1. Department of Animal Sciences, University of Missouri, Columbia, Missouri.
2. Present address: Department of Pathology & Anatomical Sciences, University of Missouri School of Medicine, Columbia, Missouri
3. Department of Biochemistry, University of Missouri, Columbia, Missouri.
4. Ontogeny and Reproduction, Centre de Recherche du Centre hospitalier de l’Université Laval (CHUL), Québec, Canada.
5. Department of Statistics, University of Missouri, Columbia, Missouri.