A ranch cow begins producing calves while still a youngster herself. But pregnancy takes a lot out of a growing heifer. Normally fewer than 85 percent successfully rebreed after their first calf – an expensive loss to ranchers.

Heifers typically begin breeding at 14 months old, while their nutritional requirements are still high, and have their first calf the next year. Getting them in shape to rebreed is a major challenge. University of Nebraska animal scientists found that increasing protein intake during a heifer's first pregnancy raises her odds of getting pregnant the second year to as much as 95 percent. That small difference adds up to big savings for ranchers.

"When you get down to it, rebreeding is (ranchers') No. 1 issue," said Terry Klopfenstein, NU beef nutritionist who worked on this Institute of Agriculture and Natural Resources research. "Once you've got them into the herd with a calf, it's expensive if they don't rebreed and drop out of the herd. Our goal is to have a calf each year but not spend much money doing it."

In summer, nature provides sufficient nutrition for growing heifers. In winter, they can't compete with older cows for limited forage resources and become protein deficient, Klopfenstein said. That deficiency lowers heifers' chances of rebreeding. Normally, ranchers cull cows that don't rebreed and typically remove 15 percent to 25 percent of the herd each year, mostly because of reproductive failure.

Klopfenstein served on the National Research Council committee that recommended using a metabolizable protein system for determining the correct supplement for heifers. Hydrolyzed feather meal was selected as a supplemental ingredient because it's inexpensive, recycles poultry feathers and is an excellent protein source, he said.

Because ranchers already supplement cattle in winter, the new system doesn't require additional work but does cost about $3 more per cow. Researchers needed to know whether the increased cost was economically justified.

To find out, Klopfenstein and IANR colleagues turned to a commercial Sandhills ranch. At two locations, they compared the performance of March-calving heifers fed conventional crude protein supplement with those receiving the new metabolizable protein supplement. Cows' ruminate physiology requires two protein types, one for the cow and one for the microbes living in the rumen. Unlike a crude protein system, the metabolizable system breaks the protein down into those two parts.

Three out of four times during the two-year experiment, rebreeding rates for heifers fed metabolizable protein increased between 4 percent and 10 percent. That translates into saving an average $20 a head with metabolizable protein supplementation, Klopfenstein said. For the small family ranch of 50 heifers, that's a $1,200 saving annually.

"The economics are really solid because they're based on data from a commercial ranch," Klopfenstein said. "If you're a ranch getting 95 percent of those cows to rebreed after they have their first calf, you wouldn't do this. But if you're marginal, in the 80 to 85 percent range, then it would be worth looking at." Few ranchers regularly achieve 95 percent, he added.

Don Adams, animal scientist at NU's West Central Research and Extension Center near North Platte, also worked on this research. He said many ranchers' rebreeding rates for 2-year-old cows don't reach even 80 percent so he expects economic gains to be even higher than $20 a head for them. Some ranchers use more expensive supplementation methods than the new system. Adapting supplements to meet cows' metabolizable protein requirements may help ranchers with high production costs trim expenses.

"I would have to think that the impacts are going to be fairly high," Adams said of the new supplementation system.

One site did achieve a 95 percent rebreeding rate from conventional protein supplementation. Klopfenstein said that high rate likely occurred because the range provided above-average nutrition that year. Those conditions are variable and unpredictable, but researchers plan to investigate further.

The U.S. Poultry and Egg Association helped fund this research.

– Gillian Klucas

Getting heifers to rebreed after their first calf is a major concern. IANR research at the Rex Ranch in Nebraska's Sandhills shows that feeding a metabolizable protein supplement improves heifer rebreeding rates and can save ranchers money.

Harry Younkin (left) and Burke Teichert, Rex Ranch manager, count heifers at the ranch near Ashby, Neb., as part of a two-year IANR study.

Cattle head back to pasture after being worked.