Adjusting rations can reduce manure problems

Researchers explore options as industry grows rapidly

By CAROL RYAN DUMAS

Capital Press

Manure is an inevitable byproduct of Idaho's growing dairy industry and presents significant challenges to operators, both in handling and land application.

Using available research, University of Idaho extension dairy specialists set out to determine if feeding strategies could reduce manure production while maintaining animal performance and health.

The answer is "yes, for both growing heifers and for the lactating cows," said Rick Norell, University of Idaho Extension dairy specialist and professor.

Current research suggests that manure production in dairy herds can be reduced by reducing the amount of feed or feeding less alfalfa and more corn silage; more starch and less fiber and by not overfeeding crude protein.

In a University of Wisconsin trial on pregnant 1,000-pound heifers, manure was reduced by 5.6 pounds a day from heifers fed at 90 percent of full intake and by 12.5 pounds per day at 80 percent of full intake.

The limited-feed diets contained more corn, protein supplement and minerals than the full-intake diet.

Precision feeding 12-month-old heifers a high corn diet or high concentrate diet on a limited intake in research by Penn State reduced wet feces by 10 pounds per head per day, increased urine production by 4.9 pounds and decreased total manure by 5.6 pounds.

Ohio State University researchers looked at feeding less alfalfa, as it directly affects urine excretion due to alfalfa's high potassium concentration. Three rations with different percentages of alfalfa and corn silage but similar proportions of forage and metabolizable protein were fed to lactating cows.

Urine excretion increased with each increment of alfalfa, and there was a 2.5 gallon difference per cow per day between the 75 percent alfalfa diet and 75 percent corn silage.

Milk production was 7.5 pounds per cow per day lower with the higher corn silage diet.

However, other researchers have observed similar milk yields between the diets and reported similar reductions in urine by feeding more corn silage, Norrell said.

While feed costs were higher for implementing some of the feeding strategies, some can be competitive when feed prices are closer to historical ranges, and nutritionists can substitute some lower-cost ingredients than what were used in the trials, Norrell said.

The bottom line is producers can reduce the volume of manure on their operations and save costs in handling manure while maintaining milk production and herd health, he said.

But "if they're going to try to make adjustments, they have to do it carefully," he said.