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Know What You've Got
Sampling pastures helps you cut feed costs.
You wouldn't dream of trying to balance your rations in the barn this winter
without knowing the quality of the ingredients in your mix. Yet during the
growing season, some graziers try to determine how much grain and supplement to
feed without analyzing their most important feed source -- their pasture.
"I've heard some say, `I've been grazing for years. I know
what's out there,'" says Karen Hoffman, a dairy grazing nutrition
specialist with Cornell Cooperative Extension based in Norwich, N.Y. "But
pasture quality not only changes during the growing season, but also varies from
year to year. If you don't sample your pasture forage from time to time, you
won't know for sure what you've got. You're just guessing."
Guessing wrong can hurt you several ways. Underestimating pasture can cost you
in wasted feed. Overestimating can hurt you in lost milk production. (The "Ouch
Factor" Hoffman calls it, when you check the milk tank and say, "Ouch!
I guess I didn't get the ration right.") Mistakes can cause cows to lose
condition and reduce reproductive performance, she adds. "I've seen cases
where samples from the pasture showed protein levels were 4 to 5 percentage
points higher than expected," says Hoffman. "There was too much
protein and not enough energy in the supplemental ration, and the cows were
losing a lot of condition getting rid of the excess protein."
don't have to sample every paddock each rotation to avoid these problems. But
knowing when to test and what to look for can help you get more from your cows
and grass. Hoffman suggests sampling pastures at least three times during the
season, focusing on times when pasture quality is likely to change:
lush. Sample regrowth after your first rotation. This will give you a good
idea of what to expect from pastures at their highest quality during the most
productive part of the growing season.
slump. Most years, fiber levels increase and quality decreases as
temperatures rise and pasture growth slows, observes Hoffman. But that's not
always the case, and you shouldn't just rely on previous years' forage analyses
to calculate your supplemental rations.
"This past summer ('96)
was a great example," says Hoffman. "It was wet and never got really
warm. In many cases, protein levels in pasture forage stayed pretty high."
That was especially true for graziers who were able to keep up with the
relatively steady pasture growth and consistently offered their stock forage
around the ideal height of about 6 inches. Those who were unable to keep up
with the grass and grazed stock on taller, more mature forage were more likely
to experience the drop in quality typical of the summer slump. "Only by
testing can you tell how much, if any, quality you lost," says Hoffman.
"Many graziers don't think of fall as a particularly difficult time to
manage pasture. But it can be challenging," says Hoffman. If August is
hot and dry, pasture growth rates can take off when temperatures cool down and
fall rains arrive. But as nighttime temperatures drop into the 40s F and days
grow increasingly short, pasture growth can slow dramatically. Depending on
weather and management, protein levels tend to rebound from summertime lows, and
the protein fractions often shift. Again, one of the most common problems
Hoffman sees at this time of the year is loss of condition when supplemental
rations underestimate the high levels of protein in the pasture. "And you
don't want your cows too skinny going into winter," she says.
times. Because weather can cause major changes in pasture quality, Hoffman
suggests sampling pastures whenever there is a significant change in weather
patterns. Also be sure to sample paddocks where you've introduced legumes by
frost seeding, or where the legume component of the stand has changed
significantly because of shifts in weather or management. "If you reseed
and change species, be sure to take samples," she suggests. "Grass
isn't just grass. Each species has its quirks and different species can respond
to changing conditions in different ways."
representative samples and only harvest those parts of the plant that your stock
are actually consuming. And don't forget to rush samples out of the field and
freeze them quickly, as heat can drastically alter the analysis, especially of
soluble protein. Discuss results with your nutritionist to determine the best
ration to make the most of your pasture. (See "Better
Also make sure you have good analyses of
your silage and stored forages, cautions Hoffman. "I can't do a good job
balancing pasture rations unless I have analyses from the other feeds. Silage
and forages can vary as much as pasture depending on weather, what field they
were grown in and when they were harvested."
Time is the
biggest barrier to better pasture forage analysis, she adds. But the potential
payoff in more milk and healthier cows far outweighs the extra effort.
©1997 Committee for
Sustainable Farm Publishing
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