Objectives

The overall objective of this project is to conduct a targeted series of research studies which will address knowledge gaps related to the production and utilisation of high quality grass silage in dairy cow diets.  This will be achieved through desk based exercises, grass plot and ensilage studies, and dairy cow feeding studies, thus achieving a holistic approach to the research programme.  Specifically, the objectives can be defined as follows:

  1. Through a short survey prior to the commencement of the project, to identify barriers to improving silage quality within Northern Ireland.
  2. Through an interrogation of the Hillsborough Feeding Information System (HFIS) data base, to identify trends in the composition of silages produced within NI over the last 15 years, and where possible, reasons for the trends. This aspect of the project will also quantify the frequency of production of very high dry matter silages, which may in itself highlight the need to undertake additional research to examine the efficiency with which these silages are utilised.
  3. Through a series of plot and ensilage studies, to identify, i) the impact of ‘winter growth’ on silage composition and fermentation characteristics, ii) the interaction of nitrogen fertiliser type  and nitrogen uptake rates over the growing season, on herbage composition and ensilability, iii) the impact of harvesting interval on the total yield of utilisable nutrients harvested over the growing season.
  4. Through a series of dairy cow feeding studies, to examine, i) the impact on cow performance of ‘winter growth herbage’ when harvested and ensiled for the production of first cut silage, ii) the impact of very high quality silage on cow performance and nutrient utilisation, and strategies to mitigate against any detrimental effects, iii) the effects on cow performance of offering herbage fresh (zero grazing) vs offering the same herbage ensiled, v) the production response of high yielding dairy cows to very high quality silages across a range of concentrate levels, and optimum concentrate strategies with very high quality silage.
  5. Through this large ‘programme based’ research project, to raise awareness of issues related to grass silage quality on NI dairy farms, cumulating in a silage open day and the publication of a silage manual.
Dr Conrad Ferris

Research Provider: AFBI

Project Lead: Conrad Ferris

Project Team: David Patterson, Debbie Hynes, Tianhai Yan, Alan Gordon

Start Date: 1st April 2018

End Date: 31st March 2022

Co-Funding: DAERA (Evidence & Innovation Strategy)

Background

Making more use of forage in livestock diets has been identified as a key object of the sustainable Land Use Management Strategy.  While ‘alternative’ forages such as whole crop silage and maize silage are included in dairy cows diets to a limited extent in Northern Ireland (NI), grass silage remains the predominant forage within the diets of housed dairy cows.  In addition, while silage feeding was previously largely confined to the ‘winter period’, an increasing proportion of cows in NI are now housed either all year, or for increasing parts of the year.  Consequently, the reliance on grass silage is increasing.  Furthermore, while historically the focus on most farms (and most research programmes) was the production of high quality first cut silage, the increasingly confined nature of our production systems means that all silage harvests (1st, 2nd, 3rd and even 4th) make important contributions to the diets of our dairy herds. While the increasing importance of silage in dairy cow diets cannot be denied, there has not been a focused silage research programme within NI for approximately 15 years.  Recognising the importance of grass silage to the NI dairy sector, this proposal seeks to develop a targeted research programme to address a number of recently identified knowledge gaps relating to the production of high quality grass silage, throughout the whole growing season, and the utilisation of high quality grass silage in the diets of high yielding dairy cows. The programme is also set within the context of increasing environmental pressures with regards both water and air quality, and recognises that making more use of quality locally produced forages has the potential to reduce concentrate usage on farms, and as a consequence P imports in concentrates, thus aligning the work with the Land Use Management Strategy for Northern Ireland.

