1. Department of Veterinary Medicine, University of Sydney; Sydney
2. Dairy Research Unit, Sydney University Farms; Camden New South Wales 2570
3. C.S.I.R.O. Division of Mathematics and Statistics; Newtown New South Wales 2042
4. C.S.I.R.O. Division of Animal Health; Private Bag No. 1, P.O. Parkville Victoria 3052