Diversity in Pasture Plants Has Big Effects on Herd and Flock Health

Before I began farming, I was an oceanographer. I used to study tiny, planktonic crustaceans called copepods that feed on microscopic algae, at the base of the food chain, and are themselves consumed by fishes. Some 70 percent of all fishes in the ocean eat copepods at some time in their lives. So naturally, oceanographers and marine biologists are interested in identifying the factors that drive copepod production. My particular interest was in how the kinds of algae that copepods eat affect their egg production – an indication of their health. In 1991, I conducted an experiment to document that relationship. I collected some copepods with a net and transferred a few females and a male to each of several jars containing filtered sea water. To one set of jars, I added a single species of alga, belonging to a group known as the diatoms. To another set of jars, I added a different algal species belonging to a group called the dinoflagellates. And to a third set of jars, I added a mixture of diatoms and dinoflagellates. The total amount of food was the same in all three groups of jars. The copepods in jars containing only diatoms produced about 10 eggs per female each day. The copepods in the dinoflagellate jars, produced about 70 eggs per female each day. That was no surprise, since dinoflagellates are known to contain more protein and lipids (energy) than diatoms. But what came next was surprising. One would expect that by mixing the less and more nutritious algae t

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11 thoughts on “Diversity in Pasture Plants Has Big Effects on Herd and Flock Health

  1. Gary, thank you for sharing! As I plan to try not mowing this season for the very same reason I am curious it you use temporary electric netting and if you have found the non-mowing to inhibit the strength of your fences?

    1. Yes, we do use temporary electric fencing and there can be a loss of charge, especially when the pasture is wet. I use a weed whacker or a small mower to cut a fence line early in the season and I try to return to the same line on each subsequent rotation (though that’s not always possible).

  2. Many variables impact health and body condition score but . . . . I’ve witnessed similar results with cattle and goats as well. The chance to pick and choose is great for them but to maximize gain per acre ranchers also need to limit access to mimic the predator driven herd behavior before european settlement. Movement and long rest balanced with a diverse diet. Good article and I look forward to the follow-up.

    1. Thanks for your comment Jesse. Fred Provenza did some really interesting research on dietary diversity. He also edited a book with Michele Meuret called, The Art & Science of Shepherding that documents the amazing French high country shepherds who move their flocks through vegetatively diverse landscapes which provides in balance in the diet and excellent growth in the livestock. A good read.

  3. Need more detail. How did the sheep in managed pasture deviate? Emaciated or obese?

    1. Thanks for your question Gary. To answer, let me say that both flocks had good body condition scores (BSCs). The way Corine calculated deviation is that she subtracted each BCS that she measured on her sheep and she did the same with the data that I measured on my sheep. She looked at the “absolute value” of each deviation, so that deviations were positive. Then she took the mean of the deviations. So this method doesn’t really look at whether the sheep were closer to 1 or 5, just where there was more variability.

    2. You probably noticed that my response to your question was not clear. The sentence “The way Corine calculated deviation is that she subtracted each BCS that she measured on her sheep…”, should read:

      “The way Corine calculated deviation is that she subtracted each BCS that she measured on her sheep from the optimal value of 3… ”

      Hope that makes it clearer.

      1. The meaning was clear enough even if the language was off a bit. Still, the needed data is the measured BCS. That’s the science part. Data.

  4. Another resource for value of grazing plant diversity is Fred Provenza’s research at Utah State. Contact Beth Burritt for help in getting this research.

    1. Here’s the website for information about research done by Fred Provenza and his colleagues: http://behave.net

      Beth Burritt manages the site and has done a great job of providing information and a list of all the research. Thanks, Beth! And thanks, Chip, for pointing this out!

    2. I had another paragraph in this article that described some of Fred’s work, but we decided to save it for another article. Stay tuned.

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