Saturday, December 6, 2014

A Few Thoughts About Grazing Sorghum-Sudangrass

It's been almost three weeks since I started grazing this field of winter-killed sorghum-sudangrass as a trial to see if it's possible to graze a field like this over part of the winter instead of feeding hay. Other people are already wintering cattle this way, so I'm not really going to discover anything earth-shattering, but I still like to try things on a small scale before I believe everything I read. 

I split this field into four sections (I'm not sure if I'd call them paddocks) and after the cattle had grazed the first quarter for about a week I opened up the second section.  Since I was still developing my winter-grazing eye and wasn't sure about how much grazing was still left, I got a little nervous and opened up the second part earlier than I planned, but in hindsight I think I could have waited much longer.  Now, I'd just estimate how many bales of hay per acre a field would have made, then I'd simply figure out how many bales of hay I'd feed in a week (factoring in some waste. etc.), and  I'd build my paddock big enough to provide a week's worth of feed (or a day, a month, etc.).  This field is about 25 acres, it should have made about 3 bales per acre, so it's the equivalent of 75 bales of hay.  I usually figure that it takes one 1200 lb. bale of hay to feed a 1200 lb. cow for a month, so I could possibly graze 75 cows for a month or 25 cows for three months if I had no wasted grass (So far, with trampling and waste, it looks like I'll be lucky to get the equivalent of about 50-60 bales?).

I've read accounts that claimed that the protein levels for winter-killed sorghum-sudangrass could be as high as 11%, which is more than enough protein for a dry cow and also kind of hard to believe. Most of the typical prairie hay that I typically feed is supposed to be below 8% protein (I've never had any hay tested, but I really should), so I typically feed about 2 lb. of 20% cubes per day to supplement the hay, and I've also been feeding about 2 lb. of cubes while they are on this field of sorghum-sudangrass.  

When I try doing this again, I think I'd add in something like cowpeas, sunn hemp, turnips, or sunflowers (I've been reading some unexpected info about the high-protein levels of sunflowers) to get protein levels high enough so that I could eliminate the cubes completely.   The money I'd save by not needing to buy cubes would easily pay for a lot of cover crop seed, plus planting a cover crop mixture would be better at building the soils in my fields.  I said it before, but I'll say it again, next year is going to be the year of the cover crop mix, but that's also what I said last year. 

This year it also seems like there are more blackbirds (I'm no birdwatcher, so I'm not sure on the exact identity of these birds) around than there usually are in the winter, they're both in the sorghum-sudangrass field and in the pasture next to it.  I don't know if the field of sorghum-sudangrass has anything to do with it, but they seem to be doing a great job of breaking up all the cow patties by scratching through them like a huge flock of hyperactive tiny chickens.   

Of course, they might also eat a bunch of grain sorghum next year before it's harvested, so I'm not sure if a bunch of blackbirds is good or bad.  But, since there isn't really anything that can be done one way or another, my best guess is that they are neither good nor bad, they just are.


  1. Never having been around grazing animals, I have to ask a dumb question. How can you tell when they've completely grazed an area? I'm guessing you don't wait until they start bawling in hunger. Can you recognize how much forage is left that they will eat and what is left that they won't? If I had to guess from the tone of your post, you too are just guessing and doing rough calculations on what your hay would have yielded. Interesting stuff to read.

    1. Cattle usually need to eat about 3% of their body weight in hay each day, which would be about 35 lbs. for a 1200 lb dry cow.

      During the winter, I typically just figure out how much hay I need to feed each day and feed a couple of days worth of hay at a time. If the hay is better quality hay (higher protein and better palatability) they'll eat more of it in a quicker time, but if hay is lower quality they'll waste more and they'll take longer to eat it.

      In 2011 in the middle of the drought, about half of my winter feed was wheat straw (it did have a lot of chaff in it since I took the chopper off and baled it right out of the back of the combine) and I had no other choice but to feed it. I alternated feeding straw and hay along with cubes. On the days when I fed the straw bales I fed more cubes trying to get them to eat the straw, but you could tell that they weren't happy about eating straw.

      On the days when I fed hay, you could easily tell the difference in the way they acted around the feeders and in the morning when I fed the cubes.

      So far, they seem to be acting like they're eating hay when they're grazing this field of sorghum-sudangrass, and if they start acting like they did when they had to eat wheat straw, I'll start supplementing them with some hay.

      When they're out on this sorghum-sudangrass, if I'd baled it I might have baled about 3 bales/acre, but I'm making a pretty conservative guesstimation that I have about 2 bales/acre worth of hay to feed (accounting for waste, weathering, leaving enough residue to feed the soil, etc.).

      The leaves are probably the better part of the dead sorghum-sudangrass, so I've divided up the field so that they don't just eat all the leaves in a few days and then just have the stalks for the rest of the time they're on the field.

      So after all that explanation, I'm just watching the cattle to see how they are acting each day (are they are chewing their cuds, are out on the field grazing, do they look full, or do they seem hungry) to gauge how much feed value is left in the sorghum-sudangrass. At the same time, I'm also making a rough calculation about how many days of grazing they should be getting from what's in the field, and I'm looking at their manure to get a rough idea about how much protein they are getting (too much protein loosens up the manure, just enough protein firms it up, and too little protein makes the manure stack up).

      It's always a guessing game, it's relatively easy to figure out how much hay to put out each day, but so far it has been easier to graze this field than I originally thought it might be.


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