June 16, 1997
CATTLE DIGESTIVE UPSET ON RYEGRASS STILL A SMALL MYSTERY
Writer: Steve Hill, (409) 845-6717, [email protected]
Contact: Dr. Hagen Lippke, (210) 278-9151, ext. 131
UVALDE -- Researchers already know ryegrass can save water and provide good forage for South Texas ranchers, but using it to best advantage with cattle can be a tricky business.
"We can say for sure that proper management of cattle at the time they go to ryegrass is the most important factor for taking advantage of its potential," said Dr. Hagen Lippke, associate professor of animal science at the experiment station in Uvalde. "But there are still things we haven't determined for certain."
He and other researchers have found that cattle with some fiber in their diet before they are turned onto the grass have good weight gains and fewer digestive problems, but the facts on exactly how and when to balance cattle diets are still somewhat elusive.
Pre-grazing diets, internal organisms and stocking density are some of the factors they know can impact weight gains on ryegrass, but controlling for all the major factors over time is a complicated and expensive matter. However, Lippke says, he and others are making progress.
Lippke has been working with ryegrass off and on since the mid-1970s and in 1990 started a new series of experiments to determine the best way to use ryegrass as forage. He's seen good weight gains on cattle; he's also seen cattle avoid the grass because it gave them digestive upset when they ate it at the wrong time.
One might not think cattle are picky eaters, and they're usually not, Lippke said. But they do have good memories, and sometimes too much of a good thing can be bad, he said.
That's because under some circumstances, if they're too hungry when they're first set out to pasture, they might overeat and suffer from digestive upset caused by low levels of the proper microbial organisms in their rumens.
The organisms are usually present in proper numbers if the cattle have had a well-balanced diet, including some fiber, before being turned out onto ryegrass, Lippke said.
Two years' worth of experiments with cattle shipped from Mexico showed gains of 2.8 pounds daily or better in early stages of pasture feeding, while later experiments with a group of hand-picked cattle showed less impressive results, usually less than 1.8 pounds daily.
However, Lippke said, that could be because the earlier cattle from Mexico were simply leaner when they were put to pasture. Or it could be because the later group, which suffered some feedyard disturbances, consumed less hay before being put to pasture.
"The animals feel terrible and learn they may not want to eat ryegrass," Lippke said. "They'll eat it when there's nothing else, but they really don't want to because they remember how they felt."
One of the ways Lippke is approaching digestive problems is by trying to determine which microbial organisms are present at various stages of pasture feeding. That involves taking rumen content samples, studying the pH balances for alkalinity or acidity, and determining which organisms are present.
"There's one primary culprit organism considered to be a lactic acid producer -- streptococcus bovis -- and we'll have to look for the trail, the persistent low pH in the rumen and the passing of lactic acid," Lippke said.
Tying that back to diet either before or during grazing will take consistent experimental conditions, something that has eluded researchers so far. But with time and enough experimentation, Lippke says, researchers will eventually determine just how, what and when ranchers should feed their cattle to get maximum weight gains.
"There are probably a host of ways," Lippke said. "But we're learning more every day."
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