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Deirdre Hennessy

Research Officer - Grassland

Research Interests

  • White clover
  • Grassland management
  • Grazing management
  • Grass physiology
  • Grass growth
  • Grass growth modelling
  • Grass based milk production systems 

Current Projects

  • Profiling milk from grass
  • Incorporating white clover into intensive grass based dairy and sheep production systems
  • PrecisionGrazing: Modelling for increased grazing management precision on Irish grassland farms (externally funded – Dept. Agriculture, Food and the Marine Research Stimulus Fund)


  • Ph.D. in Agricultural Science, The Queens University, Belfast 
  • Bachelor of Agriculture Science, University College Dublin


  • Contract Research Officer, Teagasc, AGRIC, Moorepark, Fermoy, Co. Cork - March 2008 to present
  • Post Doctorial Researcher, Teagasc Moorepark Dairy Production Research Centre, Fermoy, Co. Cork - July 2005 to Feb. 2008
  • Teagasc Walsh Fellow – Sept. 2001 to April 2005 
  • Associate Editor Irish Journal of Agriculture and Food Research – 2015 to Present
  • President of Irish Grassland Association – 2012/2013  

Egan, M, Lynch., M.B. and Hennessy, D. (2017) Including white clover in nitrogen fertilized perennial ryegrass swards: effects on dry matter intake and milk production of spring calving dairy cows. Journal of Agricultural Science, 155: 657–668.

O’Callaghan, T.F., Hennessy, D., McAuliffe, S., Kilcawley, K.N., O’Donovan, M., Dillon, P., Ross R.P. and Stanton, C. (2016) Effect of pasture versus indoor feeding systems on raw milk composition and quality over an entire lactation. Journal of Dairy Science, 99: 9424-9440.

Enriquez-Hidalgo, D., Gilliland, T. and Hennessy, D. (2016) Herbage and nitrogen yields, fixation and transfer by white clover to companion grasses in grazed swards under different rates of nitrogen fertilization. Grass and Forage Science, 71: 559-574.

Wingler, A. and Hennessy, D. (2016) Limitation of Grassland Productivity by Low Temperature and Seasonality of Growth. Frontiers in Plant Science, 7: 1130. doi: 10.3389/fpls.2016.01130

O’Connor, P.J., Minogue, D., Lewis, E., Lynch, M.B. and Hennessy, D. (2016) Applying urine collected from non-lactating dairy cows dosed with dicyandiamide (DCD) to lysimeters and grass plots: effects on nitrous oxide emissions and nitrate leaching, and on herbage production. Journal of Agricultural Science, 154: 674-688.

Beecher, M., Hennessy, D., Boland, T.M., McEvoy, M., O’Donovan, M., Lewis, E. (2015) The variation in morphology of perennial ryegrass cultivars throughout the grazing season and effects on organic matter digestibility. Grass and Forage Science 70, 19-29.

Enriquez-Hidalgo, D., Hennessy, D., Gilliland, T., Egan, M.,  Mee J.F. and Lewis, E. (2014)  Effect of rotationally grazing perennial ryegrass white clover or perennial ryegrass only swards on dairy cow feeding behaviour, rumen characteristics and sward depletion patterns. Livestock Science 169: 48-62.

Enriquez-Hidalgo, D., Gilliland, T., O’Donovan, M., Deighton, M. and Hennessy, D. (2014) The effect of grass white clover swards on herbage production, herbage dry matter intake, enteric methane emissions and milk production of dairy cows. Journal of Dairy Science, 97: 1400 – 1412.

Hurtado-Uria, C., Hennessy, D., Shalloo, L., Schulte, R.P.O. Delaby, L. and O’Connor, D. (2013). Evaluation of three grass growth models to predict grass growth in Ireland. Journal of Agricultural Science, 151, 91-104.

Ryan, W., Hennessy, D., Boland, T.M. and Shalloo, L. (2012) The effect of grazing season length on nitrogen utilisation, efficiency and nitrogen balance in spring calving dairy production systems. Journal of Agricultural Science, 150: 630-643


  • Stephen McAuliffe
  • Jack McDonnell
  • MaryAnne Hurley