Forage Quality and Grazing Steer Performance from ...

Forage quality and grazing steer performance from Tifton 85 and Tifton 78 bermudagrass pastures G. M. Hill, R. N. Gates and G. W. Burton J ANIM SCI 1993, 71:3219-3225.

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Forage Quality and Grazing Steer Performance from Tifton 85 and Tifton 78 Bermudagrass Pastures1'' G. M. Hill, R. N. Gate$,

and G. W. Burton3

Department of Animal and Dairy Science, University of Georgia, Coastal Plain Station, Tifton 31793-0748

ABSTRACT:

A new high-yielding bermudagrass hybrid, Tifton 85, produced 26% higher DM yield ( P = .05) with 11%higher IVDMD ( P = .05) than Coastal in two 3-yr yield trials. Tifton 78 and Tifton 85 were established in duplicate .81-ha pastures in 1988 and were grazed during 1989, 1990, and 1991 using a variable stocking rate method. Four tester steers per pasture with 269 kg initial BW grazed continuously for 169 d/yr beginning in April. Forage mass, targeted at 2,800 kg of DM/ha, was maintained by adjusting stocking rates at 14-d intervals to correspond with ground-level forage samples taken at 14-d intervals. Pastures received 84 kg of Nfha in March, June, and August of each year. Nutritive value was assessed using whole masticate samples from two esophageal cannulated steers grazing each pasture in late May, mid-July, or early September. The 3-yr mean masti-

cate analyses revealed similar CP for Tifton 78 and Tifton 85 in May and July, but higher ( P < .05) CP for Tifton 85 than for Tifton 78 in September. The IVDMD was higher ( P < .05) in May and September for Tifton 85 than for Tifton 78; and, mean and medium particle sizes were greater ( P < .OS) for Tifton 85 than for Tifton 78 in May, July, and September samples. The 3-yr mean ADG was similar for Tifton 78 and Tifton 85 (.65 vs -67 kg; P > . l o ) ; however, grazing daysfhectare were higher for Tifton 85 than for Tifton 78 (1,823 vs 1,319 d; P < .01). Consequently, BW gainhectare was 46%' higher for Tifton 85 than for Tifton 78 (1,156 vs 789 kg; P < .Ol). Forage quality, DM yield, and grazing performance support the hypothesis that Tifton 85 will likely become an important hay and grazing forage for the southern United States.

Key Words: Cynodon dactylon, Steers, Yields, Forage

J. Anim. Sci. 1993. 71:3219-3225

Introduction A new bermudagrass hybrid, Tifton 85, was selected as one of the highest yielding and highest quality F1 hybrids between PI 290884 from South Africa (Cynodon dactylon [L.] Pers.) and Tifton 68 bermudagrass ( Cynodon nlemfuensis Vanderyst [Burton et al., 19931). Tifton 68 is a highly digestible hybrid, but it is susceptible to winter (cold) damage (Burton and Monson, 1984). Compared with other hybrid bermudagrasses, such as Coastal, Tifton 44, and Tifton 78, Tifton 85 is taller, has larger stems and broader leaves, and is darker green in color. It has large rhizomes, but fewer rhizomes than Coastal or Tifton 44. Rapid growth rate and high IVDMD values

'Supported by state and Hatch funds allocated to the Georgia Agric. Exp. Sta. 'The authors gratefully acknowledge the technical assistance of B. G. Mullinix, Jr., C. E. Merchant, J. P. Womack, and W. J. Dillard. 'Forage Agronomist and Research Geneticist, ARS, USDA, Coastal Plain Station. Received April 12, 1993. Accepted August 11, 1993.

relative to other bermudagrass hybrids indicated the potential of Tifton 85 as a high-quality hay and pasture forage. Until Tifton 85 was selected for development, Tifton 78 bermudagrass (Burton and Monson, 1988) was considered to be one of the highest quality and most productive released hybrids available in the southeastern United States. Compared with Coastal, Tifton 78 had produced up to 25% more DMha (Burton and Monson, 1988) and 24 and 38% more BW gainha in two 3-yr grazing experiments (Hill et al., 1990, 1993). The objectives of the present study, were to compare DM yield and IVDMD of Tifton 85 with other bermudagrass hybrids in small-plot trials and to determine steer performance and forage quality of Tifton 85 and Tifton 78 pastures.

