Interactive Tools

Some Notes On Using This Calculator:

Unlike the paddock calculators of the Pasture Management workbook, utilization rates should be higher to minimize waste while still leaving sufficient residue behind to be incorporated into the soil in the spring.

Swath Grazing Calculation Guidelines:

Utilization rates will vary with swath size and snow cover. Taller, narrower swaths have better utilization rates than flatter, wider swaths. Taller swaths are easier for animals to access through the snow than flatter ones. The more snow there is on the ground, the lower the utilization rates. Animals have greater difficulty accessing the swaths beneath a heavy layer of snow, and will trample and manure on much of the swath.

Make sure to anticipate high snowfall when determining utilization rate for swath grazing.

The table below gives you ballpark guidelines on what to expect for forage yield for swath grazing. Some compare the yield tonnage for silage and apply it to swath grazing, however it’s best to expect 20% to 30% reduction in yield with harvest losses in leaving it in the swath until it’s time for grazing. Plants are typically swathed at a lower maturity than for silage as well. 

Corn Grazing Calculation Guidelines:

Animals always tend to select for, in order of palatability and preference selection, cobs, leaves, and stems. They will clean the field of cobs first before considering eating the leaves, in other words, and will turn to the stems when they have eaten as much of the leaves as they could find.

Cobs are not only the tastiest part of the corn plant (and contain the highest protein and energy available), but it’s also the least fibrous and most digestible. Leaves follow second with lower nutritional value and higher lignin/cellulose content, and stems last with the lowest nutritional value of all plant parts and high lignin/cellulose content.

Animals that are allowed a large paddock where they can stay longer than 3 or 5 days risk getting digestive upset (worse case: acidosis) after focusing mainly on cobs the first few days before turning to the more fibrous part of the plants after. Their poop will get loose (diarrhetic) during those first days, then harden up into stacked piles by the time it’s time to move them to the next paddock.

This pendulum swing in nutrition can be hard on them (and result in some sick animals, in a worse-case scenario), thus make sure animals are staying in smaller paddocks where they cannot stay for longer than 3 to 4 days (2 to 3 days is ideal). When they are in smaller areas they are competing more with each other and forcing themselves to eat the leaves and stems sooner, or balance out the amount of cobs versus stems and leaves they consume during the duration they’re in that paddock.

Utilization rates, therefore, depend on how much you want them to “clean up” or leave as little waste behind. Lower utilization rates  = leave more stems behind; higher utilization rates = “forcing” them to consume a bit of those corn stems before being moved to the next paddock.

The table below helps you decide on what utilization rate to use in corn grazing. It is also handy for swath grazing.

More Notes for Both:

The cow-days per acre calculation gives you a good idea of how many animal units (one 1000 lb cow with or without a calf consuming around 25 lb/day in dry matter forage) one acre of swath or corn grazing can support in one day, factoring in your proposed utilization rate.

Finally, the built-in conversion of imperial tons (not metric tonnes) allows you to easily work with what you have on hand to give you an answer as to how to utilize it. (Remember: 1 US ton = 0.907185 tonnes)

A Note About the Field Size Version of This Calculator:

The Field Size Needed calculator is meant to be a planning calculator, used before implementing what part of the crop or field you want to put in as swath grazing. There you can plug in the projected tonnage values according to the crop you intend to use, and adjust utilization rate and days per paddock values to accomodate for the herd (or flock) size you have that you want to do some winter grazing with.

Nine times out of ten, though, you may find you’re more likely to use the first calculator of the number of animals you need to graze, since many factors influence crop yield and the actual time you will have your herd or flock to spend grazing in the winter as opposed to winter feeding.