Hi John,
Mowing after grazing is a common short-term solution, but it certainly won't help keep your production costs low. unless it is a very serious amount, it will also simply get trampled next time your pasture rotation comes through. It is hard to offer an opinion why they are only grazing the heads without actually seeing the pasture, but it sounds like the grass has already gone to seed, so that the nutrients have largely been depleted in the stalk and leaves and have been redirected into the head for seed production - that's where the calories are now - the rest has just turned to
straw.
If you have a lot of grass that is going to seed, it is a sign that your pasture rotation needs some fine-tuning. The number one goal of the summer pasture rotation is to make the loop of your pastures fast
enough so that you prevent the grass from going to seed, but slow enough that you don't graze your grass too short on any pass (minimum 6-10% during the growing season). Too short and growth takes a long time to recover because the
roots die back too much and it also exposes the soil to too much sun, which accelerates moisture loss from the soil. As you can see, there is a huge amount of leeway between too slow and too fast. At peak growth rates, you may simply be top-grazing your pastures, just a quick graze to trim it so it doesn't go to head, before rushing on to the next bit of grass. Then as growth slows, you slow down the rotation and graze more thoroughly to you don't catch up to yourself.
This slightly oversimplified description illustrates how the grass is not just there for the cattle, but that the
cattle in your pasture rotation are in fact your primary pasture management tool.
If your pastures are overstocked, your rotation will catch up to itself, you'll start re-grazing grass again too soon, but if you are under-stocked, then your rotation has no hope of keeping up with managing the grass and you'll have to either make hay or silage, or mow afterwards, which is a poor use of your valuable forage. If you already anticipate being unable to keep up with the grass, then you could temporarily reduce the size of your pasture rotation and set aside one area to make some hay - at least then the excess grass can still be turned into something of value instead of costing you mowing time and fuel without getting anything back in return.
The grazing timing in your pasture rotation is such an important part of your farming strategy - with huge potential cost savings and/or production increases possible when you learn the right balance, that rather than trying to explain in a hurry, I encourage you to go through the
daily pasture rotation article series which explains all this in detail, with some good diagrams. The
Grass and Grazing chapter of my book also goes into even greater detail explaining the fundamental principles at the core of how you set up your pasture rotation.
And also read the articles about the
winter pasture rotation to see how your pasture rotation should change the moment your growing season ends - the two are very different, despite both using the same electric
fence grid - which is why I advocate
broad permanent electric fence corridors that can be subdivided by temporary portable electric cross-fences, this gives you the flexibility to have huge daily grazing slices during the summer when grass is growing quickly, and then ration out the winter grazing reserve with tiny grazing slices once the growing season ends.
Good luck in your detective work to figure out how to tweak your pasture rotation to avoid this problem of overly mature grass!
