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

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 )

Nitrogen Fractions for Models Rationale for Partitioning ADFCP Peptides NDFCP NPN  kd  kp %/h kd > kp %/h kd < kp 0%/h kd = 0 Soluble Protein %/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 (NH 4 NO 3 ) - 0, 39.2, 78.4, 117.6, kg N ha -1 per cutting (randomized complete block design )  2 Storage Methods - Oven 60ºC, Ensiled  2 Harvest Dates - 6/30/97, 9/22/97 Wilting time was reduced on 9/22/97, resulting in wetter silages

Protein Components Measured Licitra 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

Ona, FL 1997 N Rate Study Summation of N Fractions 6/30/97 Oven Dry

Ona, FL 1997 N Rate Study Summation of N Fractions 6/30/97 Silage

Ona, FL 1997 N Rate Study NPN (A) as a % of Total N Silage pH Date Mean SE 9/22/ /30/

Ona, FL 1997 N Rate Study Peptide (Cell Contents) (B1) N - % of Total N

Ona, FL 1997 N Rate Study Intermediate Degradable (B2) N - % of Total N

Ona, FL 1997 N Rate Study Degradable Cell Wall (B3) N - % of Total N

Ona, FL 1997 N Rate Study Unavailable Cell Wall (C) N (ADIN) - % of Total N

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.

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.

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)