Effect of Nitrogen Fertilization on the Amounts and Proportions of Protein Fractions in Tifton 85 Be

1
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
2
Objectives
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)
3
Nitrogen 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
4
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 _at_ 60ºC, Ensiled
• 2 Harvest Dates - 6/30/97, 9/22/97
• Wilting time was reduced on 9/22/97, resulting in
  wetter silages

5
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)

6
Ona, FL 1997 N Rate Study Total N in Tifton 85
Bermudagrass
7
Ona, FL 1997 N Rate StudySummation of N Fractions
6/30/97 Oven Dry
8
Ona, FL 1997 N Rate StudySummation of N Fractions
6/30/97 Silage
9
Ona, 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
10
Ona, FL 1997 N Rate StudyPeptide (Cell Contents)
(B1) N - of Total N
11
Ona, FL 1997 N Rate StudyIntermediate Degradable
(B2) N - of Total N
12
Ona, FL 1997 N Rate StudyDegradable Cell Wall
(B3) N - of Total N
13
Ona, FL 1997 N Rate StudyUnavailable Cell Wall
(C) N (ADIN) - of Total N
14
Conclusions

• 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.

15
Conclusions

• 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.

16
Conclusions

• 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)