While high quality silage offers real opportunities to cut down on the use of expensive concentrate feeds, high quality silage can be difficult to make, especially in latter cuts, and can create challenges when being offered.  For example, issues that need to be considered when making high quality silage include the impact of winter carry over grass on silage quality, optimum fertiliser N levels for multi cut silage systems to minimise fermentation problems, optimum cutting stage especially in relation to rate of fall in digestibility over the growing season, and the impact of wilting on feed efficiency. In addition, many farmers have concerns about the inclusion of high quality silage in dairy cow diets.  For example, high quality silage offered with high levels of concentrate can result in milk fat depression and increase the risk of sub-acute acidosis.  In addition, earlier research examining the response of dairy cows to silages of different qualities involved cows with maximum milk yields of approximately 32 kg/cow/day, while average winter milk yields of 35 – 40 kg are now commonplace.  The impact of silage quality on the response of cows to concentrates at these higher milk yields is largely unknown, not just at a cow level, but at a system level.  In particular, there is anecdotal evidence that even when high levels of concentrate intakes can be achieved with forage based diets, there is an increased risk of greater levels of body tissue loss with higher yielding cows. If this is true, then fertility may be negatively impacted, and cow welfare impinged.  Furthermore, with an increasing move to zero grazing type systems, it is still unclear if similar cow performance can be achieved by offering the same quality of grass either ensiled vs fresh, thus avoiding the need for daily harvesting.

In addressing these issues, the project has potential to help increase efficiency in production systems, while greatly increasing the awareness of the potential and limitations of high quality silage in dairy cow diets. The premise of this project is that high quality silage can and should play an increasing role in dairy cows diets in Northern Ireland, and that AFBI research can help overcome some of the barriers to its adoption.   This will advance the overall achievement of producing more milk from forage i.e. grass and grass silage.

 

Existing Knowledge

As already highlighted, Northern Ireland has not had a focused grass silage research programme in place for approximately 15 years.  Similarly, few other UK research institutes are currently conducting research into grass silage.  With the exception of the Scandinavian countries, most of which do not use perennial ryegrass, few other European countries have specific grass silage research programmes.  Consequently, much of the information presented in this review is at least 15 years old.

With regard to silage composition in Northern Ireland, a brief review of the composition of silages analysed within the HFIS laboratory over the last decade was recently undertaken by Yan et al. (2017a and b).  In general, DM concentrations have tended to increase, crude protein levels have fallen, and metabolisable energy (ME) concentrations have remained relatively unchanged.  However, this review did not involve an in depth analysis of geographical trends in silage composition, or make any attempt to explain the trends observed. 

Many previous studies have examined the impact of field wilting on dairy cow performance, including several studies conducted at AFBI (Gordon and Peoples, 1986: Yan et al., 1998).  In general, the results of these studies have demonstrated that when grass is subject to rapid wilting, intake is increased and milk yields normally improve.  However, the impact on energy use efficiency is less clear, with Gordon et al. (2000), in one of the few studies examining this issue using cows in respiration calorimeters, finding energy use efficiency to decrease with increasing degree of wilting.  However, in a separate analysis, Wright et al. (2000) found no reduction in the efficiency of milk production with wilting.

The adverse impact of excessive nitrate levels in herbage on ensilage characteristics is well known, and farmers understand that the crop must be left to mature sufficiently for ‘nitrate levels to fall’.  While this is generally not an issues within a two or three cut system, this can become more challenging when crops are harvested at a less mature stage. In reality there is little information on the rate of uptake of nitrogen (N) by growing crops or the rate of dilution of N (and fall in nitrate levels) in the growing crop at different stages of the growing season.  While many studies have examined the response to fertiliser N in terms of DM yield most studies simply look at the ‘end point’ (ie at harvest) in terms of herbage N composition, rather than providing information on interim changes taking place within the growing crop or the impact on the ensilability of the grass.  However, there is evidence that N levels in herbage tend to increase (at a fixed regrowth interval) as the season progresses (Binnie et al., 1997). From an environmental perspective there is increasing awareness of ammonia emissions from agriculture. The 'Making Ammonia Visible' report (January 2018) stated that 91% of all ammonia emissions in NI come from agriculture. The report recommends the use of treated or stabilised urea fertilisers which are less vulnerable to volatilisation and de-nitrification (releasing ammonia) when spread and recommends farmers switch from CAN-type nitrogen (which is also vulnerable to de-nitrification) to stabilised urea, with the use of straight urea fertiliser to be banned from 2020.

