Forage nutritional quality evaluation of bahiagrass selections

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Forage nutritional quality evaluation of bahiagrass selections
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2009 Florida Beef Report
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Myer, Bob
Blount, Ann
Coleman, Sam
Carter, Jeff
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Institute of Food and Agricultural Sciences, University of Florida
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Gainesville, Fla.
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Forage Nutritional Quality Evaluation of Bahiagrass Selections

Bob Myert
Ann Blount
Sam Coleman
Jeff Carter



Bahiagrass plant breeding efforts in the past have been based on increasing forage yield. Selection for
increased yield also resulted in a concurrent increase in bahiagrass forage quality.


Summary
Bahiagrass (Paspalum notatum Flugge) is the
major pasture forage in Florida. A bahiagrass
selection breeding program has been ongoing
since 1960 at the Coastal Plain Experiment
Station at Tifton, Georgia to increase forage
yield in 'Pensacola' (P. notatum var. sanese
Flugge) bahiagrass. However, the impact of
selection for forage yield on forage nutritional
quality is unknown. Forage quality was
evaluated from four 'Pensacola' derived
selection cycles (C) of bahiagrass (CO -
'Pensacola', C4, C9 'Tifton 9', and C23). A
total of 175 plants per cycle were grown
; ,g, i r, in a field at NFREC, Quincy. Forage
from individual one-yr old plants was harvested
by hand on October 3, 2000 and again on
November 15, 2000. The samples were dried,
ground, and analyzed using near-infrared
reflectance spectroscopy (NIRS) for dry matter
(DM), in vitro dry matter digestibility (IVOMD),
neutral detergent fiber (NDF), and crude protein
(CP). Cycle means (% DM basis combined over
both harvest dates) for IVOMD, NDF and CP
were 49.7, 81.0 and 14.2; 50.3, 79.7 and 13.7;
52.8, 78.7 and 13.2; and 52.0, 78.5 and 12 .9 for
CO, C4, C9 and C23, respectively. The greater
average IVOMD of C4 vs. CO was different (P
0.03) as well as C9 vs. C4 (P < 0.001).
Therefore, in addition to increased forage yield,


there was evidence that forage quality (IVOMD)
also increased with advancing selection cycle.
Selection for improved nutritional quality
;!i, igh plant breeding may be possible.

Introduction
Bahiagrass is the major pasture forage crop in
Florida and throughout the southern Gulf Coast.
As a C4 tropical grass, its forage nutritional
quality is low, lower than typically noted for C3
temperate grasses, such as ryegrass, at
comparable stages of growth and development.

Dr. G. W. Burton, a plant breeder with USDA
ARS, Tifton, GA, developed and used restricted
recurrent phenotypic selection (RRPS) breeding
procedure to improve bahiagrass forage yield.
Starting in 1960, Burton selected plants annually
for 24 yr using this procedure, which resulted in
morphology of the plants towards a more upright
growth habit as well as greater forage mass.
Whether or not forage nutritional quality was
improved is not known. Thus, the objective of
this research was to evaluate nutritional quality
of bahiagrass selections from four 'Pensacola'
derived RRPS selection cycles.

Material and Methods
Bahiagrass seed from four RRPS selec-


2009 Florida BeefReport










tion cycles [CO (Pensacola), C4, C9 (Tifton 9)
and C23] were obtained from G. W. Burton,
USDA-ARS, Coastal Plain Experiment Station,
Tifton, GA, and used in this study. From this
seed supply, a total of 175 plants of each cycle
were grown in a greenhouse and then
transplanted during July 1999 to a field at
NFREC Quincy, FL (30.30 N Lat.). Beginning
September 1999, foliage was harvested every 6
to 8 wk. Harvest consisted of the total top
growth that occurred at 4 in above the crown of
the individual plants. On August 15, 2000, all
plant crowns were hand clipped to 4 in diameter
and the foliage clipped to 4 in height. On
October 2, 2000 and again on November 15,
2000, foliage growth of individual plants was
cut by hand to a common height of 4 in. Foliage
was dried, weighed and recorded. In all, an
average of 164 forage samples per cycle per
harvest was obtained. Forage was not obtained
from all 175 plants per cycle per harvest due to
some plant attrition or plants not having
sufficient forage.

