The above information is completely useless, even if true. “Cattle must only eat the top 30% or 50% of grass plants” is the recommendation coming from people with classroom theory trying to counter the inevitable drop in body condition when cattle are forced to graze non-selectively (harvest efficiently / increase stocking rate / maximise profit). This statement can only become reality once cattle are trained or bred to do so.
I see the facts as:
- All animals will graze individual plants selectively. They may graze 50% of the total material if management allows it with some plants utilised fully and others left untouched. This is selective grazing and apart from poor harvest efficiency results in an increase in less palatable species.
- When a grass plant is fully utilised regrowth will initially be from root reserves. Continuous regrazing (overgrazing) will result in a decline in grass vigour. If done selectively it will result in very poor species composition.
- Veld (pasture) degradation is due to selective overgrazing at low animal impact.
- Grazing of plants is as old as time and has many benefits to plants and soil if the relationship between grass and grazers is symbiotic.
- Overgrazing of many of the palatable grass species has been occurring in nature over millennia due to the presence of territorial grazers. Therefore certain grasses are tolerant of overgrazing (strong root system / root reserves). However, these grasses also require better growing conditions (soil fertility, soil aeration, moisture) which accompany high animal impact.
- Certain of the more potentially product grasses are tolerant of overgrazing provided it is done non-selectively and at high animal impact.
- One management option to address body condition at critical times is to shorten the recovery period (better nutrition). There are no long term negative consequences IF grazing is non-selective, at high impact and grasses are allowed full recovery at some stage.
Shown below is a palatable grass plant that has been increasing in vigour and size with 7 years of dry season overgrazing by antelope in between doses of high impact non-selective grazing by cattle.
There is a lot of classroom theory being propagated by people who are not observing what is happening out on the land.
We need to observe and make common sense decisions.