While many studies have examined the response of dairy cows when offered grass silage based diets, research on the performance of dairy cows offered very high quality grass silage diets has received little attention:

With growing herd sizes (difficult to graze large herds in the autumn), and an increasing number of herds housed full time, autumn grazing has become less important on many farms.  This is especially true following harvest of third cut silage, which often takes place on land blocks some distance from the farm, and which cannot be easily grazed by dairy cows. As a consequence, herbage which grows following third harvest may remain un-grazed over the winter and is ultimately ensiled with first cut herbage.   While a number of studies in the Ireland (for example, Hennessy et al. 2006) have examined the impact of autumn/winter growth (focusing on closing date) on the yield and quality of herbage available for grazing in the spring, the impact of this herbage on silage quality and subsequent cow performance does not appear to have been examined previously. While it is recognised that strategies exist by which this herbage can be removed (for example grazing by sheep and/or young stock), on many farms these strategies are not adopted. Evidence of the impact of this winter herbage on subsequent silage quality many help change these practices.

The impact of declining silage digestibility on cow performance is well known, with a review by Gordon (1989) concluding that, on average, a 10 g/kg reduction in D value resulted in a reduction in milk yield of 0.37 kg/cow/day.  In addition, a number of other studies have demonstrated the decline in digestibility with maturity, with for example, Givens et al. (1989) observing a mean decrease of 2.5 g/kg per day with each day decline in digestibility.  However, this study (which involved samples from farms), like most other studies focused on first cut silage, and did not examine changes in digestibility of grass pre ear emergence.  In addition, as already highlighted, as cows are increasingly housed for significant parts of the ‘summer’, if not year round, the quality of silage produced during all harvests is important.  However, there is surprisingly little work available on changes in digestibility during subsequent harvests, or indeed on the overall impact of harvesting frequency on total yield of utilisable nutrients (not just dry matter).  The latter is important as while farmers are aware that more frequent harvests may reduce total DM production over the season, the impact on the yield of utilisable nutrients is less well understood. 

The popularity of zero grazing within NI has increased during recent years, and AFBI is currently conducting a research programme into the practice (E&I, 15/01/06).  Indeed, early outcomes of this research programme have highlighted that confined cows offered zero grazed grass can outperform confined cows offered grass silage based diets (Debbie McConnell, unpublished).  However, in these studies, the silage offered, while of good quality, was made from a sward with a very different digestibility than the zero grazed grass offered.  The question has however been asked, that if similar quality of grass as used within zero grazing systems was ensiled and offered, would performance differ from that achieved with zero grazed grass offered directly.  A previous AFBI study by Cushnahan and Mayne (1995) provided some insight to this, and demonstrated that fresh grass and silage from the same sward could have similar nutritive value when offered to dairy cows. However, this study involved herbage of a much lower digestibility than typically used while zero grazing.

While the benefits of high quality silage are well known, some farmers feel that very high quality silage will have such a high rate of passage through the rumen that it will be poorly utilised.  To address this, straw is often included in dairy cow diets, thus improving the quantity of effective fibre in the diet, but reducing overall diet quality.  This was examined in an earlier AFBI study by Ferris et al. (2000), with few beneficial effects of straw inclusion observed. However this study involved moderate yielding cows offered moderate concentrate levels.  The impact of concentrate type on the utilisation of very high quality silages does not appear to have been examined.

