The author wishes to thank all those who helped with the initial literature search, notably: the Master and Prof. P.A. Jewell of St. John's College, and the Librarian, Department of Applied Biology, all of the University of Cambridge; Prof. W.V. Macfarlane, and the Division Documentation de l'Institut d'Elevage et de Médecine Vétérinaire des Pays Tropicaux; and the Commonwealth Bureaux of Animal Breeding and Genetics, Animal Health, and Nutrition in the U.K.
Thanks are also due to those who have commented on the manuscript, particularly the following ILCA staff members: Mr. D.J. Pratt (former Director General), Dr. R.S. Temple, Dr. L.J. Lambourne, Dr. P.A. Konandreas and Prof. R.E. McDowell (Chairman of ILCA's Board of Trustees). The comments of the following outside referees are also gratefully acknowledged: Dr. V.A. Finch, Prof. C.R. Taylor, Prof. P.J. Van Soest, Dr. J.E. Vercoe and Prof. A.J.F. Webster.
Finally I wish to thank Mrs. S.B. Westley, Dr. R.A. Stewart and Mr. S.D. Chater for editorial assistance, and Mrs. G. Maloba for typing the draft.
