If you’re familiar with grain farming, the term “bushels per acre” is a common frame of reference for measuring yield. There are nuances around this, such as moisture level, bushel weight and protein content, but bushels per acre is a relatively well understood industry standard.
When we think about a lot of the cow-calf industry being grazing-based, our core business could be viewed as growing grass, and our cows are simply the harvesters of that forage. Because our four-legged combines don’t come with a yield monitor, we need another way to track yield rapidly and effectively.
This is where using “The Standard Animal Unit Grazing Day” or AUGD can be extremely valuable to record our yield. This simple-to-use number can give a good indication of forage yield and utilization. When paired with other metrics such as visual assessment and moisture readings, it can lead us to better understand and manage our forage base. On our ranch, we track AUGD extensively and it is an invaluable management tool.
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What is an animal unit (AU)?
Most of us do not have 1,000-pound cows, and we intuitively know that an 1,800-pound cow eats more than a 1,000-pound cow. Accounting for differences in cow size is important when judging forage availability and is fairly simple to adjust for.
A 1,500-pound cow is equal to 1.5 animal units (1,500/1,000 = 1.5), a 2,000-pound bull is equal to two animal units and a 650-pound yearling is equal to 0.65 animal units. Basically, to standardize yield we take the weight of the animal(s) in pounds and divide by 1,000.
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Many producers may not own a scale and are guessing at cow weights. Generally speaking, they guess low. If you are using auction receipts, add 10 per cent (at least) to the pay weights on your cull cows. If you are marketing skinnier-type cows, you may need to add 20 per cent or more to reflect the actual weights of your productive cows. When marketing, we weigh every cow before it leaves the yard and the shrink on cull cows is significant, often in the range of 10 to 12 per cent.
What is a grazing day (GD)?
The second part of our yield equation is the grazing day. In simplest terms, each day that an animal grazes is a grazing day. To this concept we add the standardized animal unit to arrive at animal unit grazing days. Many people may already be familiar with the term AUM or animal unit month. An AUM is simply 30 AUGD. The animal unit grazing day is defined as the amount of forage consumed by a 1,000-pound cow in one day. This equates roughly to 25 to 30 pounds of dry matter but will vary a bit depending on the stage of production, temperature and other factors. It is a bit like bushels per acre — there are some nuances, but it serves as a pretty good basic indicator.
Let’s run though an example calculation:
- A ranch has 10, 1,500-pound cows on a pasture for the month of June (30 days)
- Animal Units = 10 X 1.5 or 15 standard animal units
- Grazing days = 30 (June 1 to June 30)
- AUGD = 15 animal units x 30 grazing days = 450 animal unit grazing days (AUGD)
Grazing records and AUGD
At our ranch, we manage our grazing at a very intensive level with various record-keeping apps, charts, monitoring points and other systems. I appreciate that this can be intimidating and is likely not needed for most operations.
I firmly believe that records that aren’t used are a complete waste of time. However, the concept of an AUGD can provide a lot of clarity and simplification in terms of what we should be recording for basic grazing records. A good system is simply to hang a wall calendar with big enough squares to write on. From this we can calculate AUGD, track pasture movements and determine yield.
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Let’s use our previous example and show potential June calendar square entries into our records.
If we know our south pasture is 20 acres, from these two simple entries we can easily calculate that our 10, 1,500-pound cows were in the pasture for 30 days or 450 AUGD. If we divide the total yield by the number of acres (450/20) this works out to a yield of 22.5 AUGD/acre. For those familiar with the AUM concept that is 0.75AUM (22.5 days of grazing /30 days in a month).
We might inspect that pasture and find that we have merely grazed the surface or that we have grazed it quite hard. We may observe that use is patchy or that we have weed issues or bare soil to deal with. Perhaps when we compare yields with other pastures, we find that the south pasture is dramatically under-yielding compared to other pastures in our system.
If we look back on our calendars from previous years, maybe it shows that we continually graze the south pasture just as the forage is beginning to grow, or we may come back for another pass later in the year, so we are only taking a small part of the yield in the first pass. If we look at our rainfall, perhaps the pasture is just distressed due to drought. Keeping this simple calendar record also lets us calculate rest or recovery periods for the pasture (amount of time during the growing season where animals are not present).
These simple grazing records and the concept of AUGD as our “Ranching Bushels Per Acre” have a lot of power to help us understand our grazing business better and to improve our forage yield and ranch profitability.
