Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science


Yield, kg/ha, bulk density (BD), g/L, relative maturity (RELMA T), chemical composition and in vitro dry matter digestibility (IVDMD) were used to screen corn varieties (n = 20) of varying maturities grown under the stress of a shortened growing season suitable for the production of livestock feed. Com varieties were planted in late June of 1996. Whole shell corn (WSC) and ear corn (EC) were harvested and analyzed for RELMAT, DM, CP, NDF, ADF, starch, EE, ash content, and IVDMD. Bulk density was also quantified on WSC. Corn cobs were retained from shelled ears and analyzed for RELMAT, CP, NDF, ADF, ash content, and IVDMD. Harvest yields for WSC, EC, and corn cobs were 2179 ± 804.5, 2504 ± 1094.5 and 662 ± 134 kg DM/ha respectively. Whole shell corn and EC were sorted into groups by natural separations in yield. Whole shell corn groups were YGP 1 x 3304 ± 227; YGP 2 x 2588 ± 155; YGP 3 x 1406 ± 385 kg DM/ha. The EC yield groupings were YGP 1 x 4199 ± 232, YGP 2 x 3346 ± 233. YGP 3 x 2129 ± 263 and YGP 4 x 1279 ± 510 kg DM/ ha. As WSC yield groups groups advanced from 1 to 3, BD increased (P < .05). There was no difference (P > .05) in RELMAT, EE, ADF and ash content among yield groups. Starch and CP content were the higher (P < .05) for YGP 1 and 2 and lower (P < .05) for YGP 3. There were no differences (P > .05) in IVDMD or energy content between yield groups for WSC or EC. Beef production/ha was estimated for WSC and EC yield groups. For WSC, YGP 1, YGP 2 and YGP 3 were capable of producing 720, 571 and 311 kg of beef/ha respectively. Ear com YGP 1, YGP 2, YGP 3 and YGP 4 would produce 1100, 781, 536, and 282 kg of beef/ha. Increased WSC yield in com varieties grown under the stress of a shortened growing season was attributed to an increase in WSC starch content. Even though yield and BD influenced starch, ADF and NDF content, and corn varieties with a low BD were higher in fiber and lower in TDN content, IVDMD and energy content were not influenced by yield or BD. Relative maturity had no influence (P > .01) on chemical composition, digestibility or energy content. Selecting earlier maturing corn when the growing season was shortened gave no advantage to feed value. Therefore, BD, yield and maturity should not be used as the single criteria when predicting feed value of corn grown under the stress of a shortened growing season.

Key words: Stressed corn, Feeding value, Ear corn

Library of Congress Subject Headings

Corn -- Varieties Corn -- Effect of stress on Corn -- Yields



Number of Pages



South Dakota State University