The role and potential of very high quality silage in the diets of high yielding dairy cows is also poorly understood as most studies with these cows seek to maximise performance through concentrate supplementation. Understanding the response of dairy cows to concentrate supplementation is essential to ensure cows are correctly fed. However, silage quality is one of the key determinants of the intake and milk yield response of cows to concentrate feeding.  This was examined previously by Ferris et al. (2001) with moderate yielding cows.  The results of this study demonstrated that as concentrate level increased, the difference in performance between cows offered a high and moderate quality silage was substantially reduced.  However, the maximum milk yields in this study, even at the highest concentrate levels, were approximately 33 kg/cow/day, considerably lower than typical average milk yields of higher yielding herds today.  This is reflected in the data which is used to provide the response to concentrate supplementation within the equations behind the Hillsborough Feeding and Information System (HFIS) at present, and which suggest that irrespective of silage quality, milk yields converge at a concentrate level of approximately 17 kg/cow/day, and a milk yield of approximately 35 kg/cow/day (Figure 1).  Understanding the responses of today’s higher yielding cows when offered diets comprising high quality silage is essential, as is being able to demonstrate the concentrate sparing effects of high quality silage with high yielding cows.  Indeed, there is a perception that irrespective how good the quality of silage is, when cows are offered predominantly forage based diets, body condition score will suffer.  There is indeed some evidence to support this suggestion, with cows on high forage systems generally having a lower condition score than those on higher concentrate systems, despite similar levels of milk output (Ferris et al., 2003). However, once again these studies involved lower yielding cows, compared to those on many farms today. 

Figure 1 Modelled response to concentrate supplementation with a low, medium and high quality grass silage (as contained within HFIS)
Figure 1 Modelled response to concentrate supplementation with a low, medium and high quality grass silage (as contained within HFIS)

The project team recognise that while a significant amount of scientific literature exists, most of this is not readily available to dairy farmers, or is certainly not available in one location.  In addition, given the 15 year absence of a focused grass silage research programme in NI, there has been an ‘erosion of independent expertise’ in relation to the science of silage making.  Given the continuing and increasing importance of grass silage to the local dairy sector, the project team believe that there is a need to collate research knowledge into a ‘farmer friendly’ book/technical guide for NI dairy (and other ruminant livestock) farmers. This is planned as a key output from this project, and will incorporate the findings of this project, as well as previously published research in a way which presents key facts for farmers.  It is proposed that this book/technical guide will be launched at a ‘silage open day’ at the close of this project.

 

Additional information that the project will provide

This project recognises that a significant amount of scientific literature already exists in relation to making and feeding grass silage. However, the project team, in consultation with CAFRE and Industry representatives, have identified a number of important knowledge gaps, especially in relation to high quality silage for high yielding dairy cows, which this project will seek to address.  Through a desk based exercise, the project will begin by providing an accurate assessment of changes in the quality of silage produced in NI over the last 15 – 20 years, and attempt to provide an insight to these changes. This aspect of the project will also identify the frequency of very high DM silages produced in NI.  If this is significant, then consideration will be given to identifying if there is evidence that these higher DM silages have a lower utilisation efficiency that lower DM silages.  This could either involve a desk based exercise, or a feeding study.

Plot and mini silo studies will seek to quantify changes in nitrate, and nitrogen concentrations in herbage throughout the growing season, and use this to improve the recommendations on N fertiliser used for silage swards so as to minimise the risk of adverse fermentation and reduce denitrification (ammonia loss).  Further plot and mini silo studies will seek to quantify how silage digestibility declines throughout the growing season and quantify the total yield of digestible nutrients from multi cut silage systems.

Plot and mini silo studies will seek to quantify changes in nitrate and nitrogen concentrations in herbage throughout the growing season, and use this to improve the recommendations on N application rates for silage swards so as to minimise the risk of adverse fermentation.  Additional plot and mini silo studies will seek to quantify how silage digestibility declines, especially pre-ear emergence, and throughout the growing season, rather than focusing mainly on primary growth herbage. 

