Deciding Stocking Rates for Pastured Cattle


Tracking Your Herd’s Forage Footprint

Nothing impacts a cattle grazing farm more profoundly than the decision of how many animals to keep.  Too many head and you run out of pasture.  Too few and you are letting perfectly good forage go to waste.  The unpredictability of weather complicates things.  And the carrying capacity of a farm’s pasture is a moving target anyway–for example as it benefits from a program of rotational grazing.

 Sizing your herd’s forage footprint to match the productivity of your pasture is the kind of complex challenge that keeps farming interesting.  The key, as with most of farming, is accurate observation and good record-keeping.      

  Keeping a Pasture Log

The best tool for deciding stocking rates is a good pasture log.  This is a simple document, recording for longer term review those daily bits of personal observation that tend otherwise (if not written down) to get forgotten.  The discipline of keeping a daily log is a learned habit, well-rewarded once you have the hang of it, much like learning to not leave gates open.

The surest way to keep a pasture log is to carry it with you when you are working with the cattle.  I have farmer friends who keep tiny notebooks zipped into chest pockets of their Carhartt bibs.  They have been tracking daily bits of information about their farm this way for forty years or more.  I use a Polaris Ranger to get out to the cattle, so I have the luxury of using the Ranger’s glove compartment to store my pocket calendar and ball point pen.  While I wait for the water tanks to fill, I get the calendar out and update it.  The point I am making is: you will do better if you can write stuff down out in the field rather than relying on making a note later, when you are back in the house. 

Monthly or so, I will carry this little calendar into the house and sit down in my farm office and ‘download’ its information onto summary sheets I keep on file.  I think everyone will have their own instinct about how to track daily pasturing detail.  Some might prefer computers and could design spreadsheets for the purpose.  Others–like me–will just copy information onto handmade ledger pages.

A pasture log can provide you an accurate picture of how productive your pasture is.  The basic elements you need to record in order to be able to figure out your pasture’s productivity are:

1) Clear identification of each paddock or portion of your pasture.

2) A count of how many animals are grazing each day.

3)  Measurement of the amount of time your animals are on each paddock

4) A record of any supplemental feed given to the animals while they are on the paddock (i.e. hay).

When you have recorded these elements, you can calculate the productivity of a paddock in terms of the Cow Days of feed it has provided your animals.

Cow Days
If a paddock is grazed by ten animals for seven days, it has provided 70 Cow Days of forage.  Thirty animals for two days = 60 Cow Days.  One animal for twenty days = 20 cow days. The equation for Cow Days is simply:

          [number of animals] x [number of days] = COW DAYS. 

By using this unit of measurement, you do not really need to worry about the various sizes of paddocks (unless that interests you for some other reason).  It is the productivity of paddocks that you are recording.

[Number of Animals]

A lot of agricultural literature and research is done using the measurement unit AU (animal unit).  The standard for 1 AU is a cow weighing 1000 pounds.  A calf weighing 500 pounds would be 0.5 AU.  A bull weighing 2000 pounds would be 2 AU.  This measure is also used for other grazing species.  The idea is that you measure pasture productivity by estimating consumption of its forage, and that, for example, two 500 pound calves will eat about as much as one cow weighing 1000 pounds.  

 Referencing total AU (instead of a simple head count) turns out to be ideally suited for purposes such as keeping a pasture log.  Instead of needing to juggle, in our clumsy minds, so many particulars about herd history (the year we introduced those many young heifers, the year we kept that crazy bull…), we can record  the herd’s foraging footprint in terms of total AU, thus simplifying comparisons we will be making for years to come.

You can count your animals any way that suits you.  The main thing is that the unit of measurement you use must allow you an accurate comparative from one year to the next.  Otherwise what is the point?

[Number of Days]
Cattle like it if you move them at about the same time each day.  I tend to move my animals in the late afternoon, when the full heat of the day is starting to back off a little.  My animals like to graze in the evening, before settling down for the night, and they like to get after it again early in the morning (earlier than when I am likely to show up).  In this way it is easy for me to note that I moved my animals into a paddock Tuesday evening, then moved them out Wednesday evening–one day. 

Sometimes, when I am watering the herd in the morning, I will see they have already exhausted the paddock I had hoped could serve them through the day.  I will move them again right then and there.  In my Pasture Log, I will credit the prior evening’s paddock with only half a day’s graze.   

I have never found it necessary to record anything other than whole or half days.  This may be because I tend to strip-feed portions of a paddock without bothering to record each movement of the strip line.  If a paddock is one acre, and if I serve it up to the herd in four strip-fed portions, and if they finish that paddock in four days and then move along to another paddock, I will make only one entry: [30 Animal Units] x [4 days] = 120 Cow Days.  This is about as detailed as I feel I need to be in order to understand the productivity of my pasture.

