Well, we’re in full swing with grazing dairy replacement heifers from a local Mennonite dairyman. So far we’ve managed to graze approximately 13 acres with 30 cows. That might seem like a small amount for so many cows, but what I’m employing is a technique called “mob grazing”  – it’s essentially a replica of the American buffalo/wolf relationship that created the amazingly fertile prairies and plains of the American Mid-West, and the guinsbuck/lion, cheetah, hyena, predator relationship of the vast African savannas/grasslands. What I do is concentrate the animals in a “mob”, or relatively tight group hemmed in by electric fence (the electric fence is the predator) for a short time, usually one day or even half a day. The metric that I use to evaluate success is both subjective and objective. The objective metric is “liveweight per acre” — the number of cows and their corresponding weights added up and divided by the number of acres that they graze for any length of time (in my case each graze area is less than an acre – a lot less).  With mob grazing, a high liveweight per acre number is considered good. The higher the better.

The subjective metric is actually a eyeball evaluation of the condition of the cows. It seems obvious to animal raisers that making animals graze close together could result in lower selectivity (the amount of forage available to the animal at any given point in time). This would be true but if the animals were left in the small grazing area too long — but the idea is to move them often and in high group numbers, thus giving them a high selectivity. The component that is often overlooked and almost immediately rejected by conventional farmers and ranchers is the labor involved in moving cows and electric fence so often — this is key, and it is a cost that must be included in the evaluation of the enterprise.

The idea of mob grazing is to trample at least half of the available forage on the ground and eat approximately the other half. This is accomplished by long narrow sections of strips – encouraging the cows to move up and down. The reason for the desire for trampling grass is that grass becomes food for soil microbes. That soil life will take the “organic matter” and decompose it, increasing biological soil life, increasing fertility, and literally over time creating more topsoil. The trampling effect also has another benefit in that the sharp hooves of the cows concentrated in an area “plant seeds”. There are literally billions of seeds, grass seeds, in the soil already — why spend money for more seed?

This approach to grazing and utilization of animals is on the leading edge of farm sustainability.  With the right genetics, the right rest period for the plants and high-density grazing, farms can recreate topsoil that has been eroded away due to questionable cultivation practices or inadequate grazing management at an extremely low cost.

Filed under: Animals, Grazing/Pasture, Organic Dairy on July 5th, 2010