Grazing Management – the Science of Grass

One of the foundations of a pasture -based organic farm is rotational grazing.  We adopted this management strategy back in the 1980’s when we were still milking cows, and like everyone else were feeding them in confinement.  What that means is that you harvest the feed with machinery and bring it to the animals who are confined in the barn or yard.

How this came to be the dominant pattern of livestock farming is an interesting story.  Here in Ontario, we have winter.  So farmers must grow crops that are stored in barns or bins or silos to sustain their livestock over the winter months.  But from the earliest days of pioneer farming it was normal practice to build fences and let everyone out to graze in summer.  For sure, all the ruminants (cattle, sheep, goats, horses ; species that can digest high fibre forage and thrive on grass alone, as opposed to omnivores like pigs and chickens and people) were out in the field from spring to fall.  The typical 100 acre farm would have as much as 60 acres devoted to growing pasture and hay, some hardwood bush or swamp, and maybe 15 or 20 acres cultivated for corn, spring grains, root crops or vegetables.  This was a sustainable farming unit in the pre-industrial era, before the widespread introduction of fertilizers and pesticides.  Most of the ground was covered year round – growing a mixture of perennial grasses and legumes (nitrogen fixing broadleaf plants like alfalfa and clover) The relatively small herds were housed in traditional bank barns where straw was used for bedding, and the resulting manure employed to fertilize the corn or garden.  There was little soil erosion or danger of manure contaminating surface water.  The cycle of nutrients, while never perfect, was pretty sound, and the life of the animal, on well managed farms, was exemplary.  This pattern of mixed farming, reliant on the draft horse for field power as well as transportation, was practiced for centuries in Europe, practically unchanged from one generation to the next, before being transplanted here by our European ancestors. Unlike today’s agriculture which is absolutely addicted to oil and electricity, it was a system powered exclusively by the sun, through the miracle of photosynthesis, in cooperation with the microcosm of soil life, creating plants to feed animals and people.

The transformation of farming practices started with tractors.  In the 1940’s the first tractors began to replace horses, and by the time I was a little boy in the 1960’s, most farms had abandoned the horse culture of the past.  Field work was now much faster!  While a good man behind the one furrow plow could work 1 acre a day, the new tractor – tiny by today’s standards – could get over the same area in an hour!  Now the farmer had options. More of the farm could be cultivated now that the time consuming horse drawn implements were gone.  During the 1960’s and 70’s farmers were given government grants to pull out fence rows and make bigger fields.  Hybrid corn that would mature in our relatively short growing season was starting to become a big part of the farming picture.

I still remember when my dad built a silo and filled it with corn silage and at the same time gave up pasturing the cows.  The common experience was that if you plowed up those pasture fields and grew corn you could feed a lot more animals. Grazing cattle in the agricultural heartland of Southern Ontario came to be seen as an inefficient use of land; an outdated and wasteful practice. But this shift away from the pasture field happened in ignorance of some very basic facts. 

  1. Grazing is healthy for the animals.  They thrive out in the field and tend to get sick more often when kept in.
  2. Pasture is good for the soil, which is always protected with plants while cultivated fields are prone to erosion. 
  3. Manure is distributed on the pasture field by the animals themselves and maintains soil fertility without the farmer doing anything.  In a barn or yard runoff can pollute groundwater, and expensive energy intensive systems are required to get the manure back out on the land.
  4. A well managed pasture can rival cultivated crops in terms of productivity per acre.

This last point is the one we want to dwell on.  Unfortunately, when comparing a cornfield to a pasture field, most of those early adopters of intensive cultivation had no experience of a well managed pasture field.  This was certainly true in the case of my Dad’s who followed the typical model of grazing at the time.  You let the cows out in a 10 acre field around May 24th and when they ran out of grass you moved them to another 10 acre field. This strategy fails to realize the potential of the pasture field.  The remedy is rotational grazing.  Let me explain.

A field of grass intended for livestock is made up of many different species of plants.  The animals will select the ones they like best and eat them first.  When cattle are released into a big field, they will roam the entire acreage, eating the most succulent plants.  Then when they’ve exhausted the supply of these, they start on others.  After 3 or 4 days, the plants that were eaten on day 1 produce new leaves and these are far more tender and tasty than the bulk of vegetation that is older and coarser, so the animals retrace their steps and instead of cleaning up the leftovers, eat the new shoots.  It reminds you of unsupervised children who would go for dessert first, then be uninterested in the main course.  The problem with this is that those new shoots are needed by the plant to gather energy and replenish the roots.  If they’re snipped off as soon as they emerge, the plant can’t continue to put out more for fear of exhaustion. So the plant goes into defense mode and becomes dormant or it dies.  This is the main fault of continuous grazing, slightly oversimplified.

Rotational grazing, or what is also called “Managed Intensive Grazing”, has really taken off only since the advent of inexpensive, movable electric fencing.  We use this light fencing material to mark off a portion of the field which the herd will consume in 12 hours.  Because they are have to stay in this small area, they must eat everything by evening when the fence will be moved to give them the next portion.  A “back fence” keeps them out of the part they have eaten off yesterday, so that the plants can put out their new leaves, gather energy, replenish root reserves and continue production throughout the growing season.  When an adequate rest period has expired the field can be grazed again without hindering the growth cycle. Because the animals consume all the plants and are not allowed to graze selectively, they have a more balanced ration and avoid both the digestive problems caused by too much lush immature forage,(bloat used to be a big problem) and conversely the nutrient deficiency of over mature plants.

Given adequate moisture and fertility, a well established pasture keeps growing from spring to fall and provides an abundance of high quality forage, while building soil organic matter.  It does require some resources in fencing and time, adding to the daily morning and night duties that go along with animals.  The decision to graze rather than confine also limits the scale of operation that is feasible.  More people are needed and they have a more direct and intimate relationship with the animals.  But we think that is a good thing and we know that most of you agree.  And if you have ever compared cattle or pigs on pasture to those in confinement your senses will surely inform as to which is best.

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