Some Cattle Feed Supplements Reduce Forage Intake and Digestibility
7/97 BOZEMAN - Montana stock growers face a strange "Catch
22." Montana range forage can become deficient in protein and energy
by mid-summer, leading to a need to feed supplements. However, studies
show that some supplements may reduce both forage intake and digestibility.
The effect of the range quality drop in late summer can be significant.
In one study in the Northern Great Plains, yearling cattle that
had gained three pounds a day from mid-May to mid-July were reduced
to an average of two pounds or less per day average weight gain
for the whole summer.
Low weight gains after Aug. 1 are not only the results of inadequate
nutrients in the forage.
"Studies have shown that grain-based supplements have reduced forage
intake and digestibility to such an extent that there was no benefit
from supplementation," says John Paterson, Montana State University
Extension Service beef specialist.
Supplements can stimulate a change in the microbes in the cattle
rumen, says Paterson. The microbes in the rumen that do a good job
metabolizing grain-based supplements are not the same microbes that
work best digesting fibrous forage. By favoring the microbes that
do well with supplementation, those that do the best job on forage
may be reduced.
Paterson's comments on grain-based supplements referred to a two-year
study by Elaine Grings, Bob Short and Ron Heitschmidt of the USDA-ARS
at Fort Keogh near Miles City. Their 1986-87 study showed that after
about Aug. 1, weight gain by steers on range fell dramatically,
with some steers losing weight. Their presentation at April's Montana
Livestock and Nutrition Conference pointed out that studies in the
1990s did not support studies from the 1980's showing that protein
supplementation of yearling steers improved production efficiency.
With conditions and study results differing this much, cattle producers
will need to consider varying their use of supplements and/or changing
their grazing strategy to match conditions, says Paterson.
"When ranchers believe they have a potential deficiency, they need
to follow a logical approach to determine what is deficient," he
adds.
He recommends that they have forage tested for energy, protein and
even minerals.
If producers find that their range forage quality after Aug.1 is
deficient in most years, they need to consider different types of
supplements and a different grazing strategy, he says.
There are excellent mineral supplements on the market, says Paterson,
which probably need to be fed with protein and energy supplements
to be effective. Another option might be to change grazing strategy
to try to get more beef produced from existing resources.
"One approach might be to use what is called an 'intensive early
stocking' strategy," says Paterson. This involves stocking pastures
heavily early in the summer when forage quality and quantity are
high and then removing the cattle when nutrient supplies begin to
limit animal growth.
"Results from Fort Keogh showed that beef production per acre was
increased by an average of 24 pounds or 63 percent over season-long
grazing," says Paterson. This was so even though weight gain per
steer tended to be lower using an intensive stocking system. Because
of this contrast, producers will hear differing economic evaluations
of intensive early stocking depending on whether the evaluation
is based on production per acre or production per steer.
