Effect of Nitrogen Fertilization on the Amounts and Proportions of Protein Fractions in Tifton 85 Bermudagrass (Cynodon spp.) S.J. Rymph P. Mislevy M.B. Hall H.H. VanHorn E.C. French L.E. Sollenberger G.M. Prine
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Effect of Nitrogen Fertilization on the Amounts and Proportions of Protein Fractions in Tifton 85 Bermudagrass
(Cynodon spp.)
S.J. RymphP. Mislevy M.B. Hall H.H. VanHorn E.C. FrenchL.E. Sollenberger G.M. Prine
ObjectivesIt has been reported that crude protein or nitrogen concentration in grasses is increased with increased nitrogen fertilization (Phelps and Woods, 1890, Prine and Burton, 1956, Rogers et al., 1996).
The objectives of this study were to quantify changes in nutritionally relevant nitrogen fractions associated with increasing nitrogen fertility and ensiling of bermudagrass for use in more accurately balancing ruminant rations using currently available computer models (1996 Beef NRC, CNCPS and CPM Dairy)
Nitrogen Fractions for ModelsRationale for Partitioning
ADFCP
Peptides
NDFCP
NPN kdkp
175 - 300%/h kd > kp
0.15 - 2%/h kd < kp
0%/h kd = 0
Soluble Protein
5 - 12%/h kd kp
NDF
ADF
kd= rate of digestion, kp= rate of passage
Rate of Digestion in the rumen
Cell Contents
Cell Wall
graphic by M.B. Hall, 1996
Experimental Design N Rate X Storage Method X Harvest Season Study
Split - split plot - 4 replications
1 grass species Tifton 85 Cynodon spp.
5 N rates (NH4NO3) - 0, 39.2, 78.4, 117.6, 156.8 kg N
ha-1 per cutting (randomized complete block design )
2 Storage Methods - Oven dry @ 60ºC, Ensiled2 Harvest Dates - 6/30/97, 9/22/97
Wilting time was reduced on 9/22/97, resulting in wetter silages
Protein Components MeasuredLicitra et al., 1996
Kjeldahl - N (Crude Protein)
Trichloroacetic acid insoluble -N (TCAIN)
Borate - phosphate buffer insoluble - N (BPIN)
Neutral detergent insoluble - N (NDIN)
Acid detergent insoluble -N (ADIN)
Ona, FL 1997 N Rate Study Total N % in Tifton 85 Bermudagrass
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 39 78 117 156
N Fertilization Rate (kg/ ha /cutting)
N (
% o
f D
M)
.
6/30/97 - Oven Dry
9/22/97 - Oven Dry
6/30/97 - Silage
9/22/97 - Silage
Ona, FL 1997 N Rate StudySummation of N Fractions
6/30/97 Oven Dry
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 39 78 117 156
N Fertilization Rate (kg/ ha/ cutting)
Nit
rog
en
(%
of
DM
)
.
NPN
Peptides
Intermediate
NDIN-ADIN
ADIN
Ona, FL 1997 N Rate StudySummation of N Fractions
6/30/97 Silage
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 39 78 117 156
N Fertilization Rate (kg/ ha/ cutting)
Nit
rog
en
(%
of
DM
)
.
NPN
Peptides
Intermediate
NDIN-ADIN
ADIN
15
25
35
45
55
65
75
0 39 78 117 156
N Fert. Rate (kg/ ha /cutting)
N (
% o
f T
ota
l N
) .
6/30/97 - Oven Dry
9/22/97 - Oven Dry
6/30/97 - Silage
9/22/97 - Silage
Ona, FL 1997 N Rate StudyNPN (A) as a % of Total N
Silage pHDate Mean SE9/22/97 5.16 0.147
6/30/97 4.46 0.036
Ona, FL 1997 N Rate StudyPeptide (Cell Contents) (B1) N - % of Total N
0
10
20
30
40
50
60
0 39 78 117 156
N Fertilization Rate (kg/ ha /cutting)
N (
% o
f T
ota
l N
) .
6/30/97 - Oven Dry
9/22/97 - Oven Dry
6/30/97 - Silage
9/22/97 - Silage
Ona, FL 1997 N Rate StudyIntermediate Degradable (B2) N - % of Total N
0
10
20
30
40
50
60
0 39 78 117 156
N Fertilization Rate (kg/ ha /cutting)
N (
% o
f T
ota
l N
) .
6/30/97 - Oven Dry
9/22/97 - Oven Dry
6/30/97 - Silage
9/22/97 - Silage
Ona, FL 1997 N Rate StudyDegradable Cell Wall (B3) N - % of Total N
0
10
20
30
40
50
60
0 39 78 117 156
N Fertilization Rate (kg/ ha /cutting)
N (
% o
f T
ota
l N
) .
6/30/97 - Oven Dry
9/22/97 - Oven Dry
6/30/97 - Silage
9/22/97 - Silage
Ona, FL 1997 N Rate StudyUnavailable Cell Wall (C) N (ADIN) - % of Total N
0
10
20
30
40
50
60
0 39 78 117 156
N Fertilization Rate (kg/ ha /cutting)
N (
% o
f T
ota
l N
) .
6/30/97 - Oven Dry
9/22/97 - Oven Dry
6/30/97 - Silage
9/22/97 - Silage
ConclusionsN Fertilization
Total N concentration increased with increased N fertilization.
All N fractions increased in concentration (of DM) with increased N fertilization.
NPN (% of Total N) increased with increased N fertilization.
All other N fractions decreased as a proportion of total N.
ConclusionsEnsiling
Total N concentration was slightly lower in the silages.
NPN concentration increased with ensiling.
All other N fractions decreased except ADIN which was not changed.
ConclusionsHarvest Date
Harvest date had a significant effect on all components measured.
Likely that the large differences in silage moisture levels masked any seasonal effects on the silage. (The 9/22/97 silages were wetter than the 6/30/97 silages due to less wilting time)
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