1. Five Dairy Shorthorn male calves born in February and March 1953 and three groups of four born in each of the months February, March and April 1954 were placed out of doors on permanent pasture at birth.
2. Each calf received 6 or 8 pt. colostrum followed by approximately 45 gal. whole milk during the first 8 weeks of life, and thereafter, except for a small amount of dried grass given in Exp. 1, pasture grass comprised the sole item of diet until 6 months of age.
3. Mean growth rates for each month of life and from birth to 6 months are presented. After the first month of life, good progress was made, and it is considered that the live weights at 6 months of age are similar to those obtained with conventional methods of rearing.
4. There was a significant effect of birth weight on live-weight gain. After adjustment for birth weight, there were no significant differences in live-weight gain between February, March and April-born groups of calves.
5. Weather conditions seemed to have little effect on the incidence of scouring during the first 3 weeks of life.
6. On leys, greater weight gains were obtained than on permanent pasture.
7. No lungworm larvae were detected in faeces samples examined. In many cases there was a high level of infestation with stomach and intestinal worms as indicated by the number of trichostrongyle eggs/g. faeces. Some aspects of this infestation are discussed.
8. Satisfactory growth to 18 months of age was obtained with silage during the 6-month winter period and at grass during the following spring and summer.
9. Details of behaviour of the five calves in Exp. 1 studied at approximately monthly intervals to 6 months of age are presented.