A series of dairy cow studies will seek to address issues which will help improve utilisation of silage, and especially very high quality silage.  For example, the impact of straw inclusion and concentrate type offered as a supplement to very high quality grass silage will be examined, an important issue given that some farmers feel that high quality silage is simply utilised inefficiently by dairy cows, and as such not worth making.  In addition, the impact of feeding silage ‘contaminated’ with herbage which grows during the autumn/winter will be examined.  Results will allow advice to be given on whether it is better that this autumn/winter herbage in removed either in the autumn or the following spring, or if it can be left for inclusion within the silage with adverse effects on cow performance.  This cow study will be associated with detailed plot and ensilage studies.  Given the increasing interest in and uptake of zero grazing, the project will seek to clarify if similar cow performance could be obtained by ensiling the herbage on a single day, rather cutting and offering fresh herbage daily throughout the summer.

The project will also examine the response of higher yielding dairy cows to concentrate supplementation, across a range of silage qualities, thus providing information not currently available for these much higher yielding cows.  This information will then be used to update the response curves within the HFIS, thus allowing a more accurate prediction of the likely intake and responses to a range of silage qualities for the NI dairy sector.  This project will also seek to demonstrate the potential of very high quality silages in the diets of high yielding dairy cows, and clarify if these inevitably result in excessive body tissue loss.  These latter studies will involve offering silage made within a ‘systems’ approach, and the performance levels will be expressed, not just on a cow basis, but per ha basis.

Finally, the project will seek to collate scientific literature which is not readily available to dairy farmers, into a ‘farmer friendly’ book/technical guide for NI dairy (and other ruminant livestock) farmers. This is planned as a key output from this project, and will incorporate the findings of this project, as well as previously published research in a simple, concise and easily usable reference manual.

Scientific Objectives & Tasks

Objective Tasks required to achieve objective Milestones (target date of achievement)

Understanding silage quality in Northern Ireland

To conduct a short survey of NI dairy farmers, to understand key factors limiting improvements in silage quality.

AFBI are currently in the process of undertaking a large scale ‘grassland’ survey of the NI dairy sector, with a section of this survey covering broader silage issues.  However, the results of this will not be known until 2019. 

Consequently, Objective 11.1 involves undertaking a short survey which specifically seeks to identify the main factors limiting improvements in silage quality on NI dairy farms.  The survey will be conducted on the 24th and 25 January 2018 (prior to this project commencing) at two dairy Open Days that will be held at CAFRE - Greenmount College Dairy Centre.  The target is to survey approximately 100 farmers.

One of the issues that will be addressed within this survey is the extent to which current contractor costing systems (ie charge per ha/acre) impact on silage quality.  If this is identified as being a significant issue, then AFBI will explore with CAFRE what information/research is required to develop alternative costing systems (ie yield based systems). Should the development of an alternative costing mechanism require a research component, a CRF will be developed following discussions with DAERA leads to broaden the remit of this project.

March 2019
To identify trends in the quality of silage made in Northern Ireland over the last 15 - 20 years by interrogating the Hillsborough Feeding Information System (HFIS) data base.

Over the last two decades, several thousand grass silage samples from commercial farms in Northern Ireland have been analysed every year in the analytical laboratory of the Agri-Food and Biosciences Institute using the Hillsborough Feeding Information System (HFIS).

This task will involve analysing data from this data set to examine: 1) long term trends in silage composition in NI, 2) an evaluation of the effects of ensiling year/ensiling season and other parameters (e.g., weather conditions, long term fertiliser use) on silage nutritive quality.

In addition, the HFIS data base will be analysed to identify the proportion of very high DM silages that are made within NI each year.  This is important as there is anecdotal evidence that these high DM silages are used inefficiently.  The original proposal submitted September 17 (in section 11.2) had proposed research to further investigate this issue.  However, that aspect of the research has been removed from this proposal, but may be reconsidered (subject to a CRF) once the frequency of very high DM silages is known.