Recording Supplemental Feed

If you offer the cattle supplemental hay during their time on a particular paddock, you need to record this in your log.  At some point (in the depth of winter, when your animals are relying exclusively on hay for sustenance) you should be able to establish how many Cow Days of feed you are getting from each bale of hay.  Your best bet is to work as much as possible with uniform bales, so you can get good and familiar with how many Cow Days of feed they provide. 

 Hay is a different topic altogether—one I don’t mean to get into here.  Suffice it to say: there are times when it makes sense to supplement the forage your cattle are grazing.  And when you do this, it is important to record the supplement in your log.  On my farm, I know that a single round bale provides 30 Cow Days of feed, and if I feed a round bale to the cattle while they are in a paddock, I deduct 30 Cow Days from that paddock’s productivity total.

 Some farmers might scoff at the notion of feeding hay to animals while they are out on pasture during the grazing season.  And certainly in principle they could be right.  On the other hand, reality has a way of confounding rigid systems and I think it is important to know when to bend.  As a hectic farmer also working a full-time job in town, my most common reason for offering hay to the herd while they are grazing is simply that I will not be home to move them in the evening (because I need to be out of town that night on a business trip).  By feeding them a bale, I can leave them in a paddock (though they have eaten it down) for an additional day.  This is not ideal, but it is one way I am able to farm while honoring my obligations to the company I work for.

 Another random example: in June, having just made his first cut of hay, a farmer proposes to sell me some bales.  I go over to his farm and he shows me the bales.  “What do you think?” he says.  “They look pretty good, don’t they?”  “I’m not the one who will be eating them,” I say.  I buy one bale, load it up on the truck and take it home.  I feed it to the cattle that evening.  If they like it, I will call the farmer and offer to buy loads of the hay.  If the cattle do not like the bale, I will give the farmer that bad news.  “Sorry,” I tell him.  “My hay experts advise me against buying any more.”  Here again, I remember to deduct the number of Cow Days of feed the herd got from the hay (if they eat it!), so I do not over-credit the paddock they happen to be in that day.

 Case Study

Let’s say you have twenty acres of pasture.  Year one, on April 1st,  you put six animals on the pasture and leave them wandering all over, continuously grazing.  The pasture gives out at the end of November.  So, figuring you got 8 months’ forage for 6 animals, this would mean:

            [240 days] x [6 animals] = 1440 Cow Days

Year Two, you intend to do better than this.  You divide the pasture into ten paddocks and graze them in rotation.  You start on April 1st, this time with eight animals.  You design a strategy of rotation you think can maximize forage production (this is another subject altogether…).  This year the pasture is exhausted at the end of December.  You got 9 months’ forage for 8 animals, a solid improvement:

            [270 days] x [8 animals] = 2160 Cow Days

Year Three, you set out with an improved strategy, based on lessons learned during Year Two.  Your sense of when and why to move the herd becomes more sophisticated, more connected to the rhythm and habit of the forage plants.  You re-read several intensive grazing books and this time you understand stuff that went over your head the first time.  You decide to subdivide each paddock into two pieces, giving you a total of twenty paddocks.  Confident, you put 10 animals on the pasture April 1st.  You take the animals off the pasture in mid-January, with enough stockpiled paddocks left to provide for all of March the following Spring.  Now you are up to 10.5 months’ forage (or, more to the point, you are down to only 1.5 months’ hay).  And the pasture is radically more productive than when you started:

            [315 days] x [10 animals] = 3150 Cow Days

By now you see the pattern.  During the darkness and bitter cold of January through early March, you go to farming conferences, you read books, you reflect, and, when it comes time to start another grazing year, you set forth anew, with fresh hope and Big Ideas.  It helps to consider much of what you do experimental, meaning that failure is just as legitimate and useful as success.  It helps if you have a bit of the crack pot inventor in you.  Your many circumstances—the particular piece of ground you are farming, the climate you’re in, your personal budgetary and time constraints, the resources available to you through cooperating with neighbors, your skills (or lack of skills) when it comes to repairing equipment or building fence or keeping books, your physical health and stamina, your age, and on and on—mean your farm’s plan is necessarily unique.  As we say in the Midwest, “It’s hard to know the other fellah’s situation.”  You are the one in charge. 


Cow Days is a handy reference you can use over time to track the progress of your rotational grazing system.  Having an accurate record of how productive your pasture has been (as measured by your herd’s consumption) is critical when it comes to making decisions about stocking rates.  If you are doing things right, your soil and forage plants should be steadily improving.  And you yourself should be improving—becoming smarter.  Having a record of these improvements is gratifying to say the least.  I still remember hearing Greg Judy say, “In one year we doubled the productivity of our pasture.  Why that’s like getting a second farm for free!”


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