Grazing in Michiana
Since our cows are out year-round, as the pasture begins to grow in the spring they start to graze a bit and we gradually reduce the amount of feed at the bunk. This strategy allows the cow's digestive system to adjust to the new pasture without a lot of transition issues. The goal is to figure out how fast the grass is growing and to utilize that growth each day.
When the grass starts growing, we begin taking weekly measurements of the grass. We want to turn in to a pasture at 2,800-3,000 pounds dry matter (8-10 inches) and leave a residual amount of 1,200-1,400 (2-4 inches) in the pasture after it's grazed. It is important for me to graze down to these 2-4 inches in early spring, because this helps create a thick, dense stand for the rest of the grazing season.
As the growth rate increases in the spring, we have two options: increase the amount of acres grazed each day, or make hay on the extra if it gets ahead of the cows and begins to become too mature. Either can work; the goal is to keep the grass in a vegetative state of very high quality. But we don't want to move faster than the grass is growing, or we may run out. As I am overstocked, I usually need to increase the amount grazed as the growth rate increases.
A mistake that I made in the past, when my stocking rate was lower, was having too long of a rotation between grazing each paddock and the grass becoming too mature (begins to make seed heads). Using weekly grass measurements has helped me do a better job of managing the grass growth so it is high quality forage.
Measure: I score each paddock, based on the height. Knowing the dry matter (DM) amount helps me decide the order of which paddock to graze first (the paddock rotation). The rotation length is based on growth rate of the grass. Generally I want to start grazing each paddock at 2,800-3,000 pounds dry matter per acre (8-10 inches high) in the very early spring. We start at a lower dry matter amount per acre because it has not yet reached 2,800-3,000 pounds. We follow the same route through the fields each week as we take the measurements because we want to be consistent in our results. Density of the grass will affect how much dry matter is available in the paddock.
Determining growth rate: 1) Take the average pounds of DM per acre on the farm this week and subtract the average number of DM per acre from the previous week. Divide by the number of days between measurements. This is the daily growth/acre/day. 2) Take pounds of DM per acre going in to the paddock minus the pounds of DM per acre left after grazing to calculate the pounds of DM per acre available to graze. 3) Take the daily growth/acre/day times the total number of acres to obtain the total growth/day for the whole farm. 4) Take the total growth/day for the whole farm divided by the pounds of DM per acre available to graze to calculate the number of acres that can be grazed in one day.
Monitor and adjust: We use this as a guide and then we need to observe and adjust according to growth of the grass; pasture residuals; cow behavior (are they filling up and happily laying around cud chewing versus walking back and forth mooing); is the feed bunk cleaned up; how the manure looks; and what the bulk tank measurement is. I need to add or subtract pasture or feed at the bunk accordingly.
The herd: For the milking herd, my goal is to try and feed a total of 40-45 pounds of dry matter per head, each day. To reach that amount, I utilize the pasture growth first. Then, I subtract the pasture amount from 40-45 pounds which gives me the total of what I should be feeding at the bunk. Example: If the goal is 40 pounds dry matter per cow each day, and they are getting 16 pounds dry matter while grazing; we need to feed 24 pounds dry matter at the bunk. Keep in mind that I am overstocked and usually have to feed at least a little extra at the bunk.
For the dry cows I limit their pasture intake to 2-4 pounds dry matter per head per day because our early spring pasture is very high in potassium and can cause milk fever and other calving problems. The rest of their feed is low potassium forage and grain/mineral mix fed at the feed bunk.
When we first started grazing, we used a yardstick and did calculations by hand. It took a lot of time, but I was able to learn from it and eventually was able to better judge the grass and dry matter by looking at it. It wasn't as accurate, but it worked. By using an electronic rising plate meter to take measurements, scoring pastures has been simplified. You enter measurements into a program on the Missouri Grazing Wedge website. This tool quickly and efficiently calculates average daily growth of the grass, the order of pasture rotation, and how many acres to use each day. I have found this to be very helpful and would encourage anyone who has the resources to consider using these tools to improve their grazing management.
Editor's note: Mike Martin invites readers to send in grazing-related questions for him to answer in future columns. Readers should send their questions to: mikesue.martin@gmail.com.