The average Irish dairy farm only utilises about 7.5t DM/ha per year. Given that Irish agriculture prides itself on its ability to grow grass, our average utilisation figures should be better, and initiatives like the Teagasc Grass 10 Programme aims to increase this utilisation figure to 10t DM/ha per year. The main reasons for such low utilisation figures are grass type, grass management and inappropriate stocking rates.
Every extra ton of DM utilised could be worth €181/ha through increased output and reduced production costs.
A reseeding programme based on the best modern perennial ryegrass varieties will increase the amount of grass utilised on-farm through greater production of high-quality forage compared to older swards with low perennial ryegrass content.
Thanks to the Pasture Profit Index (PPI), it is easy to select the best grass varieties based on their Grazing Utilisation, Quality and Seasonal Growth (Link to PPI article), but these varieties still need to be managed well to maximise utilisation.
The foundations for a successful grazing season are laid during the first couple of rotations. Good grass management at this time will ensure top-quality grass throughout the grazing season, maximising grass utilisation and profitability.
Best practice management is based on using pre- and post-grazing sward height as indicators of when to begin/stop grazing a paddock.
Grazing covers of 1,200-1,400kg DM/ha down to 4cm residuals results in optimum utilisation of quality grass.
If we consider a grass plant, its life cycle can be divided into two distinct stages: the vegetative and reproductive. In the vegetative stage, the plant consists primarily of highly digestible leaves rich in protein and energy.
The perennial ryegrass plant will only ever have three living leaves at any one time. Once a fourth leaf appears, the first leaf will die, and the plant will enter the reproductive stage. During reproduction, the plant begins to lignify and produce a to ugh stem that will eventually support a seedhead. During this stage yield will greatly increase, but this comes at a significant cost in quality.
It is especially important to hit the 4cm post-grazing target in the first couple of rotations
Once once this tough material is allowed to develop due to lax grazing, its effect on quality will get progressively worse in each subsequent rotation. This will seriously impact grass utilisation throughout the grazing season resulting in more topping and wasted forage.
The aim is to balance yield and quality and utilise as much grass as possible through grazing. The second part is key, particularly in spring, to encourage the regrowth of leafy material in subsequent rotations.
When the 4cm residual target is missed in early rotations, stemmy and dead material begins to develop, gradually reducing sward quality as the grazing season progresses