January 2019
Grass growth and ensilage studies
To examine the impact of fertiliser N type at different stages of the growing season on rate of N uptake by the grass plant (weekly uptake) over a seven week growing period, herbage yield, herbage composition and ensilability. The objective is to develop improved fertiliser recommendations for the production of high quality silage. This plot study will be conducted over two successive years. This study will be conducted on four occasions over the growing season (starting mid March, mid May, late June and mid August).  On each occasion plots will be treated with either CAN or stabilised fertiliser N at appropriate rates based on RB209 Recommendations, and allowed to grow for a 5 - 7 week period.  Plots will be destructively harvested at a series of time intervals, i.e. at 2, 3, 4, 5, 6 and 7 weeks post fertiliser application. As well as yield and routine herbage analysis, the proportion of applied fertiliser which has been taken up by the grass plant (less that released from the soil) will be estimated, together with the buffering and nitrate content of the herbage.  *The herbage harvested at the end of each growing period will be ensiled in mini silos to examine the impact of N parameters on fermentation characteristics.  Preparation of a scientific paper (2 years).  

February 2019 (Year 1)

April 2020 (Year 2)

To examine the impact of herbage which grows during the late autumn/winter period on the yield and quality of first cut silage This replicated plot study will be conducted over two successive years. Following harvest of third cut silage in autumn, swards will be managed in one of three ways, as follows: 1) no further harvesting until the following spring, 2) autumn growth herbage removed after 5 weeks (likely mid October), 3) autumn growth herbage removed after 8 weeks (likely early November).  Yield and quality of herbage removed will be quantified.

 May 2019 (Year 1)

May 2020 (Year 2)

   In early May all plots will be harvested, and yield recorded, and herbage samples dissected for live/dead proportions.  Herbage from the different treatment plots will be ensiled in pipe silos for an 80 day period.  In-silo losses and herbage quality will be assessed at opening.

 August 2019 (Year 1)

August 2020 (Year 2)

Effect of harvesting interval on the total yield of utilisable nutrients

This five treatment study will seek to examine the impact of a number of harvest intervals on the total yield of utilisable nutrients over the entire growing season.  In early Spring (mid-March) a sward will be trimmed off to remove any autumn/winter growth herbage, and a series of replicated plots established.  The effect of silage harvest interval (30, 36, 45, 60 and 90 days, representing 6, 5, 4, 3 and 2 harvests/year) on the total yield of utilisable nutrients will be assessed over a 180 day period (until mid September).  This represents a total of 20 individual harvests over the season.  Total fertiliser N inputs over the season will be the same with each of the five harvesting interval treatments, with fertiliser applications based on RB209 recommendations for the respective cutting intervals.

 

When each plot is harvested the growth stage of the herbage will be defined, yield will be measured and the chemical composition of the herbage determined.  Herbage will then be ensiled (most likely using big bales/box silos).  ‘Silos’ will be opened after an 80 day ensilage period, the silage thoroughly mixed, and sufficient quantities bagged up for use in sheep digestibility studies. This will also provide an opportunity to compare the NIRS composition of the herbage as ensiled (especially ME) vs that of silage removed

December 2020 (Year 1)

December 2021 (Year 2)

 

The digestibility of each silage will be determined using sheep confined in digestibility crates (4 - 5 sheep per silage).  Digestibility measurements will be undertaken over a 21 day period with each silage.  The impact of harvesting interval on total yield of nutrients harvested, in-silo losses, silage composition, and the yield of utilisable nutrients recovered (digestible nutrients and metabolisable nutrients) will be determined. A scientific paper will be prepared.