Experimental Procedures Plot Tria 7s Tifton 85 bermudagrass was established with other hybrid bermudagrasses in two replicated small plot (2-m x 3-m plot area) trials. In Trial 1, Tifton 85,

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HILL ET AL.

Tifton 68, Tifton 44, and Coastal were established April 12, 1985; whereas in Trial 2 Tifton 85, Tifton 78, Tifton 44, and Coastal were established May 4, 1989, to determine DM production. All plots were established on a Tifton sandy loam soil and were burned each year in February. In yr 2 and 3 of each trial, four harvests were made a t intervals of approximately 6 wk beginning in mid-May. Fertilizer was split-applied in mid-March and late-June as a 4:1:2 ratio of N:P205: K2O using 196 kg of N/ha annually. Forage was harvested a t approximate heights of 5 cm using a cycle-bar mower, samples were dried at 70°C for 24 h, and DM yield and IVDMD were determined for each harvest.

Grazing Experiment In May, 1988, replicate .81-ha pastures of Tifton 78 and of Tifton 85 were each established using sprigs planted in Tifton sandy loam soils. Pastures were not grazed in 1988, but a 3-yr grazing experiment was initiated in April, 1989. Pastures were fertilized with 252 kg of N/ha each year, divided into three applications of 84 kg of N h a applied in mid-March, late June, and early August. Phosphorus and potassium were applied in mid-March to provide a 4:1:2 ratio of N: P205:KzO. Steers used in the grazing experiment were weaned in September each year and were wintered on bermudagrass hay and grain mixtures to provide ADG of .5 to .6 kg. Crossbred steers ( n = 48) that were sired by Angus, Polled Hereford, and Santa Gertrudis bulls mated to A n g u s and Polled Hereford-sired crossbred cows were assigned to four groups by breed type and BW. Groups of four tester steers each were randomly assigned to Tifton 78 and to Tifton 85 pastures in early April each year. Steers (16/yr; 269 kg initial BW) grazed in a put-and-take (Mott and Lucas, 1952) grazing management system continuously for 162, 178, and 168 d, respectively in 1989, 1990, and 1991. Steers similar to the tester steers in weight, age, background, and breeding were designated as “grazer” steers, and were used to adjust forage mass in pastures. Total pasture forage mass was targeted at approximately 2,800 kg of DM/ha because we wished to provide enough forage t o allow detection of differences in nutritive value of the forages unlimited by forages mass. Previous grazing research with Tifton 78 (Hill et al., 1990) and other bermudagrasses (Guerrero et al., 1984; Roth et al., 1990) indicated that this level of forage mass would be adequate to detect differences in steer performance and nutritive value of the two forages. At 14-d intervals beginning in April, forage mass was estimated using a double sampling procedure. Forage green weight was estimated visually by two observers within 40 quadrats (.1 m2) per pasture. Four quadrats were clipped to ground level in each pasture, and clipped samples were oven-dried. Visual estimates

