A study of the composition of sow's milk.

Most of the scanty literature on the major constituents of sow’s milk is old, and nothing has to our knowledge been published on its vitamin composition, with the exception of the fragmentary information about vitamins A and C mentioned below. Probably the main reason for this relative lack of information is the difficulty of obtaining satisfactory samples of sow’s milk. This difficulty is stressed in every paper published on the subject, and is connected with the mechanism of the ‘let down’ o f . milk over which the sow appears to have complete control. It is well known that milk cannot be obtained from the sow by milking in the way normally effective with other large animals. Small samples of milk have been obtained mainly by subterfuge. For this purpose a piglet had to be quietly removed while the sow was suckling her litter and the vacated teat quickly milked by hand. Elly & Petersen (1941) have lately devised a method for inducing the ‘let down’ of milk in the cow by the injection into her blood stream of the oxytocic principle of the pituitary. We have applied their technique to the sow with very satisfactory results, and have been able to obtain with ease from a number of sows large samples of milk at intervals throughout lactation. These samples have been analysed for major constituents and also for certain vitamins. We also obtained colostrum from the same sows in a way previously described (Braude, Kon & Thompson, 1945-6) for comparison of its composition with that of the milk. The investigation has covered the winter as well as the summer feeding of the SOW, and has included a study of the effect of season and fodder on the composition of colostrum and milk. Biological tests with guinea-pigs were also done to confirm the extraordinary richness of sow’s colostrum in ascorbic acid reported in our earlier paper (Braude et al. 1945-6).