Making a moo-ve on spring grass

Researchers at Teagasc highlight how utilising grazed grass during the spring can make farmers more sustainable and profitable.

Spring is an important time for Irish pasture-based dairy farms – cows have begun to calve, and paddocks that have been closed over winter are ready for grazing.

This spring, almost 40% more cows will calve compared to spring 2012, and as a result will require additional grass on farm. More cows grazing at the same time can result in an increased feed demand on farms, so it’s important that grazing management adapts to ensure grazed grass is maximised in the cow’s diet and the number of days spent at grass is increased.

Increasing the number of days cows have access to grass over the grazing season can also improve sustainability, as it reduces the need for alternative feed sources such as concentrate and grass silage. This is important because paddocks have greater herbage quality (minerals essential to animal health) than silage. Having more grazing days also reduces the amount of slurry (a natural fertiliser made from cow manure and water) created. Finally, it can increase animal production, which benefits profitability.

Taking action in autumn to benefit in spring

Research at Teagasc focused on meeting the greater feed demand in spring by increasing the amount of grass available on farms, by altering autumn closing date and spring grazing rotation. Spring and autumn have been identified as the most difficult times for grazing management on farms. This is because soil temperatures are reduced and therefore impact growth rates, and ground conditions are more challenging. 

Results show that carrying a bank of grass over winter for grazing in the spring successfully increased the amount of herbage available. That’s because the amount of grass available in spring is closely linked to that available at the time of closing in autumn, and can account for 50% of the variability in herbage.

However, this can have varying impacts on the production of tillers (shoots) of perennial ryegrass, depending on the level of herbage on individual paddocks. Perennial ryegrass tillers are continuously producing new leaves, some have had leaves die, some have produced daughter tillers (new shoots), and some have died over winter. This is all part of the natural tiller production cycle; however, tiller death can increase if heavy covers are left on paddocks over a long period of time, so targeted earlier grazing is vital to reduce this negative impact.

Managing paddock recovery

In early spring, paddocks that have carried greater amounts of grass over winter have increased levels of shading, resulting in increased tiller death and dead tissue in the paddock. The reduced number of tillers seen can impact the growth rate of paddocks after they are grazed in spring. An increased amount of dead material in paddocks also reduces the sward quality, which can impact animal production.

While it sounds negative, this impact on paddocks is a necessary compromise to have enough grass for the herd in spring. But there is a key step that can be taken to help paddock recovery.

Beginning on-farm grazing in early February will increase grass utilisation and help the recovery of swards. This is because grazing removes shading and allows light in to the tillers, which helps to promote the growth of new green leaves and the rapid production of daughter tillers.

The growth experienced after grazing allows these paddocks to then be available for the second rotation of grazing, beginning in early April. This is particularly beneficial in swards that accumulate higher herbage masses over winter, as shading and tiller death can be reduced.

Optimum grazing management

Grazing paddocks provide cows with grass that is extremely digestible and high in crude protein. All paddocks, irrespective of their closing date in autumn, have greater herbage quality than grass silage. Increasing the proportion of grazed grass in the diet of early lactation cows can result in greater milk production, compared with cows with greater amounts of silage in their diet.

The focus for dairy farms in the spring should therefore be on utilising the grass carried over from winter, by allowing cows to begin grazing as soon as possible in February, targeting paddocks with heavier herbage masses first and following grazing targets.  

1.4kg

Cows that have benefitted from an increased proportion of grazed grass in their diet during early lactation can produce up to 1.4kg more milk each day.

Funding

This project is funded by Teagasc’s Walsh Scholarship Programme and Dairy Research Ireland.

Contributors

Caitlin Looney
Teagasc Walsh Scholar – Grassland Research Science Department
Teagasc Animal & Grassland Research and Innovation Centre, Moorepark, Co. Cork.

Michael Egan
Research Officer – Grassland Research Science Department
Teagasc Animal & Grassland Research and Innovation Centre, Moorepark, Co. Cork.
michael.egan@teagasc.ie