March 2022

Main dairy cow feeding studies

Establishment of field blocks to produce multi harvest vs three harvest silage over a three year period. A block of land will be identified and fields divided for use in a multi-harvest vs three harvest silage production system over three successive years.  April 2018
  Protocols in relation to fertiliser N levels, slurry management, harvesting rules, and ensilage techniques will be developed. April 2019
  Herbage will be harvested off each of these land blocks according to either multi-cut or three cut silage principles for 2 - 3 successive years.  Yields will be recorded at each harvest, and the impact on sward composition monitored. September 2018
  The digestibility of silage removed at each harvest will be determine using sheep, thus providing information on yields of utilisable nutrients, and providing a link to 11.6 above. March 2019

Main dairy cow Study 1 – Response of high yielding dairy cows offered silages of two different qualities to a range of concentrate feed levels (Winter 18/19)

This will involve feeding silages made within the fields described above.

 

Establish study with freshly calved Winter calving high PLI dairy cows (60 per silage) and monitor performance (milk production, milk composition, body tissue changes, blood metabolites, energy status, and cow health and fertility) over the first 150 days of lactation

 April 2019
 

Collate and analyse data from the experiment, summarise findings and make recommendations.

Identify concentrate saving effects associated with offering very high quality silages across a range of concentrate intakes.  Identify break even concentrate feed levels. Prepare scientific paper.

 November 2019

Main Dairy cow Study 2 – Examination of the short and long term effects of including average and very high quality silage (all harvests of both silage types) in the diet of freshly calved dairy cows (2 x 2 factorial design involving two concentrate feed levels and two silage qualities) (Winter 19/20)

This will involve feeding silages made within the fields described above.

 

Establish study with freshly calved Winter calving high PLI dairy cows (60 per silage, 60 per concentrate level) and monitor performance (milk production, milk composition, body tissue changes, blood metabolites, energy status, and cow health and fertility) over the first 180 days of lactation (8 months).  The study will have a particular focus on energy status and tissue changes.

June 2020
 

Collate and analyse data from the experiment, summarise findings and make recommendations.  Prepare scientific paper.

November 2020

Subsidiary dairy cow feeding studies

To examine the impact of concentrate type and straw inclusion with a very high quality silage (12.3 MJ/kg DM) on cow performance (especially milk fat content) and on nutrient utilisation. A very high quality silage (ME = 12.3 MJ/kg DM) was produced during Summer 2017.  This silage will be offered to 24 dairy cows during spring 2018 in a three period (period length, 28 days) change over design experiment, comprising four treatments.  Treatments will be arranged in a 2 x 2 factorial design, comprising two concentrate types (conventional concentrate vs  a high fibre concentrate) and two levels of straw inclusion in the diet (zero and 1.5 kg/cow/day).  A high concentrate inclusion level (12 – 14 kg/cow/day) will be adopted. August 2018
  Data will be collated, statistically analysed, and the impact of management strategy on cow performance, especially milk fat content, examined. A scientific paper will be produced. January 2019

To examine the impact of herbage which grows during late autumn/early winter on the performance of cows offered silage made from primary growth herbage.

Swards will be managed in the autumn so as to achieve three levels of late autumn/early winter growth herbage in the sward the following spring.  This is likely to entail three different management strategies following harvest of third cut silage, namely 1) no further regrowth herbage removed that season, 2) regrowth herbage removed after 5 weeks regrowth (likely mid October), 3) regrowth herbage removed after 8 weeks regrowth (likely early November).  November 2018
  The three swards established during the previous autumn will be harvested on a single date during the following spring, and ensiled in separate silos.  The proportion of dead and living material in the swards will be quantified at harvest, together with herbage yield.  May 2019
  After herbage has been ensiled for approximately 12 weeks, herbages will be offered to 16 dairy cows in a three period change-over design experiment.  Effects of autumn/winter growth material on subsequent cow performance will be examined. October 2019
  Data will be collated, statistically analysed, and the impact of autumn/winter growth on cow performance quantified. A scientific paper will be produced. April 2020
To examine the impact of ensiling herbage at an immature stage, compared to offering the same herbage fresh, on cow performance and nutrient utilisation.

