
natural germination averaging less than 9% because of a hard seed coat. Mature smutgrass plants
are generally unpalatable to cattle. However, cattle will readily consume the regrowth of smutgrass
for several weeks following a burn or mowing. During this period of young vegetative growth the
quality is about equal to bahiagrass.
Research at Ona by McCaleb et al (1966) indicated mowing did not control smutgrass; but
helped to spread the smutgrass seed. Under continuous close mowing plant diameter decreased but
number of plants increased. When mowing stopped, plants recovered to their former density.
Cultivation and complete renovation was expensive and gave variable and unsatisfactory results.
Early herbicide research with dalapon provided satisfactory smutgrass control in both
bahiagrass and pangolagrass (Mislevy and Currey, 1980; Mislevy et al., 1980). However, in the early
1980's dalapon was removed from the market and is no longer available for smutgrass control. In
1989 DuPont received a pasture label for distribution and use of Velpar in Florida for smutgrass
control in bermudagrass and bahiagrass pastures.
Recent studies at Ona indicate broadcast spraying in July, August and early September (when
adequate moisture is available and plants are actively growing) with 0.75 to 1.0 lb/A active Velpar®,
plus 0.1% V/V silicone surfactant resulted in 90+% control of the large smutgrass type growing in
association with bahiagrass. Since the large and small smutgrass types are generally found growing
together, the same recommended rate for both the large and small smutgrass types should be used.
Mowing smutgrass to a 3" stubble and allowing plants to regrow back to a 12" height prior
to spraying with 0.75 to 1.0 lb/A active Velpar resulted in no improvement in smutgrass control when
compared with the non-mowed treatment. Mowing had no effect on bahiagrass recovery with mowed
and non-mowed treatments averaging 84 and 85% bahiagrass ground cover 1 year after treatment.
This was more than a 50% increase in bahiagrass ground cover 12 months after the herbicide
application.
Bahiagrass will turn slightly yellow about 15 to 20 days after being treated with Velpar. As
the rate of Velpar increases, the yellow color will also intensify. However, about 40 days after Velpar
application bahiagrass will turn dark green. This green color will be darker than the non-treated
pastures.
Commercial applicators and growers must remember Velpar will kill oak trees, therefore
caution must be exercised when spraying smutgrass in bahiagrass pastures with oak trees. Velpar will
also hurt pangolagrass and selected cultivars of Cynodon grasses. Consult the Velpar label for other
restrictions.
Excellent control (90+%) of the large and small smutgrass types can be obtained from Velpar
rates ranging between 0.75 to 1.0 lb active/A plus 0.1% V/V silicone surfactant. When Velpar is
applied using the large commercial applicators 1.0 lb/A provided better control than 0.75 lb/A.
Preliminary research results indicate mowing smutgrass, followed by 12 inches of regrowth prior to
herbicide application did not significantly improve smutgrass control when compared with the non-mowed treatments. Best results
are obtained when smutgrass is sprayed during July and August and
pastures are wet. Remember, Velpar requires rain within a few days after application. Bahiagrass
turns yellow 15 to 20 days after Velpar application, however about 40 days after treatment the
pastures turn dark green.
Velpar will kill oak trees, therefore caution must be exercised. Velpar will also hurt
pangolagrass and certain Cynodon cultivars.
Currey, W. L., R. Parrado, and D. W. Jones. 1973. Seed characteristics of smutgrass (Sporobolus
poiretii). Soil Crop Sci. Soc. Fla. Proc. 32:53-54.
McCaleb, J. E., E. M. Hodges, and W. G. Kirk. 1966. Smutgrass control. Florida Agric. Exp. Stn.
Circ. S-149. 10 pg.
Mislevy, P. and W. L. Currey. 1980. Smutgrass (Sporobolus poiretii) in control in south Florida.
Weed Sci. 28:316-320.
Mislevy, P., W. L. Currey, and B. J. Brecke. 1980. Herbicide and cultural practices in smutgrass
(Sporobolus poiretii) control. Weed Sci. 28:585-588.
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