[1] Univ Missouri, Dept Anim Sci, Columbia, MO 65211 USA
[2] Univ Missouri, Dept Vet Biomed Sci, Columbia, MO 65211 USA
[3] Univ Missouri, Dept Biochem & Child Hlth, Columbia, MO 65211 USA
[4] BioReagents, Golden, CO 80401 USA
[5] Populat Council, New York, NY 10021 USA