At this stage in the year, ryegrass is beginning to head out. Also, growth rate has been excellent over the past two weeks, meaning that pre-grazing yields have increased. Both of these factors have meant that there is more stem in swards.

Paddocks that were poorly grazed out because of wet weather in the first, second or even third rounds are the worst offenders. The problem with stem is that it is high in lignin which is a woody, fibrous structure that gives the stem strength to grow tall and sturdy.

Remember, all the grass plant wants to do at this time of year is grow big and tall to capture as much sunlight as possible in order to support a big seed-head.

Stem

As farmers, we want to prevent as much stem as possible because it reduces grass quality and cows prefer grazing lush, leafy grass. Furthermore, a high proportion of stem in a sward reduces growth rate.

Even on the best-run farms, stem will win out in the battle for grass quality and some corrective action will be necessary to reduce the effect of stem.

The traditional approach has been to top paddocks after grazing. While this will have benefits with improved quality in subsequent grazing swards, many farmers get topping wrong, thereby reducing its benefits and actually making things worse.

Topping too late after cows have come out of a paddock will cut regrowths. This will have a negative effect on subsequent growth as all of the plant’s energy goes into growing a shoot. Killing this seriously depletes the plant's energy reserves. This is why you usually see a reduction in growth after doing a lot of topping.

So topping too late after cows exit the field is a big issue. The other issue is topping too high. Topping is labour-intensive, so if you are going to do it, you may as well do it right. The ideal topping height is less than 4.5cm. All dungpads should be cut to this height or lower. Too often, we see farmers topping too high and not cleaning out dungpads properly.

Alternative to topping

An alternative to topping is to pre-mow paddocks in front of cows. This overcomes the problem of wasting grass by topping fields and letting the cut grass rot away.

The big problem with pre-mowing is that by cutting grass in front of cows you remove the cow’s ability to select the nice grass for herself.

So if there is a lot of stem in a paddock, the cow will eat this stem whereas if she was grazing the field without any cutting she would select the leaf and leave behind the stem.

As a result, you might see a reduction in performance if cows graze a pre-mowed field that was poor quality.

However, on the plus side, the dry matter of pre-mowed grass is usually higher than a standing crop so grass dry matter intakes often increase when grazing pre-mowed paddocks. Basically, cows can eat more grass and produce more milk. This is a good thing when high-quality grass is plentiful but you need to be careful if doing a lot of pre-mowing that growth rates don’t drop or grass becomes scarce because more of it is eaten.