The dried forage samples were ground and
analyzed for DM, IVOMD, NDF and CP using
NIRS. The NIRS was calibrated from a
subsample of 275 samples which were analyzed
using wet chemistry procedures.

Data were analyzed using GLM of SAS. The
model included harvest date and cycle. The
individual plant was the experimental unit.
Significant effects were separated using
LSMEANS comparison with the PDIFF option
of SAS.

Results
The values obtained for IVOMD and NDF in
this study were typical of late grazing season
bahiagrass; however, the CP values were
greater. The bahiagrass plants were well
fertilized during the study which could explain
the greater CP concentrations. October and
November samplings were done rather than
during the late spring and summer mo as forage
quality is typically lowest for bahiagrass during
autumn. Differences noted would be more
meaningful than earlier sampling when quality
values would overall be higher.


When combined over both harvests, an increase
in IVOMD and decreases in NDF and CP
concentrations were noted when going from CO
to C4 (P=0.03; P<0.001; P<0.001, respectively),
and again from C4 to C9 (P<0.001 for all; Table
1). A small decrease (P<0.01) in IVOMD was
noted from C9 to C23. While IVOMD was
lower for C23 compared with C9, the value was
still greater when compared with C4 or CO
(P<0.01). The further decrease noted with NDF
of C23 vs. C9, however, was not significant
(P>0.10). The trend for a decrease in CP was
continued as the decrease between C9 and C23
was significant (P<0.01). The peak at C9 for
IVOMD was mostly the result of the drop in
IVOMD for C23 compared with C9 (P<0.01)
noted for the November harvest; values were
similar (P>0.10) for the October harvest (Figure
1).

The November harvest samples were greater
(P<0.01) in IVOMD (52.4 vs. 50.1%) and CP
(14.6 vs. 12.5%) than the October harvest
samples; NDF was similar (P>0.10; 80 vs. 79%;
Figure 1). The increases noted were probably a
reflection of the cooler weather during the 6 wk
prior to the November harvest than prior to the
October harvest.

Forage yield has been reported previously. As
expected, an increase with increasing selection
cycle was noted, peaking at C9 (60% increase
vs. CO) with no further increase with C23.

From these results, there was evidence that
forage nutritional quality did increase with
advancing selection cycle. This finding is based
on the increase in IVOMD and the decrease in
NDF as selection cycle increased from 0 to 23,
in particular from CO to C9. Crude protein
concentration actually decreased with increasing
selection cycle; however, animal nutritionists
often place more emphasis on IVOMD and NDF
as determinants of forage nutritional quality than
CP. While the bahiagrass RRPS selection goal
was to increase forage yield, results of our study
indicated evidence of a concurrent improvement
in forage nutritional quality.

In addition, variation for each parameter


2009 Florida BeefReport









measured within each cycle was noted, and this
variation was consistent across the cycles. For
example, the variation (one standard deviation)
for IVOMD averaged 2.8 (range of 2.7 to 2.9).
This variation is desirable for plant breeding
improvement. Therefore, breeding for improved
forage quality within a cycle, as well as across
cycles, may be possible.


Table 1. Composition of bahiagrass


cycles (% dry matter basis; combined over both harvests).


Selection cycle
Item CO C4 C9 C23 SEa
IVOMDb 49.7 50.3 52.8 52.0 0.10
NDFc 81.0 79.7 78.7 78.5 0.10
Crude protein 14.2 13.7 13.2 12.9 0.09
aStandard error of the mean, n = average of 164/cycle/harvest.
bIn vitro organic matter digestibility. CO vs. C4, P < 0.03; C4 vs. C9, P < 0.001; C9 vs. C23, P < 0.01.
CNeutral detergent fiber. CO vs. C4, P < 0.001; C4 vs C9, P < 0.001; C9 vs. C23, P > 0.10.
dCO vs. C4, P < 0.001; C4 vs. C9, P < 0.001; C9 vs. C23, P < 0.01.


1Bob Myer, Professor, Ann Blount, Associate Professor, and Jeff Carter, Former Assistant Professor,
UF-IFAS, North Florida Research and Education Center, Marianna, FL; and Sam Coleman, Research
Animal Scientist, USDA ARS, Sub-tropical Agriculture Research Station, Brookville, FL.


