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Effect of Nitrogen Fertilization on Protein Fractions in Tifton 85 Bermudagrass

This study investigates the impact of nitrogen fertilization on the amounts and proportions of protein fractions in Tifton 85 Bermudagrass. The goal is to provide insights for accurately balancing ruminant rations using computer models. The study also examines the effects of ensiling and harvest season.

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Effect of Nitrogen Fertilization on Protein Fractions in Tifton 85 Bermudagrass

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  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 ¥ kd¥>kp NPN Soluble Protein 175 - 300%/h kd > kp Peptides Cell Contents 5 - 12%/h kd » kp NDFCP 0.15 - 2%/h kd < 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 @ 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 StudyTotal 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)

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