Why manage grazing? That’s a question often asked of us. We then wax lyrical about all of the benefits and yet we see little of it taking place across the country. This week we will take a deeper look at the benefits of rotational grazing. Table 1 was prepared by Rhidian Jones when he worked with SAC Consulting.

Increase utilisation

One of the key reasons for managing grazing is to increase the utilisation of grass. As can be seen from table 1, grazing livestock on a traditional, set stocking system will yield around 8.5t DM/ha. Unfortunately due to the way stock graze, over the course of the season some of the grass becomes stemmy and less palatable. This is especially the case in the dung and urine patches that animals tend to leave as the season moves on.

Changing from set stocking to rotational grazing means having a plan to move stock around a small number of paddocks. This may simply be a larger field split in to two or three sections, or indeed moving a larger group of stock through several fields with no divisions. This increases the yield of grass by 20% to just over 10t. The increase comes from the rest period that the grass gets between grazings.

As we often discuss, grazed grass needs to be kept in a vegetative state throughout the growing season and the key is to keep it from going beyond the three-leaf stage. At the other end of the scale, set stocking means that animals continually graze the younger, sweeter leaves and leave those that have gone beyond the three-leaf stage. Slowly, but surely, the area of grass going to seed increases as the season goes by. This is why utilisation increases from 50% to 65% in the move from set stocking to rotational grazing.

The combined factors of the increased growth and utilisation lead to total grass utilisation 56% better than under a set stocking system. This extra growth requires no extra fertiliser and indeed in the case of larger groups of stock moving around whole fields, requires no extra infrastructure either.

Effectively, barring a few extra minutes of stock handling one to two times per week, this is over a 50% increase in grass growth for free.

Many do not see the potential in this and yet if someone was to walk into the yard tomorrow morning and offer an extra 1.25t/ac of barley (on a standard 2.5t/ac yield) for only a few extra minutes of work over the season, most would jump at the chance.

If the fields were to be sub-divided further again and managed in a tighter one to three day per paddock rotation, the benefits are seen on line three of Table 1. Again, the management of the grass growth from above applies, thus the actual yield does not change. However, the move to a more intensive grazing management style also means better distribution of the dung and urine patches, and more opportunity to remove excess growth as silage.

This is where the further increase in utilisation comes from, with it increasing by 60% over set stocking systems to 85%. This sees 8.2t DM utilised, a whopping 92%. This is equivalent to our barley crop above going from 2.5t/ac up to 4.8t/ac for an investment of slightly more time and the cost of a bit more infrastructure.

Increase the energy level of grass

Managing grass to prevent it from going beyond the three-leaf stage will also lead to a higher energy level in the grass grazed. If we look at our systems above and taking a 10% increase in grass energy levels, we are looking at a potential increase in energy supply to livestock of around 70% rotational grazing and 110% in paddock grazing. What does this really mean?

Taking our three scenarios from table 2, and assuming that we are grazing 350-400kg store cattle on the grass, we are looking at a potential increase of liveweight gained per hectare of 870kg under rotational grazing and 1,350kg under paddock grazing. At an average liveweight value of £2.25/kg, this demonstrates a potential increase in output of £1,956 under the rotational grazing system and £3,038 under the paddock grazing system. A significant improvement.

Using a 12ha (square) field that is 600m long and 200 m wide, set up for cattle as an example, what are the potential costs that we face?

In order to establish a simple, four-paddock, loose rotational system the field would be split in half in both directions. This can be done with a single electric wire, but for the purposes of this exercise will use a two-wire fence. Fence requirements are shown in table 3.

This is a simple calculation and doesn’t include the smaller pieces, such as staples. However, at a rough cost of around £1,200 for the materials, it is not expensive. This is equivalent to £100/ha.

There will also be the requirement for at least one extra water trough, if not two. If we add in two water troughs, pipework and fittings at a cost of £600. This comes in at £50/ha. Adding it up, water and fencing add a cost of £150/ha to the field. Even if we were to charge a further £150/ha to install all of the above, it still leaves a potential benefit of £1,656/ha under the rotational system and £2,738 under the paddock system. Of course, as temporary grazing leys are generally down for four to five years, we can spread our £300/ha over that time, meaning an even greater payback on the investment. Or to put it another way, all you need to pay back the cost of the infrastructure investment is £60/ha/year, equivalent to an extra 27kg of liveweight gain per hectare. In other words, on our 12ha field, you only need to be able to carry an extra two cattle on it for the grazing season to pay the extra costs.

Some may say that they can’t afford to do it, we would ask, can you afford not to?

Next week we look at how each of the six focus farms have adapted some form of rotational grazing to suit their systems.