were corrected for each observer separately for each sampling period using a linear calibration between visual estimates and clipped weights. Pooled estimates were converted to a moisture-free basis using pooled DM values. Stocking rates were adjusted at 14-d intervals by addition or removal of grazer steers to achieve the targeted 2,800 kg of DM/ha in each pasture. Steers were weighed at 28-d intervals, and initial and final weights of steers were means of two consecutive full weights. Equal portions of trace mineralized salt ( NaCl [maximum] 99.0%; Fe 30%; Cu .01%; Co .0024%; Mn .lo%; Zn .lo%; I .0024%.) and Dynafose ( Pitman-Moore, Mundelein, IL; P 18.50%; Ca [maximum] 24.0%; F [maximum] .185%) were mixed together and provided free-choice along with water in each pasture. Pasture Quality and Forage Particle Size. In each year, two mature steers previously fitted with esophageal cannulas grazed each pasture at 7-d intervals in late May. mid-July, and early September. Cannulated steers grazed Coastal bermudagrass pastures before and after each forage mass sampling. Cannulated steers were confined in drylot and restricted from feed for 36 h before each sampling period. This procedure was used because Fisher et al. ( 1 9 8 9 ) showed no difference in forage particle size distribution or quality when esophageal cannulated steers were either fasted with no adaptation period or not fasted and adapted to the forage being grazed. In our study, the order of pastures sampled was reversed for the second sampling date within each period. Plastic bags were attached with rubber bands t o hollow plastic tubes inserted into the cannula. Steers were allowed to graze until the weight of the sample contents caused the bags to fall to the ground, which was generally within 10 to 20 min after grazing was initiated. This grazing deviation resulted in approximately .5 to 1.0 L of masticated forage. Extrusa samples (forage and saliva) were quick-frozen in liquid N at the pasture site. Samples were stored ( -15°C 1 and the entire sample was subsequently freeze-dried. The dried masticate samples were carefully split with approximately 15 g of sample subjected to particle size determination, and the remainder was ground through a 1-mm screen in a Wiley mill (Model 4, Thomas-Wiley Laboratory Mill, Thomas Scientific, Swedesboro, N J ) in preparation for chemical analyses and IVDMD determination. Particle separation was determined by methods described by Burns et al. (1992). The 15-g subsample was drysieved ( 1 0 min) through six screens in a Fritsch vibrator system (Fritsch Analysette 3, Tekmar, Cincinnati, O H ) set a t 3,000 oscillations/min. This provided seven particle sizes: particles retained on 4.0-, 2.8-, 1.7-. 1.0-, .5-, and .25-mm sieves, and particles that passed through the .25-mm sieve. Mean and median particle sizes (Fisher et al., 1988) were determined from cumulative percentage of weight over size.


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TIFTON 85 BERMUDAGRASS

Nutritive Value Freeze-dried masticate samples were analyzed for acid insoluble ash and crude protein (micro-Kjeldahl; total N x 6.25) using AOAC ( 1 9 9 0 ) procedures. The NDF and ADF were determined using methods of Goering and Van Soest ( 1970). The two-stage digestion methods of Tilley and Terry (1963) were used to determine IVDMD of forage samples from the plot trials and freeze-dried masticate from pastures in the grazing experiment. Ruminal fluid for the rVDMD procedure was collected from ruminally cannulated steers fed bermudagrass hay, strained through four layers of cheesecloth into an insulated thermos, and transported to the laboratory. Data from chemical and IVDMD analyses of esophageal extrusa samples from two steers grazing each pasture a t 7-d intervals were combined providing means for late May, mid-July, and early September. A total of 144 masticate samples were collected and analyzed over the 3-yr study ( 2 sampleslpasture x 2 dateslperiod x 4 pastures x 3 periods = 48 samples x 3 y r = 144 total samples).

Statistical Analyses The small-plot yield experiment was analyzed as a randomized complete block in which DM yield was the total of four clippings at different dates during the growing season each year, and IVDMD of the forages was the mean of IVDMD for the same four clipping dates used each year. Fisher's protected LSD test ( P = .05) (Steel and Torrie, 1980) was used to separate treatment effects. Statistical analyses of the steer grazing performance and laboratory analyses of masticated forage were conducted using the GLM procedure of SAS (1985). The laboratory data were analyzed as a split-split-plot where years were main plots, bermudagrass cultivars were sub-plots, and sampling dates were sub-sub-plots. Least squares means were generated with appropriate standard errors. Steer performance data were analyzed as a split-plot with year as the main plot and bermudagrass cultivar as the sub-plot. Preliminary analyses of stocking rate data indicated no differences ( P > . l o ) between treatments. Stocking rates for individual dates were highly variable for each treatment in 1989 and 1991 but not in 1990. Graphical presentations of stocking rates over time for each year showed predominantly higher stocking rates for Tifton 85 than for Tifton 78. Therefore, the sign test (Steel and Torrie, 1980) was used to determine whether there were statistical differences for the number of times stocking rates were higher for Tifton 85 than for Tifton 78 during the grazing season each year.

