|Allen, Jr., L.|
|Hall, Mary Beth|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2004
Publication Date: 1/1/2005
Citation: Newman, Y. C., L. E. Sollenberger, K. J. Boote, L. H. Allen, Jr., J. C. V. Vu, and M. B. Hall. 2005. Temperature and carbon dioxide effects on nutritive value of rhizoma peanut herbage. Crop Science. 45:316-321. Interpretive Summary: Changes in forage digestibility and nutrient content can change how well a forage supports growth and milk production by cattle. If a forage is made less digestible, it will provide less nutrients to support animal production, reducing production, or requiring more feed supplements to be fed to make up the shortfall. This can result in more expensive or less available animal products for consumers, and reduced profitability for the farmers who own the livestock. With concerns about global warming and increases in greenhouse gasses in our atmosphere, we asked the question: Will the changing environment that forage plants grow in alter the digestibility and nutrient content of forages consumed by livestock? The effect of increased growing temperature and increased atmospheric carbon dioxide (CO2) on the growth and composition of rhizoma peanut, a forage legume, was tested using 2 concentrations of CO2 and 4 temperatures (3 greater than ambient). The digestibility and composition of leaves did not change with changes in temperature, but stem fiber content increased (up to 1%) and stem digestibility decreased (by up to 11%) with increasing temperature. The digestibility of leaves and stems were relatively unaffected by the CO2 treatments. The noted decrease in digestibility could reduce the productivity of animals fed forages grown under warmer conditions.
Technical Abstract: Studies assessing the impact of climate change have focused on plant production, but forage nutritive value, especially of legumes, has often been overlooked. The objective of this study was to determine the effect of increasing temperature and atmospheric CO2 concentration on chemical composition and digestibility of rhizoma peanut (RP, Arachis glabrata Benth.) leaf and stem. In vitro digestible organic matter (IVDOM), neutral and acid detergent fiber (NDF and ADF), and lignin concentrations were determined for plants grown in all combinations of two CO2 (360 and 700 µmol mol-1) and four temperature environments (baseline, or ambient temperature in the greenhouse, B; B + 1.5; B + 3.0; and B + 4.5°C). Forage was sampled every 6 to 8 wk during two growing seasons. Neither increasing CO2 nor temperature affected leaf IVDOM, but stem IVDOM declined from 562 (B) to 552 g kg-1 (B + 4.5) with increasing temperature in Year 1 and from 577 to 511 g kg-1 in Year 2. Stem NDF increased with increasing temperature from 556 to 561 g kg-1 in Year 1 and from 519 to 526 g kg-1 in Year 2. Stem ADF (412 to 418 g kg-1) and lignin (80 to 93 g kg-1) increased linearly as temperature increased in 1 of 2 yr. Lignin as a proportion of NDF or ADF (lignin/NDF or lignin/ADF) accounted for a large proportion of the variation in stem IVDOM. The RP nutritive value decreases with increasing air temperature, but it is relatively unaffected by atmospheric CO2 concentrations in the range studied.