1. Center Research Laboratories, Ajinomoto Co., Kawasaki 210-8681, Japan
2. Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Central 6, Higashi 1-1-1, Tsukuba, Ibaraki 305-8566, Japan
3. Department of Animal Sciences, University of Illinois Urbana–Champaign, Urbana IL 61801, USA