Continued elevated carbon dioxide (CO2) concentrations in the atmosphere can reduce grassland forage quality. That leads to a reduction in weight gain among animals, scientists say.
Atmospheric levels of CO2 have risen steadily the past 150 years. Considered a major greenhouse gas because of its ability to trap heat near the earth's surface, most of the increased CO2 has come from forest clearing, industrial manufacturing plants and fossil fuel burning. It's estimated CO2 concentrations will double over today's levels by this century's end.
Jack Morgan, Agriculture Research Service (ARS) plant physiologist, in conjunction with Colorado State University, tested samples of native shortgrass prairie in northern Colorado.
In the project, a simulation test elevated atmospheric CO2 in six open-top chambers, each containing 25 plant species. Ambient air containing 360 parts per million (ppm) CO2 was infused into three containers to model present atmospheric conditions. The CO2 level added to the three remaining containers was 720 ppm.
Results showed that forage quality declined in the grasses under elevated CO2 conditions, largely due to the lower tissue nitrogen content. Production of the grasses was largely unchanged, with the exception of the least desirable of the dominant grasses (Stipa comata — needle and thread grass), which significantly increased under the increased CO2 levels.
— ARS news release
Corn is generally a more economical energy source for cows in the Midwest than hay. Now, researchers are finding the same may be true for barley in the Northern Great Plains.
South Dakota State University Cottonwood Research Station scientists allotted 96 crossbred cows to one of three, limit-fed winter diets during the last trimester of gestation: 1) limit-fed, coarse ground alfalfa hay at 1.6% body weight daily; 2) dry-rolled barley at 29% of the diet (this replaced the alfalfa hay); and 3) dry-rolled barley at 67% of the diet (replacing hay). All groups received a mineral-protein-vitamin fed at 0.5 lbs./cow/day, and the diets were formulated to maintain body condition scores.
Researchers found cows fed barley gained condition and a significant amount of weight over cows fed hay. Hay-fed cows lost body condition. Pregnancy rates were similar across diets.
Researchers concluded that barley works well as an alternative to hay for winter feeding of late-gestating cows (Ward et al. 2004. Proc. Western Section ASA Mtg. 55:22).
— The Ranch Hand by Greg Lardy, North Dakota State University