2009 Florida BeefReport











IVOMD


SE = 0.13

0 4 9 23


NDF








SE = 0.13

0 4 9 23


CP








SE = 0.12


Selection cycle


Figure 1. Mean values for each harvest of bahiagrass selection cycles (%, DM basis; & =
Oct. harvest and = Nov. harvest). IVOMD = in vitro organic matter digestibility; NDF
neutral detergent fiber; CP = crude protein.


2009 Florida BeefReport




Full Text

PAGE 1

Forage Nutritional Quality Evaluation of Bahiagrass Selections Bob Myer 1 Ann Blount Sam Coleman Jeff Carter Summary Bahiagrass (Paspalum notatum Flugge) is the major pasture forage in Florida. A bahiagrass selection breeding program has been ongoing since 1960 at the Coastal Plain Experiment Station at Tifton, Georgia to increase forage Flugge) bahiagrass. However, the impact of selection for forage yield on forage nutritional quality is unknown. Forage quality was selection cycles (C) of bahiagrass (C0 total of 175 plants per cycle were grown together in a field at NFREC, Quincy. Forage from individual one-yr old plants was harvested by hand on October 3, 2000 and again on November 15, 2000. The samples were dried, ground, and analyzed using near-infrared reflectance spectroscopy (NIRS) for dry matter (DM), in vitro dry matter digestibility (IVOMD), neutral detergent fiber (NDF), and crude protein (CP). Cycle means (% DM basis combined over both harvest dates) for IVOMD, NDF and CP were 49.7, 81.0 and 14.2; 50.3, 79.7 and 13.7; 52.8, 78.7 and 13.2; and 52.0, 78.5 and 12 .9 for C0, C4, C9 and C23, respectively. The greater average IVOMD of C4 vs. C0 was different (P = 0.03) as well as C9 vs. C4 (P < 0.001). Therefore, in addition to increased forage yield, there was evidence that forage quality (IVOMD) also increased with advancing selection cycle. Selection for improved nutritional quality through plant breeding may be possible. Introduction Bahiagrass is the major pasture forage crop in Florida and throughout the southern Gulf Coast. As a C 4 tropical grass, its forage nutritional quality is low, lower than typically noted for C 3 temperate grasses, such as ryegrass, at comparable stages of growth and development. Dr. G. W. Burton, a plant breeder with USDA ARS Tifton, GA, developed and used restricted recurrent phenotypic selection (RRPS) breeding procedure to improve bahiagrass forage yield. Starting in 1960, Burton selected plants annually for 24 yr using this procedure, which resulted in morphology of the plants towards a more upright growth habit as well as greater forage mass. Whether or not forage nutritional quality was improved is not known. Thus, the objective of this research was to evaluate nutritional quality derived RRPS selection cycles. Material and Methods Bahiagrass seed from four RRPS selecBahiagrass plant breeding efforts in the past have been based on increasing forage yield. Selection for increased yield also resulted in a concurrent increase in bahiagrass forage quality.

