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Examination of results obtained during the period 1949-54 has shown that newborn calves grow well when they are brought into our calfhouse after it has been left vacant for some time. When, however, they are brought in after the house has been occupied by a succession of experimental calves, their growth rate is less.It is well known that scouring can reduce the live-weight gain of calves, and we have now shown that the incidence of scouring and hence the live-weight gain of a particular calf is related to the time interval between the first use of our calfhouse after a period of vacancy and the day that the calf is introduced. 'Occupation time', as used in this paper, is defined as the number of days that the calfhouse has been occupied following a period of vacancy. METHODSSeveral experiments are carried out in our calfhouse each year, and the results of many of these have already been published. The calfhouse, consisting of thirteen individual pens (for detaiIs see Aschaffenburg, Bartlett, Kon, Terry, Thompson, Walker, Briggs, Cotchin & Lovell, 1g49), is always disinfected and left empty during the summer months, and is then filled up at the end of August with calves collected within 8 h of birth from about thirty farms in the Reading area. The pens are kept filled throughout the winter and spring months with a succession of calves,each calf being kept for a 3-week period. This practice was followed during the winters 1949-50, 1950-1 and 1953-4, but during 1951-2 and 1952-3 the calfhouse was left empty for a short period in the middle of the winter. Thus at the end of December 1951 there was a break of 15 days, from the middle of January 1953 one of 20 days and from the middle of February of the same year one of 17 days; these occasions allowed additional disinfection of the building. As the last two breaks were separated by a period of only 10 days during which the calf pens were occupied by eight calves mostly for a few days only, they will be considered as one break of 47 days beginning

The nutritional importance of lecithin for newborn animals has been demonstrated in America. Esh, Sutton, Hibbs & Krauss (1948) compared the performance of calves receiving colostrum for the first 7 days of life with that of calves deprived of colostrum but given skim milk containing a daily supplement of 25,000-37,500 i.u. vitamin A, and with that of calves that received in addition 3-4'5 g of soya-bean lecithin. Three of the five calves given the vitamin A supplement died within the first I I days of life, and the remaining two scoured from the 3rd to the 10th day. Low blood levels indicated that their vitamin A absorption was poor, whereas the blood level and the growth rate of the calves given lecithin as well as vitamin A were similar to those of the colostrum-fed calves. These authors also suggested that the liver storage of vitamin A was appreciably higher in calves given lecithin and vitamin A than in calves given vitamin A alone. Similarly, Esh & Sutton (1948) found that the addition of lecithin to vitamin A increased weight gains and the liver storage of vitamin A in rats. She%, Gallegos, Grummer, Phillips & Bohstedt (195 I ) found more recently that piglets deprived of colostrum scoured severely and died within 4-5 days unless 5 % of soya-bean lecithin was emulsified with the lard used in their semi-synthetic diet.

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