Results a n d Discussion Development of hybrid bermudagrasses with increased DM and nutritive value is initiated with a hybrid generation followed by a number of screening

tests to determine which hybrids display yield, disease resistance, forage quality, environmental tolerance (drought, insects, cold tolerance), and stand persistence. Small-plot experiments are finally established to determine yield and nutritive value of selections compared with released cultivars. Tifton 85 was included in two such small-plot experiments (Table 1 ) . In each experiment, Coastal and Tifton 44 bermudagrasses were included as baseline forages to represent currently recommended cultivars. In both experiments, DM yield and IVDMD were higher ( P = .05) for Tifton 85 than for other cultivars. Tifton 68, used in Exp. 1 (Table l ) , is a highly productive bermudagrass with extremely high IVDMD, acceptable yields, but minimum cold tolerance (Burton and Monson, 1984). Tifton 78, used in Exp. 2, is a recently released cultivar with very high yield potential and relatively high quality (Burton and Monson, 1988). Consequently, Tifton 85 produced an average of 11% more DM than Coastal, and was generally higher in quality, than other bermudagrass cultivars included in these trials. Weather conditions (Table 2 ) , including a severe drought in 1990, probably affected DM yield and IVDMD of all cultivars in Exp. 2. Tifton 85 was established in pastures from limited nursery stock in 1988 because of the high yields, high quality, and stand persistence recorded for this hybrid in the initial small-plot experiments (Table 1).Tifton 78 was chosen as the reference bermudagrass for establishment in the grazing comparison for Tifton 85 because of its DM yield and IVDMD (Burton and Monson, 19881, and higher animal BW gainhectare than Coastal (Hill et al., 1990, 1993). Tifton 78 has been established on many farms across the south since 1984 and has gained acceptance and popularity among producers.

Table 1. Comparison of Tifton 85 with bermudagrass hybrids in 3-year, small-plot experiments Annual Item

DM yield, tha

IVDMD,

18.6 15.2 15.7 15.5

60.3 63.6 55.0 54.3

2.0

1.4

14.7 11.3 10.4 11.0

57.3 55.7 51.3 50.2

3.8

2.2

%

EXP. 1 (1985-1987) Hybrid Tifton 85 Tifton 68 Tifton 44 Coastal

LSD ( P = ,051 EXP. 2 (1989-1991)a Hybrid Tifton 85 Tifton 78 Tifton 44 Coastal LSD ( P = ,051

aExperiment 2 IVDMD based on 1989 and 1990 data.


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HILL ET AL.

Table 2. Rainfall distribution by months during years of pasture grazing experiment compared with long-term meansa Year of trial Rainfall

1989

1990

3-yr Mean

1991

23-yr Meanb ~~

cm

Month March April May June July August September Total March through September Relative rainfall compared with 23-yr mean, % Total annual rainfall, cm

9.60 6.60 9.19 23.42 12.62 5.28 4.78

7.24 3.20 4.70 7.09 8.13 7.04 4.60

23.52 9.40 18.49 16.76 19.30 9.07 1.35

13.45 6.40 10.79 15.76 13.35 7.13 3.58

71.49 94.44 112.88

42.00 55.48 96.29

88.49 116.90 150.32

64.06 84.62 119.83

13.56 9.60 10.11 10.30 12.03 12.60 7.50 75.7

-

123.20

aRainfall recorded a t University of Georgia Coastal Plain Experiment Station, Tifton, which is an official USDA Weather Station. bMean annual rainfall for months of March through September from 1969 through 1991.