PAGE 2

tion cycles [C0 (Pensacola), C4, C9 (Tifton 9) and C23] were obtained from G. W. Burton, USDA-ARS, Coastal Plain Experiment Station, Tifton, GA, and used in this study. From this seed supply, a total of 175 plants of each cycle were grown in a greenhouse and then transplanted during July 1999 to a field at NFREC Quincy, FL (30.3 N Lat.). Beginning September 1999, foliage was harvested every 6 to 8 wk. Harvest consisted of the total top growth that occurred at 4 in above the crown of the individual plants. On August 15, 2000, all plant crowns were hand clipped to 4 in diameter and the foliage clipped to 4 in height. On October 2, 2000 and again on November 15, 2000, foliage growth of individual plants was cut by hand to a common height of 4 in. Foliage was dried, weighed and recorded. In all, an average of 164 forage samples per cycle per harvest was obtained. Forage was not obtained from all 175 plants per cycle per harvest due to some plant attrition or plants not having sufficient forage. The dried forage samples were ground and analyzed for DM, IVOMD, NDF and CP using NIRS. The NIRS was calibrated from a subsample of 275 samples which were analyzed using wet chemistry procedures. Data were analyzed using GLM of SAS. The model included harvest date and cycle. The individual plant was the experimental unit. Significant effects were separated using LSMEANS comparison with the PDIFF option of SAS. Results The values obtained for IVOMD and NDF in this study were typical of late grazing season bahiagrass; however, the CP values were greater. The bahiagrass plants were well fertilized during the study which could explain the greater CP concentrations. October and November samplings were done rather than during the late spring and summer mo as forage quality is typically lowest for bahiagrass during autumn. Differences noted would be more meaningful than earlier sampling when quality values would overall be higher. When combined over both harvests, an increase in IVOMD and decreases in NDF and CP concentrations were noted when going from C0 to C4 ( P =0.03; P <0.001; P <0.001, respectively), and again from C4 to C9 ( P <0.001 for all; Table 1). A small decrease ( P <0.01) in IVOMD was noted from C9 to C23. While IVOMD was lower for C23 compared with C9, the value was still greater when compared with C4 or CO ( P<0.01). The further decrease noted with NDF of C23 vs. C9, however, was not significant ( P>0.10). The trend for a decrease in CP was continued as the decrease between C9 and C23 was significant ( P <0.01). The peak at C9 for IVOMD was mostly the result of the drop in IVOMD for C23 compared with C9 ( P <0.01) noted for the November harvest; values were similar ( P >0.10) for the October harvest (Figure 1). The November harvest samples were greater ( P<0.01) in IVOMD (52.4 vs. 50.1%) and CP (14.6 vs. 12.5%) than the October harvest samples; NDF was similar ( P >0.10; 80 vs. 79%; Figure 1). The increases noted were probably a reflection of the cooler weather during the 6 wk prior to the November harvest than prior to the October harvest. Forage yield has been reported previously. As expected, an increase with increasing selection cycle was noted, peaking at C9 (60% increase vs. C0) with no further increase with C23. From these results, there was evidence that forage nutritional quality did increase with advancing selection cycle. This finding is based on the increase in IVOMD and the decrease in NDF as selection cycle increased from 0 to 23, in particular from C0 to C9. Crude protein concentration actually decreased with increasing selection cycle; however, animal nutritionists often place more emphasis on IVOMD and NDF as determinants of forage nutritional quality than CP. While the bahiagrass RRPS selection goal was to increase forage yield, results of our study indicated evidence of a concurrent improvement in forage nutritional quality. In addition, variation for each parameter

PAGE 3

measured within each cycle was noted, and this variation was consistent across the cycles. For example, the variation (one standard deviation) for IVOMD averaged 2.8 (range of 2.7 to 2.9). This variation is desirable for plant breeding improvement. Therefore, breeding for improved forage quality within a cycle, as well as across cycles, may be possible. Table 1 Composition of bahiagrass cycles (% dry matter basis; combined over both harvests). Selection cycle Item C0 C4 C9 C23 SE a IVOMD b 49.7 50.3 52.8 52.0 0.10 NDF c 81.0 79.7 78.7 78.5 0.10 Crude protein d 14.2 13.7 13.2 12.9 0.09 a Standard error of the mean, n = average of 164/cycle/harvest. b In vitro organic matter digestibility. C0 vs. C4, P < 0.03; C4 vs. C9, P < 0.001; C9 vs. C23, P < 0.01. c Neutral detergent fiber. C0 vs. C4, P < 0.001; C4 vs C9, P < 0.001; C9 vs. C23, P > 0.10. d C0 vs. C4, P < 0.001; C4 vs. C9, P < 0.001; C9 vs. C23, P < 0.01. 1 Bob Myer, Professor, Ann Blount, Associate Professor, and Jeff Carter, Former As sistant Professor, UF IFAS, North Florida Research and Education Center, Marianna, FL; and Sam Coleman, Research Animal Scientist, USDA ARS, Sub tropical Agriculture Research Station, Brookville, FL.

PAGE 4

IVOMD NDF CP Selection c ycle Figure 1. Mean values for each harvest of bahiagrass selection cycles (%, DM basis; = Oct. harvest and = Nov. harvest). IVOMD = in vitro organic matter digestibility; NDF = neutral detergent fiber; CP = crude protein. 30 40 50 60 70 0 4 9 23 60 70 80 90 100 0 4 9 23 SE = 0.13 0 5 10 15 20 0 4 9 23 SE = 0.13 SE = 0.12