1This research was partially funded by a grant from the Texas
Department of Agriculture Food and Fibers Research Grant Program.
Mention of trade names or commercial products in this article is solely
for the purpose of providing specific information and does not imply
recommendation or endorsement by the U.S. Department of Agriculture
(USDA). USDA is an equal opportunity provider and employer.
2Corresponding author: kristin.hales@ars.usda.gov
3Current address: Panhandle Research & Extension Center, University
of Nebraska, Scottsbluff 69361
4Current address: Department of Animal Science, University of
Nebraska, Lincoln 68583
Received October 4, 2012.
Accepted April 14, 2013.