Title: Effect of Nitrogen Fertilization on the Amounts and Proportions of Protein Fractions in Tifton 85 Be
1Effect 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
2Objectives
It 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)
3Nitrogen Fractions for ModelsRationale for
Partitioning
Rate of Digestion in the rumen
kdgtkp
NPN
Soluble Protein
175 - 300/h kd gt kp
Peptides
Cell Contents
5 - 12/h kd kp
NDFCP
0.15 - 2/h kd lt kp
NDF
Cell Wall
ADF
0/h kd 0
ADFCP
kd rate of digestion, kp rate of passage
graphic by M.B. Hall, 1996
4Experimental 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 _at_ 60ºC, Ensiled
- 2 Harvest Dates - 6/30/97, 9/22/97
- Wilting time was reduced on 9/22/97, resulting in
wetter silages
5Protein 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)
6Ona, FL 1997 N Rate Study Total N in Tifton 85
Bermudagrass
7Ona, FL 1997 N Rate StudySummation of N Fractions
6/30/97 Oven Dry
8Ona, FL 1997 N Rate StudySummation of N Fractions
6/30/97 Silage
9Ona, FL 1997 N Rate StudyNPN (A) as a of Total
N
Silage pH Date Mean SE 9/22/97 5.16
0.147 6/30/97 4.46 0.036
10Ona, FL 1997 N Rate StudyPeptide (Cell Contents)
(B1) N - of Total N
11Ona, FL 1997 N Rate StudyIntermediate Degradable
(B2) N - of Total N
12Ona, FL 1997 N Rate StudyDegradable Cell Wall
(B3) N - of Total N
13Ona, FL 1997 N Rate StudyUnavailable Cell Wall
(C) N (ADIN) - of Total N
14Conclusions
- N 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.
15Conclusions
- Ensiling
- 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.
16Conclusions
- Harvest 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)