The effect of decreased range forage quality in late summer can be significant for cow-calf producers. When mid-summer forages become deficient in protein and energy, producers often turn to supplements.

However, research indicates some supplements may reduce both forage intake and digestibility. In one Northern Great Plains study, yearling cattle gaining 3 lbs./day from mid May to mid July were reduced to an average of 2 lbs. or less/day average weight gain for the summer.

“Studies show grain-based supplements reduced forage intake and digestibility to such an extent there was no benefit from supplementation,” says John Paterson, Montana State University Extension beef specialist.

Supplements can stimulate a change in rumen microbes, Paterson says. The microbes that do a good job metabolizing grain-based supplements aren't the same as those digesting fibrous forage. By favoring the microbes that do well with supplementation, those that do the best job on forage may be reduced.

Research also suggests that when forage crude protein content falls below about 6-7%, dry matter intake also declines. At levels below this, it may be difficult for the cow to consume enough forage to meet energy requirements.

After last year's drought in many parts of the West, Patterson says, a forage analysis is critical in determining how well the resources will meet the nutrient requirements of the gestating cow.

For more on cattle nutrition research, browse the 2005 Montana Nutrition Conference proceedings at: www.animalrangeextension.montana.edu/Articles/Beef/Main-Nutrition.htm. Or visit www.beefcowcalf.com, a cow-calf production and management information Web site by BEEF magazine.
Clint Peck