In the grazing study, available forage mass in each pasture was targeted a t 2,800 kg of DM/ha. Figure 1 indicates the variation observed in yield resulting from differences in rainfall, seasonal changes, and fertilizer applications during the experiment. Although not perfect, our procedures allowed DM to be maintained near the forage mass target levels. The drought of 1990 (Table 2 ) reduced the 3-yr mean forage mass for each kind of forage, contributing to the slight reductions in measured forage mass relative to the target after May 1. Figure 1 shows that forage mass was maintained at very similar levels for the two forage treatments throughout the grazing season using the variable stocking rate procedure. Esophageal cannulated steers grazed pastures on three occasions during each grazing season, and whole masticate samples were analyzed to determine quality of available forage (Table 3 1. Statistical differences were not observed for either forage a t any sampling time for AIA, and low values for AIA suggested minimal contamination of forage masticate with sand. The CP of masticate was similar ( P > . l o ) for Tifton 78 and Tifton 85 pastures in May and July, but CP was higher ( P < . 0 5 ) in September for Tifton 85 samples. The CP of both Tifton 78 and Tifton 85 was higher ( P< .05) in July and September than in May. The interval between initial fertilizer applications each year and the May masticate sampling date was approximately 14 d longer than intervals between fertilizer applications and the July and September masticate sampling dates. Rapid spring growth of the forages probably depleted fertilizer N at a more rapid rate than a t other times during the grazing season. This factor contributed to lower CP content of the May masticate samples. The NDF was higher ( P < .05 1 for Tifton 85 than for Tifton 78 in the May masticate (Table 3 ) , but NDF was similar for the two forages at other sampling

dates. Tifton 78 had similar ( P > . 10j NDF values for all three sampling dates, but Tifton 85 had higher ( P < .05) NDF in May than in July and September. Bermudagrasses are day-length sensitive forages, and Tifton 78 and Tifton 85 produce a n abundance of stems and leaves in spring, followed by more vegetative growth later in the season. The increased proportion of robust stems produced by Tifton 85 probably contributed to the increased NDF observed in May esophageal samples for this forage. The NDF values were higher for both Tifton 78 and Tifton 85 relative to another report for Coastal bermudagrass masticate (Burns et al., 1992). Both Tifton 78 and Tifton 85 are larger stemmed plants than Coastal, which may account for increased NDF for these hybrids. Hill et al. ( 1993) reported higher NDF in clipped pasture samples of Tifton 78 than Coastal.

4'0001

1,000

i -

16APR

I

14MAY

13JUN

I

11JJL

I

I

8AUG

I

'

5SEP

I

I

30CT

Date

Figure 1. Three-year mean forage mass in Tifton 78 and Tifton 85 pastures with time during grazing seasons relative to forage mass target of 2,800 kg of DM/ha for each pasture; Tifton 78 SEM = 298 kgiha; Tifton 85 SEM = 262 kgiha.


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Table 3. Quality and particle size of whole masticate from Tifton 78 and Tifton 85 pastures at three dates Quality Item Sampling diet May Tifton 78 Tifton 85 July Tifton 78 Tifton 85 September Tifton 78 Tifton 85

SE Year 1989 1990 1991

SE

Particle size

AIA

CP

NDF

IVDMD

Mean

Median

1.9 2.2

11.9d 11.4d

73.1bc 75.4ac

58.gbC 61.gaC

1.4bc lBac

1.2b' 1.5ac

2.4 2.2

15.4c 15.5'

71.7' 72.2d

59.4' 59.1d

1.3bd 1.7ad

l.lbd 1.3ad

1.5 1.3 .18

14.2bC 15.6aC .54

71.1' 71.4d .77

53.1bd 57.3ad .99

1.2be 1.6ae .02

1.0be 1.3ad .02

1.2' 1.0' 3.4y .13

13.5 14.5 14.0 .30

73.2 71.6 72.6 .95

57.5 57.9 59.4 .70

1.4' 1.4' 1.6y .04

1.2' 1.2' 1.3Y

.03

aibMeans for pasture forage masticate within a sampling date differ at ( P < .05). csd,eMeans for a pasture forage masticate at different sampling dates differ at ( P < .05). J'9'Year means within a column differ at ( P < .05).

