Steps for Sizing Paddocks
1. Determine forage availability for land used as pasture.
This can be done by two methods: first estimating past hay yields. A yield of 5 tons per acre per year converts to 2,000 lbs dry matter (DM) per grazing rotation. The rotations would have a 15-day rest period between grazing in early spring, gradually increasing to 30 days in the summer. Yet at each grazing there would be 2,000 lbs DM/acre.
The other method is to use an online calculator developed by Cornell University and online at www.forages.org. It uses location and soil type to set DM production and then with information entered concerning animal and grass type it provides DM production and requirement.
2. Determine forage requirement: the number and size of the animals grazing and the residency of time in the paddock.
- 50 heifers weighing an average of 600 lbs = 30,000 lbs of animals
- The estimate of DM consumption is 3% of body weight or 900 lbs of forage required per day
- A grazing efficiency of 60% would be appropriate for dairy heifers newly introduced to grazing leaving 40% of the forage in the paddock
50 heifers x 600 lbs = 30,000 lb. animal weight x .03 DM intake = 900 lbs DM requirement x 60% grazing efficiency = 1,500 lb DM need from pasture per day
For a 2 day residency, 3,000 lbs of forage would be required. Using the information of forage availability from above: 2.5 acres of pasture producing 3 ton of DM of hay per year would be required.
Shade or No Shade?
It is recommended to keep shade out of paddocks. This benefits two aspects of grazing management. First, many studies have shown that shade in a pasture reduces the amount of the animals’ grazing time. Secondly, animals concentrate manure and urine in shaded areas. Removing shade helps manage nutrient cycling for pasture soils.
If shade is needed on days of high humidity or temperatures above 90 degrees F, two solutions would be to allow animals to go into a barn with good ventilation or into a fenced-in shaded area. Both of these solutions only need to be used for no more than 4-6 hours on the worst days. Grazing animals will make up for lost grazing time in the evening and at night.
The Northeast Sustainable Agriculture Research and Education program (SARE) provided funding for this fact sheet series.
Fay Benson is a Dairy Support Specialist with Cornell University Cooperative Extension of Cortland County.
Sam Leadley, Ph.D., P.A.S., is the Calf and Heifer Management consultant with Attica Veterinary Associates, Attica, NY.