Cut and carry

Published 20 June 14

Making the most of grass: DairyCo undertakes new research into the value of grass for high yielding cows

Last month has seen the start of an exciting new research project at SRUC Dumfries, under the DairyCo Grassland, Forage and Soils Research Partnership. The project is part of a two-year programme of work between both of the DairyCo Research Partnerships to evaluate the value of fresh grass in the diet of high yielding dairy cows. DairyCo research and development manager, Dr Debbie McConnell outlines why the study is taking place and talks to lead researcher Dr Mark Lee, SRUC.

The role of grass in high milk production systems

This year we have again seen that feed and forage costs remain the largest driver of profitability in GB dairy production systems. In 2012-2013 the DairyCo Milkbench+ report highlighted an average spend of 10.3ppl on feed and forage costs, an increase of over 1ppl on average compared to 2011-2012. Significant variation in milk from forage production between farms was also evident, averaging 1,521 litres/cow/year but spanning a variation of over 3,000 litres/cow/year.

Coupled with this, we face future fluctuations in the availability and cost of bought-in feedstuffs and we are also tasked with sourcing a sustainable feedstock for our dairy sector. As part of this, the dairy industry will be challenged to reduce its reliance on potential human-edible feeds such as cereals, consequently this will encourage us to maximise the role of home-grown forages such as grass (which are non-edible by humans) in dairy production systems.

Within GB we are well placed to meet these challenges, as the majority of dairy farms are located in areas with significant potential for grass production. However, although work has indicated that grazed systems remain a comparatively low cost feeding option for dairy cows, we know that the supply of fresh grass alone is insufficient to support optimal dry matter intake and, consequently, milk production in high yielding dairy cows while maintaining acceptable forage utilisation targets. Hence, we are tasked with identifying novel strategies which maximise the benefits of fresh grass as a lower-cost feeding option, while maintaining suitable production levels in these systems.

Cut and carry systems

One novel strategy for the inclusion of grass in the diet of high yielding cows is that of cut and carry or ‘zero-grazing’ systems. This involves the frequent (typically daily) cutting of fresh grass and carting to cows (usually but not exclusively housed). These systems offer a number of perceived benefits and challenges as highlighted by responses to a recent DairyCo survey (see table below).   

Table 1: Top 3 benefits and challenges to cut and carry systems highlighted by farmers in a recent DairyCo survey

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From our survey, it is also clear that farmers were undertaking cut and carry systems due to difficulty in accessing grazing or to improve forage quality (Figure 1 below). When considering grass management, the majority of respondents cut one-day’s feeding requirement of grass at a time and managed their grass in a 3-4 week rotation. Grass was cut in the morning and fed to cows within a few hours of cutting. When feeding, a range in chop lengths and inclusion rates were used (25-100% of forage DM). However, the majority of respondents highlighted that more research needs to be done to provide information on optimum feeding strategies for these systems.

Figure 1: Reasons why farmers chose to use cut and carry systems

Zero grazing 1

The information collected in this study has now been used to advise our latest research trial – the effect of increasing the proportion of fresh grass in the diet of the high yielding cow on animal performance and behaviour, forage utilisation and economics.

Cut and carry systems provide an excellent platform for solely evaluating the nutritional value of fresh grass to meet the demand of high yielding dairy cows as this does not include the actual physical demands of a grazing situation (eg energy expenditure associated with walking, grazing, etc).

When we asked survey respondents about research requirements for these systems, a large number highlighted that they would like further advice on optimum feeding strategies for fresh grass.

Research trial

Forty-eight cows have been split into three groups of 16 and allocated to one of three treatments for the course of a 16-week study. All cows averaged 45+ litres/day at the start of the study.

“Very simply, we have three groups of cows in the study – a control group which receives 100% of its dry matter (DM) intake as total mixed ration, a group receiving 25% of their DM intake as fresh grass in their diet and 75% TMR and, lastly, another group with 50% of the diet as fresh grass and 50% as TMR,” explains Dr Mark Lee, Researcher at SRUC.

Figure 2: The study comprises cows fed as a percentage of the dry matter content of the diet either (from left to right): 100% TMR, 75% TMR - 25% Grass or 50% TMR - 50% Grass.

 

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“Although we recognise that many farmers choose to offer fresh grass separately from the TMR ration, for the purpose of the experiment we have mixed the grass in with the TMR in the diet feeder,” explains Mark. This has been done to make sure the animals are eating the right proportions of grass and TMR.

“To allow this to be done with minimal damage and mulching of the grass, we add the grass to the diet feeder once the ration has been mixed, removing the knives. This has proved particularly important on days of low dry matter content in the grass.”

Figure 3: Grass is added to the ration at the end of the mixing process to ensure forage quality is maintained.

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The study measures a number of different variables over its duration. “Milk yields and cow weights within the three groups are monitored three times per day, collecting a huge amount of data relating to all the cows. We are also looking at group and individual feed intake data and monitoring animal behaviour to assess how much time they are spending feeding, resting and ruminating, compared within the different treatments,” Mark continues.

“Anecdotally, we’ve noticed that at the start of the experiment when we had quite low dry matter contents in the grass, it appeared that the group that has the 50% ration seems to be spending more time feeding than the group of 25% ration cows. In turn, they seem to spend more time feeding that the TMR group. That might be the extra time that is needed in order to get the amount of dry matter intake that they are requiring to maintain their yields. That is something which will obviously change over the course of the season and may impact on milk production,” Mark explained.

Figure 4: Cows on the 50:50 grass – TMR diet receiving their daily allowance.

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This project study will continue through the season until September. If you would like any more information on this or any other research projects, please contact Dr Debbie McConnell on 024 7647 8704.