The IVDMD of whole masticate was higher ( P < .05) in May and September for Tifton 85 than for Tifton 78 (Table 3). The IVDMD of Tifton 78 was

similar ( P > . l o ) in May and July, but IVDMD of Tifton 78 was lower ( P < .05) in September than in earlier samples. Tifton 85 masticate had higher ( P < .05) IVDMD in May than in July or September. These results indicate that even though NDF was quite high, especially in May masticate for Tifton 85, the digestibility of the forages was apparently unaffected. The higher IVDMD and CP in September masticate from Tifton 85 pastures (Table 3 ) corresponded with a slight increase in tester steer BW late in the grazing season (Figure 2). Tifton 85 had higher ( P < .05) mean and median particle sizes than Tifton 78 during each of the sampling dates (Table 3 ) . Additionally, mean particle size was greatest ( P < . 0 5 ) for each forage in May, intermediate ( P < .05) in July, and smallest ( P < .05) in September. Median particle size for Tifton 78 was greater ( P < .05) in May than in July and was greater ( P < .05)in July than in September. Median particle size was greater ( P < .05) for Tifton 85 in May than in July and September. In May, forage probably required less mastication after consumption t o form a bolus before swallowing. Therefore, larger particle size was determined in May for both treatments compared with particle size of the forages later in the growing season. If ingested forage was less brittle and more succulent earlier in the season, mastication probably did not shatter leaves and stems as much in May as in later sampling dates. Tifton 78 and Tifton 85 have not been investigated as extensively as Coastal with regard to digestibility of available forage in pastures and canopy characteristics. Although the design of experiments differed, our

mean and median particle sizes for both Tifton 78 and Tifton 85 (Table 3) were similar to those reported for Coastal bermudagrass in July samples (Fisher et al., 1991; Burns et al., 1992). Canopy component characteristics were not determined in our study. Comparisons of Tifton 85 with Coastal are warranted t o determine differences in canopy structure, particle size, and IVDMD of canopy components of these cultivars and their ultimate effects on ADG and DMI of grazing cattle. Performance of steers on Tifton 78 and Tifton 85 pastures (Table 4) indicated that tester ADG was similar ( P > . l o ) for the two forages. Mean BW was almost identical for tester steers throughout the

400-

+ 375-

t

2350-

r" m 325L

e,

2 300v,

250

I

APR

I

MAY

I

I

I

I

I

JUN

JUL

AUG

SEP

OCT

1

Month

Figure 2. Three-year mean cumulative body weight of tester steers grazing Tifton 78 and Tifton 85 bermudagrass pastures; Tifton 78 SEM = 7.71 kg; Tifton 85 SEM = 6.58 kg.


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HILL ET AL.

Table 4. Three-year mean performance of steers grazing Tifton 78 and Tifton 85 bermudagrass pastures Bermudagrass pasture Item

No. of pastures Pasture area, ha Annual forage DM/ha, kg No. of grazing days Steer performance Tester steer ADG, kg Steer grazing daysha, d Gainha, kg

Tifton 78

Tifton 85

SE

2

2

-

.81

.81

-

2,350 169

2,440 169

34.6

.65 1,319.gb 789.1'

.67 1,823.2a 1,1F~6.4~

.07 42.0 45.9

-

a,bMeans on same line bearing different superscript letters differ ( P < ,011.