The study will involve 30 dairy cows in a continuous design experiment. Cows will range in calving dates over a 2 month period.

Commencing mid-May, 15 of the earliest calving cows will be managed on a zero grazing regime for 12 weeks (fresh grass harvested daily using a ‘zero grazer’) with concentrates offered at a fixed level). 

 

Twice each week during this period the same quality of grass will be ensiled in big bales (target dry matter content of 25%), and stored for a 6 week period.  This will then be offered to the latest calving cows on the study over a 12 week period.
August 2020
 

Collate and analyse data from the experiment, summarise findings and make recommendations.

 

Prepare scientific paper.

April 2021

Practical guide to making and feeding grass silage

To prepare a book/technical guide for distribution to all dairy farmers in Northern outlining best practices in relation to making and feeding grass silage to dairy cows (based on research findings from this and earlier AFBI research programmes). Collate necessary information in a booklet format, have it proof read, and printed. March 2022

 Benefits / Outcomes

There has not been a focused silage research programme in NI for approximately 15 years.  Given that approximately 50% of forage offered to dairy cows is grass silage, the importance of re-establishing a grass silage research programme is high.  Thus one of the key benefits of this research programme will be for AFBI researchers to begin once again to focus on grass silage within our research programmes, and engage more closely with CAFRE and Industry on silage related needs, and to raise the profile and the potential of grass silage once again.  It is planned that this will cumulate in a ‘silage open day’ and the launch of a silage manual at the end of the programme.   

The overall objective is to establish a research programme that will lead to improvements in the quality of silage produced within NI.  The main benefit of the production of high quality silage will be a reduction in total concentrate usage on dairy farms. Based on the fact that this project tackles the winter feeding period when approximately 60% of concentrates are offered, a conservative estimate is that the project has the potential to reduce concentrate feed levels by 180 kg/cow/year on farms where the outcomes are adopted (approximately 1 kg/cow/day).  This is based on the review by Gordon et al. (1989) that a 10 g/kg reduction in D value would reduce milk yield by 0.37 kg/cow/day.  Assuming the reverse, that a 30 g/kg increase in D value will increase milk yield by 1.1 kg/day, and assuming a response rate of approximately 1 : 1, this would result in a concentrate saving of approximately 1 kg/day.

Assuming a concentrate cost of £260/t, and a saving of 180 kg/cow, this results in a cost saving of £46.8/cow.  However, reduced concentrate intakes will result in increased forage intakes.  Costing grass silage at £100/t DM, and assuming an extra 180 kg of forage DM is consumed (1: 1 substitution rate at higher concentrate levels), the cost of extra forage is £18/cow year.  Thus the net benefit is £28.8/cow/year.

With a dairy cow population in Northern Ireland of approximately 300, 000 cows, and assuming a 10% uptake of the full range of knowledge generated, 30, 000 cows will benefit from the research. It is of course recognised that no one farmer is likely to adopt all outcomes, but rather individual farmers would adopt components of the outcomes most appropriate to their own farm, and as such assuming this low adoption level (10%) for the full range of technologies is appropriate for this economic analysis (while in reality a higher adoption level of individual technologies is more likely in practice).

Thus if 30,000 cows (10%) are assumed to gain a benefit of £28.8/cow/year, the total benefit of the project in a single year is likely to be £864,000.

The total cost to DAERA of this project is £2.2 m.  Within three years, using these modest assumptions, the investment in this project will be paid back and over a 10 year period the cost : benefit ratio is over almost 3.

The project also has the potential to contribute to significant, although more difficult to quantify environmental benefits in terms of reduced ammonia and P emissions from dairy systems.  Section 11.3 seeks to quantify the impact of stabilised forms of urea fertiliser, the use of which have been recommended in the 'Making Ammonia Visible' report (January 2018), on herbage ensilability. In addition, making better use of forage has the potential to reduce concentrate inputs, with a subsequent reduction in phosphorus imports onto farms.