Spring is here - She'll Harvest for You

If you look out your window you will notice that there is a new color out there, green.  Spring has finally arrived in New England and do you know what that means for farmers?  First, crop season is upon them, so farmers need to prepare the ground and plant seeds.  It also means that grazing season for their animals will be here soon.  Last but certainly not least, spring means that they soon get to feed themselves. 

Cow's grazing. Photo credit Trevor Beaudry

Cow's grazing. Photo credit Trevor Beaudry

So, how does grazing work?  As a farmer, your strategy depends on the time you want to put in to grazing your animals and the production you want to get out of the fields.  If you have plenty of land and not too many animals, you can get away with just putting up fence around the area you want to graze and setting the animals free on it.  If you want to get the most productivity out of your land, while ensuring your animals get the best quality feed, you should implement a practice known as rotational grazing

With rotational grazing, the basic idea is to get the best production out of your fields while the animals do all the harvesting.  To do this, you split up your pasture into small paddocks that provide enough food for either 12 or 24 hours of grazing for the animals that will be on them.  For best quality and yields, the aim is to have the cows moving into fresh paddocks with heights of 8-12 inches depending on the forage species and leaving the paddocks when the remaining height is 3-4 inches.  This approach both maximizes forage yield and minimizes regrowth times.

Sounds simple enough; just move the animals around and they do the work (well, other than putting up fencing).  The problem is that grass grows at different rates depending on a multitude of factors: time of year, temperature, species, water levels, etc.  Therefore, the most important part of a rotational grazing plan is flexibility.  The ability to adapt and adjust your grazing plan during the grazing season is the key to your plan’s success.  In May and June, during the time known as spring, lush pastures often grow at a rate too fast for animals to keep up with.  It is often beneficial to start grazing when heights are 6 inches to get a head start and prevent parts of the pasture from over maturing which results in too much indigestible fiber in the forage. Remember, the last paddocks won’t be reached for a while and you want to get to them when they are 12 inches high at most.  Some farmers will even harvest a portion of their pasture as hay early in the season to help deal with the spring lush.  Once the summer rolls around and the heat of July and August set in, pasture doesn't regrow as quickly, especially if it is predominantly cool season grasses.  During this time of year, the rotation time usually needs to be expanded to allow proper regrowth.   

With all these variables, it would be a fairly daunting task to just start grazing a herd of cows or sheep without some extra guidance.  For this reason, there are multiple methods of estimating the amount of pasture a certain number of animals would require or the number of animals an area of pasture could support.  Most of these models are based upon animal units or AU’s.  One animal unit is defined as one 1,000 pound dry dairy cow or its equivalent in other animals.  A solid estimation is that an animal will consume 2.5 pounds of dry matter per day (the amount of food after the water has been removed) for every 100 pounds of body weight. Lactating dairy cows tend to consume more; these cows will consume 3 pounds of dry matter per 100 pounds of body weight.  You can then estimate the amount of available dry matter per acre available to you by measuring the grazeable height of your pasture and comparing it to estimated yields based upon species composition.  This calculation helps to determine how large a paddock you will need to feed your animals.

Next time you drive by a pasture with cows or other animals eating lush green grass a couple months into the summer, I hope you have an appreciation for the effort and planning that the farmer put in to ensure that his pasture would produce to its’ potential well into the hot summer months.

And remember, stay hungry. There is a fresh paddock right around the corner.