:'$ 14

;

12-

310.0

grazing season (Figure 2), consistent with data indicating that forage availability and quality were approximately equal for the two forages when forage mass was maintained at 2,800 kgiha. However, steer grazing dayshectare (Table 3) were 38% higher ( P < .01)for Tifton 85 than for Tifton 78 (1,823vs 1,319 d). Consequently, BW gain was 46% higher ( P < .01) for Tifton 85 than for Tifton 78 (1,156vs 789 k g h a ) . Figure 3 shows stocking rates by grazing seasons in each year. Results of sign tests indicated that Tifton 85 had higher stocking rates: 1989 ( T = 1, N = 9;P I .02);1991 ( T = 0,N = 12;P I.01).In 1990 stocking rates were less variable across dates, and even though a t-test indicated that stocking rates for Tifton 85 were different from those of Tifton 78, the sign test was applied to these data: 1990 ( T = 1, N = 13; P 2 .01). Increased stocking rates resulted in increased grazing dayshectare (Table 4) for Tifton 85 compared with Tifton 78.Rainfall during the study (Table 2 1 affected productivity of the forages, and Figure 3 shows the effect of the severe drought of 1990 on stocking rates. Regardless of rainfall distribution during the 3 yr, Tifton 85 pastures were stocked at higher rates in each year than Tifton 78 pastures, and gainhectare increased for each succeeding year on Tifton 85 pastures. Tifton 85 produced substantially more forage, which resulted in increased BW gainhectare for steers compared with Tifton 78. In previous studies Tifton 78 had produced large increases in steer ADG, and BW gainhectare was increased by 24 and 38%, respectively, compared with Coastal in two 3-yr experiments (Hill et al., 1990, 1993). Further examination of the data revealed a strong tendency for Tifton 85 to remain more productive later in the grazing season than Tifton 78 did. This was indicated by slight increases in the rate of BW gain for Tifton 85 tester steers after August (Figure 21, and is more evident in Figure 3, which clearly shows substantially higher stocking rates for Tifton 85 than for Tifton 78 in each year. Tifton 85 pastures remained darker green in color and seemed to respond well to the last fertilizer applications in August.

Figure 3. Stocking rates for Tifton 78 and Tifton 85 pastures during the grazing season in 1989 (A),1990 (B), and 1991 (C),with forage mass targeted at 2,800 kg of DM/ha.

Greene et al. (1990) showed that "Grazer" bermudagrass produced higher ADG in steers during August and September than Coastal. Although Tifton 85 is well adapted to the sandy soils of the lower Coastal Plain, northern limits for its survival and growth response of the hybrid on heavier soils have not been established.

Implications Tifton 85 bermudagrass has the potential for becoming the premier bermudagrass for portions of the southern United States, and for other tropical and temperate regions of the world. Northern limits of



adaptation have not been verified, but limited data suggest that Tifton 85 will persist in areas where Tifton 78 is presently adapted. Tifton 85 has produced substantially higher dry matter yields than Coastal, the dominant hybrid bermudagrass. Under continuous grazing, Tifton 85 pastures had higher nutritive value and were stocked at considerably higher levels than Tifton 78 pastures. Increased beef production from Tifton 85 pastures may be realized. Literature Cited AOAC. 1990. Official Methods of Analysis (15th Ed.). Association of official Analytical Chemists, Arlington, VA. Burns, J . C., D. S. Fisher, K. R. Pond, and D. H. Timothy. 1992. Diet Characteristics, digesta kinetics, and dry matter intake of steers grazing eastern gamagrass. J . h i m . Sci. 70:1251. Burton, G. W., R. N. Gates, and G. M. Hill. 1993. Registration of ‘Tifton 85’ bermudagrass. Crop Sci. 33:644. Burton, G. W., and W. G. Monson. 1984. Registration of Tifton 68 bermudagrass. Crop Sci. 24:1211. Burton, G. W., and W. G. Monson. 1988. Registration of Tifton 78 bermudagrass. Crop Sci. 28:187. Fisher, D. S., J . C. Burns, and K. R. Pond. 1988. Estimation of mean and median particle size of ruminant digesta. J . Dairy Sci. 71: 518. Fisher, D. S., J. C. Burns, and K. R. Pond. 1989. Esophageal plug and fasting effects on particle size distribution and quality of extrusa from grass pastures. Agron. J. 81:129. Fisher, D. S., J . C. Burns, K. R. Pond, R. D. Mochrie, and D. H. Timothy. 1991. Effects of grass species on grazing steers: 1.

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