Genetic improvement of perennial ryegrass and white clover to increase the efficiency of nitrogen use in the rumen

Project number:                    74303

Lead contractors:                 IBERS

Partners:                                   LINK: LK0687

DairyCo, EBLEX, HCC, QMS, LMC, BGS

Start & end date:                   April 2008 to March 2013

Actual end date:                    April 2013

 

The Problem:

Ruminant animals make a significant contribution to agricultural losses of nitrogenous compounds through their excreta both in terms of losses to air as ammonia and nitrous oxide and to groundwater as nitrates. There is considerable evidence that losses of N can be reduced by increasing the efficiency of rumen processes.

 

Project Aims:

  • Using marker assisted selection based approaches to develop a range of perennial ryegrass varieties with enhancement of WSC levels 8% beyond that seen in material currently available to farmers.
  • Development and field evaluation of white clover (WC) varieties with 5-10% reduction in leaf protein content
  • Carrying out an experiment with dairy cows that will test combinations of WSC: protein dietary ratios at levels of WSC made possible by germplasm development in this programme.

 

Approach:

A recurrent selection programme will be used to identify new QTLs for NUE.  Elite populations of forages will be established combining NUE QTL and other desirable agronomic traits.  Seed will be produced from subsequent potential varieties to undergo field testing.

 

Results:

Develop a range of perennial ryegrass varieties with enhancement of WSC levels 8% beyond that seen in material currently available to farmers

AberWolf (Ba14074 – int. dip.), the first variety produced during the project was Nationally Listed in England and Wales on the 12th February 2013. AberWolf has demonstrated exceptional performance during its three years of NL trials and has out-performed all other new entrants in the 2009 and 2010 sowing years for yield, D-value and persistence under both silage and grazing conditions. It is anticipated it will successfully enter the Recommended List for 2014/15 in England and Wales.

Three varieties from the project are currently in NL trials. In order of entry these are: Ba14087 (int. dip.), Ba14088 (late dip.) and Ba14124 (late dip.).  Two intermediate heading top-cross tetraploid selections have been chosen for seed production leading to phase 1 entry in Autumn 2013.

Under testing the best new varieties increased WSC content by 15% compared to existing varieties and DM yield rose by 12%.

 

Development and field evaluation of white clover varieties with 5-10% reduction in leaf protein content

The background variation in protein content within the white clover gene pools was measured and was found to be greater than anticipated. Crosses were then made between low protein genotypes, culminating in the synthesis of the variety a low protein variety Ac4835. This variety was trialled in plots over four years to confirm that no difference in dry matter yield of the clover and companion grass was observed when compared to existing varieties and the normal protein control. Quality analysis showed a general reduction in protein content compared to the three benchmark varieties. Ac4835 was also trialled in nutrient flow solution to measure the rate of nitrogen fixation. The results of this trial concluded that Ac4835 fixed a comparable quantity of nitrogen compared to control varieties.

Ac4835 was entered into National List Trials in England and Wales, during the sowing year 2013.

 

Test combinations of WSC: protein dietary ratios at levels of WSC in dairy cows

Two animal experiments were carried out in the summer of 2012. The first, compared AberWolf and Premium ryegrass varieties when fed to lactating dairy cows (n = 4 per treatment) in a straight-through design experiment. Ad libitum feed intakes, milk yields, milk composition, diet digestibility and whole-body N partitioning measurements were carried out. Preliminary results indicate that there was no statistically significant difference in the dry matter intakes or milk yields of animals consuming the two treatments. Similarly, there was no significant difference in the daily rates of urine N excretion between treatments.

The second experiment was completed in September. The treatments comprised the same two ryegrass varieties, each mixed with low protein white clover in a ratio of 70:30. Measurements were the same as for the first experiment. As for the first experiment, there were no significant difference in milk yields or urine N excretion, although the inclusion of white clover in the diet led to much higher rates of N output in urine than was found in the first experiment. In this experiment, AberWolf-fed cows ate approximately 0.5 kg DM per day more than control cows (P < 0.05), although this did not translate to changes in milk yields. Whole-tract diet digestibility was not significantly affected by treatment, with a grand mean of approximately 0.76 g/g across all treatments.

Due to the adverse weather conditions during 2012, the animal study was be repeated as part of the EU Multisward project in 2013. The data from this study will be made available to project partners and Defra by spring 2014.

 

Planned activity:

  • General messages about variety selection and new variety availability with novel traits is included in grassland management KT events and material.
  • Press releases have been completed as have various KT articles. Messages were communicated at Grass and Muck event in 2012 and further activity is planned for the Grass and Muck event in 2014 (biennial event).
  • A number of academic publications have been published in international journals from this work.